2021 Vol. 46, No. 4
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2021, 46(4): 1133-1150.
doi: 10.3799/dqkx.2020.151
Abstract:
The Nanling tectonic belt is located across the Yangtze block, the Jiangnan orogen and the Cathaysia block. It is a metallogenic belt including W-Sn-Pb-Zn-U nonferrous metals, Nb-Ta-Li-Cs and rare earth critical metals. Fundamental geological features and metallogenic geological backgrounds are summarized for the Nanling tectonic belt based on review of the advances during the latest fifteen years. The Yangtze block sutured with the Cathaysia block along the Yongzhou-Guilin-Liuzhou fault at Middle Neoproterozoic era. More attention should be paid to the Longsheng ophiolite mélange and the Yingyangguan mélange due to the lack of direct proofs for above-mentioned suture. Two stage model ages of Neoproterozoic to Mesozoic granitoids imply that 2.0-1.2 Ga is a major crustal growth stage for the Nanling tectonic belt. Similar granitic features and orientations of tectonic lines indicate that both the Kwangsian and Indosinian orogenic mechanisms are intracontinental orogeny, triggered by far-field effect of collage of blocks to the south of the South China Block. From west to east, the values of εHf(t) decrease obviously whereas the values of TDM2 increase for the Early Yanshannian granitoids along the Nanling tectonic belt. These results indicate that Late Jurassic break-off and foundering of the Paleo-Pacific plate and subsequent asthenosphere upwelling occurred at South Hunan Province, North Guangxi and North Guangdong Province. The crust-mantle interaction supplied metallogenic material and extensional background for the mineralization of W-Sn nonferrous metals in the Cathaysia block. Shale of the Neoproterozoic Datangpo Formation and the Lower Cambrian in the Yangtze block is favorable exploration targets of shale gas due to absence of Phanerozoic magmatic and tectonic activity. On the basis of sedimentation, magmatism and tectonism in the Nanling tectonic belt, Mesozoic tectonic transition from the Tethys to Paleo-Pacific regimes occurred in the South China block during Late Triassic.
The Nanling tectonic belt is located across the Yangtze block, the Jiangnan orogen and the Cathaysia block. It is a metallogenic belt including W-Sn-Pb-Zn-U nonferrous metals, Nb-Ta-Li-Cs and rare earth critical metals. Fundamental geological features and metallogenic geological backgrounds are summarized for the Nanling tectonic belt based on review of the advances during the latest fifteen years. The Yangtze block sutured with the Cathaysia block along the Yongzhou-Guilin-Liuzhou fault at Middle Neoproterozoic era. More attention should be paid to the Longsheng ophiolite mélange and the Yingyangguan mélange due to the lack of direct proofs for above-mentioned suture. Two stage model ages of Neoproterozoic to Mesozoic granitoids imply that 2.0-1.2 Ga is a major crustal growth stage for the Nanling tectonic belt. Similar granitic features and orientations of tectonic lines indicate that both the Kwangsian and Indosinian orogenic mechanisms are intracontinental orogeny, triggered by far-field effect of collage of blocks to the south of the South China Block. From west to east, the values of εHf(t) decrease obviously whereas the values of TDM2 increase for the Early Yanshannian granitoids along the Nanling tectonic belt. These results indicate that Late Jurassic break-off and foundering of the Paleo-Pacific plate and subsequent asthenosphere upwelling occurred at South Hunan Province, North Guangxi and North Guangdong Province. The crust-mantle interaction supplied metallogenic material and extensional background for the mineralization of W-Sn nonferrous metals in the Cathaysia block. Shale of the Neoproterozoic Datangpo Formation and the Lower Cambrian in the Yangtze block is favorable exploration targets of shale gas due to absence of Phanerozoic magmatic and tectonic activity. On the basis of sedimentation, magmatism and tectonism in the Nanling tectonic belt, Mesozoic tectonic transition from the Tethys to Paleo-Pacific regimes occurred in the South China block during Late Triassic.
2021, 46(4): 1151-1172.
doi: 10.3799/dqkx.2020.314
Abstract:
The West Hunan and East Guizhou district is located in the southeast margin of the Yangtze craton and developed with more than 200 Pb-Zn deposits/occurrences in carbonate rocks. In order to understand the metallogenic process of Pb-Zn deposits in West Hunan and East Guizhou district, in the paper it systematically summarizes the geological and geochemical characteristics of the typical Pb-Zn deposits, discusses the metallogenic mechanism, and establishes the metallogenic model. The Pb-Zn deposits are dominantly hosted in carbonate rocks of the Lower Cambrian, and the distribution is obviously controlled by fault and fold structure. The ore bodies are mainly stratiform, stratoid and lentoid. The minerals mainly consist of sphalerite, galena, pyrite and calcite, with less fluorite, barite, and bitumen. The Pb-Zn deposits are accompanied by extensive hydrothermal alteration dominated by calcilization. Fluid inclusions hosted in sphalerite and calcite have total homogenization temperatures concentrated of 120 to 200℃ and calculated salinities concentrated of 8% to 20% NaCleqv. Compared with the wall rocks, the hydrothermal calcite is characterized by relatively lower δ13CPDB value (range from -4.89‰ to 1.50‰) and significantly lower δ18OSMOW values (from 13.37‰ to 25.09‰). The sulfides from these Pb-Zn deposits yield narrow δ34S values (from 22.3‰ to 36.1‰). The lead isotope compositions of sulfides, with the 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb ratios ranging from 17.952 to 18.678, 15.635 to 15.832, 38.015 to 39.255, respectively, are relatively homogeneous. Integrating geological and geochemical data of the Pb-Zn deposits in West Hunan and East Guizhou district, it is suggested that low temperature and medium-high salinity ore-forming fluids were mostly derived from formation water with variable amounts of meteoric water; carbon in the ore-forming fluids was mainly sourced from carbonate wall rocks through water-rock reactions; sulfur was derived from the carbonate wall rocks by thermochemical sulfate reduction, and underlying strata supplied the metals for the Pb-Zn mineralization. The Pb-Zn deposits in West Hunan and East Guizhou district, formed in Late Silurian to Early Devonian, can be best classified as the MVT Pb-Zn deposit, and fluid mixing metallogenic model with the participation of organic matter was established in this district.
The West Hunan and East Guizhou district is located in the southeast margin of the Yangtze craton and developed with more than 200 Pb-Zn deposits/occurrences in carbonate rocks. In order to understand the metallogenic process of Pb-Zn deposits in West Hunan and East Guizhou district, in the paper it systematically summarizes the geological and geochemical characteristics of the typical Pb-Zn deposits, discusses the metallogenic mechanism, and establishes the metallogenic model. The Pb-Zn deposits are dominantly hosted in carbonate rocks of the Lower Cambrian, and the distribution is obviously controlled by fault and fold structure. The ore bodies are mainly stratiform, stratoid and lentoid. The minerals mainly consist of sphalerite, galena, pyrite and calcite, with less fluorite, barite, and bitumen. The Pb-Zn deposits are accompanied by extensive hydrothermal alteration dominated by calcilization. Fluid inclusions hosted in sphalerite and calcite have total homogenization temperatures concentrated of 120 to 200℃ and calculated salinities concentrated of 8% to 20% NaCleqv. Compared with the wall rocks, the hydrothermal calcite is characterized by relatively lower δ13CPDB value (range from -4.89‰ to 1.50‰) and significantly lower δ18OSMOW values (from 13.37‰ to 25.09‰). The sulfides from these Pb-Zn deposits yield narrow δ34S values (from 22.3‰ to 36.1‰). The lead isotope compositions of sulfides, with the 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb ratios ranging from 17.952 to 18.678, 15.635 to 15.832, 38.015 to 39.255, respectively, are relatively homogeneous. Integrating geological and geochemical data of the Pb-Zn deposits in West Hunan and East Guizhou district, it is suggested that low temperature and medium-high salinity ore-forming fluids were mostly derived from formation water with variable amounts of meteoric water; carbon in the ore-forming fluids was mainly sourced from carbonate wall rocks through water-rock reactions; sulfur was derived from the carbonate wall rocks by thermochemical sulfate reduction, and underlying strata supplied the metals for the Pb-Zn mineralization. The Pb-Zn deposits in West Hunan and East Guizhou district, formed in Late Silurian to Early Devonian, can be best classified as the MVT Pb-Zn deposit, and fluid mixing metallogenic model with the participation of organic matter was established in this district.
2021, 46(4): 1173-1198.
doi: 10.3799/dqkx.2020.311
Abstract:
Recently, a series of the Late Mesoproterozoic to Neoproterozoic tectonic blocks in the southern part of the West Dabie orogenic belt were identified by geological field mapping. These tectonic blocks are distributed along NNW-SSE trending fault, from the Lüwang in the west, to the Gaoqiao and Yongjiahe in the east, forming a tectonic mélange belt within the West Dabie orogenic belt. This tectonic mélange belt is composed of various metamorphic blocks, including ultramafic to mafic rock, silica-pelitic rock, quartzose rock, marble, carbonaceous clastic rock, bimodal volcanic rock, and eclogites. The matrix mainly consists of mica schist with strong deformation. Their protolith ages have a wide range that cluster as two age populations including 1 200-1 000 Ma and 800-700 Ma. Moreover, the 240-200 Ma ages are also recorded by the metamorphic zircons. On the basis of contact relationship and lithological assemblages, as well as their geochronologic and geochemical data, it is proposed that the tectonic blocks in the Lüwang-Gaoqiao-Yongjiahe tectonic mélange have two different geotectonic affinities, including the Late Mesoproterozoic to Early Neoproterozoic arc to back-arc basin system, and Middle to Late Neoproterozoic continental rift system. These blocks may have been brought into a deep depth by the subduction of the South China block beneath North China block during the Triassic, followed by subsequent exhumation to the surface and emplacement along the Taohua-Qijiaoshan fault. Furthermore, considering the close temporal and spatial relationships, it is inferred that the Late Mesoproterozoic to Early Neoproterozoic arc to back arc basin system in this study extended westward to the 970-820 Ma Dahongshan arc to back arc basin and 1 100-1 000 Ma Miaowan ophiolite.
