2018 Vol. 43, No. 9
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2018, 43(9): 3169-3185.
doi: 10.3799/dqkx.2018.239
Abstract:
The Erik iron deposit is one of the biggest deposits in the Taxkorgan iron deposit belt in Xinjiang, an important high-grade one recently discovered in West China, which has been rarely studied. To identify the genesis of the Erik iron deposit, ore deposit geology survey and in situ LA-ICP-MS analysis of magnetite have been conducted in this study. It is found that mineralization occurs at the Bulunkuole meta-volcano-sedimentary sucession. Ore occurrences are basically coordinated with those of host rocks, and exhibit obviously stratabound characteristics. Two main mineral associations of magnetite+anhydrite and magnetite+calcite in variable proportions commonly occurred in the high-grade iron bodies and formed dense disseminations and massive ores. Both magnetite grains from these two associations show constant contents of many elements including Mg (119×10-6-313×10-6), Al (692×10-6-1 034×10-6), Ti (540×10-6-840×10-6), V (3 340×10-6-3 971×10-6), Mn (950×10-6-1 160×10-6), Co (4×10-6-5×10-6), Ni (52×10-6-64×10-6), Zn (84×10-6-143×10-6), and Ga (26×10-6-31×10-6) and similar to those of in high-temperature hydrothermal environment. It is interpreted that the high Al, Ti, V contents, with high Ni/Cr and low Ti/V ratios in magnetites result from relatively reduced, Al-Ti-rich seafloor hydrothermal activities under a stable sedimentary environment. The (Al+Mn)-(Ti+V) feature of the Erik magnetites implies a high-temperature crystallization (300-500℃). The magnetites coexisting with anhydrite have higher Ti (690×10-6), P (27×10-6) concentrations in average, and lower Ca (36×10-6) than those coexisting with calcites (Ti=574×10-6, P=7×10-6, Ca=203×10-6). Moreover, the former are more depleted in high field strength elements of Zr, Hf, Sc, Ta, suggestting them have suffered more severely hydrothermal activities and Ca contents in magnetites are reduced with Ca2+ entering into crystal lattice of anhydrites. Integrating obtained evidences, including regional geology, ore deposit geology, magnetite composition, and we conclude that the Erik iron deposit was formed from an Early Cambrian seafloor high-temprature hydrothermal system. The development of the Erik iron deposit is related with a volcanic arc caused by southward subduction of Proto-Tethyan Plate. The Erik iron deposit is classified into a marine volcanic-sedimentary hosted Fe oxide deposit formed at or near the seafloor in submarine volcanic settings.
The Erik iron deposit is one of the biggest deposits in the Taxkorgan iron deposit belt in Xinjiang, an important high-grade one recently discovered in West China, which has been rarely studied. To identify the genesis of the Erik iron deposit, ore deposit geology survey and in situ LA-ICP-MS analysis of magnetite have been conducted in this study. It is found that mineralization occurs at the Bulunkuole meta-volcano-sedimentary sucession. Ore occurrences are basically coordinated with those of host rocks, and exhibit obviously stratabound characteristics. Two main mineral associations of magnetite+anhydrite and magnetite+calcite in variable proportions commonly occurred in the high-grade iron bodies and formed dense disseminations and massive ores. Both magnetite grains from these two associations show constant contents of many elements including Mg (119×10-6-313×10-6), Al (692×10-6-1 034×10-6), Ti (540×10-6-840×10-6), V (3 340×10-6-3 971×10-6), Mn (950×10-6-1 160×10-6), Co (4×10-6-5×10-6), Ni (52×10-6-64×10-6), Zn (84×10-6-143×10-6), and Ga (26×10-6-31×10-6) and similar to those of in high-temperature hydrothermal environment. It is interpreted that the high Al, Ti, V contents, with high Ni/Cr and low Ti/V ratios in magnetites result from relatively reduced, Al-Ti-rich seafloor hydrothermal activities under a stable sedimentary environment. The (Al+Mn)-(Ti+V) feature of the Erik magnetites implies a high-temperature crystallization (300-500℃). The magnetites coexisting with anhydrite have higher Ti (690×10-6), P (27×10-6) concentrations in average, and lower Ca (36×10-6) than those coexisting with calcites (Ti=574×10-6, P=7×10-6, Ca=203×10-6). Moreover, the former are more depleted in high field strength elements of Zr, Hf, Sc, Ta, suggestting them have suffered more severely hydrothermal activities and Ca contents in magnetites are reduced with Ca2+ entering into crystal lattice of anhydrites. Integrating obtained evidences, including regional geology, ore deposit geology, magnetite composition, and we conclude that the Erik iron deposit was formed from an Early Cambrian seafloor high-temprature hydrothermal system. The development of the Erik iron deposit is related with a volcanic arc caused by southward subduction of Proto-Tethyan Plate. The Erik iron deposit is classified into a marine volcanic-sedimentary hosted Fe oxide deposit formed at or near the seafloor in submarine volcanic settings.
2018, 43(9): 3186-3199.
doi: 10.3799/dqkx.2018.151
Abstract:
West Junggar belt, located in the core area of the Central Asian metallogenic domain, is one of the most important gold development bases in China. Accompanying intense tectonic and magmatic activities, extensive gold mineralization occurred during Paleozoic and a series of gold deposits/occurrences and mineralized points have been discovered in the West Junggar belt such as Sartohay, Hatu and Baogutu gold deposits. In the present study, the methods of local singularity analysis and sequential indicator simulation were employed to identify gold anomaly and model its uncertainty based on stream sediment geochemical data sampled from West Junggar belt, which allows for enhancing local and weak anomalies effectively. The results of simulation can be used to express probability distribution pattern of gold anomalies characterized by singularity indices less than 2. The results indicate that high probability zones of gold anomalies are closely associated with known gold deposits/occurrences, which provides an important decision-making for risk evaluation of gold resource exploration in the West Junggar belt.
West Junggar belt, located in the core area of the Central Asian metallogenic domain, is one of the most important gold development bases in China. Accompanying intense tectonic and magmatic activities, extensive gold mineralization occurred during Paleozoic and a series of gold deposits/occurrences and mineralized points have been discovered in the West Junggar belt such as Sartohay, Hatu and Baogutu gold deposits. In the present study, the methods of local singularity analysis and sequential indicator simulation were employed to identify gold anomaly and model its uncertainty based on stream sediment geochemical data sampled from West Junggar belt, which allows for enhancing local and weak anomalies effectively. The results of simulation can be used to express probability distribution pattern of gold anomalies characterized by singularity indices less than 2. The results indicate that high probability zones of gold anomalies are closely associated with known gold deposits/occurrences, which provides an important decision-making for risk evaluation of gold resource exploration in the West Junggar belt.
2018, 43(9): 3200-3217.
doi: 10.3799/dqkx.2018.559
Abstract:
Magma mixing events occurred widely and fiercely in Halagatu granitic batholith in eastern part of the East Kunlun orogenic belt, one of the ideal natural labs for magma mixing and mingling studies. We study through electron microprobe (EPMA) the lithology, petrography and mineral chemistry from the granitic batholith. The results reveal that plagioclases in the host rocks and those in the xenocrystals in MMEs have similar mineral features of anorthite-albite component value (An value). And most plagioclases in matrix of MMEs have core-rim structures with an An value discontinuity. An values of the light-colored matrix plagioclase in some MMEs are similar to those with core-rim structures. The plagioclases in gabbro diorite have a higher An value. The crystallization temperature, pressure and oxygen fugacity of the hornblendes of the host rocks are similar to those of the hornblende xenocrystals in MMEs. The crystallization temperature and pressure of the matrix hornblende in the MMEs are lower than those in the host rocks, and the oxygen fugacity is slightly higher than that in the host rocks. The hornblendes in gabbro diorite have the highest crystallization temperature and pressure and the lowest oxygen fugacity. The compositions of the plagioclase and hornblende in the host rocks of the Hatugou section and Defusheng section are different. Intermittent magma intrusions and crystallizations, together with their evolution resulted in differences in composition, physical and chemical features varying with places. The mafic magma stayed in deep the Crust with lower oxygen fugacity, providing a condition of high pressure and low oxygen fugacity for hornblende crystallization and high An value for plagioclases. With the injection of mafic magma into the host rocks, due to environmental changes, plagioclases are subject to erosion. The temperature, pressure and water saturation reduced, whilst oxygen fugacity increased because of magma intrusion and physical and chemical differences for the two magmas. Thus the residual magma in MMEs crystallized quickly to form plagioclases with core-rim structures and uniformly light color, and hornblendes with non-crystal shape and high value of oxygen fugacity.
Magma mixing events occurred widely and fiercely in Halagatu granitic batholith in eastern part of the East Kunlun orogenic belt, one of the ideal natural labs for magma mixing and mingling studies. We study through electron microprobe (EPMA) the lithology, petrography and mineral chemistry from the granitic batholith. The results reveal that plagioclases in the host rocks and those in the xenocrystals in MMEs have similar mineral features of anorthite-albite component value (An value). And most plagioclases in matrix of MMEs have core-rim structures with an An value discontinuity. An values of the light-colored matrix plagioclase in some MMEs are similar to those with core-rim structures. The plagioclases in gabbro diorite have a higher An value. The crystallization temperature, pressure and oxygen fugacity of the hornblendes of the host rocks are similar to those of the hornblende xenocrystals in MMEs. The crystallization temperature and pressure of the matrix hornblende in the MMEs are lower than those in the host rocks, and the oxygen fugacity is slightly higher than that in the host rocks. The hornblendes in gabbro diorite have the highest crystallization temperature and pressure and the lowest oxygen fugacity. The compositions of the plagioclase and hornblende in the host rocks of the Hatugou section and Defusheng section are different. Intermittent magma intrusions and crystallizations, together with their evolution resulted in differences in composition, physical and chemical features varying with places. The mafic magma stayed in deep the Crust with lower oxygen fugacity, providing a condition of high pressure and low oxygen fugacity for hornblende crystallization and high An value for plagioclases. With the injection of mafic magma into the host rocks, due to environmental changes, plagioclases are subject to erosion. The temperature, pressure and water saturation reduced, whilst oxygen fugacity increased because of magma intrusion and physical and chemical differences for the two magmas. Thus the residual magma in MMEs crystallized quickly to form plagioclases with core-rim structures and uniformly light color, and hornblendes with non-crystal shape and high value of oxygen fugacity.
2018, 43(9): 3218-3233.
doi: 10.3799/dqkx.2018.231
Abstract:
Dabu mining area is located in the southern part of the middle Gangdese metallogenic belt, which has great metallogenic potential of Cu (Mo) deposit. In this paper, petrology, LA-ICP-MS zircon U-Pb dating, rock geochemistry of the Dabu ore-bearing granodiorite body are systematically studied. The results suggest that the Dabu granodiorite pluton is one of the major ore-bearing rock body, and its LA-ICP-MS zircon U-Pb age is 16.5±0.3 Ma-16.0±0.4 Ma, with the corresponding age of Miocene (N1). The rock mass has high Al (Al2O3=15.6%-16.5%), high Na (Na2O=4.51%-4.82%), and it is calc-alkaline and weakly peraluminous. REE elements have weak positive Eu anomalies (Eu/Eu*=1.02-1.27) and positive Ce anomalies (Ce/Ce*=0.99-1.53). Trace elements ratio spider diagram displays apparent enrichments of Rb, Ba, Sr and marked depletions of Nb, Ta, Ti, Y. The Dabu granodiorite pluton belongs to Ⅰ-type granite, which is similar to the typical C-type adakite, but is obviously different from the Miocene high-K adakite in the Gangdese belt. It is concluded that Dabu granodiorite pluton is a relatively high degree of partial melting of the thickened lower crust material (garnet amphibolite) formed in the background of partial extension of the India Asian continent post-collision.
