2012 Vol. 37, No. 3
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2012, 37(3): 391-400.
doi: 10.3799/dqkx.2012.047
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Abstract:
The Devonian reef complexes in the Canning basin of western Australia and the Mississippian reef in eastern Australia were compared with those coeval reef complexes in Guilin and Mississippian reefs in Guangxi, South China, and in Akiyoshi, Japan based on the detailed studies on the Devonian reef complexes in Canning basin, western Australia and Mississippian reefs in eastern Australia and through analyzing the development pattern and evolution characteristics of Devonian and Mississippian reefs in four different paleotethys areas. The difference in reef development during the Late Devonian to Mississippian between eastern paleotethys and northern paleotethys was discussed with respect to tectonics, stratigraphy, palaeolatitude, and palaeoclimate, which greatly improves our understanding of Late Devonian to Mississippian reef development in western Australia, eastern Australia, South China, and western Japan respectively, so that the different factors that controlled the reef development in Late Paleozoic were discussed in a global perspective. The geologic interval relevant to this study comprises the important biotic extinction events, it is also a transitional period from greenhouse to icehouse and a stage of evolution, regeneration, and resuscitation for reef-building organisms. The research results are significant in understanding the difference between Late Devonian to Mississippian and early to middle Devonian reef-building organisms and reef types globally and in studying the global palaeoclimatic and palaeoenvironmental changes in this time interval.
The Devonian reef complexes in the Canning basin of western Australia and the Mississippian reef in eastern Australia were compared with those coeval reef complexes in Guilin and Mississippian reefs in Guangxi, South China, and in Akiyoshi, Japan based on the detailed studies on the Devonian reef complexes in Canning basin, western Australia and Mississippian reefs in eastern Australia and through analyzing the development pattern and evolution characteristics of Devonian and Mississippian reefs in four different paleotethys areas. The difference in reef development during the Late Devonian to Mississippian between eastern paleotethys and northern paleotethys was discussed with respect to tectonics, stratigraphy, palaeolatitude, and palaeoclimate, which greatly improves our understanding of Late Devonian to Mississippian reef development in western Australia, eastern Australia, South China, and western Japan respectively, so that the different factors that controlled the reef development in Late Paleozoic were discussed in a global perspective. The geologic interval relevant to this study comprises the important biotic extinction events, it is also a transitional period from greenhouse to icehouse and a stage of evolution, regeneration, and resuscitation for reef-building organisms. The research results are significant in understanding the difference between Late Devonian to Mississippian and early to middle Devonian reef-building organisms and reef types globally and in studying the global palaeoclimatic and palaeoenvironmental changes in this time interval.
2012, 37(3): 401-410.
doi: 10.3799/dqkx.2012.048
Abstract:
Some fossil remains of morphogenus sterile fern foliage Cladophlebis were collected from the Lower Cretaceous Bantou Formation, Yong'an City, Fujian Province. The gross morphological structure and microstructure of cuticles are studied. These fronds are at least bipinnate, main rachis broad, pinnules small, with entire margin crowdedly attached to the rachis with the whole basis. Their midveins are moderately thick, and the secondary veins at the margin are dense, mostly with a single bifurcation. The upper epidermis is free from stomata, with an indistinct outline of cells, and trichomes can be found sometimes. The stomata on the lower epidermis are longitudinally arranged. The epidermal cells are oblong or elongated, anticlinal cell walls straight or slightly undulant and moderately thick, periclinal walls slightly wrinkled. Stomata are mainly circinal, with well-developed stomata ledges. Guard cells are sunken with weak cutinization, and subsidiary cells are not distinct. The cuticular features described above fill in a gap of the epidermic structure about the genus. Additionally, comparison of epidermic features between present fossils and recent Osmunda joponsica, as well as some filices fossils is carried out. The comparison of gross morphology and cuticular features shows that specimens studied are of a new species and is named as Cladophlebis yonganensis Dai et B. N. Sun, sp. nov., and it is concluded that the fossils studied represent a certain extinct plant of filices.
Some fossil remains of morphogenus sterile fern foliage Cladophlebis were collected from the Lower Cretaceous Bantou Formation, Yong'an City, Fujian Province. The gross morphological structure and microstructure of cuticles are studied. These fronds are at least bipinnate, main rachis broad, pinnules small, with entire margin crowdedly attached to the rachis with the whole basis. Their midveins are moderately thick, and the secondary veins at the margin are dense, mostly with a single bifurcation. The upper epidermis is free from stomata, with an indistinct outline of cells, and trichomes can be found sometimes. The stomata on the lower epidermis are longitudinally arranged. The epidermal cells are oblong or elongated, anticlinal cell walls straight or slightly undulant and moderately thick, periclinal walls slightly wrinkled. Stomata are mainly circinal, with well-developed stomata ledges. Guard cells are sunken with weak cutinization, and subsidiary cells are not distinct. The cuticular features described above fill in a gap of the epidermic structure about the genus. Additionally, comparison of epidermic features between present fossils and recent Osmunda joponsica, as well as some filices fossils is carried out. The comparison of gross morphology and cuticular features shows that specimens studied are of a new species and is named as Cladophlebis yonganensis Dai et B. N. Sun, sp. nov., and it is concluded that the fossils studied represent a certain extinct plant of filices.
2012, 37(3): 411-423.
doi: 10.3799/dqkx.2012.049
Abstract:
Spectral analysis and continuous wavelet analysis were conducted on the natural gamma ray logging data from the Middle Miocene-Pliocene Hanjiang, Yuehai and Wanshan formations of well HZ0811 and HZ1811, which locate at northern Huizhou depression and Huilu low uplift at Zhuyi depression, respectively. Significant Milankovitch sedimentary cycles were identified, and "floating" astronomical time scales of well HZ0811 and HZ1811 were established through Gaussian band filtering of short eccentricity signals. The Wanshan, Yuehai and Hanjiang formations record 35, 56 and 64 short eccentricity cycles, which indicate the duration of Wanshan, Yuehai and Hanjiang formations can be estimated as 3.5, 5.6 and 6.4 Ma, respectively. The sedimentary rate of Hanjiang-Wanshan formations of well HZ0811 and HZ1811 were calculated according to floating astronomical time scale. The variations of sedimentary rate indicate significant 1.0 Ma and 0.4 Ma cyclicities, which may be related to the sea level change controlled by long eccentricity cycles.
Spectral analysis and continuous wavelet analysis were conducted on the natural gamma ray logging data from the Middle Miocene-Pliocene Hanjiang, Yuehai and Wanshan formations of well HZ0811 and HZ1811, which locate at northern Huizhou depression and Huilu low uplift at Zhuyi depression, respectively. Significant Milankovitch sedimentary cycles were identified, and "floating" astronomical time scales of well HZ0811 and HZ1811 were established through Gaussian band filtering of short eccentricity signals. The Wanshan, Yuehai and Hanjiang formations record 35, 56 and 64 short eccentricity cycles, which indicate the duration of Wanshan, Yuehai and Hanjiang formations can be estimated as 3.5, 5.6 and 6.4 Ma, respectively. The sedimentary rate of Hanjiang-Wanshan formations of well HZ0811 and HZ1811 were calculated according to floating astronomical time scale. The variations of sedimentary rate indicate significant 1.0 Ma and 0.4 Ma cyclicities, which may be related to the sea level change controlled by long eccentricity cycles.
