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Restoration of formation processes of dolomite reservoirs based on laser U-Pb dating: A case study of Ordovician Majiagou Formation, Ordos Basin, NW China

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Petroleum Exploration and Development 2022年第2期49卷 327-338页

作者： ZHOu Jingao Yu Zhou Wu Dongxu REN Junfeng ZHANG Daofeng WANG Shaoyi YIN Chen LIu Yuxin PetroChina Hangzhou Research Institute of Geology Hangzhou 310023China CNPC Key Laboratory of Carbonate Reservoir Hangzhou 310023China PetroChina Changqing Oilfield Company Xi'an 710018China China university of Petroleum(Beijing) Beijing 102249China

To address the issue of non-unique interpretation of dolomite reservoir diagenetic and porosity evolution in the previous qualitative or semi-quantitative studies, we investigate two dolomite reservoir types, i.e. weathering-crust karstic reservoirs and mound-beach reservoirs, in the Ordovician Majiagou Formation, Ordos Basin by using in-situ laser ablation U-Pb dating as well as carbon and oxygen isotopic composition analysis. The results show that:(1) According to the dating of 8 reservoir samples, the Majiagou Formation experienced 5 diagenetic stages(Stage 1: deposition of matrix dolomite or penecontemporaneous dolomitization, in 444.0–494.0 Ma;Stage 2: dogtooth-or blade-shaped dolomite cementation, in 440.0–467.0 Ma;Stage 3: dolomitic silt filling, in 316.5–381.0 Ma;Stage 4: crystalline dolomite filling, in 354.0 Ma;Stage 5: crystalline calcite filling, in 292.7–319.0 Ma).(2) Supra-salt weathering-crust karstic dolomite reservoirs went through several diagenetic processes including penecontemporaneous dolomitization, compaction, weathering-crust karstification, packing, and rupturing in succession. Gypsum mold pores formed in the phase of hypergenic karstification and were filled with such minerals as dolomitic silts and calcites, and thus the porosity decreased from 10%–40% to 3%–8%.(3) Sub-salt mound-beach dolomite reservoirs went through the diagenetic processes including penecontemporaneous dolomitization, compaction, subsea cementation, penecontemporaneous corrosion, infiltration backflow dolomitization, packing, and rupturing. The porosity of reservoirs was originally 10%–30%, decreased to 0–6% due to seawater cementation, rose back to 5%–15% owing to penecontemporaneous corrosion, and finally declined to 2%–6% as a result of crystalline dolomites and calcites packing. The above methodology for the restoration of dolomitization and porosity evolution may be helpful for the restoration of porosity evolution in other basins or series of strata.

关键词： U-Pb dating Ordos Basin Ordovician Majiagou Formation diagenesis dolomitization porosity evolution

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Geochemistry, Zircon u–pb dating and Hf Isotopic Characteristics of Neoproterozoic Granitoids in the Yaganbuyang Area, Altyn Tagh, NW China

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Acta Geologica Sinica(English Edition) 2018年第4期92卷 1366-1383页

作者： CHEN Hongjie WANG Nan Wu Cailai LEI Min ZHENG Kun ZHANG Xin GAO Dong Centre for Continental Dynamics China Geological Survey Institute of Geology Chinese Academy of Geological Sciences Beijing 100037 China China university of Geosciences Beijing 100083 China Zhengzhou Normal university College of Geography and Tourism Zhengzhou 450044 China MLR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral Resources Chinese Academy of Geological Sciences Beijing 10037 China

The South Altyn continental block is an important geological unit of the Altyn Tagh orogenic belt, in which numerous Neoproterozoic granitoids crop out. Granitoids are mainly located in the Paxialayidang-Yaganbuyang area and can provide indispensable information on the dynamics of Rodinia supercontinent aggregation during the Neoproterozoic. Therefore, the study of granitoids can help us understand the formation and evolutionary history of the Altyn Tagh orogenic belt. In this work, we investigated the Yaganbuyang granitic pluton through petrography, geochemistry, zircon u-pb chronology, and Hf isotope approaches. We obtained the following conclusions：（1） Yaganbuyang granitoids mainly consist of two-mica granite and granodiorite. Geochemical data suggested that these granitoids are peraluminous calc-alkaline or high-K calc-alkaline granite types. Zircon u-pb data yielded ages of 939~7.1 Ma for granodiorite and ~954 Ma for granitoids, respectively. （2） The ~Hf（t） values of two--mica granite and granodiorite are in the range of-3.93 to ＋5.30 and -8.64 to ＋5.19, respectively. The Hf model ages （TDM2） of two-mica granite and granodiorite range from 1.59-.05 Ga and 1.62-2.35 Ga, respectively, indicating that the parental magma of these materials is derived from ancient crust with a portion of juvenue crust. （3） Granitoids formed in a collisional orogen setting, which may be a response to Rodinia supercontinent convergence during the Neoproterozoic.