Dabu mining area is located in the southern part of the middle Gangdese metallogenic belt, which has great metallogenic potential of Cu (Mo) deposit. In this paper, petrology, LA-ICP-MS zircon U-Pb dating, rock geochemistry of the Dabu ore-bearing granodiorite body are systematically studied. The results suggest that the Dabu granodiorite pluton is one of the major ore-bearing rock body, and its LA-ICP-MS zircon U-Pb age is 16.5±0.3 Ma-16.0±0.4 Ma, with the corresponding age of Miocene (N1). The rock mass has high Al (Al2O3=15.6%-16.5%), high Na (Na2O=4.51%-4.82%), and it is calc-alkaline and weakly peraluminous. REE elements have weak positive Eu anomalies (Eu/Eu*=1.02-1.27) and positive Ce anomalies (Ce/Ce*=0.99-1.53). Trace elements ratio spider diagram displays apparent enrichments of Rb, Ba, Sr and marked depletions of Nb, Ta, Ti, Y. The Dabu granodiorite pluton belongs to Ⅰ-type granite, which is similar to the typical C-type adakite, but is obviously different from the Miocene high-K adakite in the Gangdese belt. It is concluded that Dabu granodiorite pluton is a relatively high degree of partial melting of the thickened lower crust material (garnet amphibolite) formed in the background of partial extension of the India Asian continent post-collision.
2018, 43(9): 3234-3251.
doi: 10.3799/dqkx.2018.146
Abstract:
The Jiangba Formation volcanic rocks are found in the Xiongmei area in recent years, however its petrogenesis is still unclear. This paper has carried out a systematic petrography, geochemistry and isotopy study on the intermediate-acid Jiangba Formation volcanic rocks in the Xiongmei area, Tibet. The zircon U-Pb age of 85.1±1.0 Ma has been obtained from the dacitic volcanic rocks. The dacitic and andesitic volcanic rocks show the typical geochemical characteristics of adakite, such as high contents of SiO2, Al2O3, Sr concentrations, Mg# values, and Sr/Y ratios, and low contents of Y and Yb. The dacitic and andesitic volcanic rocks are relatively enriched in LREEs (light rare earth elements), depleted in HREEs (heavy rare earth elements), and high (La/Yb)N values without obvious Eu anomalies. The spider diagram of the trace elements of the dacitic and andesitic volcanic rocks display enrichment in Th, Zr and Hf, and depletion in Nb, Ta and Ti. In addition, these dacitic volcanic rocks have positive zircon εHf(t) values (+2.7~+7.1), indicative of the participation of the depleted mantle in the magmatism. These signatures indicate the dacitic volcanic rocks and andesitic volcanic rocks were most likely derived from partial melting of a delaminated young lower crust. The rhyolitic volcanic rocks have relatively lower contents of MgO and TiO2 relative to the dacitic and andesitic volcanic rocks. These rocks are enriched in LREEs, depleted in HREEs, but show less fractionation between LREEs and HREEs than the dacitic and andesitic volcanic rocks, with strongly negative Eu anomalies. On spider diagram of the trace elements, the rhyolitic volcanic rocks show enrichment in Th, Rb and K, and strongly negative Eu, Sr, Ba, P and Ti. These indicate the rhyolitic volcanic rocks were likely derived from remelting of pure crust. These facts indicate a magmatic event caused by the delamination of the thickened lower crust in the Anglonggangri-Bangor magmatic arc of the middle Bangonghu-Nujiang suture zone during the Late Cretaceous.
The Jiangba Formation volcanic rocks are found in the Xiongmei area in recent years, however its petrogenesis is still unclear. This paper has carried out a systematic petrography, geochemistry and isotopy study on the intermediate-acid Jiangba Formation volcanic rocks in the Xiongmei area, Tibet. The zircon U-Pb age of 85.1±1.0 Ma has been obtained from the dacitic volcanic rocks. The dacitic and andesitic volcanic rocks show the typical geochemical characteristics of adakite, such as high contents of SiO2, Al2O3, Sr concentrations, Mg# values, and Sr/Y ratios, and low contents of Y and Yb. The dacitic and andesitic volcanic rocks are relatively enriched in LREEs (light rare earth elements), depleted in HREEs (heavy rare earth elements), and high (La/Yb)N values without obvious Eu anomalies. The spider diagram of the trace elements of the dacitic and andesitic volcanic rocks display enrichment in Th, Zr and Hf, and depletion in Nb, Ta and Ti. In addition, these dacitic volcanic rocks have positive zircon εHf(t) values (+2.7~+7.1), indicative of the participation of the depleted mantle in the magmatism. These signatures indicate the dacitic volcanic rocks and andesitic volcanic rocks were most likely derived from partial melting of a delaminated young lower crust. The rhyolitic volcanic rocks have relatively lower contents of MgO and TiO2 relative to the dacitic and andesitic volcanic rocks. These rocks are enriched in LREEs, depleted in HREEs, but show less fractionation between LREEs and HREEs than the dacitic and andesitic volcanic rocks, with strongly negative Eu anomalies. On spider diagram of the trace elements, the rhyolitic volcanic rocks show enrichment in Th, Rb and K, and strongly negative Eu, Sr, Ba, P and Ti. These indicate the rhyolitic volcanic rocks were likely derived from remelting of pure crust. These facts indicate a magmatic event caused by the delamination of the thickened lower crust in the Anglonggangri-Bangor magmatic arc of the middle Bangonghu-Nujiang suture zone during the Late Cretaceous.
2018, 43(9): 2911-2928.
doi: 10.3799/dqkx.2018.156
Abstract:
The Yuhai Cu deposit, recently discovered by the No.704 Geological Party of Xinjiang Geological Exploration Bureau for Nonferrous Metals, is located in the eastern part of the Dananhu-Tousuquan island arc belt, eastern Tianshan. The alteration and mineralization features, and metallogenesis of the Yuhai deposit are still controversial. Detailed studies on ore geology, biotite and sericite Ar-Ar isotopic dating, and short wavelength infra-red (SWIR) indicate that biotite-magnetite, phyllic and chlorite alteration are well developed at Yuhai. The biotite-magnetite alteration extensively occurs in the quartz diorite, the phyllic alteration zone mainly occurs in the quartz diorite, and the chlorite alteration mainly occurs in the transitional zone of biotite-magnetite and phyllic alterations belts. Chalcopyrite mineralization occurs as chalcopyrite-pyrite-magnetite and epidote-chalcopyrite assemblages, and the former is closely related to the biotite-magnetite alteration, while the latter is associated with the phyllic alteration. The results of biotite and sericite 40Ar/39Ar dating are ca. 324-314 Ma, consistent with the age of Yuhai granite (325.4±2.5 Ma) in errors. Integrating with local geology, biotite and sericite Ar-Ar systems were likely reset after their formation. Combined with previous studies, the biotite-magnetite and phyllic alterations were likely formed at 360-350 Ma, related with the emplacement of the Yuhaixi gneissic granite (or other coeval intrusions). Short wavelength infra-red (SWIR) research at Yuhai reveals that high values (>2 253 nm) of chlorite Fe-OH absorption peak (Pos2250) mainly occur in the phyllic alteration zone and its adjacent areas, pointing to the Cu bodies, which can be used as a potential exploration tool in deposit-scale.
The Yuhai Cu deposit, recently discovered by the No.704 Geological Party of Xinjiang Geological Exploration Bureau for Nonferrous Metals, is located in the eastern part of the Dananhu-Tousuquan island arc belt, eastern Tianshan. The alteration and mineralization features, and metallogenesis of the Yuhai deposit are still controversial. Detailed studies on ore geology, biotite and sericite Ar-Ar isotopic dating, and short wavelength infra-red (SWIR) indicate that biotite-magnetite, phyllic and chlorite alteration are well developed at Yuhai. The biotite-magnetite alteration extensively occurs in the quartz diorite, the phyllic alteration zone mainly occurs in the quartz diorite, and the chlorite alteration mainly occurs in the transitional zone of biotite-magnetite and phyllic alterations belts. Chalcopyrite mineralization occurs as chalcopyrite-pyrite-magnetite and epidote-chalcopyrite assemblages, and the former is closely related to the biotite-magnetite alteration, while the latter is associated with the phyllic alteration. The results of biotite and sericite 40Ar/39Ar dating are ca. 324-314 Ma, consistent with the age of Yuhai granite (325.4±2.5 Ma) in errors. Integrating with local geology, biotite and sericite Ar-Ar systems were likely reset after their formation. Combined with previous studies, the biotite-magnetite and phyllic alterations were likely formed at 360-350 Ma, related with the emplacement of the Yuhaixi gneissic granite (or other coeval intrusions). Short wavelength infra-red (SWIR) research at Yuhai reveals that high values (>2 253 nm) of chlorite Fe-OH absorption peak (Pos2250) mainly occur in the phyllic alteration zone and its adjacent areas, pointing to the Cu bodies, which can be used as a potential exploration tool in deposit-scale.
2018, 43(9): 2929-2942.
doi: 10.3799/dqkx.2018.145
Abstract:
Mineral composition of biotite is a significant indicator of revealing the crystallization conditions, petrogenesis, mineralization and evaluation of ore-bearing potential in porphyry copper deposit systems. This study utilizes electron microprobe analyses (EPMA) to determine the mineral composition of biotite in Yuhai and Sanchakou porphyry copper deposits, Xinjiang. The EPMA data shows that the characteristics of biotite are rich in magnesium and poor in iron in ore-bearing intrusions; whereas those in ore-barren intrusions are rich in iron and poor in magnesium. The biotite is mainly composed of re-equilibrated Mg-biotite in ore-bearing intrusions and is primary Fe-biotite in ore-barren intrusions. The host rocks of all the biotite are I-type granite and are formed during subduction. The ore-bearing magma was derived from the mixing of mantle and crust, however, the ore-barren magma was mainly generated from crust with involvement of juvenile crustal components during formation. The crystallization temperature and pressure of biotites are 529-677℃ and 1.1-2.8 kbar, and they formed in the condition of high oxygen fugacity. In addition, the Mg/Fe and Fe2+/(Fe2++Mg2+) of biotites may be used as a tool to discriminate between the ore-bearing and ore-barren intrusions in porphyry copper systems.