2012, 37(3): 424-432.
doi: 10.3799/dqkx.2012.050
Abstract:
Clay species of the Xuancheng red clay sediments were investigated using X-ray diffraction (XRD) method to understand the clay mineralogy and its genesis significance of the sediments in the middle to lower reaches of the Yangtze River, South China. Our results show that soil layers of the laterite profile have similar clay mineral compositions of mainly vermiculite, illite, kaolinite, and mixed-layer clays. In the XRD patterns of clay separates, there was weak peak in lower angle side of 7 Å peak, which moved towards lower angle after glycolated treatment, indicating the presence of kaolin-smectite mixed-layer clays. The 7 Å peak of the representative sample (X-18) of the upper soil profile was decomposed into three components of 7.15, 7.60, and 7.92 Å respectively, suggesting that there exists kaolinite, as well as two kaolin-smectite mixed-layer clays, with ~80% and ~95% kaolin layers respectively, and with the former in abundance and the latter in relatively less abundance. The 7 Å peak of sample (X-160) of the lower soil profile contains three components of 7.16, 7.79, and 8.35 Å respectively, with the notably weak peak of 8.35 Å suggesting that there are kaolinite and two kaolin-smectite mixed-layer clays of ~90% and ~43% kaolin layers respectively, with the latter only present in trace amounts. The intensity of the 10 Å peak increased notably with a decrease of the low-angle shoulder on the kaolinite (001) peak after formamide treatment, suggesting that kaolin in the mixed-layer kaolin-smectites is halloysite. On being heated to 400 ℃, the 10 Å peak became much more intense, indicating that certain amounts of kaolin phase derived from smectite layers with chlorite origin. No low-angle tail was observed on the 10 Å peak when heated to 600 ℃, indicating that the interstratified smectite component was not hydroxy interlayered. Mixed-layer illite-smectite and illite-vermiculite were also observed in the Xuancheng red clay sediments. The occurrence of abundant mixed-layer clays in the red clay profile suggests that the red earth sediments underwent overlap of deposit-weathering and multi-staged weathering processes. In the deposit-weathering pedogenesis process, the climate fluctuated between warm/seasonally dry and warm/humid conditions. The presence of mixed-layer illite-vermiculite in upper section indicates that the weathering degree of upper section is generally lower than that of the lower section.
Clay species of the Xuancheng red clay sediments were investigated using X-ray diffraction (XRD) method to understand the clay mineralogy and its genesis significance of the sediments in the middle to lower reaches of the Yangtze River, South China. Our results show that soil layers of the laterite profile have similar clay mineral compositions of mainly vermiculite, illite, kaolinite, and mixed-layer clays. In the XRD patterns of clay separates, there was weak peak in lower angle side of 7 Å peak, which moved towards lower angle after glycolated treatment, indicating the presence of kaolin-smectite mixed-layer clays. The 7 Å peak of the representative sample (X-18) of the upper soil profile was decomposed into three components of 7.15, 7.60, and 7.92 Å respectively, suggesting that there exists kaolinite, as well as two kaolin-smectite mixed-layer clays, with ~80% and ~95% kaolin layers respectively, and with the former in abundance and the latter in relatively less abundance. The 7 Å peak of sample (X-160) of the lower soil profile contains three components of 7.16, 7.79, and 8.35 Å respectively, with the notably weak peak of 8.35 Å suggesting that there are kaolinite and two kaolin-smectite mixed-layer clays of ~90% and ~43% kaolin layers respectively, with the latter only present in trace amounts. The intensity of the 10 Å peak increased notably with a decrease of the low-angle shoulder on the kaolinite (001) peak after formamide treatment, suggesting that kaolin in the mixed-layer kaolin-smectites is halloysite. On being heated to 400 ℃, the 10 Å peak became much more intense, indicating that certain amounts of kaolin phase derived from smectite layers with chlorite origin. No low-angle tail was observed on the 10 Å peak when heated to 600 ℃, indicating that the interstratified smectite component was not hydroxy interlayered. Mixed-layer illite-smectite and illite-vermiculite were also observed in the Xuancheng red clay sediments. The occurrence of abundant mixed-layer clays in the red clay profile suggests that the red earth sediments underwent overlap of deposit-weathering and multi-staged weathering processes. In the deposit-weathering pedogenesis process, the climate fluctuated between warm/seasonally dry and warm/humid conditions. The presence of mixed-layer illite-vermiculite in upper section indicates that the weathering degree of upper section is generally lower than that of the lower section.
2012, 37(3): 433-450.
doi: 10.3799/dqkx.2012.051
Abstract:
Some diorite stocks developed in the Xar Moron fault belt in Linxi county, Inner Mongolia. They intruded into the Shuangjing schist and display variable degrees of deformation. This study presents the petrology, geochemistry, a LA-ICPMS U-Pb zircon age and a hornblende 40Ar-39Ar age of the diorite. The diorite was emplaced in the Early Permian, as reflected by a LA-ICPMS U-Pb zircon age of 286±1 Ma. The magma is derived from enriched mantle metasomatized by slab-derived fluids or melts. The diorites were subject to epidote-amphibolite facies metamorphism during the Early Jurassic, resulting in a hornblende 40Ar-39Ar age of 188.7±1.4 Ma. Combining the new data with the latest published results from the study area and the region, we conclude that the Early Paleozoic and younger mafic rocks in the Solonker suture zone are derived from mantle that was metasomatized by subducted sediments, and that metasomatism increased with time. A stage of collision occurred before the Late Carboniferous (~310 Ma) and the Solonker suture zone underwent post-orogenic extension during the Late Carboniferous to Early Permian (~310 to 276 Ma). The diorite studied is part of a widespread diorite-granodiorite suite that formed during this period of extension in the suture zone. In the Late Permian oceanic basins occurred locally in the suture zone. The closure of these basins induced the final collision of the Solonker suture during the Late Permian to Middle Triassic (~272 to 230 Ma). Spatial variation in the timing of final collision led to the coeval formation of syn-collisional and post-collisional granites in the suture zone. Closure of the Solonker suture zone resulted in the amalgamation of the North China Craton with some microcontinents to its north. North of the accreted microcontinents, the Mongol-Okhotsk Ocean, a branch of the Paleo-Pacific Ocean, formed the remaining NE-striking oceanic domain between the Siberia Craton to the north and the North China Craton to the south. The closure of the Mongol-Okhotsk Ocean in NE Mongolia in the Early Jurassic induced the continent-continent collision recorded by the hornblende 40Ar-39Ar age from the Solonker diorite. The research area then entered post-orogenic extension, while further east the Paleo-Pacific plate subducted beneath the North China Craton. The combination of regional post-orogenic extension and distant subduction led to alternating compression and extension in the Jurassic in what is now northeastern China. After the change in the subduction direction of the Paleo-Pacific plate in the Late Jurassic, the tectonic environment in northeastern China finally became extensional and the region entered the West-Pacific tectonic domain.
Some diorite stocks developed in the Xar Moron fault belt in Linxi county, Inner Mongolia. They intruded into the Shuangjing schist and display variable degrees of deformation. This study presents the petrology, geochemistry, a LA-ICPMS U-Pb zircon age and a hornblende 40Ar-39Ar age of the diorite. The diorite was emplaced in the Early Permian, as reflected by a LA-ICPMS U-Pb zircon age of 286±1 Ma. The magma is derived from enriched mantle metasomatized by slab-derived fluids or melts. The diorites were subject to epidote-amphibolite facies metamorphism during the Early Jurassic, resulting in a hornblende 40Ar-39Ar age of 188.7±1.4 Ma. Combining the new data with the latest published results from the study area and the region, we conclude that the Early Paleozoic and younger mafic rocks in the Solonker suture zone are derived from mantle that was metasomatized by subducted sediments, and that metasomatism increased with time. A stage of collision occurred before the Late Carboniferous (~310 Ma) and the Solonker suture zone underwent post-orogenic extension during the Late Carboniferous to Early Permian (~310 to 276 Ma). The diorite studied is part of a widespread diorite-granodiorite suite that formed during this period of extension in the suture zone. In the Late Permian oceanic basins occurred locally in the suture zone. The closure of these basins induced the final collision of the Solonker suture during the Late Permian to Middle Triassic (~272 to 230 Ma). Spatial variation in the timing of final collision led to the coeval formation of syn-collisional and post-collisional granites in the suture zone. Closure of the Solonker suture zone resulted in the amalgamation of the North China Craton with some microcontinents to its north. North of the accreted microcontinents, the Mongol-Okhotsk Ocean, a branch of the Paleo-Pacific Ocean, formed the remaining NE-striking oceanic domain between the Siberia Craton to the north and the North China Craton to the south. The closure of the Mongol-Okhotsk Ocean in NE Mongolia in the Early Jurassic induced the continent-continent collision recorded by the hornblende 40Ar-39Ar age from the Solonker diorite. The research area then entered post-orogenic extension, while further east the Paleo-Pacific plate subducted beneath the North China Craton. The combination of regional post-orogenic extension and distant subduction led to alternating compression and extension in the Jurassic in what is now northeastern China. After the change in the subduction direction of the Paleo-Pacific plate in the Late Jurassic, the tectonic environment in northeastern China finally became extensional and the region entered the West-Pacific tectonic domain.
