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Boron isotopic fractionation in laboratory inorganic carbonate precipitation:Evidence for the incorpora-tion of B(OH)_3 into carbonate

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Science china earth sciences 2008年第12期51卷 1776-1785页

作者： XIAO YingKai1,2, LI HuaLing1,3, LIU WeiGuo4, WANG XiuFang1 & JIANG ShaoYong5 1 Qinghai Institute of Salt Lakes, Chinese Academy of sciences, Xining 810008, china 2 state key laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of sciences, Guiyang 550002, china 3 nanjing Institute of Geology and mineral Resources, nanjing 210016, china 4 state key laboratory of Loess and Quaternary Geology, Institute of earth Environment, Chinese Academy of sciences, Xi’an 710075, china 5 state key laboratory for mineral deposits research, department of earth sciences, nanjing university, nanjing 210093, china Qinghai Institute of Salt Lakes Chinese Academy of Sciences Xining China state key laboratory of Environmental Geochemistry Institute of Geochemistry Chinese Academy of Sciences Guiyang China nanjing Institute of Geology and mineral Resources Nanjing China state key laboratory of Loess and Quaternary Geology Institute of Earth Environment Chinese Academy of Sciences Xi’an China state key laboratory for mineral deposits research Department of Earth Sciences Nanjing University Nanjing China

A laboratory inorganic carbonate precipitation experiment at high pH of 8.96 to 9.34 was conducted, and the boron isotopic fractionations of the precipitated carbonate were measured. The data show that boron isotopic fractionation factors (αcarb-3) between carbonate and B(OH)3 in seawater range 0.937 and 0.965, with an average value of 0.953. Our results together with those reported by Sanyal and collabo-rators show that the αcarb-3 values between carbonate and B(OH)3 in solution are not constant but are negatively correlated with the pH of seawater. The measured boron isotopic compositions of carbonate precipitation (δ11Bcarb) do not exactly lie on the best-fit theoretical δ 11B4-pH curves and neither do they exactly parallel any theoretical δ 11B4-pH curves. Therefore, it is reasonable to argue that a changeable proportion of B(OH)3 with pH of seawater should also be incorporated into carbonate except for the dominant incorporation of B(OH)4- in carbonate . Hence, in the reconstruction of the paleo-pH of sea-water from boron isotopes in marine biogenic carbonates, the use of theoretical boron isotopic frac-tionation factor (α4-3) between B(OH)4- and B(OH)3 is not suitable. Instead, an empirical equation should be established.

关键词： boron isotopic fractionation biogenic carbonate B(OH)3 incorporation

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Carbon and sulfur isotopic compositions of basal Datangpo Formation, northeastern Guizhou, South china:Implications for depositional environment

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Progress in Natural Science:Materials International 2008年第4期18卷 421-429页

作者： Xi Chen, Da Li, Hong-Fei Ling , Shao-Yong Jiang state key laboratory for mineral Deposit research, department of earth sciences, nanjing university, nanjing 210093, china state key laboratory for mineral Deposit research Department of Earth Sciences Nanjing University Nanjing 210093 China

Isotopic compositions of Mn-carbonate and organic carbon from the same individual samples and sulfur isotopic compositions of pyrites in the basal Datangpo Formation were analyzed. Highly 34S-enriched pyrites (d34Spyrite=31.7-59.4‰) were precipitated in rel- atively occlusive pore water under anoxic condition in sediments, which is consistent with the observation of large and scattered pyrite framboids. The sulfidic deep ocean was not "oxidized" in the early Datangpo interglacial interval, thus the level of seawater sulfate remained low and marine d34Ssulphate remained high. Low d13Ccar (average 7.4‰) and abnormal relationship between d13Ccar and frac-tionation (Dcar-org) imply that the negative d13Ccar excursion may have resulted from oxidation of part of a large organic carbon reser-voir. High Dcar-org (average 25.1‰) implicates high CO2 level in the atmosphere. Small standard deviation (1.0‰) of d13Ccar values indicates the Mn-carbonate was precipitated near the water-sediment interface under dysoxic conditions rather than in occlusive pore water in sediments.

