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Timing the termination of the Doushantuo negative carbon isotope excursion: evidence from U-Pb ages from the Dengying and Liuchapo formations,South China

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Science Bulletin 2018年第21期63卷 1431-1438页

作者： Mingzhong Zhou Taiyi Luo Warren D.Huff Zhiqing Yang Guanghong Zhou Tian Gan Hua Yang Di Zhang School of Geographical and Environmental Sciences Guizhou Normal University State Key Laboratory of Ore Deposit Geochemistry Institute of Geochemistry Chinese Academy of Sciences Department of Geology University of Cincinnati Beijing SHRIMP Center Chinese Academy of Geological Sciences School of Geography and Tourism Guizhou Education University College of Earth Sciences University of Chinese Academy of Sciences

The Doushantuo negative carbon isotope excursion(DOUNCE) is the largest known marine inorganic carbon isotope anomaly. The origin of this pronounced negative excursion is still an enigmatic issue that attracts geologists. Time constraints on the excursion are the critical information that would provide insight into its genesis. In previous decades, the timing of its termination has been constrained by the widely cited zircon U-Pb age of 550.5 ± 0.8 Ma for the tuff at the top of the Miaohe Member at the Jiuqunao section in the Yangtze Gorges area, South China. However, results of recent studies indicate that the reliability of this time constraint needs to be re-evaluated. Here, a geochronological study was carried out using two K-bentonites from Fanglong in South China. A K-bentonite in the lower Dengying Formation yielded a U-Pb age of 557 ± 3 Ma, while a K-bentonite in the basal Liuchapo Formation yielded an age of 550 ± 3 Ma. Based on regional correlations between the Ediacaran successions in South China,the age(557 ± 3 Ma) for the K-bentonite in the lower Dengying Formation may serve as a second critical timing constraint for the ending of the DOUNCE. Combined with available estimates of the DOUNCE duration, our new data indicate that the DOUNCE has a maximum onset age ～570 Ma.

关键词： Doushantuo formation Dengying formation Shuram carbon isotope excursion South China

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Paired δ^13Ccarb-δ^13Corg Evolution of the Dengying Formation from Northeastern Guizhou and Implications for Stratigraphic Correlation and the Late Ediacaran Carbon Cycle

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Journal of Earth Science 2020年第2期31卷 342-353页

作者： Yi Ding Daizhao Chen Xiqiang Zhou Taiyu Huang Chuan Guo Rumana Yeasmin Key Laboratory of Petroleum Resources Research Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China Institution of Earth Science Chinese Academy of SciencesBeijing 100029China University of Chinese Academy of Sciences Beijing 100049China Hunan Provincial Key Laboratory of Shale Gas Resource Utilization Hunan University of Science and TechnologyXiangtan 411201China Department of Geological Sciences Jahangirnagar UniversitySavar Dhaka 1342Bangladesh

This study provides δ^13C profiles from a lower-slope(Well ZK102)to basin(Bahuang Section)environment to better understand the temporal and spatial variability in δ^13Ccarb-δ^13Corg of the Yangtze Block during the Late Ediacaran.Our new δ^13C profiles together with the reported data suggest that the Upper Ediacaran successions from different depositional environments are generally bounded by negative δ^13Ccarb and/or δ^13Corg excursions in the underlying and overlying strata.Moreover,the Upper Ediacaran δ^13Ccarb profiles generally can be subdivided into two positive excursions and an interjacent negative excursion,whereas the paired δ^13Corg profiles from different depositional environments have individual variation trends.On the other hand,these data show a large surface-to-deep waterδ^13C gradient(~5‰variation in δ^13Ccarb,>10‰variation in δ^13Corg)which can be reasonably explained by the heterogeneity of the biological activities in the redox-stratified water column.Furthermore,the decoupled δ^13Ccarb-δ^13Corg pattern with large δ^13Corg perturbations at the lower slope precluded the existence of a large dissolved organic carbon reservoir at the Yangtze Block during the Late Ediacaran.Thus,the high δ^13Ccarb values in the Upper Ediacaran succession could be balanced by large amounts of buried organic carbon likely associated with high productivity.

