新疆-甘肃北山金矿南带的成矿流体演化和成矿机制
Evolution of ore-forming fluids and formational mechanism for gold deposits in the southern Bei Shan, Xinjiang-Gansu border area of China
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摘要: 北山金矿南带是西北5省区规模最大的金矿带。选择北山南带的新金厂、老金厂和小西弓金矿床,在矿床地质和岩相学研究的基础上,对脉石英的流体包裹体进行了显微温度计和激光拉曼探针气体成分测定;对石英和矿石黄铁矿的包裹体H2O,CO2和CH4进行了H和C同位素组成测定,对石英和黄铁矿分别做了O和S同位素组成测定。3个金矿床的脉石英含有富CO2+CH4、H2O溶液以及H2O-CO2+CH4包裹体。小西弓金矿床流体包裹体的均一化温度主要介于270℃-450℃,一部分H2O溶液包裹体圈闭了高盐度流体(16.43—18.63wt.%NaCl equiv.),大部分H2O溶液包裹体和全部富CO2+CH。包裹体代表了中-低盐度(2.8%-13.6%)流体。新金厂金矿床流体包裹体的均一化温度主要介于210℃-346℃;一部分流体包裹体圈闭了高盐度(10.98%~14%NaCl equiv.)流体,一部分H2O溶液包裹体和绝大多数富CO2+CH4包裹体圈闭了中-低盐度(2.9%-8.81%NaCl equiv.)流体。老金厂金矿床H2O溶液包裹体的均一化温度主要分布于141℃-400℃,含盐度介于1.4%-8.28%,属于中-低盐度流体。进行了大气降水-围岩^18O/^16O、D/H交换反应模拟。小西弓矿床早期硫化物-石英脉金矿成矿流体对应较高的水/岩比(=0.01—0.05),其^18O/^16O和D/H组成更受钾长花岗岩者控制,硫化物的δ^34S值也接近钾长花岗岩的黄铁矿者,指示热液流体围绕着钾长花岗岩的对流淋滤。成矿晚期,围绕着花岗岩侵入体的热液对流崩溃,矿区围岩内发育更大尺度的彼此分离的弥漫性流体渗透淋滤;相应地,小西弓矿床晚期蚀变岩金矿成矿流体的8D值对应低水/岩比(0.005-≈0.01),其δ^18O值变化范围较宽,受当地中元古界变质岩控制,蚀变岩型金矿黄铁矿的δ^34S值也接近中元古界长英质片岩的黄铁矿者。新金厂金矿和老金厂金矿成矿流体的δD值和δ^18O值对应的水/岩值分别介于0.004—0.01和0.007~0.02,与岩浆流体或者下二叠统哲斯群辉绿岩和英安岩围岩具有更密切的关系。新金厂金矿和老金厂金矿黄铁矿样品的δ^34S值介于-2.58‰和-6.32‰,指示S来源于下二叠统哲斯群辉绿岩、英安岩和碳质板岩围岩。3个金矿的石英包裹体CO2(δ^13C=-2.20‰--9.14‰),以及石英和黄铁矿包裹体CH4(δ^13C=013.10‰--27.40‰)不平衡;前者来源于幔源岩浆去气,后者来源于哲斯群碳质板岩或者中元古界长英质片岩中的还原碳。3个金矿黄铁矿包裹体的CO(δ^13C=-10.79‰--23.62‰)主要来源于哲斯群碳质板岩或中元古界长英质片岩中的还原碳,但是,也混合了较少的岩浆CO2。包裹体CO2和CH4δ^13C值的系统变化,也反映了从岩浆侵位和去气、流体对流,到围岩中流体大面积弥漫性渗透淋滤的演化过程。CH4介入成矿流体,导致流体不混溶和金的沉淀。北山金矿南带的形成既不同于典型的造山带型金矿床,也不同于与侵入岩有关的金矿床。我们提出北山金矿南带的成矿模式为:岩浆去气和流体对流、岩石挤压破碎、流体弥漫性渗透淋滤。
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[1] Ashley PM and Craw D.2004. Structural controls on hydrothermal alteration and gold-antimony mineralization in the Hillgrove area,NSW,Australia.Mineralium Deposita,39:223 -239
[2] Baker T and Lang J R.2001. Fluid inclusion characteristics of intrusionrelated gold mineralization,Tombstone-tungsten magmatic belt,Yukon Territory,Canada.Mineralium Deposita,36:563-582
[3] Barnett DE and Bowman JR.1995. Coupled mass transport and kinetically limited isotope exchange:Applications and exchange mechanisms.Geology,23 (3):225-228
[4] Bierlein FP and Crowe DE.2000. Phanerozoic orogenic lode gold deposits.Rev.Econ.Geol.,13:103-139
[5] Bierlein FP and Maher S.2001. Orogenic disseminated gold in Phanerozoic fold belts-examples from Victoria,Australia and elsewhere.Ore Geol.Review,18:113-148
[6] Boiron MC,Cathelineau M,Banks DA,et al.1996. P-T-X conditions of late Hercynian fluid penetration and the origin of granite-hosted gold quartz veins in northwestern Iberia:A multidisciplinary study of fluid inclusions and their chemistry.Geochim Cosmochim Acta,60 (1):43-57
[7] Boiron MC,Barakat A,Cathelineau M,et al.2001. Geometry and P-VT-X conditions of microfissural ore fluid migration:the Mokrsko gold deposit (Bohemia).Chemical Geology,173:207 -225
[8] Bowers TS and Helgeson HC.1983. Calculation of the thermodynamic and geochemical consequences of non-ideal mixing in the system H2O-CO2-NaCl on phase relations in geologic systems:Equation of state for H2 O-CO2-NaCl fluids at high pressures and temperature.Geochim Cosmochim Acta,47:1247 -1275
[9] Bowman JR,Willett SD and Cook SJ.1994. Oxygen isotopic transport and exchange during fluid flow:One-dimensional models and applications.American Journal of Science,294:1-55