Mineral composition of biotite is a significant indicator of revealing the crystallization conditions, petrogenesis, mineralization and evaluation of ore-bearing potential in porphyry copper deposit systems. This study utilizes electron microprobe analyses (EPMA) to determine the mineral composition of biotite in Yuhai and Sanchakou porphyry copper deposits, Xinjiang. The EPMA data shows that the characteristics of biotite are rich in magnesium and poor in iron in ore-bearing intrusions; whereas those in ore-barren intrusions are rich in iron and poor in magnesium. The biotite is mainly composed of re-equilibrated Mg-biotite in ore-bearing intrusions and is primary Fe-biotite in ore-barren intrusions. The host rocks of all the biotite are I-type granite and are formed during subduction. The ore-bearing magma was derived from the mixing of mantle and crust, however, the ore-barren magma was mainly generated from crust with involvement of juvenile crustal components during formation. The crystallization temperature and pressure of biotites are 529-677℃ and 1.1-2.8 kbar, and they formed in the condition of high oxygen fugacity. In addition, the Mg/Fe and Fe2+/(Fe2++Mg2+) of biotites may be used as a tool to discriminate between the ore-bearing and ore-barren intrusions in porphyry copper systems.
2018, 43(9): 2943-2965.
doi: 10.3799/dqkx.2018.148
Abstract:
The Yuhaixi Mo deposit, located in the eastern part of the Dananhu-Tousuquan island arc belt, was discovered by the No.704 Geological Party of Xinjiang Geological Exploration Bureau for Nonferrous Metals in 2015. Rocks occurring at Yuhaixi contain the Carboniferous Yanchi Formation, Neogene Putaogou Formation and felsic-mafic plutons (gneissic granite, granite, diorite and gabbro dike). LA-ICP-MS zircon U-Pb dating reveals that gneissic granite and diorite replaced at ca. 364 Ma and 306 Ma, respectively. Yuhaixi intrusions are characterized by high εHf(t) (10.5-14.2) and εNd(t) (0.9-4.0) values, and low ISr (0.703 282-0.704 111) values, indicating depleted-mantle or juvenile-crust sources. The gneissic granite is characterized by low Mg# value (22-27), and Zr/Hf (28-33), Ti/Zr (10-29) and Ti/Y (94-149) ratios, implying a juvenile-crust source. The diorite and the gabbro dike are marked by low Si2O content (47.55%-57.54%), high Mg# values (51-59), and Ti/Zr (20-380) and Ti/Zr (246-269) ratios, which indicate that these rocks were likely formed by the part melting of the depleted mantle. However, diorite and the gabbro dike samples are rich in LREEs and LILEs (e.g., Rb, Sr), with low Ce/Pb ratios (6.5-12.0), suggesting the mixing of crustal component. Combining with the regional geological studies, the Yuhaixi gneissic granite was likely derived from the juvenile low crust, related with the north subduction of the Kangguer ocean plate; the diorite was also formed under a subducion setting by the partial melting of depleted mantle, and mixed with crustal component when it traversed the crust; the gabbro dike was probably derived from the depleted mantle, mixing with crustal component as well, in a post-collisional extension setting, the age of which was latter than 306 Ma.
The Yuhaixi Mo deposit, located in the eastern part of the Dananhu-Tousuquan island arc belt, was discovered by the No.704 Geological Party of Xinjiang Geological Exploration Bureau for Nonferrous Metals in 2015. Rocks occurring at Yuhaixi contain the Carboniferous Yanchi Formation, Neogene Putaogou Formation and felsic-mafic plutons (gneissic granite, granite, diorite and gabbro dike). LA-ICP-MS zircon U-Pb dating reveals that gneissic granite and diorite replaced at ca. 364 Ma and 306 Ma, respectively. Yuhaixi intrusions are characterized by high εHf(t) (10.5-14.2) and εNd(t) (0.9-4.0) values, and low ISr (0.703 282-0.704 111) values, indicating depleted-mantle or juvenile-crust sources. The gneissic granite is characterized by low Mg# value (22-27), and Zr/Hf (28-33), Ti/Zr (10-29) and Ti/Y (94-149) ratios, implying a juvenile-crust source. The diorite and the gabbro dike are marked by low Si2O content (47.55%-57.54%), high Mg# values (51-59), and Ti/Zr (20-380) and Ti/Zr (246-269) ratios, which indicate that these rocks were likely formed by the part melting of the depleted mantle. However, diorite and the gabbro dike samples are rich in LREEs and LILEs (e.g., Rb, Sr), with low Ce/Pb ratios (6.5-12.0), suggesting the mixing of crustal component. Combining with the regional geological studies, the Yuhaixi gneissic granite was likely derived from the juvenile low crust, related with the north subduction of the Kangguer ocean plate; the diorite was also formed under a subducion setting by the partial melting of depleted mantle, and mixed with crustal component when it traversed the crust; the gabbro dike was probably derived from the depleted mantle, mixing with crustal component as well, in a post-collisional extension setting, the age of which was latter than 306 Ma.
2018, 43(9): 2966-2979.
doi: 10.3799/dqkx.2018.168
Abstract:
Interpretations of the Re-Os isochron age of metallic sulfides are crucial to the reconstruction of ore-formation age of metallic deposits. Re-Os dating of pyrites from Meiling Cu deposit in eastern Tianshan, NW China indicates that the disseminated and massive ores show large variations in both Os concentrations and isotopic ratios. Our isotopic data of the two kinds of ores have defined good Re-Os correlations and the isochron ages are 523±59 Ma and 707±99 Ma, respectively. The two isochron ages are both significantly older than the true formation age of the Meiling Cu deposit. Together with the good correlations between 187Os/188Os ratio and the reciprocal of the common Os (i.e., 1/192Os, R2 are 0.997 3 and 0.994 5 for the disseminated and massive ores, respectively), we suggest that the initial Os isotopic compositions of these samples are heterogeneous and the two ages are mixed isochron ages. The mathematical deduction demonstrates that the observed Re-Os isochron correlations are the result of binary mixing without complete isotopic equilibrium at the time of formation, primarily due to limited diffusional exchange of Os isotopes between refractory Os-bearing inclusions and silicate minerals. The initial Os isotopic compositions may approach the value of continental crust. Crustal contamination during the formation of the deposit was responsible for the initial Os isotopic heterogeneity in the metallic sulfide system. It is concluded that whether there is a good Re-Os isochron correlation for samples can be used to constrain the geological meaning of Re-Os isochron ages when the Re-Os isotopic system of metallic sulfides is used to date the formation age of metallic deposit.
Interpretations of the Re-Os isochron age of metallic sulfides are crucial to the reconstruction of ore-formation age of metallic deposits. Re-Os dating of pyrites from Meiling Cu deposit in eastern Tianshan, NW China indicates that the disseminated and massive ores show large variations in both Os concentrations and isotopic ratios. Our isotopic data of the two kinds of ores have defined good Re-Os correlations and the isochron ages are 523±59 Ma and 707±99 Ma, respectively. The two isochron ages are both significantly older than the true formation age of the Meiling Cu deposit. Together with the good correlations between 187Os/188Os ratio and the reciprocal of the common Os (i.e., 1/192Os, R2 are 0.997 3 and 0.994 5 for the disseminated and massive ores, respectively), we suggest that the initial Os isotopic compositions of these samples are heterogeneous and the two ages are mixed isochron ages. The mathematical deduction demonstrates that the observed Re-Os isochron correlations are the result of binary mixing without complete isotopic equilibrium at the time of formation, primarily due to limited diffusional exchange of Os isotopes between refractory Os-bearing inclusions and silicate minerals. The initial Os isotopic compositions may approach the value of continental crust. Crustal contamination during the formation of the deposit was responsible for the initial Os isotopic heterogeneity in the metallic sulfide system. It is concluded that whether there is a good Re-Os isochron correlation for samples can be used to constrain the geological meaning of Re-Os isochron ages when the Re-Os isotopic system of metallic sulfides is used to date the formation age of metallic deposit.
2018, 43(9): 2980-2986.
doi: 10.3799/dqkx.2018.283
Abstract:
3D resource modeling of the narrow vein ore body is challenging due to its small thickness and large grade variations along the vein. This paper completed the three-dimensional modeling for narrow vein ore body of Meiling-Hongshi copper mine in Xinjiang, by building two-dimensional variation function Gaussian transformation into a single 3D block model. This study makes up for the lack of spatial morphology and grade change characteristics in the two-dimensional model. In addition, it avoids the high-smoothing effect of single-layer three-dimensional block model. The innovative monolayer 3D block modeling is not only more helpful to the partition of blocks in actual mining production, but also provides a basis for mineral resources evaluation and development design, which can facilitates future three-dimensional modeling of similar orebodies.
3D resource modeling of the narrow vein ore body is challenging due to its small thickness and large grade variations along the vein. This paper completed the three-dimensional modeling for narrow vein ore body of Meiling-Hongshi copper mine in Xinjiang, by building two-dimensional variation function Gaussian transformation into a single 3D block model. This study makes up for the lack of spatial morphology and grade change characteristics in the two-dimensional model. In addition, it avoids the high-smoothing effect of single-layer three-dimensional block model. The innovative monolayer 3D block modeling is not only more helpful to the partition of blocks in actual mining production, but also provides a basis for mineral resources evaluation and development design, which can facilitates future three-dimensional modeling of similar orebodies.
2018, 43(9): 2987-3000.
doi: 10.3799/dqkx.2018.232
Abstract:
The Duotoushan Fe-Cu deposit is a typical submarine volcanic rock-hosted iron oxide deposit and situated in the western margin of the Aqishan-Yamansu belt, eastern Tianshan. Nevertheless, studies on its ore minerals are absent. As a common mineral in many types of hydrothermal deposits, mineral chemistry of magnetite can reveal the ore-forming processes in mineralization systems. In this paper, we present integrated study on paragenesis and mineral chemistry data of magnetite at the Duotoushan deposit, eastern Tianshan. Based on the mineral paragenesis and mineral assemblages, it is found that there are three representative magnetite types in the Duotoushan deposit. The granular M1a type magnetite grains coexist with epidote, amphibole and pyrite, whereas the M1b magnetite is intergrown with quartz, epidote, amphibole and pyrite. The branch shape magnetite grains of M2 type coexist with amphibole only. Due to depletion in Ti (84×10-6-1 117×10-6), Al (417×10-6-5 273×10-6) and high field-strength elements, all the magnetite grains are identified as a hydrothermal origin. Compared with the M2 magnetite, M1a and M1b magnetite are enriched in Si, Ca, Al and Mn, which can be attributed to the influence of micro-scale inclusions. The gradually reduced concentrations of titanium in the magnetite samples from M1a to M2 may be attributed to the decreasing crystallization temperatures. In addition, the variable compositions of vanadium and chromium suggest oxygen fugacity decreased first and then increased during the fluids evolution. Given that M2 magnetite contains higher magnesium contents and geological constrains, we propose that seawater may have contributed to the hydrothermal system during late magnetite mineralization stage.