Recently, a series of the Late Mesoproterozoic to Neoproterozoic tectonic blocks in the southern part of the West Dabie orogenic belt were identified by geological field mapping. These tectonic blocks are distributed along NNW-SSE trending fault, from the Lüwang in the west, to the Gaoqiao and Yongjiahe in the east, forming a tectonic mélange belt within the West Dabie orogenic belt. This tectonic mélange belt is composed of various metamorphic blocks, including ultramafic to mafic rock, silica-pelitic rock, quartzose rock, marble, carbonaceous clastic rock, bimodal volcanic rock, and eclogites. The matrix mainly consists of mica schist with strong deformation. Their protolith ages have a wide range that cluster as two age populations including 1 200-1 000 Ma and 800-700 Ma. Moreover, the 240-200 Ma ages are also recorded by the metamorphic zircons. On the basis of contact relationship and lithological assemblages, as well as their geochronologic and geochemical data, it is proposed that the tectonic blocks in the Lüwang-Gaoqiao-Yongjiahe tectonic mélange have two different geotectonic affinities, including the Late Mesoproterozoic to Early Neoproterozoic arc to back-arc basin system, and Middle to Late Neoproterozoic continental rift system. These blocks may have been brought into a deep depth by the subduction of the South China block beneath North China block during the Triassic, followed by subsequent exhumation to the surface and emplacement along the Taohua-Qijiaoshan fault. Furthermore, considering the close temporal and spatial relationships, it is inferred that the Late Mesoproterozoic to Early Neoproterozoic arc to back arc basin system in this study extended westward to the 970-820 Ma Dahongshan arc to back arc basin and 1 100-1 000 Ma Miaowan ophiolite.
2021, 46(4): 1199-1216.
doi: 10.3799/dqkx.2020.193
Abstract:
The tectono-magmatic evolution of the South China block during Early Mesozoic remains controversial. In this paper, it conducts the comprehensive study of petrology, zircon U-Pb geochronology, whole-rock element and Sr-Nd-Hf isotopic geochemistry for Late Triassic Taibao pluton with mafic microgranular enclaves (MMEs) in the Lianshan area, located in the northwest Guangdong Province. LA-ICP-MS U-Pb zircon analysis yielded 206Pb/238U weighted mean ages of 219.8±1.8 Ma, 220.5±1.0 Ma, 221.5±1.7 Ma and 220.2±1.1 Ma for four granite samples respectively, indicating that the pluton was formed during the Late Indosinian period. The host rocks are high K calc-alkaline granite, with lower SiO2, higher total alkalis and A/CNK values ranging in 0.79-1.16. The mafic microgranular enclaves show lower SiO2, higher FeO, MgO with contents of 55.13%-62.56%, 2.31%-4.60% and 5.53%-6.63%, respectively. Both of them show enrichment in light rare earth elements, and depletion in Ba, Sr, and Ti. They have relatively low εNd(t) values (-3.42 to -2.60 and -0.90 to -0.52)and younger Nd model ages (TDM2=1.30-1.35 Ga and 1.10-1.13 Ga, respectively). Zircon εHf(t) values of the host rocks are scattered (-2.6-+4.3, with average value of +0.7) and the corresponding two-stage model ages are 0.95-1.39 Ga. The results suggest that the Taibao host granodioritic rocks and the MMEs were likely produced by mixing of depleted mantle and lower crust-derived magmas, under the post-orogenic (Indosinian) extensional tectonic setting. These results, considered with the coetaneous basic magmatic activities in the adjacent area, indicate that the transition from the Paleo-Tethys to the Paleo-Pacific tectonic regimes of the South China block occurred during the Late Triassic (233 Ma).
The tectono-magmatic evolution of the South China block during Early Mesozoic remains controversial. In this paper, it conducts the comprehensive study of petrology, zircon U-Pb geochronology, whole-rock element and Sr-Nd-Hf isotopic geochemistry for Late Triassic Taibao pluton with mafic microgranular enclaves (MMEs) in the Lianshan area, located in the northwest Guangdong Province. LA-ICP-MS U-Pb zircon analysis yielded 206Pb/238U weighted mean ages of 219.8±1.8 Ma, 220.5±1.0 Ma, 221.5±1.7 Ma and 220.2±1.1 Ma for four granite samples respectively, indicating that the pluton was formed during the Late Indosinian period. The host rocks are high K calc-alkaline granite, with lower SiO2, higher total alkalis and A/CNK values ranging in 0.79-1.16. The mafic microgranular enclaves show lower SiO2, higher FeO, MgO with contents of 55.13%-62.56%, 2.31%-4.60% and 5.53%-6.63%, respectively. Both of them show enrichment in light rare earth elements, and depletion in Ba, Sr, and Ti. They have relatively low εNd(t) values (-3.42 to -2.60 and -0.90 to -0.52)and younger Nd model ages (TDM2=1.30-1.35 Ga and 1.10-1.13 Ga, respectively). Zircon εHf(t) values of the host rocks are scattered (-2.6-+4.3, with average value of +0.7) and the corresponding two-stage model ages are 0.95-1.39 Ga. The results suggest that the Taibao host granodioritic rocks and the MMEs were likely produced by mixing of depleted mantle and lower crust-derived magmas, under the post-orogenic (Indosinian) extensional tectonic setting. These results, considered with the coetaneous basic magmatic activities in the adjacent area, indicate that the transition from the Paleo-Tethys to the Paleo-Pacific tectonic regimes of the South China block occurred during the Late Triassic (233 Ma).
2021, 46(4): 1217-1230.
doi: 10.3799/dqkx.2020.168
Abstract:
In this study, 120 detrital zircons from the sandstone at the top of the Liantuo Formation in the Huangniuyan Section of the Three Gorges area were measured for U-Pb dating and Lu-Hf isotopic compositions. The U-Pb ages of the zircons from the Huangniuyan Section cluster at~800-880 Ma, ~2 000 Ma, ~2 500 Ma, ~2 700 Ma, among which the youngest zircon age is 724±8 Ma. According to the previous geochronological study of tuff on the top of the Liantuo Formation, the sedimentary age of the sandstone in the upper most part of the Liantuo Formation is limited to~724-714 Ma. The sedimentary time of the Liantuo sandstone is close to the U-Pb age of the youngest detrital zircon, which may reflect a rapid recycling of crustal materials. The Hf isotopic two-stage model ages (TDM2) of zircon are concentrated at~3.7-3.1 Ga, ~2.5-2.0 Ga and~1.3-1.0 Ga, which indicates that the provenance of the sandstone has juvenile crustal growth in the Paleo-Mesoarchean, Paleoproterozoic and Late Mesoproterozoic. By comparing the detrital zircon U-Pb ages and Hf isotopic data from different sections of the Liantuo Formation in the nucleus of the Yangtze craton reported in recent years, it is suggested that the Huangniuyan Section has distinct detrital zircon U-Pb ages and Hf isotopic compositions compared with the Wangfenggang Section, revealing different provenance between them.
In this study, 120 detrital zircons from the sandstone at the top of the Liantuo Formation in the Huangniuyan Section of the Three Gorges area were measured for U-Pb dating and Lu-Hf isotopic compositions. The U-Pb ages of the zircons from the Huangniuyan Section cluster at~800-880 Ma, ~2 000 Ma, ~2 500 Ma, ~2 700 Ma, among which the youngest zircon age is 724±8 Ma. According to the previous geochronological study of tuff on the top of the Liantuo Formation, the sedimentary age of the sandstone in the upper most part of the Liantuo Formation is limited to~724-714 Ma. The sedimentary time of the Liantuo sandstone is close to the U-Pb age of the youngest detrital zircon, which may reflect a rapid recycling of crustal materials. The Hf isotopic two-stage model ages (TDM2) of zircon are concentrated at~3.7-3.1 Ga, ~2.5-2.0 Ga and~1.3-1.0 Ga, which indicates that the provenance of the sandstone has juvenile crustal growth in the Paleo-Mesoarchean, Paleoproterozoic and Late Mesoproterozoic. By comparing the detrital zircon U-Pb ages and Hf isotopic data from different sections of the Liantuo Formation in the nucleus of the Yangtze craton reported in recent years, it is suggested that the Huangniuyan Section has distinct detrital zircon U-Pb ages and Hf isotopic compositions compared with the Wangfenggang Section, revealing different provenance between them.
