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Sun W.,Chengdu Center | Chen M.,Chengdu Center | Zeng S.-Q.,Chengdu Center | Zeng S.-Q.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources
Geological Bulletin of China | Year: 2013

The Lower part of Suowa Formation in the north Qiangtang depression of Tibet has been correlated to the Late Jurassic. However, dating evidence of the upper part of the formation remains insufficient. Three reefal units from Suowa Formation in Bandaohu area are gende morphologically and composed of corals and stromatoporoids frameworks. The community structures show that benthic metazoanl taxa are mainly of Pachythecopora pachytheca Deng, Actinostromaria motianlingensis Dong et Wang and Spon-giomorpha robusta Yang et Wang, and subordinately of Latusastraea xigazeensis Liao et Xia, Preverastraea sp., Ptychochaetes cf glo-bosus Koechlin and Spongiomorpha asiatica xainzaensis Deng. The pollen assemblages marked by Dicheiropollis etruscus from the upper part of the Suowa Formation are initial elements of the Early Cretaceous in the surrounding areas of the Tethys. Moreover, Senegalosporites and Steevesipollenites have never been recorded from horizons in advance of the Cretaceous, and they are common in the pollen assemblages of the late Early Cretaceous and even later. Therefore, coral and pollen assemblages indicate that the main part of the Suowa Formation is correlated to the Upper Jurassic, and the upper part of the formation is reasonably assigned to the Lower Cretaceous.


Du Q.,Chengdu Institute of Geology and Mineral Resources | Du Q.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources | Wang Z.,Chengdu Institute of Geology and Mineral Resources | Wang Z.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources | And 7 more authors.
Precambrian Research | Year: 2013

The Yangtze Block is an important component in reconstructing the Proterozoic tectonic evolution of South China within the Rodinia supercontinent. The geochronology and paleoenvironment of the Liantuo Formation in the Yangtze Block are still highly controversial. An integrated approach of facies analysis, paleogeography and geochronology provides new insights into understanding the sedimentology and paleogeography of the formation. Here, results are presented from a detailed U-Pb zircon examination of geochronology and paleoenvironment of the Liantuo Formation in the Yangtze Block. The formation was deposited in the period of ca. 790-730. Ma, which coeval with the development of the Wuqiangxi Formation in the middle-upper part of the Banxi Group. The top of the Liantuo Formation gives a U-Pb age of 736. ±. 5.8. Ma, which signifies an onset time of the Sturtian glaciation as ca. ≤730. Ma. The zircon U-Pb ages reveal magmatic events that were correlated with Neoproterozoic continental growth indicating that the Rodinia initiated rifting occurred at ca. 824. Ma and extensive rift-related magmatism took place at ca. 780. Ma in the northern Yangtze Block. Moreover, these results provide geochronological and petrologic evidence that confirms the stratigraphic framework of the Nanhuan System, thereby promoting a better understanding of the Neoproterozoic tectonic development of South China. © 2013 Elsevier B.V.


Wang Z.,Chengdu Institute of Geology and Mineral Resources | Wang Z.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources | Wang J.,Chengdu Institute of Geology and Mineral Resources | Wang J.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources | And 8 more authors.
Journal of Asian Earth Sciences | Year: 2013