2012, 37(3): 451-462.
doi: 10.3799/dqkx.2012.052
Abstract:
This paper presents an integrated Re-Os isotope and trace element investigation of the Neoproterozoic to Cambrian organic-bearing black mudstones in the eastern Three Gorges, the Yangtze Craton. Their sedimentary environmental evolution and geological significance are then discussed. It shows that (1) initial Os isotopic ratios of fine-grained sedimentary rocks from the strata display regular variations along the stratigraphic column. Of the strata, layers with negative δ13C excursions are coupled with high initial Os isotopic ratios; (2) the Nantuo tillite displays higher initial Os isotopic ratio than that of the overlying cap carbonate, while the overlying successive strata show an increase trend with several fluctuations; (3) geochemical features of U/Th ratio and δU value for the samples suggest that the Liantuo sandstone and Nantuo tillite were formed within oxidation environments, whereas black mudstones of the Doushantuo, Dengying and Shuijingtuo Formations were formed within reductive environments; (3) negative correlation between Y/Ho ratio and δCe value for the black mudstones is likely indicative of variable involvement of seafloor hydrothermal activity during some sediments deposited, which likely accounts for their low Os isotopic ratios. The correlation between high initial Os isotopic ratios and pulsed oxidation of deep ocean as well as appearance of metazoan in Late Neoproterozoic-Early Cambrian afford a new clue for the linking of continental weathering extent with oxygen content in atmosphere and ocean. These Os isotopic and trace element features infer that the Nantuo tillites were formed in an environment where the earth's surface had not been fully covered by ice layer, and continent-derived inputs by intensive weathering played an important role.
This paper presents an integrated Re-Os isotope and trace element investigation of the Neoproterozoic to Cambrian organic-bearing black mudstones in the eastern Three Gorges, the Yangtze Craton. Their sedimentary environmental evolution and geological significance are then discussed. It shows that (1) initial Os isotopic ratios of fine-grained sedimentary rocks from the strata display regular variations along the stratigraphic column. Of the strata, layers with negative δ13C excursions are coupled with high initial Os isotopic ratios; (2) the Nantuo tillite displays higher initial Os isotopic ratio than that of the overlying cap carbonate, while the overlying successive strata show an increase trend with several fluctuations; (3) geochemical features of U/Th ratio and δU value for the samples suggest that the Liantuo sandstone and Nantuo tillite were formed within oxidation environments, whereas black mudstones of the Doushantuo, Dengying and Shuijingtuo Formations were formed within reductive environments; (3) negative correlation between Y/Ho ratio and δCe value for the black mudstones is likely indicative of variable involvement of seafloor hydrothermal activity during some sediments deposited, which likely accounts for their low Os isotopic ratios. The correlation between high initial Os isotopic ratios and pulsed oxidation of deep ocean as well as appearance of metazoan in Late Neoproterozoic-Early Cambrian afford a new clue for the linking of continental weathering extent with oxygen content in atmosphere and ocean. These Os isotopic and trace element features infer that the Nantuo tillites were formed in an environment where the earth's surface had not been fully covered by ice layer, and continent-derived inputs by intensive weathering played an important role.
2012, 37(3): 463-474.
doi: 10.3799/dqkx.2012.053
Abstract:
A suite of Cenozoic shoshonitic basalts bearing abundant mantle-derived xenoliths and xenocrysts outcropped in Maguan area, Yunnan Province. This study provides results of petrological and geochemical characteristics of the Cenozoic shoshonitic volcanic rocks, aiming to offer some food to thoughts related to volcanism and mantle-crust interation induced by to the continental collision between India and Asia plates. Results showed that Cenozoic shoshonitic basalts from this area have relatively high and variable alkali contents (2.94%-8.23%), and are rich in potassium (average K2O/Na2O of 21 samples is 1.26). They are classified as shoshonitic basalts or basanite. They are enriched in both light rare earth elements (LREE) and large ion lithophile elements (LILE), and distribution patterns in the chondrite-normalized diagram and primitive-normalized spidergram collectively resemble the pattern of OIB. The shoshonitic basalts contain abundant mantle-derived xenoliths and xenocrysts, and are poorly crystallized with very low contents of phenocrysts, and have considerably high abundance of compatible elements such as Ni, implying that the Cenozoic basaltic rocks of Maguan area are representatives of primary magma derived from mantle sources. The relatively low Mg# of rocks, ranging from 0.49 to 0.72, can either be ascribed to the intrinsic characteristics of the source region or to the mixing of crust and mantle materials in the source region, which needs to be further studied. The Cenozoic shoshonitic basalts formed in a within-plate tectonic setting, the petrogenesis of which is related to the lateral extrusion of asthenospheric mantle along the southeastern of Tibetan plateau induced by the Indo-Asia collision.
A suite of Cenozoic shoshonitic basalts bearing abundant mantle-derived xenoliths and xenocrysts outcropped in Maguan area, Yunnan Province. This study provides results of petrological and geochemical characteristics of the Cenozoic shoshonitic volcanic rocks, aiming to offer some food to thoughts related to volcanism and mantle-crust interation induced by to the continental collision between India and Asia plates. Results showed that Cenozoic shoshonitic basalts from this area have relatively high and variable alkali contents (2.94%-8.23%), and are rich in potassium (average K2O/Na2O of 21 samples is 1.26). They are classified as shoshonitic basalts or basanite. They are enriched in both light rare earth elements (LREE) and large ion lithophile elements (LILE), and distribution patterns in the chondrite-normalized diagram and primitive-normalized spidergram collectively resemble the pattern of OIB. The shoshonitic basalts contain abundant mantle-derived xenoliths and xenocrysts, and are poorly crystallized with very low contents of phenocrysts, and have considerably high abundance of compatible elements such as Ni, implying that the Cenozoic basaltic rocks of Maguan area are representatives of primary magma derived from mantle sources. The relatively low Mg# of rocks, ranging from 0.49 to 0.72, can either be ascribed to the intrinsic characteristics of the source region or to the mixing of crust and mantle materials in the source region, which needs to be further studied. The Cenozoic shoshonitic basalts formed in a within-plate tectonic setting, the petrogenesis of which is related to the lateral extrusion of asthenospheric mantle along the southeastern of Tibetan plateau induced by the Indo-Asia collision.
2012, 37(3): 475-488.
doi: 10.3799/dqkx.2012.054
Abstract:
This paper presents whole-rock K-Ar dating results and geochemical data of the Late Mesozoic basalts in the Liaoyuan area, Jilin Province, and geochemical data of minerals from the entrained mantle xenoliths, with the aim of constraining the origin of the basalts and the nature of the Late Mesozoic lithosphere mantle. The whole-rock K-Ar dating results indicate that Liaoyuan basalts formed in the Late Cretaceous (91.7±1.7 Ma, 82.5±1.9 Ma, 99.3±1.6 Ma, 82.2±2.4 Ma). They have SiO2 = 45.1%-45.9%, Na2O+K2O= 4.50%-6.72%, and Mg# [100×Mg/(Mg+Fe2+)]=60-63, suggesting that they belong to the alkaline series. Liaoyuan basalts are enriched in light rare earth elements (LREEs), and depleted in heavy rare earth elements (HREEs) [(La/Yb)N=12.0-14.0], and have no Eu anomalies. Their trace element patterns are similar to that of OIB. The entrained peridotite xenoliths consist mainly of spinel lherzolites in which olivines have relatively low Mg# (87.1-91.2). The major and trace element data of the minerals from the xenoliths indicate that the Late Cretaceous lithosphere mantle beneath the Liaoyuan area be composed mainly of the juvenile one. The incompatible elements of clinopyroxenes from the peridotite xenoliths vary from the enrichment to the depletion, suggesting that the lithosphere mantle has experienced partial melting and fluid/melt metasomatism, and that the metasomatizing agents are mainly silicate melt and minor carbonate melt. The Late Cretaceous basalts in the Liaoyuan area were derived from partial melting of asthenospheric mantle. Combined with the studies on the regional geology, we conclude that the basalts formed under the back-arc extensional setting related to the subduction of the Paleo-Pacific plate.