关键词： Cisotope S isotope Paleoenvironment Datangpo Mn-carbonate

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Advances in research of sulphide ore textures and their implications for ore genesis

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Progress in Natural Science:Materials International 2006年第10期16卷 1007-1021页

作者： GU Lianxing, ZHENG Yuanchuan, TANG Xiaoqian, WU Changzhi and HU Wenxuan (state key laboratory for Endogenic Metal deposits research, department of earth sciences, nanjing university, nanjing 210093, china) state key laboratory for Endogenic Metal deposits research Department of Earth Sciences Nanjing University Nanjing 210093 China

Important advances in research of sulphide ore textures in recent years have deepened our understanding of ore genesis of related mineral deposits. Pressure solution of sulphide minerals has been suggested as a mechanism for remobilization of ore materials, whereas pressure solution of the gangues is believed to raise the grade of the primary ores. We have known that precipitation of base metal sulphides from fluids prefers crystal and crack surfaces of pyrite to form overgrowth. Therefore, pyrite-bearing embryo beds in a sedimentary sequence can be acted as effective crystal seed beds and are favorable for fluid overprinting to form huge statabound deposits. Texture studies of various sulphides can be used to interpret the entire history of sedimentation, diagenesis, deformation and metamorphism of the ores. The study of chalcopyrite disease in sphalerite has brought about the idea of zone refining, and given a new explanation to metal zonation in massive sulphide deposits. Ductile shearing of sulphide ores may form ore mylonites, which will become oreshoots enriched in Cu, Au and Ag during late-stage fluid overprinting. Despite that various modern analytical techniques are being rapidly developed, ore microscopy remains to be an unreplaceable tool for ore geologists. Combined with these modern techniques, this tool will help accelerate the development of theories on ore genesis.

关键词： pyrite pyrrhotite chalcopyrite pressure sulution overgrowth mylonite.

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Potash-rich volcanic rocks and lamprophyres in western Shandong Province:^(40)Ar-^(39)Ar dating and source tracing

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Chinese Science Bulletin 2002年第2期47卷 91-99页

作者： QIU Jiansheng, XU Xisheng & LO Ching-Huastate key laboratory of mineral Deposit research of nanjing university, nanjing 210093, china department of earth sciences, nanjing university, nanjing 210093, china department of Geology, Taiwan Unive state key laboratory of mineral Deposit research of nanjing university Nanjing China department of earth sciences Nanjing University Nanjing China department of Geology Taiwan University Taibei China

Highly precise 40Ar-39Ar dating results demon-strate that the ages of potash-rich volcanic rocks in western Shandong Province are 114.7-124.3 Ma, and that of the lamprophyres is 119.6 Ma. The potash-rich volcanic rocks have relatively high (87Sr/86Sr)i ratios ( 0.708715-0.711418) and distinctly negative εNd values ( -11.47--17.54), and are enriched in radiogenic lead (206Pb/204Pb=17.341-17.622, 207Pb/204Pb=15.525-15.538, 208Pb/204Pb=37.563-37.684). Similarly, the lamprophyres also have quite low εNd values (-11.57 - -19.64). Based on the fact that the Sr, Nd and Pb isotopic compositions of potash-rich volcanic rocks are very consistent with that of the clinopyroxene separates, and by integrating comprehensive analyses of their tectonic settings, and extensive comparisons of the Sr, Nd isotopic composi-tions with that of the related simultaneous rocks, it is con-cluded that the potash-rich volcanic rocks and lamprophyres in western Shandong Province were most possibly derived from the partial melting

关键词： potash-rich volcanic rocks lamprophyres 40Ar-39Ar dating Sr-Nd-Pb isotope tracing western Shandong Province.

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Mid-low temperature metallogenic province of South china: A continental-scale mineralization and temperature zoning

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Chinese Science Bulletin 1999年第S2期44卷 27-29页

作者： MA Dongsheng state key laboratory for research of mineral deposits, nanjing university nanjing 210093, china state key laboratory for research of mineral deposits Nanjing University Nanjing 210093 China

CHARACTERIZED by Au,Sb and Hg mineralization, the mid-low temperature metallogenic province in Southchina is composed of the Au-Sb belt in the Proterozoic group on the Jiangnan Old Land, and the Hunan-Guizhou Hg belt in the Cambrian system, the SW china Carlin-type Au belt in the Permian andTriassic, and the Mid-Hunan Sb belt in the Devonian. The latter three are located in the basins respectively on the NW,SW and SE of the Jiangnan Old Land. The province holds nearly 50% Sb ore reserves and supplies about 70% annual antimony mine production in the world, and about 80% both ofexplored reserves and annual output of Hg in china. In the last twenty years, discovery of the micrograined dissemination Au deposits in the SW china Au belt made an important breakthrough in

关键词： South china continental-scale mineralization ore-forming temperature zoning.