2021, 46(4): 1231-1247.
doi: 10.3799/dqkx.2020.170
Abstract:
A study of LA-ICP-MS zircon U-Pb dating for Jinjiling pluton from Jiuyishan area in Nanling granite belt was carried out. The results show that the diagenetic age of the main medium grained porphyritic syenite and the complement fine-grained porphyritic monzonite are 156.40±0.66 Ma and 153.00±2.20 Ma, respectively. Combined with the existing data, their ages are restricted between (156.40±0.66)-(159.00±0.45) Ma and (146.00±0.86)-(153.00±2.20) Ma, which indicates that the Jinjiling pluton was formed during the early Yanshanian. Geochemical data show that the Jinjiling pluton is characterized by enriched silicone-alkali, depleted calcium-magnesium and metal uminous-peraluminous (A/KNC=0.97-1.14). The content of rare earth elements of the main granite are significantly higher than those of the complement granites, which is 488.63×10-6-571.67×10-6and 166.33×10-6-275.51×10-6, respectively. The main granite is enriched in light rare earth elements (LREE), with the complement granite having no obvious fractionation, both of which show negative Eu anomalies and (La/Yb)N values ranging from 10.27 to 15.84 and 0.38 to 1.13, respectively. The differentiation index (DI) are 88.76-89.20, 90.66-94.06, which indicate that the complement granite has undergone stronger magmatic differentiation. The Jinjiling pluton is enriched in large ion lithophile elements (LILE, e.g., Rb, K, Th, U, Nd and Hf) and relatively depleted in high field strength elements (HFSEs, e.g., Ba, Sr, P, Nb and Ti), with Ga/Al(104) ratios of 3.32-5.02 (average 3.50), Zr+Nb+Ce+Y of 255.5×10-6-554.9×10-6(average 422.37×10-6) and zircon saturation temperatures TZr of 780.31-820.67℃ (average 803.77℃), similar to geochemical features of A-type granites. The Jinjiling pluton has higher initial Sr isotope values of 0.712 58 to 0.732 51, lower εNd(t) values of -6.2 to -7.0 and εHf(t) values of -4.2 to -5.5, revealing that the source area of the Jinjiling pluton is mainly composed of crustal materials, without any contributions from mantle or new continental crust materials. The model ages of Nd and Hf are relatively close, with 1 465-1 566 Ma and 1 459-1 541 Ma, respectively, suggesting that the source rocks were separated from the mantle reservoir during the Mesoproterozoic. Combined with the geological evolution of Nanling area, it is inferred that the tectonic background of Jinjiling pluton is an intracontinental extensional environment caused by subduction of Pacific plate.
A study of LA-ICP-MS zircon U-Pb dating for Jinjiling pluton from Jiuyishan area in Nanling granite belt was carried out. The results show that the diagenetic age of the main medium grained porphyritic syenite and the complement fine-grained porphyritic monzonite are 156.40±0.66 Ma and 153.00±2.20 Ma, respectively. Combined with the existing data, their ages are restricted between (156.40±0.66)-(159.00±0.45) Ma and (146.00±0.86)-(153.00±2.20) Ma, which indicates that the Jinjiling pluton was formed during the early Yanshanian. Geochemical data show that the Jinjiling pluton is characterized by enriched silicone-alkali, depleted calcium-magnesium and metal uminous-peraluminous (A/KNC=0.97-1.14). The content of rare earth elements of the main granite are significantly higher than those of the complement granites, which is 488.63×10-6-571.67×10-6and 166.33×10-6-275.51×10-6, respectively. The main granite is enriched in light rare earth elements (LREE), with the complement granite having no obvious fractionation, both of which show negative Eu anomalies and (La/Yb)N values ranging from 10.27 to 15.84 and 0.38 to 1.13, respectively. The differentiation index (DI) are 88.76-89.20, 90.66-94.06, which indicate that the complement granite has undergone stronger magmatic differentiation. The Jinjiling pluton is enriched in large ion lithophile elements (LILE, e.g., Rb, K, Th, U, Nd and Hf) and relatively depleted in high field strength elements (HFSEs, e.g., Ba, Sr, P, Nb and Ti), with Ga/Al(104) ratios of 3.32-5.02 (average 3.50), Zr+Nb+Ce+Y of 255.5×10-6-554.9×10-6(average 422.37×10-6) and zircon saturation temperatures TZr of 780.31-820.67℃ (average 803.77℃), similar to geochemical features of A-type granites. The Jinjiling pluton has higher initial Sr isotope values of 0.712 58 to 0.732 51, lower εNd(t) values of -6.2 to -7.0 and εHf(t) values of -4.2 to -5.5, revealing that the source area of the Jinjiling pluton is mainly composed of crustal materials, without any contributions from mantle or new continental crust materials. The model ages of Nd and Hf are relatively close, with 1 465-1 566 Ma and 1 459-1 541 Ma, respectively, suggesting that the source rocks were separated from the mantle reservoir during the Mesoproterozoic. Combined with the geological evolution of Nanling area, it is inferred that the tectonic background of Jinjiling pluton is an intracontinental extensional environment caused by subduction of Pacific plate.
2021, 46(4): 1248-1268.
doi: 10.3799/dqkx.2020.364
Abstract:
In order to understand the evolution process of ore-forming fluid and the migration mechanism of ore-forming elements in Xitian tungsten tin polymetallic deposit, to further reveal the ore-forming mechanism and guide the next exploration work in this area. The fluid inclusions of wolframite, cassiterite and transparent minerals were studied by petrographic observation, infrared microthermometry and in situ LA-ICP-MS analysis of fluid inclusions. The results show that fluid-melt inclusions are developed in beryl and wolframite in Xitian tungsten tin polymetallic deposit, and the highest homogenization temperature is 760℃. At the early stage of mineralization, the fluid homogenization temperature is 360-500℃, the salinity is mainly 28.44%-41.50% NaCleqv. At the main mineralization stage, the homogenization temperature is 280-450℃, the salinity is mainly 3.0%-20.03% NaCleqv. At the late mineralization stage, the homogenization temperature is 120-280℃, and the salinity is 0.35%-6.58% NaCleqv. LA-ICP-MS analysis shows that W, Cu, Mo elements are preferentially enriched in the volatile, while Pb, Zn, Sn, Fe, Mn elements are preferentially enriched in the high salinity brine phase. The ore forming fluid in Xitian W-Sn polymetallic deposit comes from Yanshanian granite, and the mineralization of W-Sn started from the stage of magma-hydrothermal transition, and the ore-forming fluid has the characteristics of high temperature, high salinity and rich CO2. The ore-forming fluid comes from the dissolution of magmatic fluid, which has experienced two immiscible processes in the evolution process. In the process of immiscible phase separation, the ore-forming elements migrate selectively and distribute unevenly in each phase. Fluid immiscibility, water rock reaction, fluid mixing and fluid cooling are the main reasons for the precipitation of W-Sn minerals in the deposit.
In order to understand the evolution process of ore-forming fluid and the migration mechanism of ore-forming elements in Xitian tungsten tin polymetallic deposit, to further reveal the ore-forming mechanism and guide the next exploration work in this area. The fluid inclusions of wolframite, cassiterite and transparent minerals were studied by petrographic observation, infrared microthermometry and in situ LA-ICP-MS analysis of fluid inclusions. The results show that fluid-melt inclusions are developed in beryl and wolframite in Xitian tungsten tin polymetallic deposit, and the highest homogenization temperature is 760℃. At the early stage of mineralization, the fluid homogenization temperature is 360-500℃, the salinity is mainly 28.44%-41.50% NaCleqv. At the main mineralization stage, the homogenization temperature is 280-450℃, the salinity is mainly 3.0%-20.03% NaCleqv. At the late mineralization stage, the homogenization temperature is 120-280℃, and the salinity is 0.35%-6.58% NaCleqv. LA-ICP-MS analysis shows that W, Cu, Mo elements are preferentially enriched in the volatile, while Pb, Zn, Sn, Fe, Mn elements are preferentially enriched in the high salinity brine phase. The ore forming fluid in Xitian W-Sn polymetallic deposit comes from Yanshanian granite, and the mineralization of W-Sn started from the stage of magma-hydrothermal transition, and the ore-forming fluid has the characteristics of high temperature, high salinity and rich CO2. The ore-forming fluid comes from the dissolution of magmatic fluid, which has experienced two immiscible processes in the evolution process. In the process of immiscible phase separation, the ore-forming elements migrate selectively and distribute unevenly in each phase. Fluid immiscibility, water rock reaction, fluid mixing and fluid cooling are the main reasons for the precipitation of W-Sn minerals in the deposit.
2021, 46(4): 1269-1281.
doi: 10.3799/dqkx.2020.362
Abstract:
Based on the systematic carbon and oxygen isotope and organic carbon testing, the carbon and oxygen isotope characteristics of the Devonian in the Central Hunan depression were analyzed by fully proving the validity of the testing data. Results show that the δ13C values of Devonian are less affected by later alteration in the Central Hunan area. The δ13C of Devonian gradually decreases from the bottom to the top and shows a significant negative shift at the bottom of the Oujiachong Formation, and then gradually increases upward. The δ18O curve shows a slowly increasing trend from Middle Devonian to Upper Devonian. The above curves are similar to the carbon and oxygen isotopic curves of the global Devonian strata, and have a relatively consistent trend of change. The shape and migration degree of δ13C curve of Devonian strata in the area are highly comparable with Longmenshan Section in Sichuan Province, Qilinzhai Section in Dushan, Lali Section in Guangxi, and Euramerican platform section, which can be used as the basis for stratigraphic division and correlation in the area and analysis of paleo-marine environment evolution. Results show that there are differences between the δ13C curve and the sea level change from the top of Qiziqiao Formation to the bottom part of Shetianqiao Formation, indicating that the regional paleowater depth change is comprehensively dominated by the regional tectonic activities and the global sea level changes. There is a significant correlation between the δ13C positive drift and the high TOC in the shale of this area, which indicates that the organic-rich shale intervals at the lower part of Shetianqiao Formation and the upper part of Menggongao Formation are the products of large-scale transgression. The intervals consist of the main shale gas exploration target strata of Devonian in the study area.