Although some Archean zircons (xenocrysts) have been reported in various places in the South China, Archean outcrops within the Yangtze Block have been spotted only in the Kongling terrain. Recently, the findings of a Neoarchean K-granite pluton emplaced within the Yangpo Group have opened a new window to study the formation and evolution of the Yangtze Block. We conducted a combined study of zircon U-Pb and whole-rock major and trace elements for seven quartz schist and two granite samples from the Yangpo Group in the Huji region, South China. It is another Archean outcrop in the Yangtze Block except for the Kongling terrain. Results of LA-ICP-MS dating for the detrital zircons from the quartz schist of the Yangpo Group indicate two age groups originating from two significant magmatic events at ~2.8Ga and ~3.05Ga, as well as the ~2.9Ga and ~3.2-3.3Ga magmatism identified in a previous study. The quartz schists of the Yangpo Group show high SiO2 content and K2O/Na2O ratios, and low TiO2, Fe2O3, and MgO contents. Two granitic samples from the Yaozishan pluton display relatively high SiO2 and high alkali contents, low MgO, TiO2, and P2O5 content, and high A/KNC ratios (1.21-1.31), exhibiting an aluminous feature. At the same time, the two samples show positive anomalies of HFSE (Zr, Hf, Y) and LILE (Rb, U, Th, La), and high Rb/Sr and 104×Ga/Al ratios. These geochemical observations are typical of A-type granites. The LA-ICP-MS dating results of the Jinshan and Yaozishan Granitic plutons further confirm the within-plate rifting and A-type granite emplacing event at ~2.65Ga. Compared with the Jinshan A-type granite, the Yaozishan A-type granite has a distinct feature of abnormally high 104Ga/Al ratios (6.19-6.23) and lower zirconium saturation temperature (772-778°C), which indicates that the Yaozishan A-type granite emplacing at ~2673Ma be associated with an early episode of the plate rifting event in the middle Neoarchean. These results suggest that the Yangpo Group be developed from ~2.8Ga to ~2.7Ga, as filling sequence of a passive continental margin or intracratonic basin. Thus, our study reveals for the first time that the preliminary cratonization of the Central Yangtze Block ended ~2.8Ga followed by the filling of the craton basin, plate collision at ~2.7Ga, and post-collision rifting at ~2.65Ga. © 2013 Elsevier Ltd.


Peng Q.,Chengdu Institute of Geology and Mineral Resources | Peng Q.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources | Du B.,Chengdu Institute of Geology and Mineral Resources | Du B.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources
Xinan Shiyou Daxue Xuebao/Journal of Southwest Petroleum University | Year: 2013

Shale gas, as a clean energy of great prospects, has become the research hotspot in petroleum geology field, recently. Shale gas exploration of Qiangtang Basin, where several high quality mud-shale source rocks developed, is still in initial stage. Through the analysis of key geological parameters of domestic and international main shale gas basins in exploration and development, we sum up the evaluation standard of favorable shale gas exploration targets. Based on the comprehensive evaluation of the main mud-shale hydrocarbon source rock thickness, organic matter maturity, organic matter type, organic carbon content of Qiangtang Basin, we discover that in Qiangtang Basin, two sets of favorable shale gas exploration layer developed: mud-shale layer of the upper Triassic, mud-shale layer of lower Jurassic Quse Formation. And we select five favorable shale gas areas: Zangxiahe favorable area, Woruoshan favorable area, Tumengela favorable area, Biluocuo favorable area, Mugouriwang favorable area.


Fu X.,Chengdu Institute of Geology and Mineral Resources | Fu X.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources | Wang J.,Chengdu Institute of Geology and Mineral Resources | Wang J.,Key Laboratory for Sedimentary Basin and Oil and Gas Resources | And 4 more authors.
International Journal of Coal Geology | Year: 2013

The Tumen coal mine has the largest coal resources in Tibet, which have been developed and utilized as an important energy source in the last decades. It has raised some health problems during the coal exploration and utilization in Tibet. Fifty Late Triassic coal (or coaly) samples were picked up from the Qiangtang Basin (Tumen mine, Woruoshan and Hongshuihe areas) to determine the minerals, potentially hazardous elements and their mode of occurrence and possible sources. Coal samples from the Qiangtang Basin have medium- and high-ash yields (15.20-47.88%) with low or medium-high total sulfur content (0.04-4.86%). Minerals in Qiangtang Basin coal include clay minerals, dolomite, quartz, pyrite, siderite, and hematite, and trace amounts of halite, feldspar, anhydrite, barite, chromite, and galena. Potentially hazardous trace elements in coal samples include As, Hg, Pb, and Se. Arsenic is controlled mainly by aluminosilicate minerals. Mercury occurs mainly as an organic-bound form. The organically bound Pb is dominant. Selenium is controlled mainly by Fe-bearing (probably pyrite). A proportion of the elevated concentrations of As, Hg, Pb and Se in Qiangtang Basin coal may be related to underlying shale bed. These elements might have been eroded or leached from the shale bed, which were subsequently transported and accumulated syngenetically in the coal-forming peat swamps. The enrichment of As, Hg, Pb, and Se in Qiangtang Basin coal, however, is also partly to be related to magmatic/hydrothermal fluids. © 2013 Elsevier B.V.

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