关键词： Yangtze Block Late Ediacaran Dengying Formation pairedδ^13Ccarb-δ^13Corg stratigraphic correlation carbon cycle

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Analysis of the Oldest Carbonate Gas Reservoir in China——New Geological Significance of the Dengying Gas Reservoir in the Weiyuan Structure, Sichuan Basin

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Journal of Earth Science 2019年第2期30卷 348-366页

作者： Xiao Liang Shugen Liu Shubei Wang Bin Deng Siyu Zhou Wenxin Ma State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Chengdu University of Technology Institute of Geological Exploration and Development of CNPC Chuanqing Drilling Engineering Research Institute of Petroleum Exploration and Development Petro China Southwest Oil&Gas Field Company BGP Inc. China National Petroleum Corporation

The Weiyuan Structure is the largest surface structure in the Sichuan Basin. However, the abundance of the Dengying Formation gas reservoir in the Weiyuan Structure is low. The height of the gas column is 244 m, but the integrated abundance is only 26.4%. After nearly 40 years of exploration, the Gaoshi1 Well and Moxi8 Well yielded gas flows that marked an important exploration success after the discovery of the Sinian Dengying Formation gas reservoir in the Weiyuan Structure, Sichuan Basin, Lower-Paleozoic in 1964. Combined with research examples of oil and gas migration and gas chimneys around the world, the authors used comprehensive geological-geophysical-geochemical research methods to provide a reasonable explanation of the low abundance of the gas reservoir in the Weiyuan Structure based on the surface and subsurface data. The latest research results show that(1) currently, the Weiyuan Structure is the apex of the Dengying Formation in the Mid-Sichuan Basin. The Guang'an, Longnüsi, Gaoshiti-Moxi, and Weiyuan structures are a series of traps in the Dengying Formation with gradual uplifting spill and closure points during the regional uplift of the Himalayan period. The natural gas of the Dengying Formation accumulated in different ways over a wide range and long distance in the Sichuan Basin.(2) At approximately 40 Ma, the Weiyuan area started to uplift and form the present structure, and it is the only outcropped area with the Triassic Jialingjiang Formation and Leikoupo Formation in the surface of the Sichuan Basin(except the steep structural belt in East Sichuan). Caused by the uplift and denudation, the core of the Weiyuan Structure has formed an escaping "skylight" for natural gas. The evidence of a gas chimney includes(1) the component percentage of non-hydrocarbon gas, which decreased from the bottom to the top,(2) the pressure coefficient is normal because the gas reservoir from the Upper Sinian to the Lower Permian commonly have a normal pressure coefficient(an average of 1.0), and(3) the isotope g

关键词： Sichuan Basin Weiyuan Structure Dengying Formation late reconstruction differential accumulation gas chimney

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Hydrothermal sedimentation and lead-zinc deposit in Dengying formation of the Sinian system in Panxi region

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Chinese Science Bulletin 1999年第S2期44卷 67-68页

作者： ZHU Laiming and RONG Tianjun Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China Institute of Geochemistry Chinese Academy of Sciences Guiyang 550002 China

IN addition to vanadium titano-magnetite, lead-zinc ore is also one of the mineral resources with great exploring potentiality in the Panxi region of Sichuan Province, China. In the carbonate rock strata of theSinian Dengying Formation which account for about 3.5%-11.4% of the total thickness of the strataexposed in the Panxi region there are quite a number of the Pb-Zn deposits that account for 53.4% of thetotal Pb-Zn ore reserve in the whole region. Furthermore, some large Pb-Zn deposits such as the Tianbaoshan Pb-Zn deposit in Huili, the Daliangzi Pb-Zn deposit in Huidong and the Yinchanggou Pb-Zn deposit in Ningnan are also hosted in the Sinian Dengying Formation. Why? Previous studies indicated that the high background values of Pb and Zn, favorable lithofacies andpaleogeographic conditions and good ore-hosting structures made the Sinian Dengying Formation a pre-

关键词： hydrothermal sedimentation lead-zinc deposit Dengying formation Panxi region.