Based on the systematic carbon and oxygen isotope and organic carbon testing, the carbon and oxygen isotope characteristics of the Devonian in the Central Hunan depression were analyzed by fully proving the validity of the testing data. Results show that the δ13C values of Devonian are less affected by later alteration in the Central Hunan area. The δ13C of Devonian gradually decreases from the bottom to the top and shows a significant negative shift at the bottom of the Oujiachong Formation, and then gradually increases upward. The δ18O curve shows a slowly increasing trend from Middle Devonian to Upper Devonian. The above curves are similar to the carbon and oxygen isotopic curves of the global Devonian strata, and have a relatively consistent trend of change. The shape and migration degree of δ13C curve of Devonian strata in the area are highly comparable with Longmenshan Section in Sichuan Province, Qilinzhai Section in Dushan, Lali Section in Guangxi, and Euramerican platform section, which can be used as the basis for stratigraphic division and correlation in the area and analysis of paleo-marine environment evolution. Results show that there are differences between the δ13C curve and the sea level change from the top of Qiziqiao Formation to the bottom part of Shetianqiao Formation, indicating that the regional paleowater depth change is comprehensively dominated by the regional tectonic activities and the global sea level changes. There is a significant correlation between the δ13C positive drift and the high TOC in the shale of this area, which indicates that the organic-rich shale intervals at the lower part of Shetianqiao Formation and the upper part of Menggongao Formation are the products of large-scale transgression. The intervals consist of the main shale gas exploration target strata of Devonian in the study area.
2021, 46(4): 1282-1294.
doi: 10.3799/dqkx.2020.253
Abstract:
The mudstone of the Devonian Shetianqiao Formation is one of the key strata for shale gas exploration in South China. In order to reveal the lithofacies characteristics and controlling factors of Shetianqiao Formation in Shaoyang sag of Xiangzhong depression, the lithofacies, sedimentary environment and its control on lithofacies development of mudstone were studied on the basis of systematical core description and test results of mineralogy and geochemistry, and the control of sedimentary environment evolution on lithofacies type is discussed in this study. Four lithofacies are identified, including siliceous mudstone, mixed mudstone, chert and calcareous mudstone, according to the differences of mineral component content. The Shetianqiao Formation can be divided into 5 lithofacies assemblages. Lithofacies assemblages Ⅰ and Ⅲ are relatively rich in silica, while the content of calcite in assemblages Ⅱ, Ⅳ, and Ⅴ is relatively high. The sedimentary environment analysis indicates that the mudstone of Shetianqiao Formation was formed at the continental margin setting. It was mainly developed in a relatively hot and dry climate, but the climate was relatively warm and humid in the early and middle stages. The middle stage developed the warmest and wettest climate. And the sea levels rose first and then fell in this period. The middle section is characterized by excess silica attributed to the biological origin and little influence by hydrothermal fluids. Terrestrial input was relatively stable and was the lowest in the middle stage. The coupling relationship between sedimentary environment and lithofacies types indicates that the lithofacies are mainly controlled by paleoclimate, terrestrial input, change in sea level, and biological origin. The siliceous components of mudstone are mainly contributed by the terrestrial input. The enriched silica in the middle section is mainly of biological origin. When the climate was hot and dry, the mudstone lithofacies was dominated by the calcium-riched lithofacies in the later period.
The mudstone of the Devonian Shetianqiao Formation is one of the key strata for shale gas exploration in South China. In order to reveal the lithofacies characteristics and controlling factors of Shetianqiao Formation in Shaoyang sag of Xiangzhong depression, the lithofacies, sedimentary environment and its control on lithofacies development of mudstone were studied on the basis of systematical core description and test results of mineralogy and geochemistry, and the control of sedimentary environment evolution on lithofacies type is discussed in this study. Four lithofacies are identified, including siliceous mudstone, mixed mudstone, chert and calcareous mudstone, according to the differences of mineral component content. The Shetianqiao Formation can be divided into 5 lithofacies assemblages. Lithofacies assemblages Ⅰ and Ⅲ are relatively rich in silica, while the content of calcite in assemblages Ⅱ, Ⅳ, and Ⅴ is relatively high. The sedimentary environment analysis indicates that the mudstone of Shetianqiao Formation was formed at the continental margin setting. It was mainly developed in a relatively hot and dry climate, but the climate was relatively warm and humid in the early and middle stages. The middle stage developed the warmest and wettest climate. And the sea levels rose first and then fell in this period. The middle section is characterized by excess silica attributed to the biological origin and little influence by hydrothermal fluids. Terrestrial input was relatively stable and was the lowest in the middle stage. The coupling relationship between sedimentary environment and lithofacies types indicates that the lithofacies are mainly controlled by paleoclimate, terrestrial input, change in sea level, and biological origin. The siliceous components of mudstone are mainly contributed by the terrestrial input. The enriched silica in the middle section is mainly of biological origin. When the climate was hot and dry, the mudstone lithofacies was dominated by the calcium-riched lithofacies in the later period.
2021, 46(4): 1295-1310.
doi: 10.3799/dqkx.2020.275
Abstract:
In order to better understand the complex tectonic framework on the southern margin of South China block (SCB) between Permian and Triassic, the petrology, geochemistry and chronology of three newly discovered Late Permian ultramafic intrusions in the Yunkai area of West Guangdong were studied. These rocks are located at Yangchun Sanjia on the eastern edge of the Yunkai terrane and at Gaozhou Dajing and Dong'an in the middle of the Yunkai terrane. They are intrusive rocks in schist and paragneiss of the Yunkai Group and out putted as laccoliths or dykes which main lithologies are pyroxenite, hornblendite, amphibolite and plagioclase amphibolite. Zircon SHRIMP and LA-ICP-MS U-Pb age of ultramafic rocks are 253-259 Ma. These intrusive rocks are rich in titanomagnetite, titanite and apatite, showing strong enrichment of Fe-Ti-P, and exhibiting moderate enrichment of LREE and depletion in Nb-Ta-Zr-Hf. Ultramafic rocks exhibit relatively low εNd(t)(-3.4 to -10.0) of whole rocks, εHf(t) (-1.2 to -9.5) and δ18O(7.01‰-9.71‰) values of zircon, showing the enriched lithosphere mantle source affinity. In this study, it is suggested that the influence range of Permian Emeishan mantle plume(~259 Ma) may have spread to Yunkai area. Yunkai Late Permian ultramafic intrusions are generated from the partial melting of the lithospheric mantle which resulted from heat flow of mantle plume. Fe-Ti-P-rich minerals were assembled at the late stage of magma crystallization.
In order to better understand the complex tectonic framework on the southern margin of South China block (SCB) between Permian and Triassic, the petrology, geochemistry and chronology of three newly discovered Late Permian ultramafic intrusions in the Yunkai area of West Guangdong were studied. These rocks are located at Yangchun Sanjia on the eastern edge of the Yunkai terrane and at Gaozhou Dajing and Dong'an in the middle of the Yunkai terrane. They are intrusive rocks in schist and paragneiss of the Yunkai Group and out putted as laccoliths or dykes which main lithologies are pyroxenite, hornblendite, amphibolite and plagioclase amphibolite. Zircon SHRIMP and LA-ICP-MS U-Pb age of ultramafic rocks are 253-259 Ma. These intrusive rocks are rich in titanomagnetite, titanite and apatite, showing strong enrichment of Fe-Ti-P, and exhibiting moderate enrichment of LREE and depletion in Nb-Ta-Zr-Hf. Ultramafic rocks exhibit relatively low εNd(t)(-3.4 to -10.0) of whole rocks, εHf(t) (-1.2 to -9.5) and δ18O(7.01‰-9.71‰) values of zircon, showing the enriched lithosphere mantle source affinity. In this study, it is suggested that the influence range of Permian Emeishan mantle plume(~259 Ma) may have spread to Yunkai area. Yunkai Late Permian ultramafic intrusions are generated from the partial melting of the lithospheric mantle which resulted from heat flow of mantle plume. Fe-Ti-P-rich minerals were assembled at the late stage of magma crystallization.
2021, 46(4): 1311-1327.
doi: 10.3799/dqkx.2020.229
Abstract:
Neoproterozoic bimodal volcanic rocks from the Dingyuan Formation within the western Dabie terrain consist of rhyolite, rhyolitic tuff and basalt. Elemental, whole-rock Sr-Nd and zircon Hf isotopic analyses were carried out in this study for these volcanic rocks, in order to better understand their petrogenesis and geodynamic processes along the northern margin of Yangtze block. The rhyolite is characterized by high concentrations of SiO2 and Al2O3, belongs to the calc-alkaline series, and is peraluminous. It is enriched in light rare earth elements (LREEs) and shows unapparent Eu anomaly. The basalt has SiO2 of 48.26% to 51.71%, Mg# values of 0.32 to 0.59, and is weakly enriched in light rare earth elements. The rhyolite has initial 87Sr/86Sr ratios ranging from 0.703 5 to 0.707 7, and negative εNd(t) values of -10.6 to -6.5, with calculated two-stage Nd model ages of 1.69 to 2.00 Ga, while the basalt has (87Sr/86Sr)i of 0.706 1 to 0.708 1, εNd(t) of -6.6 to +3.4, and the Nd model ages (TDM) values of 1.44 to 2.02 Ga. In situ zircon Hf isotopic analyses show that the εHf(t) values of zircons from the rhyolite vary from -19.2 to -7.2, with calculated two-stage Hf model ages of 1.77 to 2.59 Ga. The geochemical and Sr-Nd-Hf isotopic signatures suggest that the rhyolite has a close affinity to S-type granite, and is derived from partial melting of the ancient crust of the Yangtze block. The basalt is most likely derived from an enriched lithospheric mantle, with fractional crystallization and assimilation of crustal materials during the evolution of the magma. It is proposed that the Neoproterozoic bimodal volcanic suites from the Dingyuan and the Qijiaoshan formations are erupted coevally, but have different sources and magmatic processes. The bimodal volcanic rocks in this study provide evidences for an enriched lithospheric mantle beneath the Dabie terrain at ca.740 Ma, and a rifting extensional setting for the north margin of the Yangtze block.