关键词： granites geochemistry U-Pb dating Hf isotopic characteristics Altyn Tagh orogen belt

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Chronology and Sources of Mesozoic Intrusive Complexes in the Xuzhou-Huainan Region, Central China: Constraints from SHRIMP Zircon U-Pb dating

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Acta Geologica Sinica(English Edition) 2004年第1期78卷 96-106页

作者： XuWenliang WANGQinghai LIuXiaochun WANGDongyan GuOJinghui CollegeofEarthSciences JilinUniversityChangchunJilin130061 InstituteofGeomechanics ChineseAcademyofGeologicalSciencesBeijing100081 InstituteofGeologyandGeophysics ChineseAcademyofSciencesBeijing100029

SHRIMP zircon U-Pb dating in the Liguo and Jiagou intrusives indicates that they were formed at -130 Ma in the Early Cretaceous. Most inherited zircons in the Liguo intrusive were formed at 2509±43 Ma. Most inherited and detrital zircons in the Jiagou intrusive were formed at -2500 Ma, -2000 Ma and -1800 Ma. The SHRIMP zircon U-Pb dating in two gneiss xenoliths from the Jiagou intrusive yields the ages of 2461±22 Ma and 2508±15 Ma, respectively. The dating results from inherited and detrital zircons in the intrusives and the gneiss xenoliths imply that the magmas could be derived from the partial melting of the basement of the North China Block (NCB). The magmatism is strong and extensive in the periods from 115 to 132 Ma, which is of typical bimodal characteristics. It is suggested that the lithospheric thinning in the eastern North China Block reached its peak in 115-132 Ma.

关键词： Mesozoic intrusive complex zircon U-Pb dating source of magma Xuzhou-Huainana region China

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Slope Year for the U-Pb dating Method and Its Applications

Slope Year for the U-Pb Dating Method and Its Applications

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中国科学院地质与地球物理研究所2015年度（第15届）...

作者： Jie Yuan Key Laboratory of Earth and Planetary Physics Institute of Geology and Geophysics Chinese Academy of Science

The slope year t for the U-Pb dating method is given as t=1/((λ-λ)In λ/λk,whereλ and λ are the decay constants for u and u,respectively,and k is the slope of the tangent line at a point on either the Concordia or Discordia line.These two lines are determined by the initial pb concentrations in minerals.If pb = pb 0,the line is the Concordia.However,if pb≠0∧ pb =0(∧ is the logical operator "and",also known as the logical conjunction),pb=0 ≠pb 0 or pb≠0∧ pb≠0,the line is Discordia.The Concordia line is of the form pb/u =(pb/u+1)λλ)-1(where p stands for the present),while the Discordia line has the form pb/u=k×(pb/u)+b(where k and b are the slope and intercept of the straight line,respectively).

关键词： Slope Year U-Pb dating Zircon Mass Spectrum Isotope Initial pb Isotope Concentration

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In situ U-Pb dating of xenotime by laser ablation(LA)-ICP-MS

In situ U-Pb dating of xenotime by laser ablation(LA)-ICP-MS

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中国科学院地质与地球物理研究所第11届（2011年度）...

作者： LIu ZhiChao~(1,2),Wu FuYuan~(1*),GuO ChunLi~3,ZHAO ZiFu~4,YANG JinHui~1 & SuN JinFeng~(1,2) 1 State Key Laboratory of Litho spheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China 2 Graduate university of Chinese Academy of Sciences,Beijing 100049,China 3 Institute of Mineral Deposits,Chinese Academy of Geological Sciences,Beijing 100037,China 4 School of Earth and Space Sciences,university of Science and Technology of China,Hefei 230026,China

Xenotime is an ideal mineral for u-Th-pb isotopic dating because of its relatively high u and Th contents,but typically low concentration of common pb.These characteristics,and the fact that it is widespread throughout various types of rocks,suggest that the u-Th-pb dating of xenotime has broad applications.Studies of U-Pb dating on xenotime by ion microprobe(such as SHPJMP) have increased in recent years,whereas studies by laser ablation(LA)-ICP-MS are still rare.In this study,we developed a technique for U-Pb dating of xenotime using the 193 nm ArF laser-ablation system and Agilent 7500a Q-ICP-MS.To evaluate the reliability of our method,a xenotime standard,BS-1,was analyzed and calibrated against another xenotime standard,MG-1.The weighted mean pb/u ages of 510.1±5.2 Ma(2a,n = 21),509.8±4.3 Ma(2 a,n = 21) and 510.0±4.6 Ma(2a,n = 21) were obtained using beam diameters of 16,24 and 32μm,respectively.These ages are identical to those determined by ID-TTMS method(weighted mean pb/u age of 508.8±1.4 Ma),which supports the reliability of our LA-ICP-MS method.We also analyzed xenotimes in leucogranites from South Tibet and granites from Xihuashan in southern China,and obtained accurate and precise ages.Nevertheless,we observed systematic differences in pb/u fractionation among xenotime,monazite and zircon.The matrix-effect resulted in either under-correction or over-correction of fractionation,and thus led to inaccurate ages.Thus,a matrix -matched material is required for U-Pb dating of xenotime by LA-ICP-MS.