[10] Brown PE and Lamb WM.1989. P-V-T properties of fluids in the system H2 O ± CO2 ± NaC1:New graphical presentations and implications for fluid inclusion studies.Geochim Cosmochim Acta,53:1209-1221
[11] Christie AB and Brathwaite RL.2003. Hydrothermal alteration in metasedimentary rock-hosted orogenic gold deposits,Reefton goldfield,South Island,New Zealand.Mineralium Deposita,38:87-107
[12] Craig H.1961. Isotopic variations in meteoric waters.Science,133:1702-1703
[13] Criss RE,Gregory RT and Taylor HP.1987. Kinetic theory of oxygen isotope exchange between minerals and water.Geochim Cosmochim Acta,51:1099-1108
[14] Deines P.1980. The carbon isotopic composition of diamonds:Relationship to diamond shape,color,occurrence and vapor composition.Geochim Cosmochim Acta,44:943 -961
[15] GBGMR.1989. Memoir of Gansu Regional Geology.Gansu Bureau of Geological Mineral and Resource.Beijing:Geological Publishing House,1 -691 (in Chinese with English abstract)
[16] Goldfarb RJ,Groves DI and Gardoll S.2001. Orogenic gold and geological time:a global synthesis.Ore Geol.Review,18:1 -75
[17] Gregory RT,Criss RE and Taylor HP.1989. Oxygen isotope exchange kinetics of mineral pairs in closed and open systems:Applications to problems of hydrothermal alteration of igneous rocks and Precambrian iron formations.Chemical Geology,75:1 -42
[18] Groves DI,Goldfarb RJ and Gebre-Mariam M.,and others.1998. Orogenic gold deposits:a proposed classification in the context of their crustal distribution and relationship to other gold deposit types.Ore Geol.Review,13:7 -27
[19] Jia Y and Kerrich R.1999. Nitrogen isotope systematics of mesothermal lode gold deposits:Metamorphic,granitic,meteoric water,or mantle origin? Geology,27:1051
[20] Lang JR and Baker T.2001. Intrusion-related gold systems:the present level of understanding.Mineralium Deposita,36:477 -489
[21] Liu W,Li XJ and Qin KZ.2002. Oxygen isotope exchange and flow geometry of meteoric-derived water within an alkali granite pluton:exchange mechanism and advective cooling.Acta Petrologica Sinica,18 (3):331-339 (in Chinese with English abstract)
[22] Liu W,Li XJ and Deng J.2003. Sources of ore-forming fluids and metallic materials in the Jinwozi lode gold deposit,eastern Tianshan Mountains of China.Science in China,Series D,46 (Supp.),135-153(in Chinese)
[23] Liu XY and Wang Q.1995. Geotectonics and its evolution of the Bei Shan orogenic belt in the northwestern China.Geoscience Research,No.28:37 -48 (in Chinese with English abstract)
[24] Lowenstern J B.2001. Carbon dioxide in magmas and implications for hydrothermal systems.Mineralium Deposita,36:490-502
[25] Lu HZ,Li BL,Shen K,et al.1990. Geochemistry of fluid inclusions.Beijing:Geological Publishing House (in Chinese with English abstract)
[26] Matthews A.1979. Oxygen isotope equilibration systematics between quartz and water.The American Mineralogist,64(1):232 -241
[27] Naden J and Shepherd T J.1989. Role of methane and carbon dioxide in gold deposition.Nature,342:793-795
[28] Nie FJ,Jiang SH,Bai DM,et al.2002. Metallogenic studies and ore prospecting in the conjunction area of Inner Mongolia autonomous region,Gansu province and Xinjiang Uygur autonomous region (Beishan Mt.),northwestern China.Beijing:Geological Publishing House (in Chinese with English abstract)