This paper presents whole-rock K-Ar dating results and geochemical data of the Late Mesozoic basalts in the Liaoyuan area, Jilin Province, and geochemical data of minerals from the entrained mantle xenoliths, with the aim of constraining the origin of the basalts and the nature of the Late Mesozoic lithosphere mantle. The whole-rock K-Ar dating results indicate that Liaoyuan basalts formed in the Late Cretaceous (91.7±1.7 Ma, 82.5±1.9 Ma, 99.3±1.6 Ma, 82.2±2.4 Ma). They have SiO2 = 45.1%-45.9%, Na2O+K2O= 4.50%-6.72%, and Mg# [100×Mg/(Mg+Fe2+)]=60-63, suggesting that they belong to the alkaline series. Liaoyuan basalts are enriched in light rare earth elements (LREEs), and depleted in heavy rare earth elements (HREEs) [(La/Yb)N=12.0-14.0], and have no Eu anomalies. Their trace element patterns are similar to that of OIB. The entrained peridotite xenoliths consist mainly of spinel lherzolites in which olivines have relatively low Mg# (87.1-91.2). The major and trace element data of the minerals from the xenoliths indicate that the Late Cretaceous lithosphere mantle beneath the Liaoyuan area be composed mainly of the juvenile one. The incompatible elements of clinopyroxenes from the peridotite xenoliths vary from the enrichment to the depletion, suggesting that the lithosphere mantle has experienced partial melting and fluid/melt metasomatism, and that the metasomatizing agents are mainly silicate melt and minor carbonate melt. The Late Cretaceous basalts in the Liaoyuan area were derived from partial melting of asthenospheric mantle. Combined with the studies on the regional geology, we conclude that the basalts formed under the back-arc extensional setting related to the subduction of the Paleo-Pacific plate.
2012, 37(3): 489-500.
doi: 10.3799/dqkx.2012.055
Abstract:
Jiyuan basin is located in the north of Qinling orogen and regarded as a Triassic-Jurassic synorogenic basin. This paper presents a great number of detrital zircon U-Pb ages for synorogenic sediments in age ranging from the Middle Triassic to Middle Jurassic in the Jiyuan basin. The results show seven major age groups at 2.9-1.7 Ga, 1.6-1.0 Ga, 1.0-0.8 Ga, 800-650 Ma, 520-380 Ma, 350-245 Ma and ~220 Ma. It is obvious that age group of 2.9-1.7 Ga is directly derived from the Precambrian basement of North China Craton whereas other groups are typical characteristics of the Qinling orogenic belt. An important observation is that the Qinling-sourced detrital zircons become older from the Middle Triassic to the Early Jurassic sedimentary sequences, which is characterized by the main age clusters at 350-245 Ma occurring in the T2-T31 strata while age groups at 1.6-1.0 Ga, 1.0-0.8 Ga, 800-650 Ma and 520-380 Ma increase successively in the T32-J21 samples. In addition, little grains of age groups at 1.6-1.0 Ga, 520-380 Ma and ~220 Ma are presented in the J22 sample. The above-mentioned findings indicate that unroofing pattern of Qinling orogenic belt developed by the denudation of sendiments from young covers to old basements in order, then to the Carnian plutons. Integrated with the data reported from Hefei and Huangshi basins, it is well established that the intensity of unroofing increased from the west to the east in the Early Jurassic, and the denudation timing of the ultra high pressure (UHP)-high pressure (HP) rocks or Carnian plutons changed successively from the Early Jurassic in the east to the Middle Jurassic in the west.
Jiyuan basin is located in the north of Qinling orogen and regarded as a Triassic-Jurassic synorogenic basin. This paper presents a great number of detrital zircon U-Pb ages for synorogenic sediments in age ranging from the Middle Triassic to Middle Jurassic in the Jiyuan basin. The results show seven major age groups at 2.9-1.7 Ga, 1.6-1.0 Ga, 1.0-0.8 Ga, 800-650 Ma, 520-380 Ma, 350-245 Ma and ~220 Ma. It is obvious that age group of 2.9-1.7 Ga is directly derived from the Precambrian basement of North China Craton whereas other groups are typical characteristics of the Qinling orogenic belt. An important observation is that the Qinling-sourced detrital zircons become older from the Middle Triassic to the Early Jurassic sedimentary sequences, which is characterized by the main age clusters at 350-245 Ma occurring in the T2-T31 strata while age groups at 1.6-1.0 Ga, 1.0-0.8 Ga, 800-650 Ma and 520-380 Ma increase successively in the T32-J21 samples. In addition, little grains of age groups at 1.6-1.0 Ga, 520-380 Ma and ~220 Ma are presented in the J22 sample. The above-mentioned findings indicate that unroofing pattern of Qinling orogenic belt developed by the denudation of sendiments from young covers to old basements in order, then to the Carnian plutons. Integrated with the data reported from Hefei and Huangshi basins, it is well established that the intensity of unroofing increased from the west to the east in the Early Jurassic, and the denudation timing of the ultra high pressure (UHP)-high pressure (HP) rocks or Carnian plutons changed successively from the Early Jurassic in the east to the Middle Jurassic in the west.
2012, 37(3): 501-506.
doi: 10.3799/dqkx.2012.056
Abstract:
Pentlandite inclusion presenting perfect crystal form with hexagonal symmetry in a diamond from Liaoning of China was confirmed based on electron microprobe analysis data.X-ray diffraction peaks obtained from single crystal diffractometer with CCD area detector demonstrate that pentlandite has rhombohedral and cubic structures by the powder method indexing procedure distinction and computation. Unit cell parameters of rhombohedral structure are as follows: a＝0.690 62 nm, c＝1.720 95 nm, V＝0.710 85 nm3 (hexagonal); aR＝0.698 61 nm, α＝59.244 5°, and V＝0.236 95 nm3 (rhombohedral). The presence of rhombohedral phase in diamond inclusions reveals that the formation condition of the pentlandite in the mantle at ultrahigh-pressure and cubic phase is the results of phase transformation of the pentlandite inclusions in the atmospheric pressure since the diamond breaks.
Pentlandite inclusion presenting perfect crystal form with hexagonal symmetry in a diamond from Liaoning of China was confirmed based on electron microprobe analysis data.X-ray diffraction peaks obtained from single crystal diffractometer with CCD area detector demonstrate that pentlandite has rhombohedral and cubic structures by the powder method indexing procedure distinction and computation. Unit cell parameters of rhombohedral structure are as follows: a＝0.690 62 nm, c＝1.720 95 nm, V＝0.710 85 nm3 (hexagonal); aR＝0.698 61 nm, α＝59.244 5°, and V＝0.236 95 nm3 (rhombohedral). The presence of rhombohedral phase in diamond inclusions reveals that the formation condition of the pentlandite in the mantle at ultrahigh-pressure and cubic phase is the results of phase transformation of the pentlandite inclusions in the atmospheric pressure since the diamond breaks.