The Duotoushan Fe-Cu deposit is a typical submarine volcanic rock-hosted iron oxide deposit and situated in the western margin of the Aqishan-Yamansu belt, eastern Tianshan. Nevertheless, studies on its ore minerals are absent. As a common mineral in many types of hydrothermal deposits, mineral chemistry of magnetite can reveal the ore-forming processes in mineralization systems. In this paper, we present integrated study on paragenesis and mineral chemistry data of magnetite at the Duotoushan deposit, eastern Tianshan. Based on the mineral paragenesis and mineral assemblages, it is found that there are three representative magnetite types in the Duotoushan deposit. The granular M1a type magnetite grains coexist with epidote, amphibole and pyrite, whereas the M1b magnetite is intergrown with quartz, epidote, amphibole and pyrite. The branch shape magnetite grains of M2 type coexist with amphibole only. Due to depletion in Ti (84×10-6-1 117×10-6), Al (417×10-6-5 273×10-6) and high field-strength elements, all the magnetite grains are identified as a hydrothermal origin. Compared with the M2 magnetite, M1a and M1b magnetite are enriched in Si, Ca, Al and Mn, which can be attributed to the influence of micro-scale inclusions. The gradually reduced concentrations of titanium in the magnetite samples from M1a to M2 may be attributed to the decreasing crystallization temperatures. In addition, the variable compositions of vanadium and chromium suggest oxygen fugacity decreased first and then increased during the fluids evolution. Given that M2 magnetite contains higher magnesium contents and geological constrains, we propose that seawater may have contributed to the hydrothermal system during late magnetite mineralization stage.
2018, 43(9): 3086-3099.
doi: 10.3799/dqkx.2018.171
Abstract:
The Xiaobaishitou W-Mo deposit is one of the typical W-Mo deposits in North Xinjiang, located in the eastern Tianshan Orogen. The ore body mainly occurs in the contact zone between Triassic biotite granite and crystalline limestone of the Mesoproterozoic Kawabulag Group. However, the characteristics of metallogenic fluid and genetic type of the Xiaobaishitou deposit remain relatively unclear. Based on the ore textures, structures and mineral assemblages observed, it is inferred that the deposit has been formed in a five-stage hydrothermal process, namely dry skarn, wet skarn, oxide, sulfide and carbonate stages. Scheelite and molybdenite occurred in oxide and sulfide stages, respectively. Microthermometric data show that the ore fluid system evolved from CO2-rich, probably magmatic hydrothermal to CO2-poor, meteoric fluid. The microthermometric results also suggest that metal precipitation resulted from fluid mixing and cooling. Here we propose that the Xiaobaishitou W-Mo deposit may be a skarn mineral system.
The Xiaobaishitou W-Mo deposit is one of the typical W-Mo deposits in North Xinjiang, located in the eastern Tianshan Orogen. The ore body mainly occurs in the contact zone between Triassic biotite granite and crystalline limestone of the Mesoproterozoic Kawabulag Group. However, the characteristics of metallogenic fluid and genetic type of the Xiaobaishitou deposit remain relatively unclear. Based on the ore textures, structures and mineral assemblages observed, it is inferred that the deposit has been formed in a five-stage hydrothermal process, namely dry skarn, wet skarn, oxide, sulfide and carbonate stages. Scheelite and molybdenite occurred in oxide and sulfide stages, respectively. Microthermometric data show that the ore fluid system evolved from CO2-rich, probably magmatic hydrothermal to CO2-poor, meteoric fluid. The microthermometric results also suggest that metal precipitation resulted from fluid mixing and cooling. Here we propose that the Xiaobaishitou W-Mo deposit may be a skarn mineral system.
2018, 43(9): 3100-3111, 3125.
doi: 10.3799/dqkx.2018.290
Abstract:
Qiongkuduke Ag-polymetallic deposit is located in the central Xiaoshitouquan area, eastern of the Harlik arc. The Qiongkuduke deposit is the largest Ag-polymetallic deposit in the Xiaoshitouquan area. However, the mineralization mechanism of the deposit needs to be further studied. This paper focuses on the study of the homogenization temperature and the hydrogen and oxygen isotopic compositions of the fluid inclusions of the Qiongkuduke deposit based on the previous researches, to discuss the features of ore-forming fluids source. It is found by systematically petrographic observations that fluid inclusions are mainly small, sparse, and aqueous. The homogenization temperature of fluid inclusions ranges from 152 to 280℃ and the salinity ranges from 2.73% to 13.50% NaCleqv in the early stage of mineralization (stage Ⅰ), and the homogenization temperature of fluid inclusions ranges from 131 to 261℃ and the salinity ranges from 0.35% to 9.59% NaCleqv in the main stage of mineralization (stage Ⅱ), indicating that the homogenization temperature and salinity of the ore-forming fluid decrease from the early stage to the main stage of mineralization.The ore-forming fluid belongs to the H2O-NaCl system with the gas phase mainly composed of H2O together with minor CO2 and N2, while the liquid phase is mainly composed of Na+, K+, Cl- together with minor SO42-. The hydrogen and oxygen isotopic compositions of fluid inclusions of the Qiongkuduke deposit show that the δDH2O value varies from -89.5‰ to -85.1‰ whereas the δ18OH2O value varies from -8.671‰ to -5.94‰. Combined with the inclusion composition analysis, the ore-forming fluid of the Qiongkuduke deposit is the mixture of magmatic water and atmospheric water. Regarding the regional tectonic setting, geological characteristics of the deposit, the features of ore-forming fluids and the characteristics of isotope analysis, we conclude that the Qiongkuduke Ag-polymetallic deposit belongs to the epithermal deposit.
Qiongkuduke Ag-polymetallic deposit is located in the central Xiaoshitouquan area, eastern of the Harlik arc. The Qiongkuduke deposit is the largest Ag-polymetallic deposit in the Xiaoshitouquan area. However, the mineralization mechanism of the deposit needs to be further studied. This paper focuses on the study of the homogenization temperature and the hydrogen and oxygen isotopic compositions of the fluid inclusions of the Qiongkuduke deposit based on the previous researches, to discuss the features of ore-forming fluids source. It is found by systematically petrographic observations that fluid inclusions are mainly small, sparse, and aqueous. The homogenization temperature of fluid inclusions ranges from 152 to 280℃ and the salinity ranges from 2.73% to 13.50% NaCleqv in the early stage of mineralization (stage Ⅰ), and the homogenization temperature of fluid inclusions ranges from 131 to 261℃ and the salinity ranges from 0.35% to 9.59% NaCleqv in the main stage of mineralization (stage Ⅱ), indicating that the homogenization temperature and salinity of the ore-forming fluid decrease from the early stage to the main stage of mineralization.The ore-forming fluid belongs to the H2O-NaCl system with the gas phase mainly composed of H2O together with minor CO2 and N2, while the liquid phase is mainly composed of Na+, K+, Cl- together with minor SO42-. The hydrogen and oxygen isotopic compositions of fluid inclusions of the Qiongkuduke deposit show that the δDH2O value varies from -89.5‰ to -85.1‰ whereas the δ18OH2O value varies from -8.671‰ to -5.94‰. Combined with the inclusion composition analysis, the ore-forming fluid of the Qiongkuduke deposit is the mixture of magmatic water and atmospheric water. Regarding the regional tectonic setting, geological characteristics of the deposit, the features of ore-forming fluids and the characteristics of isotope analysis, we conclude that the Qiongkuduke Ag-polymetallic deposit belongs to the epithermal deposit.
2018, 43(9): 3112-3125.
doi: 10.3799/dqkx.2018.159
Abstract:
Jinba gold deposit is typical of the Ertix tectonic metallogenic belt, however, exsiting studies on its characteristics of tectonic alteration, evolution of ore-forming fluid and the source of hydrothermal fluid are insuffienct and the relationship between magmatic activity and Jinba gold deposit in the area is not clear. We carried out hydrothermal alteration, fluid inclusions and mineral sources based on the study of the geological characteristics of the deposit so as to provide useful information and reference for the genesis, mineralization and prospecting of Jinba gold deposit. It is found that sericitization, pyritization, silicification develop widely, which is an important sign of prospecting. Gold mineralization in the area is closely related to plagioclase granite and diorite, the drilling rock samples show gradual weakening mineralization and alteration from the center to the outside, with significant changes. The interpenetration texture and recrystallized texture characteristics of SEM-CL show that the deformation and metamorphism are very strong. And it has the characteristics of hydrothermal quartz. The hydrothermal mineralization is divided into four mineralization stages:magnetite quartz stage, gold-pyrite-quartz stage, gold-polymetallic sulfide-quartz stage, and quartz-carbonatation stage. Through the study on fluid inclusions, it is confirmed that the types of fluid inclusions in the Jinba gold deposit are:aqueous inclusions (LH2O-VCO2), CO2-H2O inclusions (LCO2-LH2O) and carbonic fluid inclusions. H2O and CO2 are the main ore-forming fluids in the gold deposit. There are two homogenization temperature peaks:260-280℃ and 380-400℃, with salinity from 0.88% to 13.72% Nacleqv and density from 0.90 to 0.95 g/cm3, so the fluid characteristics reflect that it is in medium-high temperature, low salinity and low-density environment. The composition of sulfur isotope present the ore-forming materials are derived from the deep crust. The data of δ18OH2O (1.49‰-5.31‰) and δDH2O (-78.0‰——80.5‰) suggest that meteoric water involves in the mineralization.
Jinba gold deposit is typical of the Ertix tectonic metallogenic belt, however, exsiting studies on its characteristics of tectonic alteration, evolution of ore-forming fluid and the source of hydrothermal fluid are insuffienct and the relationship between magmatic activity and Jinba gold deposit in the area is not clear. We carried out hydrothermal alteration, fluid inclusions and mineral sources based on the study of the geological characteristics of the deposit so as to provide useful information and reference for the genesis, mineralization and prospecting of Jinba gold deposit. It is found that sericitization, pyritization, silicification develop widely, which is an important sign of prospecting. Gold mineralization in the area is closely related to plagioclase granite and diorite, the drilling rock samples show gradual weakening mineralization and alteration from the center to the outside, with significant changes. The interpenetration texture and recrystallized texture characteristics of SEM-CL show that the deformation and metamorphism are very strong. And it has the characteristics of hydrothermal quartz. The hydrothermal mineralization is divided into four mineralization stages:magnetite quartz stage, gold-pyrite-quartz stage, gold-polymetallic sulfide-quartz stage, and quartz-carbonatation stage. Through the study on fluid inclusions, it is confirmed that the types of fluid inclusions in the Jinba gold deposit are:aqueous inclusions (LH2O-VCO2), CO2-H2O inclusions (LCO2-LH2O) and carbonic fluid inclusions. H2O and CO2 are the main ore-forming fluids in the gold deposit. There are two homogenization temperature peaks:260-280℃ and 380-400℃, with salinity from 0.88% to 13.72% Nacleqv and density from 0.90 to 0.95 g/cm3, so the fluid characteristics reflect that it is in medium-high temperature, low salinity and low-density environment. The composition of sulfur isotope present the ore-forming materials are derived from the deep crust. The data of δ18OH2O (1.49‰-5.31‰) and δDH2O (-78.0‰——80.5‰) suggest that meteoric water involves in the mineralization.