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Oxygen isotope geochemistry of phosphorite and dolomite and palaeo-ocean temperature estimation:A case study from the Neoproterozoic Doushantuo Formation, Guizhou Province, South china

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Progress in Natural Science:Materials International 2004年第1期14卷 78-85页

作者： LING Hongfei, JIANG Shaoyong*, FENG Hongzhen, CHEN Yongquan, CHEN Jianhua and YANG Jinghong(state key laboratory for mineral deposits research, department of earth sciences, nanjing university, nanjing 210093, china) nanjing Univ Dept Earth Sci State Key Lab Mineral Deposits Res Nanjing 210093 Peoples R China

The Neoproterozoic Doushantuo Formation at Weng’an in Guizhou Province of South china consists of phosphorites and dolomites. Three types of samples are recongnized for the phosphate bearing rocks. In Type I samples, interstitial phosphates occur within the dolomite rocks, whereas in Type III samples, interstitial dolomites occur within the phosphorites; both of them may have diagenetic origin. The Type II samples are interbedded phosphorites and dolomites. Oxygen isotopic compositions of phosphate and coeval carbonate were analyzed. Phosphates of Type I and II samples show similar low δ 18 O phos (SMOW) values of 10.9‰～12.1‰ and 10.7‰～ 12.8‰ , respectively, whereas Type III phosphates show higher δ 18 O phos (SMOW) values of 13.2‰～15.0‰. Dolomites from Type I and II samples have δ 18 O carb (PDB) and δ 13 C carb (PDB) values of -6.2‰～-3.4‰ and -2.2‰～-0.7‰, respectively, whereas interstitial dolomites from Type III samples show lower δ 18 O carb (PDB) and δ 13 C carb (PDB) values of -12.9‰～-8.6‰ and -4.4‰～-2.6‰. Petrology and oxygen isotope data suggest that diagenetic alteration may have partially affected the studied rocks, but the dolomites from Type I and phosphates from Type III samples represent the most pristine isotopic compositions of primary carbonates and phosphates precipitated from seawater. Calculations of palaeocean temperatures from the most 18 O enriched dolomite and phosphate indicate a temperature range of 32.2 ℃ to 34.0 ℃ for the seawater of the Doushantuo Formation period. Ce anomaly also suggests more oxic conditions and possibly shallower water depth in the upper strata of the Doushantuo Formation at Weng’an, Guizhou Province.

关键词： oxygen isotopes phosphate dolomite Doushantuo Formation Neoproterozoic South china

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Study on lithogeochemistry of Middle Jurassic basalts from southern china represented by the Fankeng basalts from Yongding of Fujian Province

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Science china earth sciences 2006年第10期49卷 1020-1031页

作者： ZHOU Jincheng1,2, JIANG Shaoyong1,2, WANG Xiaolei1,2, YANG Jinghong 1,2 & ZHANG Mengqun 3 1. state key laboratory of mineral Deposit research, nanjing university, nanjing 210093, china 2. department of earth sciences, nanjing university, nanjing 210093, china 3. Modern Analysis Center, nanjing university, nanjing 210093, china state key laboratory of mineral Deposit research Nanjing University Nanjing China department of earth sciences Nanjing University Nanjing China Modern Analysis Center Nanjing University Nanjing China

There exists an E-W trending Middle Jurassic volcanic zone in southern china. The Fankeng basalts in the Yongding basin of Fujian Province are considered to be a typical example. The Fankeng basalts have TiO2 contents in the range of 1.92%-3.21%. They are classified as high-Ti basalts. They also have higher total Fe (averaging FeO* = 11.09%). The Middle Jurassic Fankeng basalts from southwestern Fujian have obvious distinctive lithogeochemical features from early Cre- taceous basalts from southeastern coast of china. They have higher HFSE, such as Th, Nb, Ta, Zr and Ti. Their element ratios related with HFSE, such as Zr/Ba, La/Nb, La/Ta ,Zr/Y, Ti/Y, Ba/Nb, K/Ti and Rb/Zr are similar to those of OIB. The most samples have ε Nd(T) of-0.70-0.24, which are near chondrite. Some samples have higher ε Nd(T) of ***, these basaltic magmas might be derived from depleted asthenospheric mantle. The lithogeochemical characteristics of the Fankeng basalts may be caused by interaction between asthenosphere and lithosphere at the time. The (Early-) Middle Jurassic basalts and gabbros from southeastern Hunan, southern Jiangxi and northern Guangdong provinces show similar geochemical features to those of the Fankeng basalts from the Yongding of Fujian. Occurrence of these OIB-type basalts in the area may be regarded as the petrological mark of upwelling of asthenosphere at the time. Upwelling of asthenosphere has led to tectonic extension and the formation of rifted basin in the area.

关键词： interaction between asthenosphere and lithosphere, lithogeochemistry, basalts, Middle Jurassic, southern china.