2012, 37(3): 507-514.
doi: 10.3799/dqkx.2012.057
Abstract:
Tibet chagele Copper-lead-zinc deposit is in the west end of those copper-polymetallic deposits found in Nyainqentanglha copper-lead-zinc-silver metallogenic belt, and there are two types of mineralization in the mining area, namely, copper-lead-zinc mineralization of the contact metasomatic filling and copper-molybdenum mineralization of porphyry. The zircon LA-ICP-MS U-Pb age and molybdenite Re-Os age show that two types of mineralization almost formed at the same time. The petrogenic age of the northern granite-porphyry related to copper-lead-zinc-silver mineralization is 62.1±1.1 Ma (MSWD=2.7), the southern granite-porphyry which is related to copper-molybdenum mineralization is 63.28±0.86 Ma (MSWD=3.2), and the molybdenite Re-Os age of the south is 61.49±0.60 Ma (MSWD=1.5), which formed at syn-collision stage after northward subduction of the Yarlung Zangbo oceanic basin. This study improves and enriches the time evolvement sequence and genesis of the collision metallogenic stage in Nyainqentanglha copper-lead-zinc-silver mineralization belt, and it also extends westwards its length by 200 km (Qingdu in Xietongmen-Chagele in Angren). As a result, it is found to be a huge copper-lead-zinc-silver metallogenic belt, extending in the direction of east-west more than 800 km, with deposits mainly formed in collection stage. In addition, this study provides important basis to the prospecting of the same deposits in the west of the belt.
Tibet chagele Copper-lead-zinc deposit is in the west end of those copper-polymetallic deposits found in Nyainqentanglha copper-lead-zinc-silver metallogenic belt, and there are two types of mineralization in the mining area, namely, copper-lead-zinc mineralization of the contact metasomatic filling and copper-molybdenum mineralization of porphyry. The zircon LA-ICP-MS U-Pb age and molybdenite Re-Os age show that two types of mineralization almost formed at the same time. The petrogenic age of the northern granite-porphyry related to copper-lead-zinc-silver mineralization is 62.1±1.1 Ma (MSWD=2.7), the southern granite-porphyry which is related to copper-molybdenum mineralization is 63.28±0.86 Ma (MSWD=3.2), and the molybdenite Re-Os age of the south is 61.49±0.60 Ma (MSWD=1.5), which formed at syn-collision stage after northward subduction of the Yarlung Zangbo oceanic basin. This study improves and enriches the time evolvement sequence and genesis of the collision metallogenic stage in Nyainqentanglha copper-lead-zinc-silver mineralization belt, and it also extends westwards its length by 200 km (Qingdu in Xietongmen-Chagele in Angren). As a result, it is found to be a huge copper-lead-zinc-silver metallogenic belt, extending in the direction of east-west more than 800 km, with deposits mainly formed in collection stage. In addition, this study provides important basis to the prospecting of the same deposits in the west of the belt.
2012, 37(3): 515-525.
doi: 10.3799/dqkx.2012.058
Abstract:
Xiongcun metallogenic district, one of the large-size metallogenic areas discovered along Gangdise metallogenic belt, is located in the middle of the southern margin of Gangdise orogenic belt. Its south margin is Shigatse forearc basin. The latest exploration data indicate that Xiongcun metallogenic district is composed of No. Ⅰ, Ⅱ and Ⅲ porphyry copper-gold orebodies. In this paper, Xiongcun orebody No.Ⅰ is taken as the research subject. The Re-Os model ages of molybdenit (4 samples) from Xiongcun orebody No.Ⅰ are similar, ranging from 160.1±2.3 Ma to 163.4±2.3 Ma; its isochron age is 161±11 Ma (MSWD=4.2) and error is big; its weight average age is 161.5±2.7 Ma (MSWD=2.0) and error is small. So ore forming age of Xiongcun orebody No. Ⅰ is (160.1±2.3)-(163.4±2.3) Ma and the most probability is 161.5±2.7 Ma. This age is similar to zircon U-Pb age (164.3±1.9 Ma) of mineralization porphyry (hornblende quartz diorite porphyry with big quartz eyes), so the ore forming age of Xiongcun orebody No.Ⅰ is Middle Jurassic. In addition, mineralized porphyry and tuff show geochemical characteristics similar to those of volcanic rocks in an arc or active continental margin, such as relative enrichment of LREE and LILE, depletion of HFEE, HFS and Eu anomalies. We conclude that northward subduction of Neo-Tethys resulted in mineralization of the Xiongcun orebody No.Ⅰ in the Middle Jurassic; the tectonic setting is the island-arc environment. The deposit type of Xiongcun orebody No.Ⅰ is island arc type porphyry copper-gold deposit.
Xiongcun metallogenic district, one of the large-size metallogenic areas discovered along Gangdise metallogenic belt, is located in the middle of the southern margin of Gangdise orogenic belt. Its south margin is Shigatse forearc basin. The latest exploration data indicate that Xiongcun metallogenic district is composed of No. Ⅰ, Ⅱ and Ⅲ porphyry copper-gold orebodies. In this paper, Xiongcun orebody No.Ⅰ is taken as the research subject. The Re-Os model ages of molybdenit (4 samples) from Xiongcun orebody No.Ⅰ are similar, ranging from 160.1±2.3 Ma to 163.4±2.3 Ma; its isochron age is 161±11 Ma (MSWD=4.2) and error is big; its weight average age is 161.5±2.7 Ma (MSWD=2.0) and error is small. So ore forming age of Xiongcun orebody No. Ⅰ is (160.1±2.3)-(163.4±2.3) Ma and the most probability is 161.5±2.7 Ma. This age is similar to zircon U-Pb age (164.3±1.9 Ma) of mineralization porphyry (hornblende quartz diorite porphyry with big quartz eyes), so the ore forming age of Xiongcun orebody No.Ⅰ is Middle Jurassic. In addition, mineralized porphyry and tuff show geochemical characteristics similar to those of volcanic rocks in an arc or active continental margin, such as relative enrichment of LREE and LILE, depletion of HFEE, HFS and Eu anomalies. We conclude that northward subduction of Neo-Tethys resulted in mineralization of the Xiongcun orebody No.Ⅰ in the Middle Jurassic; the tectonic setting is the island-arc environment. The deposit type of Xiongcun orebody No.Ⅰ is island arc type porphyry copper-gold deposit.
2012, 37(3): 526-534.
doi: 10.3799/dqkx.2012.059
Abstract:
Multicycle tectonic evolution controls the hydrocarbon-generation evolution, and causes variegated genesis of hydrocarbon fluid source in the multicycle superimposed basin. The temperature is the essential factor to hydrocarbon-generation evolution, and it could be reflected by burial depth of geologic body, so the control of tectonic deformation on hydrocarbon-generation evolution of hydrocarbon fluid source is mainly displayed by the burial history of geologic body. According to the tectonic evolution characteristics, there are four kinds of different deformation in Yangtze block, such as inversion of fault depression, inversion of fault block, thrusting and composite superimpose, then, the four patterns of tectonic evolution-burial history are also established about the marine strata in Meso-Cenozoic. Based on the response of hydrocarbon fluid source to the type of tectonic evolution-burial history, the study indicates that there are vestigal protogenic hydrocarbon and hydrocarbon generated secondly from kerogen in Lower Yangtze region and Jianghan fault depression of whose tectonic evolution-burial history is consuming exposure-fault depression burial, and vestigal protogenic hydrocarbon in the western Hunan-Hubei and Dahongshan area in Middle Yangtze region of which is consuming uplift-marine strata exposure, kerogen-cracking gas, oil-cracking gas and vestigal protogenic hydrocarbon in the thrust belts of Longmenshan and Dabashan of which is late low uplift-thrust burial, kerogen-cracking gas and oil-cracking gas in the northern Jiangnan uplift of which is consuming uplift-thrust burial, kerogen-cracking gas, oil-cracking gas and bitumen-cracking gas in Upper Yangtze region whose type of ones is durative burial-later uplift.
