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Wang P.,China University of Geosdences | Wang P.,Beijing Huaxia Jianlong Mining Science and Technology Co.
Geology in China

The Sishanling iron deposit is located in the northern margin of North China platform and geographically lies in Benfen area, Liaoning Province. The ores are composed of magnetite and hematite and controlled by Anben Formation of Achean Cigou Group, the sedimentary facies is of the oxide - silicate phase. Through the study of element geochemistry of the main minerals, ores and wall rocks, the authors have obtained some useful information: Metamorphic faciès has reached low amphibolite facies, and the BIF can be classified as mafic volcanic - muddy sandstone - ferrosilicic sedimentary formation. The metamorphic volcanic rocks are characterized by oceanic tholeiite. The shale-normalized REE patterns of the ores display depletion of light REE relative to heavy REE, high ratios of Y/Ho and distinct positive anomalies of La, Y. Eu shows stronger positive anomalies in comparison with the other main BIFs in North China platform. The geochemical information of the BIF shows that the ore-forming elements came from the mixed solution of volcanic-hydrothermal solution and sea water, and that the hydrothermal solution was related to the mantle material. Source

Meng F.,China University of Geosdences | Mao J.-W.,Chinese Academy of Geological Sciences | Ye H.-S.,Chinese Academy of Geological Sciences | Zhou K.,Geological Society of China | And 2 more authors.
Geology in China

The Laojunshan Intrusion is situated in northern Qinling orogenic belt, which is located in southern Heigou-Luanchuan faulted zone in the Qinling orogenic belt. Based on the contact relationship, the evolution of the intrusion can be divided from early to late into three stages, i.e., small-porphyry fine-medium-grained biotite monzonitic granite, mid-porphyry medium-coarse grained biotite monzonitic granite and big-porphyry medium-coarse grained biotite monzonitic granite. They are characterized by concentric zoning. All the three stages of granites have similar niineralogical and geochemical characteristics. They are composed of potash feldspar, plagioclase, biotite and quartz, but there are obvious differences in the rock texture. They are characterized by high Si (>70%) and alkali (8.28-9.53%) and low Ca (0.68%-2.42%) . They also have relatively high Ba, Sr, Nb, Zr, Th and Rb concentrations and comparatively low Co, Ni, Cr, V and Sc concentrations, belonging to I-type granite. The SHRIMP U-Pb zircon dating of the second and third stage rocks yielded ages of 111 ±1Ma (MSWD =0.41) and 108±1Ma (MSWD =0.39) respectively, suggesting Late Mesozoic. It is inferred that the Laojunshan Intrusion resulted from large-scale late Mesozoic magmatism in eastern China. Source

Zhou S.-Y.,China University of Geosdences | Zhou S.-Y.,Sinopec | Ma Y.,China University of Geosdences
Geology in China

The northern part of the Pre-Caspian Basin of Kazakhstan is rich in oil and gas, in which 39 oil and gas fields have been found. Lower Carboniferous and lower Permian strata constitute important oil and gas producing horizons. Recent exploration indicates that there exist lots of beach facies limestones of Middle Carboniferous Bashkirian stage, suggesting that the Middle Carboniferous strata may become a new exploration target. Based on the exploration data, this paper has made a detailed description of macroscopic and microscopic features of Bashkirian beach facies limestones, which will provide an important clue to future oil and gas exploration. Source

Zhang Y.-F.,China University of Geosdences | Jiang J.-W.,Petrochina
Geology in China

Plant fossils of 38 species in 22 genera in Middle Jurassic were collected from Lower Yaopo Formation, Upper Yaopo Formation and Longmen Formation on the southern slope of the Jiulong Hill in Mentougou district, Beijing. Statistical data show that the Middle Jurassic flora of the Western Hills in Beijing is dominated by Filicopsida (27.6%), Cycadopsida (25%)and Ginkgopsida (25%), among which Coniopteris with 5 species and Cladophlebis with 17 species were found. The Nearest Living Relatives Method and morphologic features analysis were used to analyze palaeoclimate. The result indicates that the nearest living relative plants of dominant fossils are Osmundaceae, Dicksoniaceae and Cycadopsida, which mainly live in a humid-warm tropical or subtropical climate, and warm-humid climate is also identified from the diversity of Cladophlebis, large feathery compound leaves of Cycadopsida and coarse stems of Equisetales, etc. Consequendy, the Middle Jurassic flora in the Western Hills of Beijing reflects a humid-warm subtropical climate. In addition, the climate had changed into drier and warmer according to the species and the quantity reduction of plant fossils from the Lower Yaopo Formation through Upper Yaopo Formation to Longmen Formation. Source

He J.Y.,China University of Geosdences | He J.Y.,Petrochina | Jia C.Z.,Petrochina | Wu G.H.,Petrochina | Xu B.,Peking University
Acta Petrologica Sinica

Study on several Sinian outcrop sections in Aksu area indicates that unconformity, large cave collapse breccias, solutio: caves, solution pores, solution fissures and grooves should be the identifying features of Sinian paleo-karstification. Horizone-phreati zone and deep-slow-flowing zone are the main parts of the karst vertical zonation. Large cave congeries and honeycomb formation cave are significant evidences of horizone-phreatic zone. The characteristic of deep-slow-flowing zone is isolated caves which are alway associated with the fractures. The paleo-karst model of Sinian is higher-phreatic gentle-slope paleo-karst. Source

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