2018, 43(9): 3126-3140.
doi: 10.3799/dqkx.2018.134
Abstract:
The Jinwozi gold deposit is located in the central Beishan area, southern margin of the subduction-collision zone between the Late Paleozoic Tarim and Kazakhstan plates. The ore genesis of the Jinwozi gold deposit belongs to the orogenic type.However, the temporal and spatial evolution of ore-forming fluid and the metallogenic mechanism remain relatively unclear. The fluid inclusions in quartz from different mineralization stages and depths were analyzed by petrography, microscopic temperature measurement and laser Raman spectrum in this paper.The hydrothermal ore-forming process can be divided into three stages according to mineral assemblages and crosscutting relationships among the veins, from early to late, i.e., pyrite-quartz stage (early stage); quartz-pyrite-polymetallic sulfide stage (middle stage); quartz-carbonate stage (late stage). The gold mineralization mainly occurs in the middle stage.Two types of fluid inclusions are identified based on petrography and laser Raman spectroscopy:NaCl-H2O inclusions (W-type) and CO2-H2O-NaCl inclusions (C-type). Both of the two fluid inclusion types can be observed in the early stage and middle stage quartz; while only the W-type inclusions occur in the late stage.The homogenization temperatures of early stage fluid inclusions range from 200℃ and 300℃, with salinities of 1.4%-14.8% NaCleqv. The fluid inclusions of middle stage are homogenized between 160℃ and 260℃, with salinities of 0.4%-14.5% NaCleqv; and in late stage they are 120-180℃ and of 0.2%-7.6% NaCleqv, respectively.From early to late stage, the ore-forming fluid system evolved from a CO2-H2O-NaCl system to a NaCl-H2O system, with the homogenization temperature and salinities decreasing gradually. The results show that the ore-forming fluid system has evolved from the mesothermal, medium-low salinity, CO2-rich metamorphic water to the mesothermal-epithermal, low salinity and CO2-poor meteoric water. From the shallow to deep of the orebody, the homogenization temperature and salinity firstly increase and then decrease, which might be caused by the multi-superposition of ore-forming fluids. The homogenization temperature and ore-forming depth increase gradually from southwest to northeast area at Jinwozi gold deposit, which indicates that the northeastern intrusion may be a heat source center. Therefore, it is prospected that there will be a good metallogenic potential in the northeastern mining area. The physicochemical and hydrogen-oxygen isotopic data of fluid inclusions show that fluid mixing might be the dominant mechanism of gold deposition.
The Jinwozi gold deposit is located in the central Beishan area, southern margin of the subduction-collision zone between the Late Paleozoic Tarim and Kazakhstan plates. The ore genesis of the Jinwozi gold deposit belongs to the orogenic type.However, the temporal and spatial evolution of ore-forming fluid and the metallogenic mechanism remain relatively unclear. The fluid inclusions in quartz from different mineralization stages and depths were analyzed by petrography, microscopic temperature measurement and laser Raman spectrum in this paper.The hydrothermal ore-forming process can be divided into three stages according to mineral assemblages and crosscutting relationships among the veins, from early to late, i.e., pyrite-quartz stage (early stage); quartz-pyrite-polymetallic sulfide stage (middle stage); quartz-carbonate stage (late stage). The gold mineralization mainly occurs in the middle stage.Two types of fluid inclusions are identified based on petrography and laser Raman spectroscopy:NaCl-H2O inclusions (W-type) and CO2-H2O-NaCl inclusions (C-type). Both of the two fluid inclusion types can be observed in the early stage and middle stage quartz; while only the W-type inclusions occur in the late stage.The homogenization temperatures of early stage fluid inclusions range from 200℃ and 300℃, with salinities of 1.4%-14.8% NaCleqv. The fluid inclusions of middle stage are homogenized between 160℃ and 260℃, with salinities of 0.4%-14.5% NaCleqv; and in late stage they are 120-180℃ and of 0.2%-7.6% NaCleqv, respectively.From early to late stage, the ore-forming fluid system evolved from a CO2-H2O-NaCl system to a NaCl-H2O system, with the homogenization temperature and salinities decreasing gradually. The results show that the ore-forming fluid system has evolved from the mesothermal, medium-low salinity, CO2-rich metamorphic water to the mesothermal-epithermal, low salinity and CO2-poor meteoric water. From the shallow to deep of the orebody, the homogenization temperature and salinity firstly increase and then decrease, which might be caused by the multi-superposition of ore-forming fluids. The homogenization temperature and ore-forming depth increase gradually from southwest to northeast area at Jinwozi gold deposit, which indicates that the northeastern intrusion may be a heat source center. Therefore, it is prospected that there will be a good metallogenic potential in the northeastern mining area. The physicochemical and hydrogen-oxygen isotopic data of fluid inclusions show that fluid mixing might be the dominant mechanism of gold deposition.
2018, 43(9): 3141-3153.
doi: 10.3799/dqkx.2018.135
Abstract:
The Wulasigou Cu deposit is a recent discovered ore deposit, located in Devonian volcanic-sedimentary basin of the Altay orogenic belt. Vein-shaped orebodies are hosted in the Kangbutiebao Formation and controlled by the NW-trending faults. In order to investigate the origin of ore-forming fluid and metal, a series of S-Pb-Sr-Nd-C-H-O isotopic analysis was carried out. According to field work and microscopic observation, the mineralization stages of the Wulasigou Cu deposit can be divided into pyrite-magnetite-quartz, chalcopyrite-chlorite-epidote-quartz and quartz-carbonate stages. The δ34S values of sulfide samples in this deposit are 0.1‰-3.2‰ (average:1.6‰), falling into the range of the δ34S values of wall rocks (-4.7‰-18.68‰), indicating that sulfur may be mainly derived from the Kangbutiebao Formation. The calcite sample shows δ13CV-PDB‰=-1.1‰ and δ18OV-PDB‰=-20.3‰, indicating that the marine carbonate strata and organic carbon are probably the sources of carbon. The Pb isotopes of eight pyrite samples are 206Pb/204Pb=17.939-18.508 (average 18.255), 207Pb/204Pb=15.519-15.674 (average 15.578), 208Pb/204Pb=37.881-38.653 (average 38.209), similar to those of the Kangbutiebao Formation. The ISr(220 Ma) values of pyrite are 0.710 4-0.711 7 (average 0.711 1), with initial 143Nd/144Nd values of 0.512 002-0.512 240 (average 0.512 103). The Sr-Nd-Pb isotopic compositions indicate that the metal sources of Wulasigou Cu deposit may be mainly from the Kangbutiebao Formation but with additional minerals. The δDV-SMOW values of the fluid range from -103.8‰ to -92‰ (average -99.2‰), the δ18OV-SMOW values for quartz and calcite are concentrated at 9.4‰-11.5‰ (average 10.4‰), and the δ18OH2O values range from 2.1‰ to 4.2‰ (average 3.1‰), indicating that the hydrothermal fluids may be originated from metamorphic water with the effect of meteoric water combined with physical and chemical characteristics of fluid inclusions. The metallogenic material of the Wulasigou Cu deposit is mainly derived from the metamorphic devolatilization of the host rock, which is consistent with the ore-forming mechanism of the orogenic deposit.
The Wulasigou Cu deposit is a recent discovered ore deposit, located in Devonian volcanic-sedimentary basin of the Altay orogenic belt. Vein-shaped orebodies are hosted in the Kangbutiebao Formation and controlled by the NW-trending faults. In order to investigate the origin of ore-forming fluid and metal, a series of S-Pb-Sr-Nd-C-H-O isotopic analysis was carried out. According to field work and microscopic observation, the mineralization stages of the Wulasigou Cu deposit can be divided into pyrite-magnetite-quartz, chalcopyrite-chlorite-epidote-quartz and quartz-carbonate stages. The δ34S values of sulfide samples in this deposit are 0.1‰-3.2‰ (average:1.6‰), falling into the range of the δ34S values of wall rocks (-4.7‰-18.68‰), indicating that sulfur may be mainly derived from the Kangbutiebao Formation. The calcite sample shows δ13CV-PDB‰=-1.1‰ and δ18OV-PDB‰=-20.3‰, indicating that the marine carbonate strata and organic carbon are probably the sources of carbon. The Pb isotopes of eight pyrite samples are 206Pb/204Pb=17.939-18.508 (average 18.255), 207Pb/204Pb=15.519-15.674 (average 15.578), 208Pb/204Pb=37.881-38.653 (average 38.209), similar to those of the Kangbutiebao Formation. The ISr(220 Ma) values of pyrite are 0.710 4-0.711 7 (average 0.711 1), with initial 143Nd/144Nd values of 0.512 002-0.512 240 (average 0.512 103). The Sr-Nd-Pb isotopic compositions indicate that the metal sources of Wulasigou Cu deposit may be mainly from the Kangbutiebao Formation but with additional minerals. The δDV-SMOW values of the fluid range from -103.8‰ to -92‰ (average -99.2‰), the δ18OV-SMOW values for quartz and calcite are concentrated at 9.4‰-11.5‰ (average 10.4‰), and the δ18OH2O values range from 2.1‰ to 4.2‰ (average 3.1‰), indicating that the hydrothermal fluids may be originated from metamorphic water with the effect of meteoric water combined with physical and chemical characteristics of fluid inclusions. The metallogenic material of the Wulasigou Cu deposit is mainly derived from the metamorphic devolatilization of the host rock, which is consistent with the ore-forming mechanism of the orogenic deposit.
2018, 43(9): 3154-3168.
doi: 10.3799/dqkx.2018.321
Abstract:
The typical tin ores related to A-type granite have been discovered in Kalamaili region, east of the Junggar, North Xinjiang. However, little has been known about the metallogenetic mechanism of the tin ores so far. This study on petrology and geochemistry of four mineralization-alteration zones from the Kamusite and Ganliangzi tin deposits show that the ores and metallogenic rock body are the products of the fractional crystallization of homologous magma with the ores forming at the later stage, and there are two alteration zoning patterns:(1) (red) fine-grained Bt-granite→greisenized fine-grained granite→tin-bearing quartz veins; (2) fine-grained Bt-granite→tin-bearing greisen→tin-bearing silicification veins. The elements migration of the altered zone show that SiO2 was externally supplied, Na2O and K2O moved out in varying degrees, more Fe2O3 was supplied than lost, and Th/U ratios kept decreasing in the whole mineralized process, which suggests that the on-going silicification and alkali metasomatism in the whole process result in the changes of metallogenic environment from basic to acidic and the increases of oxygen fugacity. The migration of trace elements (eg. W, Cu, Bi, In) was significantly positively associated with the enrichment of tin, while that of others (eg. Pb, Rb, Nb, Ta) was negative, together with the most active component of F and Cl, and these elements played important roles in the process of migration, enrichment and precipitation of tin. This indicates that the elements from the metallogenic rock body were lost while the fluid played an important role in the process of Sn mineralization, and the enrichment and mineralization of Sn was probably caused in the transition stage from magmatic to hydrothermal system.