Multicycle tectonic evolution controls the hydrocarbon-generation evolution, and causes variegated genesis of hydrocarbon fluid source in the multicycle superimposed basin. The temperature is the essential factor to hydrocarbon-generation evolution, and it could be reflected by burial depth of geologic body, so the control of tectonic deformation on hydrocarbon-generation evolution of hydrocarbon fluid source is mainly displayed by the burial history of geologic body. According to the tectonic evolution characteristics, there are four kinds of different deformation in Yangtze block, such as inversion of fault depression, inversion of fault block, thrusting and composite superimpose, then, the four patterns of tectonic evolution-burial history are also established about the marine strata in Meso-Cenozoic. Based on the response of hydrocarbon fluid source to the type of tectonic evolution-burial history, the study indicates that there are vestigal protogenic hydrocarbon and hydrocarbon generated secondly from kerogen in Lower Yangtze region and Jianghan fault depression of whose tectonic evolution-burial history is consuming exposure-fault depression burial, and vestigal protogenic hydrocarbon in the western Hunan-Hubei and Dahongshan area in Middle Yangtze region of which is consuming uplift-marine strata exposure, kerogen-cracking gas, oil-cracking gas and vestigal protogenic hydrocarbon in the thrust belts of Longmenshan and Dabashan of which is late low uplift-thrust burial, kerogen-cracking gas and oil-cracking gas in the northern Jiangnan uplift of which is consuming uplift-thrust burial, kerogen-cracking gas, oil-cracking gas and bitumen-cracking gas in Upper Yangtze region whose type of ones is durative burial-later uplift.
2012, 37(3): 535-544.
doi: 10.3799/dqkx.2012.060
Abstract:
The concept of "high-quality source-rock-control hydrocarbon accumulation" is being accepted gradually by explorers since being put forward. No evaluation criteria based on solid evidences such as the definition of high-quality source rocks and its identification method have been brought forward so far. To tackle this issue, we have identified in this paper, by taking the Wuerxun sag in Hailaer basin as an example, the existence of high-quality source rocks and the lower limit for evaluation of high-quality source rocks, based on the inflection point on the relationship curve of hydrocarbon expulsion (which is calculated by the material balance principle) versus total organic carbon (TOC). The results show that when TOC is low, all source rocks have limited hydrocarbon expulsion, thus they cannot be high-quality source rocks. Nonetheless, when TOC rises to some threshold, hydrocarbon expulsion increases significantly with TOC. This inflection point should be the lower limit of high-quality source rocks: those with TOC greater than the inflection point value are high-quality source rocks. For the sake of simplicity and practicability, it is recommended based on the recognition of quantitative evaluation that TOC=2.0% is regarded as the lower limit of high-quality source rocks, although the lower limit of high-quality source rocks is also related to the type and maturity of the organic matters in the source rocks and so on. The application of such criteria in the research area indicates that the high-quality source rocks in K1n2 and K1n1 contribute 71% and 87% to the oil generated respectively, and 85% and 94% to the oil expelled respectively. The distribution of high-quality source rocks is also closely related to the distribution of hydrocarbon reservoirs in the region, demonstrating that high-quality source rocks control hydrocarbon accumulation.
The concept of "high-quality source-rock-control hydrocarbon accumulation" is being accepted gradually by explorers since being put forward. No evaluation criteria based on solid evidences such as the definition of high-quality source rocks and its identification method have been brought forward so far. To tackle this issue, we have identified in this paper, by taking the Wuerxun sag in Hailaer basin as an example, the existence of high-quality source rocks and the lower limit for evaluation of high-quality source rocks, based on the inflection point on the relationship curve of hydrocarbon expulsion (which is calculated by the material balance principle) versus total organic carbon (TOC). The results show that when TOC is low, all source rocks have limited hydrocarbon expulsion, thus they cannot be high-quality source rocks. Nonetheless, when TOC rises to some threshold, hydrocarbon expulsion increases significantly with TOC. This inflection point should be the lower limit of high-quality source rocks: those with TOC greater than the inflection point value are high-quality source rocks. For the sake of simplicity and practicability, it is recommended based on the recognition of quantitative evaluation that TOC=2.0% is regarded as the lower limit of high-quality source rocks, although the lower limit of high-quality source rocks is also related to the type and maturity of the organic matters in the source rocks and so on. The application of such criteria in the research area indicates that the high-quality source rocks in K1n2 and K1n1 contribute 71% and 87% to the oil generated respectively, and 85% and 94% to the oil expelled respectively. The distribution of high-quality source rocks is also closely related to the distribution of hydrocarbon reservoirs in the region, demonstrating that high-quality source rocks control hydrocarbon accumulation.
2012, 37(3): 545-555.
doi: 10.3799/dqkx.2012.061
Abstract:
The principle and method of high resolution sequence stratigraphy are employed to deal with seismic reflection profiles, well logs and core data. The sequence stratigraphic framework of post-rift inversion successions has been reconstructed in north of Songliao basin. According to the information of basin fillings, lacustrine level changes and regional tectonic evolution, the geological property and formation mechanism of sequence boundaries are analyzed. The sedimentary filling evolution model is built in post-rift inversion successions. The study indicates that both the 1st-order unconformity SB02 and the 2nd-order ones SB03/SB11 in post-rift inversion successions are responding surfaces to regional compression tectonic events. The styles of systems tracts in the 3rd-order sequences are controlled by lacustrine level changes and provenance supply. The 7 4th-order sequences identified in the second and third members of Nenjiang Formation formed under the conditions of enough provenance and low tectonic subsidence rate during the highstand systems tract of 3rd-order lacustrine level cycle. An important isochronous stratigraphic architecture has been provided for exploration of subtle reservoir in the middle-shallow layers in north of Songliao basin.
The principle and method of high resolution sequence stratigraphy are employed to deal with seismic reflection profiles, well logs and core data. The sequence stratigraphic framework of post-rift inversion successions has been reconstructed in north of Songliao basin. According to the information of basin fillings, lacustrine level changes and regional tectonic evolution, the geological property and formation mechanism of sequence boundaries are analyzed. The sedimentary filling evolution model is built in post-rift inversion successions. The study indicates that both the 1st-order unconformity SB02 and the 2nd-order ones SB03/SB11 in post-rift inversion successions are responding surfaces to regional compression tectonic events. The styles of systems tracts in the 3rd-order sequences are controlled by lacustrine level changes and provenance supply. The 7 4th-order sequences identified in the second and third members of Nenjiang Formation formed under the conditions of enough provenance and low tectonic subsidence rate during the highstand systems tract of 3rd-order lacustrine level cycle. An important isochronous stratigraphic architecture has been provided for exploration of subtle reservoir in the middle-shallow layers in north of Songliao basin.
2012, 37(3): 556-564.
doi: 10.3799/dqkx.2012.062
Abstract:
The Songliao basin evolved into the late down-warping stage, and shallow-water deltas had extensively developed in the third Member of Nenjiang Formation, Upper Cretaceous. In the third member of the Xinli area, three depositional cycles were identified to be evolved from shallow-lake subfacies to delta front subfacies respectively, indicating gradually shallowing lake. Accordingly, three sand-units of Ⅲ, Ⅱ and Ⅰ were divided from the bottom to top. Based on abundant data of dense wells, sedimentary facies maps and sandbodies structures of subaqueous distributary channel in each sand-units were analyzed in detail, and a series of changes accompanied with basin flattening and shallowing gradually were summed up as follows: deltas farther extended; subaqueous distributary channels more stabilized; single channel farther elongated; channels less bifurcated and converged; crevasse splay occurred more frequently; subaqueous interdistributary bays distributed more extensively. Consequently subaqueous distributary channel sandbodies less connected with each other and can be described as moderately thick sheet-shaped, narrow-thin strap-shaped to speckle-shaped, and wide-thick strap-shaped respectively, which resulted in oil pools styles transforming from tectonic reservoirs to lithologic reservoirs. Finally, corresponding to the three sand-units respectively, three depositional models were summarized to be reticular, ramiform and meandering river-liking.