Neoproterozoic bimodal volcanic rocks from the Dingyuan Formation within the western Dabie terrain consist of rhyolite, rhyolitic tuff and basalt. Elemental, whole-rock Sr-Nd and zircon Hf isotopic analyses were carried out in this study for these volcanic rocks, in order to better understand their petrogenesis and geodynamic processes along the northern margin of Yangtze block. The rhyolite is characterized by high concentrations of SiO2 and Al2O3, belongs to the calc-alkaline series, and is peraluminous. It is enriched in light rare earth elements (LREEs) and shows unapparent Eu anomaly. The basalt has SiO2 of 48.26% to 51.71%, Mg# values of 0.32 to 0.59, and is weakly enriched in light rare earth elements. The rhyolite has initial 87Sr/86Sr ratios ranging from 0.703 5 to 0.707 7, and negative εNd(t) values of -10.6 to -6.5, with calculated two-stage Nd model ages of 1.69 to 2.00 Ga, while the basalt has (87Sr/86Sr)i of 0.706 1 to 0.708 1, εNd(t) of -6.6 to +3.4, and the Nd model ages (TDM) values of 1.44 to 2.02 Ga. In situ zircon Hf isotopic analyses show that the εHf(t) values of zircons from the rhyolite vary from -19.2 to -7.2, with calculated two-stage Hf model ages of 1.77 to 2.59 Ga. The geochemical and Sr-Nd-Hf isotopic signatures suggest that the rhyolite has a close affinity to S-type granite, and is derived from partial melting of the ancient crust of the Yangtze block. The basalt is most likely derived from an enriched lithospheric mantle, with fractional crystallization and assimilation of crustal materials during the evolution of the magma. It is proposed that the Neoproterozoic bimodal volcanic suites from the Dingyuan and the Qijiaoshan formations are erupted coevally, but have different sources and magmatic processes. The bimodal volcanic rocks in this study provide evidences for an enriched lithospheric mantle beneath the Dabie terrain at ca.740 Ma, and a rifting extensional setting for the north margin of the Yangtze block.
2021, 46(4): 1328-1348.
doi: 10.3799/dqkx.2020.101
Abstract:
For revealing provenance and tectonic setting of Lengjiaxi Group in the central Jiangnan orogen, a synthetic study on petrology, sedimentology, geochemistry and zircon geochronology of Huanghudong Formation in Yueyang area was carried out. All greywacke samples are rich in matrix (mostly more than 25%), feldspar (15%-25%) and lithic fragments (15%-30%), poor in quartz (25%-40%), with poor sorting and poor-medium rounding. These samples are characterized by medium SiO2(63.39%-72.88%, mean: 70.14%) contents, high (Fe2O3T+MgO)* (6.04%-8.29%, mean: 6.81%) and TiO2* (0.67%-0.92%, mean: 0.74%) contents, high K2O/Na2O (0.84-2.35, mean: 1.43) ratios, and low Al2O3/SiO2 (0.17-0.28, mean: 0.20) ratios, resembling those of continental island arc greywackes. Their medium index of compositional variation (ICV, mean: 0.86) and chemical index of alteration values (CIA, mean: 70-80) demonstrate that the source contains recycled ancient sediments and first-cycle materials which underwent moderate chemical weathering. Greywackes have high contents in ΣREE (mean: 173.02×10-6), with chondrite-normalized REE patterns similar to upper crust and PAAS, showing enriched LREE ((La/Yb)N mean: 7.32), subhorizontal HREE curves and moderate Eu (Eu/Eu*: 0.58-0.70, mean: 0.66) negative anomalies. However, compared to the upper crust, greywackes HREE contents are significantly enriched with an average (La/Yb)ucc value of 0.70. LA-ICP-MS zircon U-Pb dating of one layered tuff sample yields zircon U-Pb age of 824±3.1 Ma. Low textural and compositional maturity, NEE-SE paleocurrent, contents and ratios of characteristic elements, provenance and tectonic discrimination diagrams of Huanghudong Formation greywackes, and combined with other geological observations, suggest that the Lengjiaxi Group of Yueyang area in the central Jiangnan orogen might be formed in a back-arc basin. The sources are of high compositional maturity from interior Yangtze block in stable tectonic setting in the north, and of low compositional maturity from continental island arc with strong tectonic activity in the south, respectively.
For revealing provenance and tectonic setting of Lengjiaxi Group in the central Jiangnan orogen, a synthetic study on petrology, sedimentology, geochemistry and zircon geochronology of Huanghudong Formation in Yueyang area was carried out. All greywacke samples are rich in matrix (mostly more than 25%), feldspar (15%-25%) and lithic fragments (15%-30%), poor in quartz (25%-40%), with poor sorting and poor-medium rounding. These samples are characterized by medium SiO2(63.39%-72.88%, mean: 70.14%) contents, high (Fe2O3T+MgO)* (6.04%-8.29%, mean: 6.81%) and TiO2* (0.67%-0.92%, mean: 0.74%) contents, high K2O/Na2O (0.84-2.35, mean: 1.43) ratios, and low Al2O3/SiO2 (0.17-0.28, mean: 0.20) ratios, resembling those of continental island arc greywackes. Their medium index of compositional variation (ICV, mean: 0.86) and chemical index of alteration values (CIA, mean: 70-80) demonstrate that the source contains recycled ancient sediments and first-cycle materials which underwent moderate chemical weathering. Greywackes have high contents in ΣREE (mean: 173.02×10-6), with chondrite-normalized REE patterns similar to upper crust and PAAS, showing enriched LREE ((La/Yb)N mean: 7.32), subhorizontal HREE curves and moderate Eu (Eu/Eu*: 0.58-0.70, mean: 0.66) negative anomalies. However, compared to the upper crust, greywackes HREE contents are significantly enriched with an average (La/Yb)ucc value of 0.70. LA-ICP-MS zircon U-Pb dating of one layered tuff sample yields zircon U-Pb age of 824±3.1 Ma. Low textural and compositional maturity, NEE-SE paleocurrent, contents and ratios of characteristic elements, provenance and tectonic discrimination diagrams of Huanghudong Formation greywackes, and combined with other geological observations, suggest that the Lengjiaxi Group of Yueyang area in the central Jiangnan orogen might be formed in a back-arc basin. The sources are of high compositional maturity from interior Yangtze block in stable tectonic setting in the north, and of low compositional maturity from continental island arc with strong tectonic activity in the south, respectively.
2021, 46(4): 1349-1358.
doi: 10.3799/dqkx.2020.351
Abstract:
Geological surveying is challenging in high-altitude mountains with dense vegetation in Nanling because it is inaccessible both for human and material resources. It is necessary to design reasonable field survey routes in advance according to the topographical linear characteristics of the area. Moreover, the topographical linear characteristics can provide the auxiliary information for local tectonic movement. Remotely sensed technology has become an important method for geological research and geological survey due to its macroscopic, multi-scale and multi-level characteristics. However, in areas with high vegetation coverage, optical remote sensing images are difficult to penetrate vegetation, while microwave radar images can do because of its good vegetation penetration. Therefore, the topographical linear feature extraction method based on Sentinel-1 (radar satellite) and DEM data in areas with high vegetation coverage is proposed. This method first uses the likelihood ratio edge detection algorithm to extract the edge features in Sentinel-1 images. Then, the linear features of DEM are enhanced to generate mountain shadow images, and then the main linear features such as ridge lines and valley lines are extracted by Canny edge detection operator. Finally, taking the feature line extracted from DEM as the center, a buffer zone is established and intersected with the result from radar images, and then the local straight line fitting is done by using the Douglas-Puck algorithm to obtain the final topographical linear features in the study area. The results show that the proposed method comprehensively considers the micro-detail information of radar images and the macro-trend information of DEM data, and can remove false edges and noise points while retaining the main topographical linear features, and the extraction effect is good.
Geological surveying is challenging in high-altitude mountains with dense vegetation in Nanling because it is inaccessible both for human and material resources. It is necessary to design reasonable field survey routes in advance according to the topographical linear characteristics of the area. Moreover, the topographical linear characteristics can provide the auxiliary information for local tectonic movement. Remotely sensed technology has become an important method for geological research and geological survey due to its macroscopic, multi-scale and multi-level characteristics. However, in areas with high vegetation coverage, optical remote sensing images are difficult to penetrate vegetation, while microwave radar images can do because of its good vegetation penetration. Therefore, the topographical linear feature extraction method based on Sentinel-1 (radar satellite) and DEM data in areas with high vegetation coverage is proposed. This method first uses the likelihood ratio edge detection algorithm to extract the edge features in Sentinel-1 images. Then, the linear features of DEM are enhanced to generate mountain shadow images, and then the main linear features such as ridge lines and valley lines are extracted by Canny edge detection operator. Finally, taking the feature line extracted from DEM as the center, a buffer zone is established and intersected with the result from radar images, and then the local straight line fitting is done by using the Douglas-Puck algorithm to obtain the final topographical linear features in the study area. The results show that the proposed method comprehensively considers the micro-detail information of radar images and the macro-trend information of DEM data, and can remove false edges and noise points while retaining the main topographical linear features, and the extraction effect is good.