The typical tin ores related to A-type granite have been discovered in Kalamaili region, east of the Junggar, North Xinjiang. However, little has been known about the metallogenetic mechanism of the tin ores so far. This study on petrology and geochemistry of four mineralization-alteration zones from the Kamusite and Ganliangzi tin deposits show that the ores and metallogenic rock body are the products of the fractional crystallization of homologous magma with the ores forming at the later stage, and there are two alteration zoning patterns:(1) (red) fine-grained Bt-granite→greisenized fine-grained granite→tin-bearing quartz veins; (2) fine-grained Bt-granite→tin-bearing greisen→tin-bearing silicification veins. The elements migration of the altered zone show that SiO2 was externally supplied, Na2O and K2O moved out in varying degrees, more Fe2O3 was supplied than lost, and Th/U ratios kept decreasing in the whole mineralized process, which suggests that the on-going silicification and alkali metasomatism in the whole process result in the changes of metallogenic environment from basic to acidic and the increases of oxygen fugacity. The migration of trace elements (eg. W, Cu, Bi, In) was significantly positively associated with the enrichment of tin, while that of others (eg. Pb, Rb, Nb, Ta) was negative, together with the most active component of F and Cl, and these elements played important roles in the process of migration, enrichment and precipitation of tin. This indicates that the elements from the metallogenic rock body were lost while the fluid played an important role in the process of Sn mineralization, and the enrichment and mineralization of Sn was probably caused in the transition stage from magmatic to hydrothermal system.
2018, 43(9): 3252-3266.
doi: 10.3799/dqkx.2018.999
Abstract:
The determination of metamorphic deformation process in Lancang Group can reveal the evolution history of Lancangjiang tectonic belt. Based on the "tectonic-metamorphic" study of the medium-low glacial facies metamorphic rocks and the high-pressure metamorphic rocks exposed in the Shuangjiang-Huimin area, this paper presents the following findings on the metamorphic rocks in the Lancang Group:(1) the Fold cleavage S2 under the extrusion system is the regional foliation. The facies S1 represented by the quartz veins in the metamorphic rocks are consistent with the S0, and S1 is nearly parallel with S2 after the second stage. (2) The tectonic pattern and the metamorphic deformation period are basically the same in the resarch area, showing two-stage middle and deep tectonic stratigraphy in Permian-Triassic, which is shallow-surface deformation superposition of the Jurassic-Cenozoic. (3) The high-pressure metamorphic rocks record two periods of deep tectonic deformation, and the tourmaline and garnet have a distinct two-stage growth pattern. The core (M1aD1a) may represent the peak eclogite facies metamorphism, The edge represents the blue lithofacies (M1bD1b) stage during the exhumation process. The high-pressure metamorphic rocks are consistent with the tectonic level and deformation pattern of the second stage (M2D2) of the metamorphic rocks, which represents the process of the compressive stress after the exhumation process. Both shear-type cleavages S2 indicate that the upper disk shear sliding toward to cleavages. Combined with the Cenozoic Sanjiang area occurred near the 90° block rotation, the recovery of the second phase of the disk against the thrust of the role of E. By the 40Ar-39Ar dating of quartz sandstone muscovite in Xingfu area, phengite and blue amphibole in Xiaoheijiang, and reinterpreting the 40Ar-39Ar age of the blue amphibole in Xiaoheijiang, it is concluded that Lancang Group has 4 tectonic stages:(1) Metamorphism of blueschist facies in the first stage (D1b) of high-pressure metamorphic rocks, ~250 Ma. (2) The second phase (M2D2) is extrusion in the middle level, 215-214 Ma. (3) The shallow metamorphic rocks N-S to the longitudinal folds belong to the third stage (D3a):111.9-103.7 Ma with the late (D3b) thrust, ~82.28 Ma. (4) The fourth period near the E-W to the vertical fold:the new generation (probably later than 59.18 Ma).
The determination of metamorphic deformation process in Lancang Group can reveal the evolution history of Lancangjiang tectonic belt. Based on the "tectonic-metamorphic" study of the medium-low glacial facies metamorphic rocks and the high-pressure metamorphic rocks exposed in the Shuangjiang-Huimin area, this paper presents the following findings on the metamorphic rocks in the Lancang Group:(1) the Fold cleavage S2 under the extrusion system is the regional foliation. The facies S1 represented by the quartz veins in the metamorphic rocks are consistent with the S0, and S1 is nearly parallel with S2 after the second stage. (2) The tectonic pattern and the metamorphic deformation period are basically the same in the resarch area, showing two-stage middle and deep tectonic stratigraphy in Permian-Triassic, which is shallow-surface deformation superposition of the Jurassic-Cenozoic. (3) The high-pressure metamorphic rocks record two periods of deep tectonic deformation, and the tourmaline and garnet have a distinct two-stage growth pattern. The core (M1aD1a) may represent the peak eclogite facies metamorphism, The edge represents the blue lithofacies (M1bD1b) stage during the exhumation process. The high-pressure metamorphic rocks are consistent with the tectonic level and deformation pattern of the second stage (M2D2) of the metamorphic rocks, which represents the process of the compressive stress after the exhumation process. Both shear-type cleavages S2 indicate that the upper disk shear sliding toward to cleavages. Combined with the Cenozoic Sanjiang area occurred near the 90° block rotation, the recovery of the second phase of the disk against the thrust of the role of E. By the 40Ar-39Ar dating of quartz sandstone muscovite in Xingfu area, phengite and blue amphibole in Xiaoheijiang, and reinterpreting the 40Ar-39Ar age of the blue amphibole in Xiaoheijiang, it is concluded that Lancang Group has 4 tectonic stages:(1) Metamorphism of blueschist facies in the first stage (D1b) of high-pressure metamorphic rocks, ~250 Ma. (2) The second phase (M2D2) is extrusion in the middle level, 215-214 Ma. (3) The shallow metamorphic rocks N-S to the longitudinal folds belong to the third stage (D3a):111.9-103.7 Ma with the late (D3b) thrust, ~82.28 Ma. (4) The fourth period near the E-W to the vertical fold:the new generation (probably later than 59.18 Ma).
2018, 43(9): 3267-3284.
doi: 10.3799/dqkx.2017.585
Abstract:
There are many acid intrusive rocks and a few norite gabbros in Tumuertai, located in central-northern margin of the North China Block. The research on the norite gabbro is limited and the evolution between the norite gabbro and cotemporary intrusive rocks has hardly been discussed. Base on the method of chronology and geochemistry, SHRIMP zircon U-Pb data indicate that the formation age of the granodiorite is 275.3±2.6 Ma; LA-ICP-MS zircon U-Pb data indicate that the formation age of the norite gabbro is 270.1±4.2 Ma, and both were formed in the Early-Permian. Geochemical data indicate that the norite gabbro is depleted in SiO2 (46.2%-49.8%) and high field strength elements (HFSEs, e.g., Nb, Ti and Zr), and is enriched in Mg# (59.16-67.58) and large ion lithophile elements (LILEs, e.g., Cs, Ba and Sr), and displays low REE abundances and flat REE pattern with obviously positive Eu anomalies (δEu=1.02-2.41), which is similar to mantle derived intrusive rocks. These granodiorite samples have SiO2=65.6%-67.0%, K2O=3.71%-4.15%, A/CNK=0.94-0.98, belong to high-K calc-alkaline I-type granitoids. They also show strong enrichments in light rare earth elements (LREEs) and LILEs (e.g., Cs, Rb and K), and depletions in HFSEs (e.g., Nb, Ta and Th) and heavy rare earth (HREEs), with weakly negative Eu anomalies (δEu=0.61-0.69). Combining with its common mafic inclusions, we consider that its primary magma could be possibly contributed by magma mixing in a continental arc setting. The spatio-temporal relationship of the granodiorite-norite gabbro and their geochemical characteristics suggest that mafic magmas derived from the depleted mantle wedge which was metasomatized by the subducted slab-derived magma. The mafic magmas not only heated to melt the crust, but also mixed with the crust-derived melts to form the diverse granitoids. In summary, we conclude that the granodiorite-norite gabbro formed in a subduction tectonic setting and the Paleo-Asian Ocean was not closed in Early Permian.
There are many acid intrusive rocks and a few norite gabbros in Tumuertai, located in central-northern margin of the North China Block. The research on the norite gabbro is limited and the evolution between the norite gabbro and cotemporary intrusive rocks has hardly been discussed. Base on the method of chronology and geochemistry, SHRIMP zircon U-Pb data indicate that the formation age of the granodiorite is 275.3±2.6 Ma; LA-ICP-MS zircon U-Pb data indicate that the formation age of the norite gabbro is 270.1±4.2 Ma, and both were formed in the Early-Permian. Geochemical data indicate that the norite gabbro is depleted in SiO2 (46.2%-49.8%) and high field strength elements (HFSEs, e.g., Nb, Ti and Zr), and is enriched in Mg# (59.16-67.58) and large ion lithophile elements (LILEs, e.g., Cs, Ba and Sr), and displays low REE abundances and flat REE pattern with obviously positive Eu anomalies (δEu=1.02-2.41), which is similar to mantle derived intrusive rocks. These granodiorite samples have SiO2=65.6%-67.0%, K2O=3.71%-4.15%, A/CNK=0.94-0.98, belong to high-K calc-alkaline I-type granitoids. They also show strong enrichments in light rare earth elements (LREEs) and LILEs (e.g., Cs, Rb and K), and depletions in HFSEs (e.g., Nb, Ta and Th) and heavy rare earth (HREEs), with weakly negative Eu anomalies (δEu=0.61-0.69). Combining with its common mafic inclusions, we consider that its primary magma could be possibly contributed by magma mixing in a continental arc setting. The spatio-temporal relationship of the granodiorite-norite gabbro and their geochemical characteristics suggest that mafic magmas derived from the depleted mantle wedge which was metasomatized by the subducted slab-derived magma. The mafic magmas not only heated to melt the crust, but also mixed with the crust-derived melts to form the diverse granitoids. In summary, we conclude that the granodiorite-norite gabbro formed in a subduction tectonic setting and the Paleo-Asian Ocean was not closed in Early Permian.
Protolith Property and Metamorphic Evolution of Amphibolites in Guntuling Area, Eastern Heilongjiang
2018, 43(9): 3285-3301.
doi: 10.3799/dqkx.2018.563
Abstract:
The Heilongjiang complex which mainly outcrops to the east of Mudanjiang fault, is distributed in band trending north-south along the western margin of Jiamusi massif. However, there are few reports about the mineral composition and evolution of the metamorphism of the Heilongjiang complex, and the previous studies are mostly concentrated in the typical Heilongjiang complex with metamorphic degree of greenschist facies to blueschist facies. Therefore, geochemical characteristics and metamorphic evolution of amphibolite are studied in this paper. Amphibolites consist mainly of garnet-zoisite-bearing amphibolite and garnet-biotite-amphibole-bearing schist outcopped in Guntuling area, eastern Heilongjiang. Garnet-zoisite-bearing amphibolite is characterized by the enrichment of K and Ti, distinctly depleted Hf, and low ratio of Ta/Yb at (0.09-0.16). Furthermore, LREE has weakly negative anomalies relative to HREE, chondrite-normalized REE diagram shows a flat pattern and has no obvious abnormality, which is similar to the features of MORB. Garnet-biotite-amphibole-bearing schist is characterized by the enrichment of K, Th and Ti; furthermore, LREE has weakly enrichments relative to HREE in the chondrite-normalized REE pattern and has no obvious abnormality, which is almost consistent with OIB. Geochemistry and metamorphic evolution of amphibolites show that majority of them are oceanic tholeiite originated from the environment of the mid-ocean ridge, and minority of them are calc-alkaline basalt originated from the environment of intraplate (continental margin) or oceanic island. The amphibolites have undergone three successive stages:the progressive metamorphic phase of the high greenschist facies (T=400-500℃, P=400-500 MPa), peak metamorphic stage of low amphibolite facies (T=550-640℃, P=590-630 MPa) and near isobaric cooling stage of high-greenschist facies (T=530-560℃, P=530-560 MPa). It records a clockwise P-T path from early increased temperature and pressure to late isothermal depressurization. It is inferred that the metamorphism of amphibolite is probably associated with the collision between the Jiamusi Massif and the Songnen Massif.