The Songliao basin evolved into the late down-warping stage, and shallow-water deltas had extensively developed in the third Member of Nenjiang Formation, Upper Cretaceous. In the third member of the Xinli area, three depositional cycles were identified to be evolved from shallow-lake subfacies to delta front subfacies respectively, indicating gradually shallowing lake. Accordingly, three sand-units of Ⅲ, Ⅱ and Ⅰ were divided from the bottom to top. Based on abundant data of dense wells, sedimentary facies maps and sandbodies structures of subaqueous distributary channel in each sand-units were analyzed in detail, and a series of changes accompanied with basin flattening and shallowing gradually were summed up as follows: deltas farther extended; subaqueous distributary channels more stabilized; single channel farther elongated; channels less bifurcated and converged; crevasse splay occurred more frequently; subaqueous interdistributary bays distributed more extensively. Consequently subaqueous distributary channel sandbodies less connected with each other and can be described as moderately thick sheet-shaped, narrow-thin strap-shaped to speckle-shaped, and wide-thick strap-shaped respectively, which resulted in oil pools styles transforming from tectonic reservoirs to lithologic reservoirs. Finally, corresponding to the three sand-units respectively, three depositional models were summarized to be reticular, ramiform and meandering river-liking.
2012, 37(3): 565-572.
doi: 10.3799/dqkx.2012.063
Abstract:
Junggar basin is a large superposed basin in West China that experienced multi-stage tectonics. Preliminary study indicated that Jurassic reservoirs in the central part of Junggar basin experienced multi-stage hydrocarbon filling from multiple sources and late adjustment and reconstruction. The geologic and geochemical character of the Jurassic reservoir was investigated by integrating data of geology, drilling and geochemistry. The result indicates that reservoirs after reversing adjustment in Shawodi and Moxizhuang blocks located in the north limb of Che-Mo paleo-uplift are usually scattered in a small scale and their type is usually transforming from structural reservoir into stratigraphic/lithologic hydrocarbon reservoir, and have extremely complex oil-water contact or gas-water contact, low porosity and permeability, low oil saturation and resistivity, but heavier oil density and greater viscosity; the paleo oil-gas-water contact determined by grain-containing-oil inclusion (GOI) analysis is lower than the present, and there is a high content of soluble organic matters (i.e. non-hydrocarbon and asphaltine) in present water layers. However, the reservoir which experienced synthetic adjustment in Yongjin block located in the south limb of Che-Mo paleo-uplift has higher paleo oil-water contact verified by GOI value than the present, and paleo oil column is lower than the present. It means that the reservoir scale is expanding.
Junggar basin is a large superposed basin in West China that experienced multi-stage tectonics. Preliminary study indicated that Jurassic reservoirs in the central part of Junggar basin experienced multi-stage hydrocarbon filling from multiple sources and late adjustment and reconstruction. The geologic and geochemical character of the Jurassic reservoir was investigated by integrating data of geology, drilling and geochemistry. The result indicates that reservoirs after reversing adjustment in Shawodi and Moxizhuang blocks located in the north limb of Che-Mo paleo-uplift are usually scattered in a small scale and their type is usually transforming from structural reservoir into stratigraphic/lithologic hydrocarbon reservoir, and have extremely complex oil-water contact or gas-water contact, low porosity and permeability, low oil saturation and resistivity, but heavier oil density and greater viscosity; the paleo oil-gas-water contact determined by grain-containing-oil inclusion (GOI) analysis is lower than the present, and there is a high content of soluble organic matters (i.e. non-hydrocarbon and asphaltine) in present water layers. However, the reservoir which experienced synthetic adjustment in Yongjin block located in the south limb of Che-Mo paleo-uplift has higher paleo oil-water contact verified by GOI value than the present, and paleo oil column is lower than the present. It means that the reservoir scale is expanding.
2012, 37(3): 573-579.
doi: 10.3799/dqkx.2012.064
Abstract:
Based on the measured data of Late Permian coal-bearing strata in western Guizhou Province, the sedimentary controlling factor of "unattached multiple superimposed coalbed-methane system" formation is preliminarily discussed in this paper. It shows that the depositional conditions of coal-bearing strata have laid the material physical properties foundation for "unattached multiple superimposed coalbed-methane system". The characteristics of sequence stratigraphic framework limit gas connectivity between gas units. The siderite mudstone with low-permeability, which is distributed near the maximum flooding surface, makes the vertical sub-strata of gas between the gas-bearing units relatively independent. There is correlation between coalbed methane contents and the sea level. Coalbed methane contents near to the maximum flooding surface are relatively low. The interface can be regarded as a stand-alone boundary for gas-forming units in the coalbed-methane system. The sequence boundary connects the gas units, making the coal seams near to sequence boundary with the similar gas bearing characteristics.
Based on the measured data of Late Permian coal-bearing strata in western Guizhou Province, the sedimentary controlling factor of "unattached multiple superimposed coalbed-methane system" formation is preliminarily discussed in this paper. It shows that the depositional conditions of coal-bearing strata have laid the material physical properties foundation for "unattached multiple superimposed coalbed-methane system". The characteristics of sequence stratigraphic framework limit gas connectivity between gas units. The siderite mudstone with low-permeability, which is distributed near the maximum flooding surface, makes the vertical sub-strata of gas between the gas-bearing units relatively independent. There is correlation between coalbed methane contents and the sea level. Coalbed methane contents near to the maximum flooding surface are relatively low. The interface can be regarded as a stand-alone boundary for gas-forming units in the coalbed-methane system. The sequence boundary connects the gas units, making the coal seams near to sequence boundary with the similar gas bearing characteristics.
2012, 37(3): 580-586.
doi: 10.3799/dqkx.2012.065
Abstract:
Fluorescence intensity of organic inclusion, especially petroleum inclusions, is an effective means to identify organic inclusions and indicate oil mature of petroleum inclusions. Based on fluorescence of petroleum, using fluorescence spectrum analysis method, oil and gas charging period could be studied by analyzing main peak value (λmax), fluorescence intensity (Imax) and fluorescence spectrum Q quotient. Thirty-eight samples coming from Yijianfang-Yingshan Formation of North Tarim have been studied through polarizing optical microscopy and fluorescence microscopy, etc. Through fluorescence color, microscopical spectrum figure and fluorescence spectrum Q quotient, three kinds of petroleum inclusions have been divided and they show three fluorescence: their color are yellow-green, green and blue-white, these syngenetic brine inclusions temperatures are 56.5, 88.3, 130.1 ℃ respectively. According to earth chemistry methods and main parameters, such as fluorescence intensity, fluorescence spectrum Q quotient and syngenetic brine inclusions temperatures, it is concluded that there are at least three periods oil and gas chargings coming from two different source rock in reservoir in study area, and they showed reservoir features with multi-source and multi-period hydrocarbon-charging.
Fluorescence intensity of organic inclusion, especially petroleum inclusions, is an effective means to identify organic inclusions and indicate oil mature of petroleum inclusions. Based on fluorescence of petroleum, using fluorescence spectrum analysis method, oil and gas charging period could be studied by analyzing main peak value (λmax), fluorescence intensity (Imax) and fluorescence spectrum Q quotient. Thirty-eight samples coming from Yijianfang-Yingshan Formation of North Tarim have been studied through polarizing optical microscopy and fluorescence microscopy, etc. Through fluorescence color, microscopical spectrum figure and fluorescence spectrum Q quotient, three kinds of petroleum inclusions have been divided and they show three fluorescence: their color are yellow-green, green and blue-white, these syngenetic brine inclusions temperatures are 56.5, 88.3, 130.1 ℃ respectively. According to earth chemistry methods and main parameters, such as fluorescence intensity, fluorescence spectrum Q quotient and syngenetic brine inclusions temperatures, it is concluded that there are at least three periods oil and gas chargings coming from two different source rock in reservoir in study area, and they showed reservoir features with multi-source and multi-period hydrocarbon-charging.
2012, 37(3): 587-592.
doi: 10.3799/dqkx.2012.066
Abstract:
Google Map or other remote sensing image publication systems can only publish three-band color image. As a result, users can only see combined three-band image information without access to information of other bands combined. Different from the Google Map, the method proposed in this paper implements the combination of multi-band remote sensing image, displaying and roaming in the browser site by using HTML5 technology. It can ensure that users see information of different bands combination and save a large amount of disk space at server site.