2021, 46(4): 1359-1373.
doi: 10.3799/dqkx.2020.146
Abstract:
The characteristics of the Lower Ordovician in the Jingshan-Zhongxiang area are significantly different from those in the Three Gorges and southern Suizhou. Therefore, correlation of lithostratigraphy and biostratigraphy between them is helpful to understanding the paleogeograpghy as well as the geological evolution during the Early Ordovician in the northern margin of the Yangtze platform. Based on detailed study on the lithostratigraphy and the fossil assemblage, the Wenxiakou Formation and Zhongxiang Formation of the Lower Ordovician are established. The Wenxiakou Formation consists predominantly of flat pebble limestone, oolitic limestone and bioclastic limestone, which belongs to shoal facies of platform margin to shallow shelf facies. According to the fossils such as gastropods, cephalopods and brachiopods, this formation is confirmed as a deposition from Middle-Late Tremadocian to Early Florian, which is underlain conformably by the Loushanguan Formation. This succession can be correlated to the Nanjinguan Formation, Fenxiang Formation and Honghuayuan Formation in Three Gorges area, and can also be compared with the bottom of Gaojiawan Formation in southern Suizhou area. The Zhongxiang Formation is characterized by grey or dark grey shales with some siltstones and lenticular bioclastic limestone and is assumed to have been deposited in the neritic continental shelf zone. Based on the abundant fossils such as brachiopods, trilobites, crinoid stems, graptolite and cephalopods, this formation is considered to be formed at the age of Floian and has a conformable contact with the Wenxiakou and Dawan formations. It can be compared with the lowest part to Dawan Formation in Three Gorges and the middle-upper part of the Gaojiawan Formation in southern Suizhou, respectively.
The characteristics of the Lower Ordovician in the Jingshan-Zhongxiang area are significantly different from those in the Three Gorges and southern Suizhou. Therefore, correlation of lithostratigraphy and biostratigraphy between them is helpful to understanding the paleogeograpghy as well as the geological evolution during the Early Ordovician in the northern margin of the Yangtze platform. Based on detailed study on the lithostratigraphy and the fossil assemblage, the Wenxiakou Formation and Zhongxiang Formation of the Lower Ordovician are established. The Wenxiakou Formation consists predominantly of flat pebble limestone, oolitic limestone and bioclastic limestone, which belongs to shoal facies of platform margin to shallow shelf facies. According to the fossils such as gastropods, cephalopods and brachiopods, this formation is confirmed as a deposition from Middle-Late Tremadocian to Early Florian, which is underlain conformably by the Loushanguan Formation. This succession can be correlated to the Nanjinguan Formation, Fenxiang Formation and Honghuayuan Formation in Three Gorges area, and can also be compared with the bottom of Gaojiawan Formation in southern Suizhou area. The Zhongxiang Formation is characterized by grey or dark grey shales with some siltstones and lenticular bioclastic limestone and is assumed to have been deposited in the neritic continental shelf zone. Based on the abundant fossils such as brachiopods, trilobites, crinoid stems, graptolite and cephalopods, this formation is considered to be formed at the age of Floian and has a conformable contact with the Wenxiakou and Dawan formations. It can be compared with the lowest part to Dawan Formation in Three Gorges and the middle-upper part of the Gaojiawan Formation in southern Suizhou, respectively.
2021, 46(4): 1374-1415.
doi: 10.3799/dqkx.2020.387
Abstract:
In recent years, researches on nanogeoscience and planetary sciences have achieved significant progresses mostly due to the applications of various microscopic and micro-spectroscopic approaches. Among these techniques, transmission electron microscopy (TEM), known as high spatial resolution and strong comprehensive analysis capability, plays an important role in simultaneously imaging and characterizing morphological, structural, chemical, and micromagnetic properties down to atomic scales. In this review it briefly introduces the development history, mechanical structure and working principles of transmission electron microscope, and the sample preparation involved in the TEM technique as well. Based on some recent progresses achieved in the Electron Microscope Lab at the IGGCAS, this review also shows and focus on the fundamental functions and applications of transmission electron microscope in some typical researches in earth and planetary sciences. Finally, it tentatively discusses the current situation and future trend of transmission electron microscopy in earth and planetary sciences.
In recent years, researches on nanogeoscience and planetary sciences have achieved significant progresses mostly due to the applications of various microscopic and micro-spectroscopic approaches. Among these techniques, transmission electron microscopy (TEM), known as high spatial resolution and strong comprehensive analysis capability, plays an important role in simultaneously imaging and characterizing morphological, structural, chemical, and micromagnetic properties down to atomic scales. In this review it briefly introduces the development history, mechanical structure and working principles of transmission electron microscope, and the sample preparation involved in the TEM technique as well. Based on some recent progresses achieved in the Electron Microscope Lab at the IGGCAS, this review also shows and focus on the fundamental functions and applications of transmission electron microscope in some typical researches in earth and planetary sciences. Finally, it tentatively discusses the current situation and future trend of transmission electron microscopy in earth and planetary sciences.
2021, 46(4): 1416-1436.
doi: 10.3799/dqkx.2020.094
Abstract:
The volcanic magmatic activity has not been observed in the Gonghe basin and its surrounding orogenic belts since the Cenozoic. Heat generation from the magma of concealed granite body during the Indosinian period and the radioactive elements within the stratum are difficult to form the heat source of hot dry rock resources in the Gonghe basin. However, it has been widely recognized that this basin is a high-temperature geothermal abnormal basin. Nowadays, two hot dry rock masses were verified in the Qiabuqia of the Gonghe County and the Reshuiquan of the Guide County basically. Sixteen target areas of the hot dry rock exploration were also delineated in this region. Evidences from the regional gravity and aeromagnetic survey, regional natural seismic imaging profile, tomographic exploration of natural seismic background noise at basin scale, ultra-high resolution gravity anomalies, as well as linear inversion of resistivity and phase velocity of Rayleigh wave group all show that partial melting layer was developed in the crust of the Gonghe basin. This partial melting layer, located in the inner plate environment and characterized by high heat flow, constitutes the regional heat source of the hot dry rock resources in the Gonghe basin. The MT exploration reflects that the partial melting layer within the crust of the western basin of the Gonghe basin is characterized by a depth of 15-35 km, length of about 41 km and 34 km in east-west and north-south directions respectively, thickness of 2-12 km. Comprehensive analysis shows that this partial melting layer, marked by a melting degree of 4%-7% and temperature of about 574℃ at 15 km depth, is mainly located under the main detachment nappe interface between the nappe systems of the Guinan Nanshan and Gonghe, and above the main detachment nappe interface of Xinghai large composite nappe system. Heat generation from the continuous dynamic shear friction at the deep structural, multi-level, and near horizontal detachment nappe interface during the Neoid period is the main factor for the formation of the partial melting layer.
The volcanic magmatic activity has not been observed in the Gonghe basin and its surrounding orogenic belts since the Cenozoic. Heat generation from the magma of concealed granite body during the Indosinian period and the radioactive elements within the stratum are difficult to form the heat source of hot dry rock resources in the Gonghe basin. However, it has been widely recognized that this basin is a high-temperature geothermal abnormal basin. Nowadays, two hot dry rock masses were verified in the Qiabuqia of the Gonghe County and the Reshuiquan of the Guide County basically. Sixteen target areas of the hot dry rock exploration were also delineated in this region. Evidences from the regional gravity and aeromagnetic survey, regional natural seismic imaging profile, tomographic exploration of natural seismic background noise at basin scale, ultra-high resolution gravity anomalies, as well as linear inversion of resistivity and phase velocity of Rayleigh wave group all show that partial melting layer was developed in the crust of the Gonghe basin. This partial melting layer, located in the inner plate environment and characterized by high heat flow, constitutes the regional heat source of the hot dry rock resources in the Gonghe basin. The MT exploration reflects that the partial melting layer within the crust of the western basin of the Gonghe basin is characterized by a depth of 15-35 km, length of about 41 km and 34 km in east-west and north-south directions respectively, thickness of 2-12 km. Comprehensive analysis shows that this partial melting layer, marked by a melting degree of 4%-7% and temperature of about 574℃ at 15 km depth, is mainly located under the main detachment nappe interface between the nappe systems of the Guinan Nanshan and Gonghe, and above the main detachment nappe interface of Xinghai large composite nappe system. Heat generation from the continuous dynamic shear friction at the deep structural, multi-level, and near horizontal detachment nappe interface during the Neoid period is the main factor for the formation of the partial melting layer.
2021, 46(4): 1437-1446.
doi: 10.3799/dqkx.2020.097
Abstract:
The deformation and stability of rock slope are very important to engineering construction. Taking the right bank bedding rock slope of a hydropower project on Yalongjiang River as an example, in this paper it studies and summarizes the formation mechanism, development characteristics and the relationship with weak structural plane dip and development depth of sliding-shearing deformation and failure mode by in-situ investigation, theoretical analysis and numerical calculation. The research results show that sliding-shearing deformation and failure mode usually occurs in the bedding rock slope with poor mechanical properties or in the strong-weak weathering rock masses. The sliding-shearing deformation and failure of rock mass slope are closely related to the dip and development position of steep weak structural plane. The weak structural plane with 45°-65° dip or horizontal distance of less than 80 m from the slope surface is obviously influence to sliding-shearing deformation and failure of slope, and the influence of the horizontal distance between the weak structural plane and the slope surface is stronger than dip of weak structural plane on sliding-shearing deformation and failure of slope. This study is of great engineering significance and practical value to supplement the deformation and failure types of rock slope.
The deformation and stability of rock slope are very important to engineering construction. Taking the right bank bedding rock slope of a hydropower project on Yalongjiang River as an example, in this paper it studies and summarizes the formation mechanism, development characteristics and the relationship with weak structural plane dip and development depth of sliding-shearing deformation and failure mode by in-situ investigation, theoretical analysis and numerical calculation. The research results show that sliding-shearing deformation and failure mode usually occurs in the bedding rock slope with poor mechanical properties or in the strong-weak weathering rock masses. The sliding-shearing deformation and failure of rock mass slope are closely related to the dip and development position of steep weak structural plane. The weak structural plane with 45°-65° dip or horizontal distance of less than 80 m from the slope surface is obviously influence to sliding-shearing deformation and failure of slope, and the influence of the horizontal distance between the weak structural plane and the slope surface is stronger than dip of weak structural plane on sliding-shearing deformation and failure of slope. This study is of great engineering significance and practical value to supplement the deformation and failure types of rock slope.