The Heilongjiang complex which mainly outcrops to the east of Mudanjiang fault, is distributed in band trending north-south along the western margin of Jiamusi massif. However, there are few reports about the mineral composition and evolution of the metamorphism of the Heilongjiang complex, and the previous studies are mostly concentrated in the typical Heilongjiang complex with metamorphic degree of greenschist facies to blueschist facies. Therefore, geochemical characteristics and metamorphic evolution of amphibolite are studied in this paper. Amphibolites consist mainly of garnet-zoisite-bearing amphibolite and garnet-biotite-amphibole-bearing schist outcopped in Guntuling area, eastern Heilongjiang. Garnet-zoisite-bearing amphibolite is characterized by the enrichment of K and Ti, distinctly depleted Hf, and low ratio of Ta/Yb at (0.09-0.16). Furthermore, LREE has weakly negative anomalies relative to HREE, chondrite-normalized REE diagram shows a flat pattern and has no obvious abnormality, which is similar to the features of MORB. Garnet-biotite-amphibole-bearing schist is characterized by the enrichment of K, Th and Ti; furthermore, LREE has weakly enrichments relative to HREE in the chondrite-normalized REE pattern and has no obvious abnormality, which is almost consistent with OIB. Geochemistry and metamorphic evolution of amphibolites show that majority of them are oceanic tholeiite originated from the environment of the mid-ocean ridge, and minority of them are calc-alkaline basalt originated from the environment of intraplate (continental margin) or oceanic island. The amphibolites have undergone three successive stages:the progressive metamorphic phase of the high greenschist facies (T=400-500℃, P=400-500 MPa), peak metamorphic stage of low amphibolite facies (T=550-640℃, P=590-630 MPa) and near isobaric cooling stage of high-greenschist facies (T=530-560℃, P=530-560 MPa). It records a clockwise P-T path from early increased temperature and pressure to late isothermal depressurization. It is inferred that the metamorphism of amphibolite is probably associated with the collision between the Jiamusi Massif and the Songnen Massif.
2018, 43(9): 3302-3323.
doi: 10.3799/dqkx.2018.207
Abstract:
The Early Cretaceous clastic rocks were deposited on Lingshan island, the eastern segment of the Sulu orogenic belt. However, the accurate depositional age, formation mechanism and tectonic setting of the Early Cretaceous clastic rocks are still controversial. In this study, we conducted systematically detrital zircon LA-ICP-MS U-Pb dating for two sets of clastic rocks on Lingshan island, and carried out Lu-Hf isotopic analyses for the representative detrital zircons. The results show as follows:(1) The detrital zircon U-Pb analyses demonstrate that the Fajiaying Formation and the clastic rocks from the bottom of the Bamudi Formation were deposited in the mid-late periods of Early Cretaceous, showing the synchronous depositional ages within the uncertainties, 127±3 Ma and 128±4 Ma, respectively. (2) Moreover, two sets of clastic rocks have the same age spectra and similar Hf isotopic compositions, indicating that the sandstone or mudstone characterized by soft sedimentary deformations and pebbly cearse sandstone have the similar sedimentary provenance, which was single and mainly derived from the Jiaobei terrane akin to the North China craton attributes, and then from the Sulu orogenic belt. (3) In comparison with the Jiaolai basin, the detrital zircons of the Laiyang Group in Lingshan island show different age spectra. We argue that the sedimentary rocks from Lingshan island might be deposited in an individual basin controlled by the fault different from the Jiaolai basin during Early Cretaceous. Integrated with previous studies, the Fajiaying Formation of the Laiyang Group on Lingshan island was possibly formed at the end of evolution of a lacustrine faulted-basin, and subsequently deposited a set of fluvial sediments characterized by pebbly sandstones at the top of the lacustrine sediments. Later on, the no-diagenetic sediments suffered from the strong volcanic earthquake, resulting in the soft sedimentary deformations and slump structures.
The Early Cretaceous clastic rocks were deposited on Lingshan island, the eastern segment of the Sulu orogenic belt. However, the accurate depositional age, formation mechanism and tectonic setting of the Early Cretaceous clastic rocks are still controversial. In this study, we conducted systematically detrital zircon LA-ICP-MS U-Pb dating for two sets of clastic rocks on Lingshan island, and carried out Lu-Hf isotopic analyses for the representative detrital zircons. The results show as follows:(1) The detrital zircon U-Pb analyses demonstrate that the Fajiaying Formation and the clastic rocks from the bottom of the Bamudi Formation were deposited in the mid-late periods of Early Cretaceous, showing the synchronous depositional ages within the uncertainties, 127±3 Ma and 128±4 Ma, respectively. (2) Moreover, two sets of clastic rocks have the same age spectra and similar Hf isotopic compositions, indicating that the sandstone or mudstone characterized by soft sedimentary deformations and pebbly cearse sandstone have the similar sedimentary provenance, which was single and mainly derived from the Jiaobei terrane akin to the North China craton attributes, and then from the Sulu orogenic belt. (3) In comparison with the Jiaolai basin, the detrital zircons of the Laiyang Group in Lingshan island show different age spectra. We argue that the sedimentary rocks from Lingshan island might be deposited in an individual basin controlled by the fault different from the Jiaolai basin during Early Cretaceous. Integrated with previous studies, the Fajiaying Formation of the Laiyang Group on Lingshan island was possibly formed at the end of evolution of a lacustrine faulted-basin, and subsequently deposited a set of fluvial sediments characterized by pebbly sandstones at the top of the lacustrine sediments. Later on, the no-diagenetic sediments suffered from the strong volcanic earthquake, resulting in the soft sedimentary deformations and slump structures.
2018, 43(9): 3324-3336.
doi: 10.3799/dqkx.2018.565
Abstract:
The "Macaoyuan Group" in Kongzihe-Zhangcunping area, regarded as the sole sediment of Qingbaikou Period in North Kongling area, plays an important role to understanding the convergence and cracking of Rodinia Supercontinent. Here, new petrology, sedimentology, and detrital zircon chronology studies are conducted on 12 sections in Kongzihe-Zhangcunping area. The "Macaoyuan Group" is similar with the Nantuo Formation in the distribution and gravel features. The U-Pb ages of detridal zircon indicate the "Macaoyuan Group" is younger than 786 Ma, and the Nantuo Formation is constrained between 657 Ma and 635 Ma. The new findings indicate that the diamictite of "Macaoyuan Group" in North Kongling area is Neoproterozoic tillite, most likely time-equivalent to the Nantuo Formation. The sediment provenance is from the Kongling Group, Shennongjia Group and Huangling granite.
The "Macaoyuan Group" in Kongzihe-Zhangcunping area, regarded as the sole sediment of Qingbaikou Period in North Kongling area, plays an important role to understanding the convergence and cracking of Rodinia Supercontinent. Here, new petrology, sedimentology, and detrital zircon chronology studies are conducted on 12 sections in Kongzihe-Zhangcunping area. The "Macaoyuan Group" is similar with the Nantuo Formation in the distribution and gravel features. The U-Pb ages of detridal zircon indicate the "Macaoyuan Group" is younger than 786 Ma, and the Nantuo Formation is constrained between 657 Ma and 635 Ma. The new findings indicate that the diamictite of "Macaoyuan Group" in North Kongling area is Neoproterozoic tillite, most likely time-equivalent to the Nantuo Formation. The sediment provenance is from the Kongling Group, Shennongjia Group and Huangling granite.
2018, 43(9): 3001-3017.
doi: 10.3799/dqkx.2018.997
Abstract:
The Tongyuliang is a newly discovered copper deposit in recent years, which is located in the Aqishan-Yamansu Carboniferous volcanic belt of eastern Tianshan, Xinjiang, NW China. However, the research for this hydrothermal copper deposit is limited. The SHRIMP zircon U-Pb dating of diorite porphyrite which is genetically related with the copper deposit is 317.7±2.4 Ma. It can be inferred that the ore-forming epoch of this deposit may be Late Carboniferous. The major elements data show that the diorite porphyrites contain 56.71%-66.03% of SiO2, 49.75-55.29 of Mg#, 5.15%-6.40% of Na2O+K2O and 4.49-53.62 of Na2O/K2O, and the aluminium index (A/CNK)=0.9-1.1. The diorite porphyrites are relatively enriched in sodium and alumina and belong to the low K (IAT) series. They have low ∑REE (39.56×10-6-60.60×10-6) and are enriched in LREE relative to HREE. The primitive mantle normalized trace elements spider diagram is characterized by Ba, U, K, Sr (large ion lithophile elements) enrichment and Nb, Ta, Ti (high field strength elements) depletion, which shows the island-arc volcanic characteristics. The (87Sr/86Sr)i ratios range from 0.704 030 to 0.704 413, and εNd(t) values vary from 1.02 to 6.42, which indicates that the magma source of diorite porphyrites may be derived from depleted mantle source. The geochronology, geochemistry, and isotope characteristics of diorite porphyrites suggest that the Tongyuliang copper deposit was formed in the arc setting. Combining existing geological data, the ore-bearing materials probably came from the mantle wedge, which had undergone metasomatism induced by southward subduction of Paleo-Kangguer oceanic plate. In early Late Carboniferous, the fluids which contained copper element intruded, and the Tongyuliang copper deposit formed after sub-volcanics replaced their own bodies or volcanic rocks when they reached the upper area.
The Tongyuliang is a newly discovered copper deposit in recent years, which is located in the Aqishan-Yamansu Carboniferous volcanic belt of eastern Tianshan, Xinjiang, NW China. However, the research for this hydrothermal copper deposit is limited. The SHRIMP zircon U-Pb dating of diorite porphyrite which is genetically related with the copper deposit is 317.7±2.4 Ma. It can be inferred that the ore-forming epoch of this deposit may be Late Carboniferous. The major elements data show that the diorite porphyrites contain 56.71%-66.03% of SiO2, 49.75-55.29 of Mg#, 5.15%-6.40% of Na2O+K2O and 4.49-53.62 of Na2O/K2O, and the aluminium index (A/CNK)=0.9-1.1. The diorite porphyrites are relatively enriched in sodium and alumina and belong to the low K (IAT) series. They have low ∑REE (39.56×10-6-60.60×10-6) and are enriched in LREE relative to HREE. The primitive mantle normalized trace elements spider diagram is characterized by Ba, U, K, Sr (large ion lithophile elements) enrichment and Nb, Ta, Ti (high field strength elements) depletion, which shows the island-arc volcanic characteristics. The (87Sr/86Sr)i ratios range from 0.704 030 to 0.704 413, and εNd(t) values vary from 1.02 to 6.42, which indicates that the magma source of diorite porphyrites may be derived from depleted mantle source. The geochronology, geochemistry, and isotope characteristics of diorite porphyrites suggest that the Tongyuliang copper deposit was formed in the arc setting. Combining existing geological data, the ore-bearing materials probably came from the mantle wedge, which had undergone metasomatism induced by southward subduction of Paleo-Kangguer oceanic plate. In early Late Carboniferous, the fluids which contained copper element intruded, and the Tongyuliang copper deposit formed after sub-volcanics replaced their own bodies or volcanic rocks when they reached the upper area.