Google Map or other remote sensing image publication systems can only publish three-band color image. As a result, users can only see combined three-band image information without access to information of other bands combined. Different from the Google Map, the method proposed in this paper implements the combination of multi-band remote sensing image, displaying and roaming in the browser site by using HTML5 technology. It can ensure that users see information of different bands combination and save a large amount of disk space at server site.
2012, 37(3): 593-597.
doi: 10.3799/dqkx.2012.067
Abstract:
AVO analysis has been successful with many cases in hydrocarbon detection in Tertiary turbidite reservoir in Angola deep water region. But there were some failed drilling cases relying on prospects from AVO study. Therefore, data oriented approach is proposed based on intensive analysis of seismic data, subtle rock physics study and forward modeling in order to improve hydrocarbon detection.
AVO analysis has been successful with many cases in hydrocarbon detection in Tertiary turbidite reservoir in Angola deep water region. But there were some failed drilling cases relying on prospects from AVO study. Therefore, data oriented approach is proposed based on intensive analysis of seismic data, subtle rock physics study and forward modeling in order to improve hydrocarbon detection.
2012, 37(3): 598-604.
doi: 10.3799/dqkx.2012.068
Abstract:
For the strata with features of extreme hardness, strong abrasiveness, high frequency of interbedding, with quartz and gravel interlayer, PDC bit is barely to be employed as a result of low ROP and service life, embodied as fast wear of working layer, easily breaking of diamond compact, etc. The roller bit is not suit for this kind of strata either, and drilling accident might be caused by losing teeth. To solve this problem, the pulsing impregnated petroleum bit with low-temperature electroplating is developed, and numerical simulation is employed for the hydraulic performance of bit flow field. Field applications show that this kind of new bit enjoys the advantage of long service life and high ROP.
For the strata with features of extreme hardness, strong abrasiveness, high frequency of interbedding, with quartz and gravel interlayer, PDC bit is barely to be employed as a result of low ROP and service life, embodied as fast wear of working layer, easily breaking of diamond compact, etc. The roller bit is not suit for this kind of strata either, and drilling accident might be caused by losing teeth. To solve this problem, the pulsing impregnated petroleum bit with low-temperature electroplating is developed, and numerical simulation is employed for the hydraulic performance of bit flow field. Field applications show that this kind of new bit enjoys the advantage of long service life and high ROP.
2012, 37(3): 605-611.
doi: 10.3799/dqkx.2012.069
Abstract:
3D fluorescent spectra analysis was conducted to understand the characteristics of dissolved organic matter (DOM) from soil of unsaturated zone and its potential influence on arsenic transport into groundwater. The results show that the humic-like component is the major constituent of DOM. The decrease in fluorescence intensity with depth is attributed to the reduction in aromatic functional groups. The irregular variation of the intensity in localized depth indicates the changes in DOM components or its major functional groups on soil section. Fluorescence information of DOM can be specifically decomposed by PARAFAC into four components, which are respectively similar to microbial reduced quinones, microbial oxidized quinones, terrestrial fulvic acid and so on. It is suggested that arsenic may be complexed by humic-DOMs and migrate with them into groundwater and the mobilization of arsenic also can be associated with the microbial quinones. Thus, 3D fluorescent spectra have been demonstrated to be a convenient and effective tool in DOM characterization and facilitate further study on effects on arsenic mobilization.
3D fluorescent spectra analysis was conducted to understand the characteristics of dissolved organic matter (DOM) from soil of unsaturated zone and its potential influence on arsenic transport into groundwater. The results show that the humic-like component is the major constituent of DOM. The decrease in fluorescence intensity with depth is attributed to the reduction in aromatic functional groups. The irregular variation of the intensity in localized depth indicates the changes in DOM components or its major functional groups on soil section. Fluorescence information of DOM can be specifically decomposed by PARAFAC into four components, which are respectively similar to microbial reduced quinones, microbial oxidized quinones, terrestrial fulvic acid and so on. It is suggested that arsenic may be complexed by humic-DOMs and migrate with them into groundwater and the mobilization of arsenic also can be associated with the microbial quinones. Thus, 3D fluorescent spectra have been demonstrated to be a convenient and effective tool in DOM characterization and facilitate further study on effects on arsenic mobilization.
2012, 37(3): 612-620.
doi: 10.3799/dqkx.2012.070
Abstract:
The low-penetrability aquifer plays an important role in hydrogeology and engineering geology activities, including groundwater exploitation, porewater release from aquitard, migration and transformation of pollutants, and reposition of high radioactive waste. For understanding the low-penetrability aquifer, it's important to investigate the evolution of pore water. In this paper, pore water was extracted by mechanical squeeze in a bore of Caofeidian with a depth of 0-100 m. The analysis of porewater indicates that the pore water is alkaline, and the total dissolved solid is between 7.26 and 26.89 g/L, decreasing with depth; and Cl/Br in continental sediment tends to infinity, while that in marine sediment is 279-280. It can be concluded that the pore water is sedimentary water revealing the freshwater and seawater characteristics in continental and marine sediment respectively with no clear signs of modern seawater intrusion. The trend of Cl-, Na+ is dominated by evaporation; SO42- is controlled both by sulfate reduction and gypsum dissolution; cation exchange and adsorption mainly influence Ca2+, K+ and Na+. The reconstruction of Late Pleistocene temperature is 5.21-5.81 ℃ using δ18O, with much higher temperatures calculated by shallow data within 40 m attributed to mixing and diffusion of modern pore water.
The low-penetrability aquifer plays an important role in hydrogeology and engineering geology activities, including groundwater exploitation, porewater release from aquitard, migration and transformation of pollutants, and reposition of high radioactive waste. For understanding the low-penetrability aquifer, it's important to investigate the evolution of pore water. In this paper, pore water was extracted by mechanical squeeze in a bore of Caofeidian with a depth of 0-100 m. The analysis of porewater indicates that the pore water is alkaline, and the total dissolved solid is between 7.26 and 26.89 g/L, decreasing with depth; and Cl/Br in continental sediment tends to infinity, while that in marine sediment is 279-280. It can be concluded that the pore water is sedimentary water revealing the freshwater and seawater characteristics in continental and marine sediment respectively with no clear signs of modern seawater intrusion. The trend of Cl-, Na+ is dominated by evaporation; SO42- is controlled both by sulfate reduction and gypsum dissolution; cation exchange and adsorption mainly influence Ca2+, K+ and Na+. The reconstruction of Late Pleistocene temperature is 5.21-5.81 ℃ using δ18O, with much higher temperatures calculated by shallow data within 40 m attributed to mixing and diffusion of modern pore water.
2012, 37(3): 621-626.
doi: 10.3799/dqkx.2012.071
Abstract:
This study investigates the adsorption behavior of organochlorine pesticides DDTs (p, p'-DDT, p, p'-DDE and p, p'-DDD) onto organo-diatomite (OD), which was modified by Cetyltrimethylammonium Bromide (CTMAB). The strengthen mechanisms and optimization design of the adsorption process are also discussed. The results show that the cationic surfactant could change the Zeta potential, BET surface area and hydrophobic characteristics of diatomite, which lead to the better adsorption efficiency of DDTs. The adsorption efficiency of the three DDTs onto OD follows the order of p, p'-DDT > p, p'-DDE > p, p'-DDD. According to the value of R2, it can be concluded that the Redlich-Peterson model fit best for the adsorption data.
This study investigates the adsorption behavior of organochlorine pesticides DDTs (p, p'-DDT, p, p'-DDE and p, p'-DDD) onto organo-diatomite (OD), which was modified by Cetyltrimethylammonium Bromide (CTMAB). The strengthen mechanisms and optimization design of the adsorption process are also discussed. The results show that the cationic surfactant could change the Zeta potential, BET surface area and hydrophobic characteristics of diatomite, which lead to the better adsorption efficiency of DDTs. The adsorption efficiency of the three DDTs onto OD follows the order of p, p'-DDT > p, p'-DDE > p, p'-DDD. According to the value of R2, it can be concluded that the Redlich-Peterson model fit best for the adsorption data.