关键词： xenotime laser ablation（LA）-ICP-MS U-Pb dating

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u-pb Zircon dating of the Yeniutan Granitic Intrusion in the Western Sector of the North Qilian Mountains

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Acta Geologica Sinica(English Edition) 2000年第4期74卷 781-785页

作者： MAO Jingwen ZHANG Zuoheng JIAN Ping WANG Zhiliang YANG Jianmin ZHANG Zhaochong Institute of Mineral Resources Chinese Academy of Geological Sciences Beijing 100037 Institute of Geology Chinese Academy of Geological Sciences Beijing 100037

Zircons from granodiorite and biotite granite in the Yeniutan granitic intrusion in the western North Qilian Mountains yielded a weighted mean 206pb/238u apparent age of 460±3 Ma, suggesting that the intrusion originated during the late stage of plate subduction. Its related Ta'ergou and Xiaoliugou deposits are two of the few large tungsten deposits formed in the plate subduction environment in the world. The U-Pb dating of the zircons from the biotite granite gave a discordant lower intercept age of 183±4 Ma, which implies that the Yanshanian event was probably superimposed on the North Qilian region.

关键词： U-Pb dating granodiorite biotite granite tungsten deposit North Qilian Mountains

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Tracing magma mixing in granite genesis:in situ U-Pb dating and Hf-isotope analysis of zircons

Tracing magma mixing in granite genesis:in situ U-Pb dating ...

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中国科学院地质与地球物理研究所2006学术年会

作者： Simon A.Wilde State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences

In situ zircon u-pb and Hf-isotopic data have been determined for mafic microgranular enclaves and host granitoids from the Early Cretaceous Gudaoling baholith in the Liaodong Peninsula,NE China,in order to constrain the sources and petrogensis of granites.The zircon u-pbage of the enclaves(120±1Ma) is identical to that of the host monzogranite(120±1Ma), establishing that the mafic and felsic magmas were coeval.The Hf isotopic composition of the enclaves[ε(t)=+4.5 to -6.2]is distinct from the host monzogranite[ε(t)=-15.1 to -25.4], indicating that both depleted mantle and crustal sources contributed to their origin.The depleted mantle component was not previously revealed by geochemical and Nd and Sr isotopic studies, showing that zircon Hf isotopic data can be a powerful geochemical tracer with the potential to provide unique petrogenetic information.Some wallrock contamination is indicated by inherited zircons with considerably older u-pb ages and low initial Hf isotopic compositions.Hafnium isotopic variations in Early Cretaceous zircons rule-out simple crystal-liquid fractionation or restite unmixing as the major genetic link between enclaves and host rocks.Instead,mixing of mantle-derived mafic magmas with crustal-derived felsic magmas,coupled with assimilation of wall rocks,is compatible with the data.

关键词： granite genesis U-Pb dating Hf-isotope zircon

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Monazite and xenotime u-Th-pb geochronology by ion microprobe:dating highly fractionated granites at Xihuashan tungsten mine,SE China

Monazite and xenotime U-Th-Pb geochronology by ion microprob...

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中国科学院地质与地球物理研究所2013年度（第13届）...

作者： Q.L.Li X.H.Li Z.W.Lan C.L.Guo Y.N.Yang Y.Liu G.Q.Tang State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of Sciences Institute of Mineral Resources Chinese Academy of Geological Sciences university of Chinese Academy of Sciences