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Laser ablation in situ U-Pb dating and its application to diagenesis-porosity evolution of carbonate reservoirs

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Petroleum Exploration and Development 2019年第6期46卷 1127-1140页

作者： SHEN Anjiang HU Anping CHENG Ting LIANG Feng PAN Wenqing FENG Yuexing ZHAO Jianxin Key Laboratory of Carbonate reservoirs CNPCXihu DistrictHangzhou 310023China PetroChina Hangzhou Research Institute of Geology(HIPG) Xihu DistrictHangzhou 310023China Radiogenic Isotope Facility School of Earth and Environmental SciencesThe University of QueenslandBrisbaneQLD 4072Australia Beijing SHRIMP Center Institute of GeologyChinese Academy of Geological Sciences(CAGS)Haidian DistrictBeijing 100037China Research Institute of Exploration and Development PetroChina Tarim OilfieldKorla 841000China

Through the development and calibration of a reference material which is 209.8 Ma old using a newly-developed Laser Ablation(LA)Multi-Collector Inductively Coupled Plasma Mass Spectrometry(MC-ICP-MS)technique,we successfully overcome the difficulty in sampling and dating ultra-low U-Pb ancient marine carbonates,which was previously untenable by isotope dilution(ID)methods.We developed the LA-MC-ICP-MS in situ U-Pb dating technique for ancient marine carbonates for the study of diagenesis-porosity evolution history in Sinian Dengying Formation,Sichuan Basin.By systematically dating of dolomitic cements from vugs,matrix pores and fractures,we found that the burial and diagenetic process of dolomite reservoirs in Sinian Dengying Formation was characterized by progressive filling-up of primary pores and epigenic dissolution vugs.The filling of vugs happened in three stages,early Caledonian,late Hercynian-Indosinian and Yanshanian-Himalayan,while the filling of matrix pores mainly took place in early Caledonian.The unfilled residual vugs,pores and fractures constitute the main reservoir sapce.Based on the above knowledge,we established the diagenesis-porosity evolution history of the dolomite reservoir in Sinian Dengying Formation,Sichuan Basin.These findings are highly consistent with the tectonic-burial and basin thermal histories of the study area.Our study confirmed the reliability of this in situ U-Pb dating technique,which provides an effective way for the investigation of diagenesis-porosity evolution history and evaluation of porosity in ancient marine carbonate reservoirs before hydrocarbon migration.

关键词： laser ablation in-situ U-Pb dating Sichuan Basin Sinian Dengying Formation diagenesis-porosity evolution carbonates

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A Model of Hydrothermal Dolomite Reservoir Facies in Precambrian Dolomite, Central Sichuan Basin, SW China and its Geochemical Characteristics

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Acta Geologica Sinica(English Edition) 2019年第1期93卷 130-145页

作者： GU Yifan ZHOU Lu JIANG Yuqiang JIANG Chan LUO Mingsheng ZHU Xun School of Geosciences & Technology Southwest Petroleum University Exploration Division PetroChina Southwest Oil & Gas Field Company Shunan Division of Petrochina Southwest Oil&Gas Field Company Exploration and Development Institute of Southwest Oil&Gas Field Company PetroChina