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Hydrogen and oxygen compositions of altered rocks from Qixia gold deposit and their genetic significance, Shandong, china

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Chinese Science Bulletin 1999年第S2期44卷 8-9页

作者： ZHAI Jianping, LU Jianjun, HU Kai and XU Guangping department of earth sciences, state key, laboratory of mineral deposits, nanjing university, 210093, china department of earth sciences State Key Laboratory of Mineral Deposits Nanjing University 210093 China

1 Sample and analytic methods The Qixia gold deposit is one of the important quartz vein-type deposits hosted in metamorphic rockin east Shandong Province, china. About 12 samples were collected at different depths of the Qixia goldmineral district to investigate the variations in the hydrogen and oxygen isotope compositions of alteredrocks. Hydrogen was extracted by melting samples and oxygen was obtained through oxidation by BrF5.The isotope compositions were measured with MAT252, and the precisions for oxygen and hydrogen isotope analyses were±0.2‰ and 2‰, respectively. All the analyses were fulfilled at the state key *** mineral Deposit research in nanjing university. The δD and δ18O values relative to SMOW are givenin table 1.

关键词： hydrogen and oxygen isotopes altered rocks Qixia gold deposit Shandong.

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Evolution of chlorite composition in the Paleogene prototype basin of Jiyang Depression, Shandong, china, and its implication for paleogeothermal gradient

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Science china earth sciences 2007年第11期50卷 1645-1654页

作者： ZHAO Ming1, CHEN XiaoMing1, JI JunFeng1, ZHANG Zhe1 & ZHANG Yun2 1 state key laboratory for mineral deposits research, department of earth sciences, nanjing university, nanjing 210093, china 2 Jiangsu Survey Institute of Engineering and Physics, nanjing 210008, china state key laboratory for mineral deposits research Department of Earth Sciences Nanjing University Nanjing China Jiangsu Survey Institute of Engineering and Physics Nanjing China

The Dongying Basin, Huimin Basin, and Zhanhua Basin constitute the Jiyang Depression in Shandong Province. They are major oil and gas exploring districts within the depression. Through reconstructions of the paleotemperature of the three basins facilitated with the chlorite geothermometry, the thermal history of the Paleogene prototype basin in Jiyang Depression and its geologic significance were explored. This study reveals that the Si^(4+) component in chlorites reduces gradually as its buried depth increases, while the AI~Ⅳ component increases accordingly. The chlorite type changes from silicon-rich diabantite to silicon-poor ferroamesite and prochlorite. The prochlorite in this district only appears in the deep buried depth, high temperature, and relatively old stratigraphies; while the diabantite appears in the shallower buried, low temperature, and newly formed strata; the ferroamesite exists in the conditions between prochlorite and diabantite formation. The diagenetic temperatures of the chlorites in these Paleogene basins are 171 — 238℃ for the Dongying Basin, 160—202℃ for the Huimin Basin, and 135—180℃ for the Zhanhua Basin. The differences of the chlorite diagenetic temperatures in the three basins were controlled by the duration time of the structural depressing processes. Higher temperature indicates longer depression time. The relationship between the chlorite diagenetic temperature and its buried depth indicates that the average paleogeothermal gradient is about 38.3℃ /km in the Paleogene prototype basin of Jiyang Depression. It was higher than the present geothermal gradient (29—30℃/km). This phenomenon was attributed to the evolution of the structural dynamics in the depression basin.

关键词： Paleogene,Jiyang depression,chlorite component,chlorite geothermometry,paleotemperature,paleogeothermal gradient

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The relationship between epithermal and low temperature mineralizations

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Chinese Science Bulletin 1999年第S2期44卷 226-227页

作者： HUA Renmin state key laboratory of mineral Deposit research, nanjing university, nanjing 210093, china state key laboratory of mineral Deposit research Nanjing University Nanjing 210093 China

THE term epithermal as a kind of hydrothermal mineralization was first used by Lindgren in 1933. It describes those ore-forming systems occurring at depths mainly less than 1 km, and at temperatures less than300℃. Epithermal deposits of Cenozoic ages are widely distributed in the Circum-Pacific belt, especiallyin the Southwest Pacific area. From the 1980s on, the study of epithermal ore deposits became an important field of mineral deposit research. Hayba et *** Hedenquist classified the epithermal systemas adularia-sericite or acid-sulphate types, and low sulphidation or high sulphidation types, *** low temperature mineralization, which was exemplified by the deposits in southwest china, refers tothe system at temperature mainly less than 200℃. Besides the distinction in temperature, however, thereexist many differences between epithermal and low temperature mineralizations.

关键词： epithermal mineralization low temperature.

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