2018, 43(9): 3018-3035.
doi: 10.3799/dqkx.2018.603
Abstract:
The bimodal volcanic rocks distributed in the Balikun area are important to study on the timing of oceanic closure and the tectonic transition process of the Central Asian orogenic belt (CAOB), which are critical to deciphering the geological history of CAOB. In this paper, data on major and trace elements and Sr-Nd isotopes of whole rocks, and in-situ U-Pb age of zircons are reported for Carboniferous volcanic rocks in the Balikun area, in order to investigate their sources, petrogenesis and implications for the Carboniferous evolution of study area. The main results are obtained as follows:(1) Late Carboniferous volcanic rocks from Erdaogou Formation, mainly basalts, trachybasalts, basaltic-trachyandesite, trachyte rhyolitic and volcaniclastics, are bimodal volcanic rocks. The zircon U-Pb age of the Erdaogou basaltic-trachyandesite and trachybasalt and rhyolite yield a early Late Carboniferous age (312±4 Ma, 312±3 Ma and 308±3 Ma respectively). (2) The basaltic volcanic rocks and the acidic volcanic rocks from Erdaogou Formation show the same magma source. The Erdaogou basaltic volcanic rocks were derived from mantle which were modified by slab fluids at an rifting stage. The magma was derived by partial melting (5%-25%) of asthenosphere mantle. The acid rocks were generated from the direct fractional crystallization of basaltic magma. (3) Two episodes of Late Paleozoic bimodal suites have been identified and it is proposed that the essentially bimodal character of the complex reflects the features of back-arc rifting magmatism in Balikun area.
The bimodal volcanic rocks distributed in the Balikun area are important to study on the timing of oceanic closure and the tectonic transition process of the Central Asian orogenic belt (CAOB), which are critical to deciphering the geological history of CAOB. In this paper, data on major and trace elements and Sr-Nd isotopes of whole rocks, and in-situ U-Pb age of zircons are reported for Carboniferous volcanic rocks in the Balikun area, in order to investigate their sources, petrogenesis and implications for the Carboniferous evolution of study area. The main results are obtained as follows:(1) Late Carboniferous volcanic rocks from Erdaogou Formation, mainly basalts, trachybasalts, basaltic-trachyandesite, trachyte rhyolitic and volcaniclastics, are bimodal volcanic rocks. The zircon U-Pb age of the Erdaogou basaltic-trachyandesite and trachybasalt and rhyolite yield a early Late Carboniferous age (312±4 Ma, 312±3 Ma and 308±3 Ma respectively). (2) The basaltic volcanic rocks and the acidic volcanic rocks from Erdaogou Formation show the same magma source. The Erdaogou basaltic volcanic rocks were derived from mantle which were modified by slab fluids at an rifting stage. The magma was derived by partial melting (5%-25%) of asthenosphere mantle. The acid rocks were generated from the direct fractional crystallization of basaltic magma. (3) Two episodes of Late Paleozoic bimodal suites have been identified and it is proposed that the essentially bimodal character of the complex reflects the features of back-arc rifting magmatism in Balikun area.
2018, 43(9): 3036-3048.
doi: 10.3799/dqkx.2018.150
Abstract:
The Xiaorequanzi copper deposit is one of the earliest copper deposits discovered in the eastern Tianshan orogen. However, the characters and evolution of ore-forming fluid and the metallogenic mechanism remain relatively unclear. The fluid inclusions from different mineralization stages were analyzed by microscopic temperature measurement and laser-Raman spectrum in this paper. The mineralization process of the Xiaorequanzi deposit can be divided into VMS, hydrothermal overprinting and supergene mineralization periods. Among them, the VMS period can be subdivided into the pyrite and chalcopyrite-sphalerite stages, whilst the hydrothermal overprinting period can be subdivided into the quartz-sulfide and carbonate stages. Two types of fluid inclusions were identified in VMS period. The aqueous inclusions yield homogenization temperatures of 234-392℃, with salinities of 3.5%-13.3% NaCleqv. The hydrothermal overprinting period contains aqueous inclusions yielding homogenization temperatures of 122-296℃, with salinities of 1.4%-12.1% NaCleqv. These microthermometric results show that the ore fluid system evolved from high temperature, middle-high salinity magmatic hydrothermal to low temperature, middle-low salinity seawater. Thus, the deposit could be classified as VMS metallogenic system which has suffered hydrothermal overprinting.
The Xiaorequanzi copper deposit is one of the earliest copper deposits discovered in the eastern Tianshan orogen. However, the characters and evolution of ore-forming fluid and the metallogenic mechanism remain relatively unclear. The fluid inclusions from different mineralization stages were analyzed by microscopic temperature measurement and laser-Raman spectrum in this paper. The mineralization process of the Xiaorequanzi deposit can be divided into VMS, hydrothermal overprinting and supergene mineralization periods. Among them, the VMS period can be subdivided into the pyrite and chalcopyrite-sphalerite stages, whilst the hydrothermal overprinting period can be subdivided into the quartz-sulfide and carbonate stages. Two types of fluid inclusions were identified in VMS period. The aqueous inclusions yield homogenization temperatures of 234-392℃, with salinities of 3.5%-13.3% NaCleqv. The hydrothermal overprinting period contains aqueous inclusions yielding homogenization temperatures of 122-296℃, with salinities of 1.4%-12.1% NaCleqv. These microthermometric results show that the ore fluid system evolved from high temperature, middle-high salinity magmatic hydrothermal to low temperature, middle-low salinity seawater. Thus, the deposit could be classified as VMS metallogenic system which has suffered hydrothermal overprinting.
2018, 43(9): 3049-3064.
doi: 10.3799/dqkx.2018.129
Abstract:
The Xiaojianshan gold depost is located in the Kanggurtag gold belt of the East Tianshan mountains, but the relationship between the mineralization and the intrusive rocks in the mining area is not clear. Based on the systematic study of petrography, petrogeochemistry and chronology, the results show that Xiaojianshan granite is dominated by adamellite, with SiO2 concentrations of 66.30%-68.31%, Al2O3 of 16.65%-18.28%, K2O of 3.25%-4.00%, Na2O of 2.38%-3.46%, and K2O/Na2O (0.94-1.68) with an average value of 1.41, belonging to peraluminous high-K cale-alkaline series. The granite is enriched in the light rare earth elements ((La/Yb)N values of 7.68-9.04) and LILEs like Rb and K, but is relatively depleted in the high field strength elements (Ta, Th, U, Nb and Ti). This granite has negligible Eu anomalies (δEu=1.02-1.25) and weak negative Ce anomaly (δCe=0.79-0.86). In the Nb-Y diagram, the samples all fall into the area of the volcanic arc-syncollisional granite; In the Rb-(Y+Nb) diagram, the samples fall into the area of volcanic arc granite; LA-ICP-MS zircon U-Pb dating shows that granite age is 257.0±2.3 Ma and formed in Late Permian and concordance with the extrusion strike slip structure and metallogenic time of the Kanggur gold belt. The Zr/Hf (31.90-37.60) and Nb/Ta (4.96-11.28) values of the samples show the characteristics of the partial melting of the crust, therefore, the granite is the partial melting product of the tectonic compression of the deep crust, and the emplacement process is closely related to gold mineralization.
The Xiaojianshan gold depost is located in the Kanggurtag gold belt of the East Tianshan mountains, but the relationship between the mineralization and the intrusive rocks in the mining area is not clear. Based on the systematic study of petrography, petrogeochemistry and chronology, the results show that Xiaojianshan granite is dominated by adamellite, with SiO2 concentrations of 66.30%-68.31%, Al2O3 of 16.65%-18.28%, K2O of 3.25%-4.00%, Na2O of 2.38%-3.46%, and K2O/Na2O (0.94-1.68) with an average value of 1.41, belonging to peraluminous high-K cale-alkaline series. The granite is enriched in the light rare earth elements ((La/Yb)N values of 7.68-9.04) and LILEs like Rb and K, but is relatively depleted in the high field strength elements (Ta, Th, U, Nb and Ti). This granite has negligible Eu anomalies (δEu=1.02-1.25) and weak negative Ce anomaly (δCe=0.79-0.86). In the Nb-Y diagram, the samples all fall into the area of the volcanic arc-syncollisional granite; In the Rb-(Y+Nb) diagram, the samples fall into the area of volcanic arc granite; LA-ICP-MS zircon U-Pb dating shows that granite age is 257.0±2.3 Ma and formed in Late Permian and concordance with the extrusion strike slip structure and metallogenic time of the Kanggur gold belt. The Zr/Hf (31.90-37.60) and Nb/Ta (4.96-11.28) values of the samples show the characteristics of the partial melting of the crust, therefore, the granite is the partial melting product of the tectonic compression of the deep crust, and the emplacement process is closely related to gold mineralization.
2018, 43(9): 3065-3085.
doi: 10.3799/dqkx.2018.157
Abstract:
Xierqu is a newly discovered Fe-Cu deposit in the Kalatag district of the eastern Tianshan, NW China. However, the genesis of deposit remains relatively unclear. Electron probe, fluid inclusion and H, O isotopes are studied in this paper. It is found that the ore body is hosted by volcanic rocks and pyroclastic rocks of the Dananhu Formation, and controlled by NW-trending faults. The ore is dominated by massive and banding structures, and is mainly of granular and metasomatic ore textures. The metallic minerals are comprised of magnetite, and the gangue minerals consist of garnet, epidote, chlorite and calcite. Based on the ore textures, structures and observed mineral assemblages, the deposit was formed in a four-stage hydrothermal process, namely dry skarn, magnetite sulfide and carbonate stages. Microthermometric data shows that the ore fluid system evolved from middle-high temperature (304-352℃), probably magmatic hydrothermal to lower temperature (151-270℃) meteoric fluid, which is confirmed by H-O isotopes. We thus propose that the Xierqu Fe-Cu deposit may be considered as a skarn mineral system.
Xierqu is a newly discovered Fe-Cu deposit in the Kalatag district of the eastern Tianshan, NW China. However, the genesis of deposit remains relatively unclear. Electron probe, fluid inclusion and H, O isotopes are studied in this paper. It is found that the ore body is hosted by volcanic rocks and pyroclastic rocks of the Dananhu Formation, and controlled by NW-trending faults. The ore is dominated by massive and banding structures, and is mainly of granular and metasomatic ore textures. The metallic minerals are comprised of magnetite, and the gangue minerals consist of garnet, epidote, chlorite and calcite. Based on the ore textures, structures and observed mineral assemblages, the deposit was formed in a four-stage hydrothermal process, namely dry skarn, magnetite sulfide and carbonate stages. Microthermometric data shows that the ore fluid system evolved from middle-high temperature (304-352℃), probably magmatic hydrothermal to lower temperature (151-270℃) meteoric fluid, which is confirmed by H-O isotopes. We thus propose that the Xierqu Fe-Cu deposit may be considered as a skarn mineral system.