Hydrothermal mineral assemblages and related hydrothermally enhanced fracturing are common in the Precambrian Dengying Formation of Central Sichuan Basin. Petrographic and geochemical analyses of core samples show that the hydrothermal dolomite reservoirs of Dengying Formation consist of four main types of pores in the reservoir facies. These include: 1) hydrothermal dissolution vug(or pore), 2) intercrystalline pore, 3) residual inter-breccia vug(or pore), and 4) enlarged dissolved-fracture. There are three different fabrics dolomite in hydrothermal dolomite reservoirs, namely, saddle dolomite, fine-medium dolomite and micritic dolomite. Micritic dolomite is the original lithology of host rock. Saddle dolomite with curved or irregular crystal faces was directly crystallized from hydrothermal fluids(average temperature 192°C). Fine-medium dolomites are the products of recrystallization of micritic dolomite, resulting in abnormal geochemical characteristics, such as slight depletion of δ^(18)O, significant enrichment of Mn-Fe and ^(87)Sr/^(86)Sr, and positive Eu anomaly. A model for the distribution of various hydrothermal dolomite reservoir facies is proposed here, which incorporates three fundamental geological controls: 1) extensional tectonics and tectono-hydrothermal events(i.e., the Xingkai Taphrogenesis of Late Sinian-Early Cambrian, and Emei Taphrogenesis of Late Permian), 2) hydrothermal fluid storage in clastic rocks with large thickness(e.g., Nanhua System of Chengjiang Formation and part of Doushantuo Formation), and 3) confining bed for hydrothermal fluids(such as, the shale in Qiongzhusi Formation). The supply of hydrothermal fluid is critical. Large basement-rooted faults and associated grid-like fracture system may function as the channels for upward migration of hydrothermal fluid flow. The intersection of the above-mentioned faults(including the conversion fault), especially transtensional sags above negative flower structures on wrench faults can serve as a key target for future hydrocarbon expl

关键词： hydrothermal dolomite reservoir facies geochemical characteristics Precambrian Dengying Formation central Sichuan Basin

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Discovery of seismites in Upper Sinian stratiform lead-zinc deposits in Dadu River valley, Sichuan, China: Implication for ore genesis

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Science China Earth Sciences 2006年第11期49卷 1135-1146页

作者： LIN Fangcheng1,2 & PAN Guitang2 1. Geoscience College, Chengdu University of Technology, Chengdu 610059, China 2. Chengdu Institute of Geology and Mineral Resources, Chengdu 610082, China Geoscience College Chengdu University of Technology Chengdu China Chengdu Institute of Geology and Mineral Resources Chengdu China

A number of lead-zinc sulphide deposits have been discovered in recent years in dolo- mitic rocks of the Upper Sinian Dengying Formation in the Dadu River valley region, Sichuan Province, China. The lead-zinc mineralization is closely associated with a black siliceous exhalite that has been traced over 50 km of strike. This makes Dadu River valley the most extensive stratiform non-ferrous sulphide horizon having been discovered to date in China. In a previous study by the first author (LIN), these deposits were recognised as belonging to the broad spectrum of lead-zinc sedimentary exhala- tive (SEDEX) deposits. In this paper, seismites and seismogenetic structures occurring in close association with the Dadu River valley mineralized zone are described. The close spatial and temporal relationship between the seismites and mineralization provides strong evidence for the hypothesis that the lead-zinc SEDEX deposits formed in direct response to earthquake activities around the Sinian-Cambrian boundary. The earthquakes are postulated to be an effective dynamic mechanism for triggering the upward migration of deep circulating ore fluids along synsedimentary growth faults and their exhalation onto the sea-floor to form the extensive deposits of stratiform lead-zinc sulphide ore.

关键词： seismites, earthquake, lead-zinc deposit, hydrothermal exhalation, Upper Sinian Dengying Age.

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Mineralogical correlation between primary and replacement dolomites

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Science China Earth Sciences 1997年第1期40卷 91-98页

作者：黄志诚杨守业陈智娜 Department of Earth Sciences Nanjing University Nanjing 210093 China

Primary dolostones occur in the Upper Sinian Dengying Formation. Based on mineralogieal study the indicators for correlation between the primary dolomites which are not influenced by the diagenesis and the replacement dolomites of different periods have been obtained. It is shown that the primary dolomites are characterized by crystal forms precipitated and deposited directly from sea water, stable and homogeneous distribution of Mg and Ca, ideal chemical composition, regular modulated microstructures, low positive δ13C and low negative δ18O.

关键词： primary dolomite replacement dolomite mineralogy Dengying Formation

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