Zircon,monazite,and xenotime have proven to be valuable chronometers for various geological processes due to their commonly high-u-Th and low common pb contents.However,zircons that have crystallized in highly fractionated granites often have such high-u contents that radiation damage can lead to scattered u-pb ages when measured with secondary ion mass spectrometry(SIMS). In this study,monazite and xenotime were separated from a number of highly fractionated granites at the Xihuashan tungsten mine,Southeast China,for alternative dating methods by SIMS.For monazite analysis,obvious excess pb signal(mainly from interference of ThNdO) was observed in high-Th(>2 wt%) monazite,which hinders pb-based common pb corrections. A pb-based common pb correction method was used instead.By employing power law relationships between pb/u versus uO/u,pb/Th versus ThO/Th and suitable exponentials,monazites with TI1O2 contents in the range of～3-19%do not exhibit this matrix effect.Independent SIMS u-pb ages and Th-pb ages of three phases of Xihuashan granite samples were consistent with each other and yielded dates of 158.7±0.7,158.0±0.7,and 156.9±0.7 Ma,respectively.Xenotime does show marked matrix effects due to variations of u,Th,and Y[or total rare earth element(REE),referred as ZREE hereafter]contents. Suitable correction factors require end-member standards with extremely high or low u,Th,and Y(or ZREE) contents. No excess pb was observed,indicating that the pb-based common pb correction method is feasible. Independent pb/pb ages can be obtained,although multi-collector mode is necessary to improve precision.The main difficulties with dating xenotime are when high-Th (u) mineral inclusions are ablated.We can identify when this occurs,however,by comparing the measured uO/u and ThO/Th with those in xenotime standards.Three xenotime samples from the first phase of Xihuashan granite yielded a weighted mean 207pb/pb date of 159.5±4.4 Ma(MSWD = 1.0) and a pb/u date of 159.4±0.9 Ma(MSWD =1.6),which are consistent with monazite u-pb

关键词： SIMS Monazite Xenotime Zircon U-Pb dating Highly fractionated granites

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Lower activity time constraint on the ore-controlling Erdaogou fault in the Qingchengzi orefield of the Liaodong Peninsula,NE China

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Acta Geochimica 2022年第2期41卷 267-274页

作者： Yan Zhao Yuewen Feng Peng Zhang Linlin Kou Zhongzhu Yang Shenghui Li Wei Wang Shenyang Center China Geological SurveyShenyang 110034China Beijing Institute of Exploration Engineering CGSBeijing 100083China 103 Branch of Non-Ferrous Geological Bureau of Liaoning Province Dandong 118008China

The Erdaogou fault,also known as the 101 fault,comprises the most important NE strike component in the ore-controlling system in the Qingchengzi orefield,Liaodong Peninsula.Due to the poor outcrop conditions in the field,the Erdaogou fault lacks activity time constraint.We demonstrate the constraint activity time of the fault since we observe a lamprophyre that was cut through by the Erdaogou fault in the Taoyuan area,central to the Qingchengzi orefield.Zircon grains from the lamprophyre dyke exhibit typical oscillatory zoning and yield weighted mean u–pb age of 223.8±1.1 Ma(MSWD=1.5).The lower activity time limit of the Erdaogou fault is thus first constrained as 224 Ma or so and is correlated with the crystallization age of the Xinling and Shuangdinggou plutons within the orefield.Taking previous mineralization studies into consideration,a Triassic tectonic-magmatism-mineralization model is approved in the Qingchengzi orefield.

关键词： The Erdaogou fault LA-ICP-MS U-Pb dating Activity time The Qingchengzi orefield Liaodong Peninsula

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Zircon u-pb Geochronology of Baoyintu Group in the Northwestern Margin of the North China Craton and Its Geological Significance

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地球科学学刊:英文版 2023年第5期34卷 1511-1526页

作者： Chengwu Ding Yifei Liu Pan Dai Sihong Jiang Chengzhen Ding School of Resources and Environmental Engineering Shandong University of TechnologyZibo 255000China MNR Key Laboratory of Metallogeny and Mineral Assessment Institute of Mineral ResourcesChinese Academy of Geological SciencesBeijing 100037China Geophysical Research Institute of BGP Inc.China National Petroleum Corporation Zhuozhou 072751China

The Baoyintu uplift is located at the northwestern margin of the North China Craton(NCC). The affiliation and evolution history of the uplift have been unresolved until now. Here we present LA-ICP-MS and SHRIMP u-pb data for zircons extracted from samples of monzogranitic orthogneiss and the Baoyintu Group in the uplift. The 1 679 ± 13 Ma date for the orthogneiss demonstrates that Late Palaeoproterozoic rocks do exist in the uplift. The ca. 1 413 Ma minimum age of detrital zircons in metasedimentary rocks shows that the maximum age of the Baoyintu Group is Mesoproterozoic. The age distribution of detrital zircons in the first unit of the Group form clusters at ca. 2 680, 2 450, 1 800 and 1 560 Ma, which partly correspond to tectonic-magmatic-metamorphic events previously recognised in the NCC, and show that the metasedimentary rocks are largely sourced from different parts of the NCC. These confirm that the Baoyintu uplift is part of the NCC. Amphibolite with a dolerite protolith from the third unit of Baoyintu Group shows evidence for metamorphism during ca. 877–851 Ma. This combined with published geochronological data indicate the presence of Neoproterozoic magmatic and metamorphic events in the NCC, which significantly increases our understanding of the Proterozoic tectonic evolution of the region and its possible correlation with the Rodinian Supercontinent.

关键词： Proterozoic Baoyintu Group zircon U-Pb dating North China Craton geochemistry

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