2021, 46(4): 1447-1466.
doi: 10.3799/dqkx.2020.165
Abstract:
In addition to its beautiful structure, the newly discovered orbicular rocks in the central and southern parts of the Great Xing'an volcanic belt in the Uragai region are of great importance to the exploration of the subduction history of the Great Xing'an Range in the NE China. On the basis of detailed field geological survey, in this paper it makes a comprehensive study on the geochemistry and Sr-Nd isotope characteristics of the orbicular rocks and its host rocks in Uragai area, Inner Mongolia, and discusses its magmatic source and formation mechanism. The analysis results show that the Uragai orbicular rock and its host rocks have high silica (SiO2=75.35%-76.21%) and alkali (K2O+Na2O=7.30%-7.45%), but low aluminium (Al2O3=9.82%-11.30%), Mg# value (Mg#=4.52-14.47), chromium (Cr=14.5×10-6-22.5×10-6), and nickel (Ni=1.84×10-6-3.97×10-6), indicating a crustal magmatic source. Trace and rare earth elements (REEs) show post-orogenic volcanic rock features: obviously enriched in large ion lithophile elements (LILEs, e.g., Rb, Th, K, LREE) and high field strength elements (HFSEs, e.g., Nb, Ta, Zr, HREE). The Nb negative anomaly is not obvious in N-MORB standardized diagram, with significant differentiation between light rare earth elements (LREE) and heavy rare earth elements (HREE) (LREE/HREE=5.21-6.70). The initial 87Sr/86Sr (0.705 9-0.713 7) is higher than the MORB of modern ocean (0.702 29-0.703 34), which also suggests a crustal source. However, the 143Nd/144Nd (0.512 456-0.512 528) was lower than the value of modern oceans (0.512 99-0.513 30), and with εNd value from +4.8 to +6.2, which shows depleted mantle signature. Study shows that the magmatic source of Uragai orbicular rock and its host rocks originated from the lower crust, and with participation of depleted mantle material. The obviously depleted Sr, Ba and Eu suggest the fractional crystallization course, and the rocks formed in a stable in-plate tectonic environment. Major and trace element diagrams also show the post-orogenic A-type granite features. The study shows that the orbicular rocks have few reliable geological ages, probably resulted from sufficient low temperature fluids which blocked the crystallization course. The abundant trapped zircons or other refractory minerals may provide a material basis for the formation of orbicular rocks. The zircon LA-ICP-MS U-Pb age of graphic granite in the main face of the orbicular rocks is 142.2±2.7 Ma, and the average age of diabase dikes in the orbicular rocks is 140.5 Ma, and the zircon LA-ICP-MS U-Pb age obtained from orthophyre, which is surrounding rocks of the main face of the orbicular rocks, is 349.5±3.4 Ma, These age information restricted the formation age of orbicular rocks at Early Cretaceous(141 Ma±), its host rocks is Early Carboniferous, which is totally different with host rocks of orbicular rocks in and abroad. Comprehensive research shows that the formation mechanism of orbicular rock and its host rocks in Uragai area is related to late stage magmatic activity in the Great Xing'an volcanic belt, largely controlled by the post-orogenic extension tectonic setting of the Mongol-Okhotsk Ocean in the Early Cretaceous, and it is a product of the large-scale regional extension and strong magmatic underplating in the Great Xing'an Range.
In addition to its beautiful structure, the newly discovered orbicular rocks in the central and southern parts of the Great Xing'an volcanic belt in the Uragai region are of great importance to the exploration of the subduction history of the Great Xing'an Range in the NE China. On the basis of detailed field geological survey, in this paper it makes a comprehensive study on the geochemistry and Sr-Nd isotope characteristics of the orbicular rocks and its host rocks in Uragai area, Inner Mongolia, and discusses its magmatic source and formation mechanism. The analysis results show that the Uragai orbicular rock and its host rocks have high silica (SiO2=75.35%-76.21%) and alkali (K2O+Na2O=7.30%-7.45%), but low aluminium (Al2O3=9.82%-11.30%), Mg# value (Mg#=4.52-14.47), chromium (Cr=14.5×10-6-22.5×10-6), and nickel (Ni=1.84×10-6-3.97×10-6), indicating a crustal magmatic source. Trace and rare earth elements (REEs) show post-orogenic volcanic rock features: obviously enriched in large ion lithophile elements (LILEs, e.g., Rb, Th, K, LREE) and high field strength elements (HFSEs, e.g., Nb, Ta, Zr, HREE). The Nb negative anomaly is not obvious in N-MORB standardized diagram, with significant differentiation between light rare earth elements (LREE) and heavy rare earth elements (HREE) (LREE/HREE=5.21-6.70). The initial 87Sr/86Sr (0.705 9-0.713 7) is higher than the MORB of modern ocean (0.702 29-0.703 34), which also suggests a crustal source. However, the 143Nd/144Nd (0.512 456-0.512 528) was lower than the value of modern oceans (0.512 99-0.513 30), and with εNd value from +4.8 to +6.2, which shows depleted mantle signature. Study shows that the magmatic source of Uragai orbicular rock and its host rocks originated from the lower crust, and with participation of depleted mantle material. The obviously depleted Sr, Ba and Eu suggest the fractional crystallization course, and the rocks formed in a stable in-plate tectonic environment. Major and trace element diagrams also show the post-orogenic A-type granite features. The study shows that the orbicular rocks have few reliable geological ages, probably resulted from sufficient low temperature fluids which blocked the crystallization course. The abundant trapped zircons or other refractory minerals may provide a material basis for the formation of orbicular rocks. The zircon LA-ICP-MS U-Pb age of graphic granite in the main face of the orbicular rocks is 142.2±2.7 Ma, and the average age of diabase dikes in the orbicular rocks is 140.5 Ma, and the zircon LA-ICP-MS U-Pb age obtained from orthophyre, which is surrounding rocks of the main face of the orbicular rocks, is 349.5±3.4 Ma, These age information restricted the formation age of orbicular rocks at Early Cretaceous(141 Ma±), its host rocks is Early Carboniferous, which is totally different with host rocks of orbicular rocks in and abroad. Comprehensive research shows that the formation mechanism of orbicular rock and its host rocks in Uragai area is related to late stage magmatic activity in the Great Xing'an volcanic belt, largely controlled by the post-orogenic extension tectonic setting of the Mongol-Okhotsk Ocean in the Early Cretaceous, and it is a product of the large-scale regional extension and strong magmatic underplating in the Great Xing'an Range.
2021, 46(4): 1467-1480.
doi: 10.3799/dqkx.2020.269
Abstract:
The West Hill of Beijing experienced multiple stages of deformation since Mesozoic,and is considered as an important window to decipher the tectonic evolution of the North China block. Structural analyses and the EBSD data show that the Ordovician carbonate rocks in Huangyuan of Zhoukoudian is characterized by four stages of deformation,among which the D2 NE-SW-striking compressional structures shaped the main structural style. The D1 is represented by top-to-the-SEE (110°-120°) shearing bands and the penetrative stretching lineation L1,and the pervasive foliation S1 has replaced the sedimentary bedding S0. From north to south,the D2 deformation can be subdivided into two subzones including buckle fold and ductile shear zone,showing a consistent kinematics of top-to-the-SE thrusting as indicated by the fold vergence and shearing bands,respectively. The D3 is featured by the NWW-directed normal slipping superimposed on the foliation S2,and the D4 displays nearly N-S-trending high-angle normal faults. According to the youngest zircon U-Pb age peak (~116 Ma) of a diorite intrusion,it infers that the D1 happened in the late Early Cretaceous,and the D2 occurred in the Late Cretaceous,i.e.,the Late Yanshanian stage,probably as a response to the continental-continental collision after the closure of the Mongol-Okhotsk Ocean.
The West Hill of Beijing experienced multiple stages of deformation since Mesozoic,and is considered as an important window to decipher the tectonic evolution of the North China block. Structural analyses and the EBSD data show that the Ordovician carbonate rocks in Huangyuan of Zhoukoudian is characterized by four stages of deformation,among which the D2 NE-SW-striking compressional structures shaped the main structural style. The D1 is represented by top-to-the-SEE (110°-120°) shearing bands and the penetrative stretching lineation L1,and the pervasive foliation S1 has replaced the sedimentary bedding S0. From north to south,the D2 deformation can be subdivided into two subzones including buckle fold and ductile shear zone,showing a consistent kinematics of top-to-the-SE thrusting as indicated by the fold vergence and shearing bands,respectively. The D3 is featured by the NWW-directed normal slipping superimposed on the foliation S2,and the D4 displays nearly N-S-trending high-angle normal faults. According to the youngest zircon U-Pb age peak (~116 Ma) of a diorite intrusion,it infers that the D1 happened in the late Early Cretaceous,and the D2 occurred in the Late Cretaceous,i.e.,the Late Yanshanian stage,probably as a response to the continental-continental collision after the closure of the Mongol-Okhotsk Ocean.