[29] Ohmoto H.1986. Stable isotope geochemistry of ore deposits.In:Valley JW,Taylor HP and O \'Neil JR (eds).Stable Isotopes in High Temperature Geological Processes.Mineralogical Society of America,Reviews in Mineralogy,16:528-536
[30] O\' Neil JR and Taylor HP.1967. The oxygen isotope and cation exchange chemistry of feldspar.American mineralogist,52:1414-1437
[31] Potter RW and Clynne MA.1978. Solubility of highly soluble salts in aqueous media-Part Ⅰ:NaCl,KCl,CaCl2,Na2 SO4,and K2 SO4 solubilities to 100℃.J.Res.US.Geol.Survey,6:701-705
[32] Richet P,Bottinga Y and Javoy M.1977. A review of hydrogen,carbon,nitrogen,oxygen,sulfur,and chlorine stable isotope fractionation among gaseous molecules.Ann Rev Earth Planet Sci,5:65 -110
[33] Roedder E:1984. Fluid Inclusions.Reviews in Mineralogy,12:250-290
[34] Rombach CS and Newberry RJ.2001. Shotgun deposit:granite porphyryhosted gold-arsenic mineralization in southwestern Alaska.Mineralium Deposita,36:607-621
[35] Schoell M.1984. Stable isotopes in petroleum research.In:Brooks J and Welte D (eds).Advances in Petroleum Geochemistry,V.1. London:Academic Press,215 -243
[36] Schwartz MO.1989. Determining phase volumes of mixed CO2-H2 O inclusions using microthermometric measurements.Mineralium Deposita,24:43-47
[37] Sheppard SMF.1986. Characterization and isotopic variations in natural waters.In:Valley JW,Taylor HP and O\' Neil JR (eds).Stable Isotopes in High Temperature Geological Processes.Mineralogical Society of America,Reviews in Mineralogy,16:173
[38] Shiro Y and Sakai H.1972. Calculation of the reduced partition function ratios of α-,β-quartz and calcite.Bulletin of the Chemical Society of Japan,45:2355 -2359
[39] Sven EW and Klemd R.2004. Fluid inclusion studies of the Abawso gold prospect,near the Ashanti Belt,Ghana.Mineralium Deposita,39:31 -45
[40] Swanenberg HEC.1980. Fluid inclusions in high-grade metamorphic rocks from SW Norway.Geologica Ultraiectina,Univ Utrecht,25:147
[41] Taylor BE.1986. Magmatic volatiles:Isotopic variation of C,H,and S.In:Valley JW,Taylor HP and O\' Neil JR (eds).Stable Isotopes in High Temperature Geological Processes.Mineralogical Society of America,Reviews in Mineralogy,16:185-220
[42] Wei L.2000. Two disequilibrium quartz-feldspar 18O/16O fractionations within the Aral granite batholith,Altay mountains of China:Evidence for occurrence of two stages of O and H isotopic exchange of a heterogeneous granite system with aqueous fluids.Journal of Petrology,41 (9):1455-1466
[43] Zhang WH and Chen ZY.1998. Geology of fluid inclusions.Beijing:Geological Publishing House (in Chinese with English abstract)
[44] Zhou JY,Cui BF,Xiao HL,et al.2000. Evolution of the eastern segment of the Bei Shan rift and metallogenic regulation of gold ore deposits.Volcanology and Mineral Resources,21 (1):7-16 (in Chinese with English abstract)
[45] 甘肃省地质矿产局.1989.甘肃省区域地质志.中华人民共和国地质矿产部专报,(一)区域地质,第19号.北京:地质出版社,1-691
[46] 刘伟,李新俊,邓军.2002a.东天山金窝子石英脉金矿床成矿流体和成矿物质的来源.中国科学(D辑).32(增刊):105-119
[47] 刘伟,李新俊,秦克章.2002b.碱性花岗岩的动力学氧同位素交换和流体流动几何学:交换机制和平流冷却.岩石学报.18(3):331-339
[48] 刘雪亚,王荃.1995.中国西部北山造山带的大地构造及其演化.地学研究.第28号:37-48
[49] 卢焕章,李秉伦,沈崑等.1990.流体包裹体地球化学.北京:地质出版社
[50] 聂凤军,江思宏,白大明等.2002.北山地区金属矿床成矿规律及找矿方向.北京:地质出版社
[51] 张文淮,陈紫英.1998.流体包裹体地质学.北京:地质出版社
[52] 周济元,崔炳芳,肖惠良等.2000.甘新北山东段裂谷演化及金矿成矿规律.火山地质与矿产.21(1):7-16
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