| 胶东金青顶和大尹格庄金矿床花岗质围岩的蚀变地球化学研究 |
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| 引用本文：.2002.Geochemical Study of Granitic wall-rock Alteration in Dayingezhuang Gold Deposit of Alteration Rock Type and Jinqingding Gold Deposit of Quartz-vein Type[J].Mineral Deposits,21(2):187~199 |
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| 基金项目:国家自然科学基金项目(编号：49133120) |
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| 中文摘要:研究了大尹格庄金矿床和金青顶金矿床的花岗质围岩及其蚀变岩的主元素、微量元素和氧同位素等特征。结果表明郭家店花岗岩和金青顶花岗岩Nb、Ta、P、Ti相对亏损，Nd(t)值为-11.9～-14.5，为前寒武纪地壳岩石熔融的产物。大尹格庄围岩蚀变较强，主要为沿断裂带发育的绢英岩化及深部的钾长石化，金青顶蚀变较弱。在绢英岩化和绢云母化蚀变过程中，两矿床Na2O和REE降低，Au、Ag升高，金青顶变化幅度相对较小。热液带入的组分均为Au、Ag、As、Co、Cu、K2O等，在大尹格庄带入组分还包括Pb、Zn、Fe、SiO2。似伟晶状钾长石化均使两矿区K2O显著升高，Au和Ag略有升高，其余组分降低，尤其轻稀土降低显著。引起大尹格庄矿床围岩发生绢英岩化和似伟晶状钾长石化的初始流体δ18O值下限分别为3.3‰和4.4‰，以岩浆热液占主导；引起金青顶矿床围岩发生似伟晶状钾长石化和绢云母化的初始流体的δ18O值下限分别为2.1‰和1.2‰，也以岩浆热液为主，但不排除有大气降水参与。 |
| 中文关键词:主元素 微量元素 氧同位素 围岩蚀变 大尹格庄 金青顶金矿 胶东 |
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| Geochemical Study of Granitic wall-rock Alteration in Dayingezhuang Gold Deposit of Alteration Rock Type and Jinqingding Gold Deposit of Quartz-vein Type |
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| Abstract:In order to understand the change in elements in the wall-rocks of the Dayingezhuang and the Jinqingding gold deposits during hydrothermal alteration and the sources of the ore-forming fluids, the authors studied the composition of major and trace elements and oxygen isotopes in the unaltered and altered granitic wall-rocks. The Guojiadian and the Jingqingding granites which are related to the two deposits respectively are depleted in Nb, Ta, P, Ti, and have εNd(t) values of -11.9～-14.5, indicating their derivation from Precambrian crustal sources. The intensities of wall_rock alterations of the two deposits are somewhat different. In the Dayingezhuang glod deposit alterations are relatively strong, with sericite_quartz alteration along the fault zone and potash_feldspar alteration in the lower position. The Jinqingding gold deposit has limited and zoning wall-rock alterations, from the gold_bearing pyrite-quartz vein outwards to sericitization granite to K-feldspar alteration. The most prominent changes in chemical composition, however, are similar in sericite_quartz alteration in Dayingezhuang and sericitization in Jinqingding, i.e. decrease in Na and REE and increase in Au and Ag, though differences exist in amounts of the changes, with generally smaller changes in Jinqingding. In these alterations the components added to the wall_rocks from the fluids include Au, Ag, As, Co, Cu, K in both deposit areas and Pb, Zn, Fe, Si only in Dayingezhuang. When wall-rocks were subjected to potash-feldspar alteration in both deposits, K increased evidently and Au and Ag also increased to a less extent, while other components, especially LREE, decreased. Initial δ18O values of fluid causing the alterations were calculated according to Taylor′s models of closed and open systems of water-rock interaction. In Dayingezhuang area, the fluid causing sericite-quartz alteration and pagmatitic K-feldspar alteration had initial δ18O value higher than 3.3‰ and 4.4‰, respectively, which suggests that the fluid was dominated by magmatic thermal solution. In Jinqingding area, initial δ18O values of the fluid causing pagmatitic K-feldspar alteration were higher than 2.1‰, and the fluid responsible for the sericitization had initial δ18O value not lower than 1.2‰, indicating a main source of magmatic thermal solution, but a small amount of meteoric water might also have played a certain role. |
| keywords:composition of elements and oxygen isotopes, hydrothermal alteration, Dayingezhuang and Jinqingding gold deposits, Eastern Shandong |
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