2021, 46(4): 1481-1489.
doi: 10.3799/dqkx.2020.131
Abstract:
In redox fluctuation areas such as groundwater level fluctuation zone,surface water-groundwater interaction zone,O2 reacts with Fe(Ⅱ) to produce reactive oxygen species (ROSs),such as ·OH,·O2-,H2O2,etc. These ROSs are of biological toxicity and may have impact on the survival of microorganisms,and different functional microorganisms may respond differently to ROSs produced by Fe(Ⅱ) chemical oxidation. To validate this scientific hypothesis,a Fe (Ⅱ) oxidizing bacteria Pseudogulbenkiania sp. strain 2002 (strain 2002),two ammonia oxidation bacteria Rhodococcus sp. (A1) and Arthrobacter oxydans (A2) were selected as model strains,and contrasted with the iron reducing bacteria Shewanella oneidensis strain MR-1 (MR-1).The numbers of microorganisms,changes of cell structures,and the contribution of ROS were studied. The results show that different functional microorganisms respond differently to Fe(Ⅱ) chemical oxidation. After oxidation of 0.2 mmol/L Fe(Ⅱ) for 60 min,the MR-1 numbers decreased by 1.61 orders of magnitude,A1 and A2 decreased by 0.74 and 1.37 orders of magnitude,respectively,while the survival of strain 2002 was virtually unaffected by Fe (Ⅱ) oxidation. It was observed through transmission electron microscope that the outer membranes of MR-1,A1 and A2 bacteria cells were damaged to varying degrees,while strain 2002 was intact. The results of quenching test show that ROS produced in solution and in the cell caused death of functional microorganisms,but different microorganisms had different response mechanisms to ROS due to their adsorption ability to Fe(Ⅱ) and their resistance to ROS. The results of this study are of great significance for interpreting the microbial community evolution in the redox fluctuation region and the biogeochemical processes in the Great Oxygen Explosion in the history of the earth.
In redox fluctuation areas such as groundwater level fluctuation zone,surface water-groundwater interaction zone,O2 reacts with Fe(Ⅱ) to produce reactive oxygen species (ROSs),such as ·OH,·O2-,H2O2,etc. These ROSs are of biological toxicity and may have impact on the survival of microorganisms,and different functional microorganisms may respond differently to ROSs produced by Fe(Ⅱ) chemical oxidation. To validate this scientific hypothesis,a Fe (Ⅱ) oxidizing bacteria Pseudogulbenkiania sp. strain 2002 (strain 2002),two ammonia oxidation bacteria Rhodococcus sp. (A1) and Arthrobacter oxydans (A2) were selected as model strains,and contrasted with the iron reducing bacteria Shewanella oneidensis strain MR-1 (MR-1).The numbers of microorganisms,changes of cell structures,and the contribution of ROS were studied. The results show that different functional microorganisms respond differently to Fe(Ⅱ) chemical oxidation. After oxidation of 0.2 mmol/L Fe(Ⅱ) for 60 min,the MR-1 numbers decreased by 1.61 orders of magnitude,A1 and A2 decreased by 0.74 and 1.37 orders of magnitude,respectively,while the survival of strain 2002 was virtually unaffected by Fe (Ⅱ) oxidation. It was observed through transmission electron microscope that the outer membranes of MR-1,A1 and A2 bacteria cells were damaged to varying degrees,while strain 2002 was intact. The results of quenching test show that ROS produced in solution and in the cell caused death of functional microorganisms,but different microorganisms had different response mechanisms to ROS due to their adsorption ability to Fe(Ⅱ) and their resistance to ROS. The results of this study are of great significance for interpreting the microbial community evolution in the redox fluctuation region and the biogeochemical processes in the Great Oxygen Explosion in the history of the earth.
2021, 46(4): 1490-1504.
doi: 10.3799/dqkx.2020.089
Abstract:
In order to reveal the adsorption characteristics of alluvial and lacustrine soil cadmium,in this paper it takes alluvial soils of Jiangxin Town and alluvial,lacustrine soils of Dalong Town as the research object in Dangtu County,Anhui Province. The isothermal adsorption experiment and adsorption kinetics experiment of soil cadmium were carried out. The results of isothermal adsorption experiments show that the soil cadmium adsorbance (S),the isothermal adsorption constant (K) and solid-liquid partition coefficient (Kd) of alluvial soils are significantly greater than those of the lacustrine soils,which indicates that the cadmium adsorption capacity of alluvial soils is stronger than that of lacustrine soils. The adsorption kinetics experiment shows that the largest adsorbance,balance adsorbance of soil cadmium in alluvial soils are bigger than those of the lacustrine soils,and the adsorption rate of alluvial soils is also higher than that of lacustrine soils,especially in the early stage of adsorption experiments. The correlation analysis between isothermal adsorption constant K,balance adsorption rate Vb and soil physical and chemical properties shows that soil pH is the main factor for the adsorption capacity of soil cadmium in the study area,which is followed by the physical clay content. Soil pH is the main factor of cadmium adsorption capacity for alluvial soils in the study area. The cadmium adsorption capacity for lacustrine soils is affected by pH,organic matter content,Cd content and the physical clay content synthetically in the study area. It has great significance to reveal the law of Cd migration and transformation in soil and water system and the prevention and control of Cd pollution in soil.
In order to reveal the adsorption characteristics of alluvial and lacustrine soil cadmium,in this paper it takes alluvial soils of Jiangxin Town and alluvial,lacustrine soils of Dalong Town as the research object in Dangtu County,Anhui Province. The isothermal adsorption experiment and adsorption kinetics experiment of soil cadmium were carried out. The results of isothermal adsorption experiments show that the soil cadmium adsorbance (S),the isothermal adsorption constant (K) and solid-liquid partition coefficient (Kd) of alluvial soils are significantly greater than those of the lacustrine soils,which indicates that the cadmium adsorption capacity of alluvial soils is stronger than that of lacustrine soils. The adsorption kinetics experiment shows that the largest adsorbance,balance adsorbance of soil cadmium in alluvial soils are bigger than those of the lacustrine soils,and the adsorption rate of alluvial soils is also higher than that of lacustrine soils,especially in the early stage of adsorption experiments. The correlation analysis between isothermal adsorption constant K,balance adsorption rate Vb and soil physical and chemical properties shows that soil pH is the main factor for the adsorption capacity of soil cadmium in the study area,which is followed by the physical clay content. Soil pH is the main factor of cadmium adsorption capacity for alluvial soils in the study area. The cadmium adsorption capacity for lacustrine soils is affected by pH,organic matter content,Cd content and the physical clay content synthetically in the study area. It has great significance to reveal the law of Cd migration and transformation in soil and water system and the prevention and control of Cd pollution in soil.
2021, 46(4): 1505-1517.
doi: 10.3799/dqkx.2020.128
Abstract:
It is a scientific issue to be addressed as how to build a geo-hazard early warning and forecasting system with dynamically scalable performance,data and information to share,and dynamic service scalability. Based on micro-service architecture with domain model,a geo-hazard early warning and forecasting system based on micro-service framework is constructed in this study by splitting the system into many small businesses characterized by a single service,in a separate process running on containers organized by a container cloud platform named OpenShift. OpenShift provides technical support for rapid deployment of micro-services and dynamic extended service capabilities. Router shading is good for providing traffic isolation and protection for high flow and concurrency businesses. Research result has a certain significance and practical value for providing technical support for the further construction of large comprehensive early warning and prediction system of geo-hazards based on hybrid cloud.
It is a scientific issue to be addressed as how to build a geo-hazard early warning and forecasting system with dynamically scalable performance,data and information to share,and dynamic service scalability. Based on micro-service architecture with domain model,a geo-hazard early warning and forecasting system based on micro-service framework is constructed in this study by splitting the system into many small businesses characterized by a single service,in a separate process running on containers organized by a container cloud platform named OpenShift. OpenShift provides technical support for rapid deployment of micro-services and dynamic extended service capabilities. Router shading is good for providing traffic isolation and protection for high flow and concurrency businesses. Research result has a certain significance and practical value for providing technical support for the further construction of large comprehensive early warning and prediction system of geo-hazards based on hybrid cloud.
2021, 46(4): 1518-1536.
doi: 10.3799/dqkx.2020.113
Abstract:
Based on the extensive investigation of rotational motion with its theory, seismometers, practical observations and their engineering applications, the researches and developments on rotational motion are summarized. The definition of the rotational component and the method of calculating the rotational component indirectly through the translational component are introduced in detail. On the basis of introducing some real observations of the rotational motions, in this paper it focuses on the classification of rotational seismograph with its respective principle, advantages and disadvantages. Also, the examples of rotational-component observation are presented. Moreover, the applications of rotational components in natural earthquake and exploration seismology are discussed. Our investigation demonstrates that the research of rotational motion is still in the experimental and initial stage, especially in China, and that the difference of seismic wave fields under different sources and different media should be the hotspots of the field research. And the development trend is to manufacture equipment with high precision and sensitivity with wider frequency band. The superiorities of the six-component observations need to be elaborated to reverse the fine structure of underground medium and earthquake sources in seismology and engineering through jointly utilizing of the rotational and translational components.
Based on the extensive investigation of rotational motion with its theory, seismometers, practical observations and their engineering applications, the researches and developments on rotational motion are summarized. The definition of the rotational component and the method of calculating the rotational component indirectly through the translational component are introduced in detail. On the basis of introducing some real observations of the rotational motions, in this paper it focuses on the classification of rotational seismograph with its respective principle, advantages and disadvantages. Also, the examples of rotational-component observation are presented. Moreover, the applications of rotational components in natural earthquake and exploration seismology are discussed. Our investigation demonstrates that the research of rotational motion is still in the experimental and initial stage, especially in China, and that the difference of seismic wave fields under different sources and different media should be the hotspots of the field research. And the development trend is to manufacture equipment with high precision and sensitivity with wider frequency band. The superiorities of the six-component observations need to be elaborated to reverse the fine structure of underground medium and earthquake sources in seismology and engineering through jointly utilizing of the rotational and translational components.
