Study on Ore-forming Fluid Inclusions and Geological Characteristics of the Gongpoquan Porphyry Copper Deposit in Beishan, Gansu Province
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摘要: 公婆泉铜矿位于甘肃-蒙古-北山斑岩铜矿成矿带公婆泉岛弧区,为典型的斑岩型铜矿,赋矿围岩主要为英安斑岩、花岗闪长斑岩和石英闪长玢岩.矿石矿物主要有黄铜矿和斑铜矿,其次有少量的黄铁矿、闪锌矿、方铅矿以及蓝辉铜矿等.对含矿石英脉中流体包裹体研究表明,公婆泉铜矿主要有4类流体包裹体:纯气相包裹体(I型)、纯液相包裹体(II型)、原生富液相气液两相包裹体(IIIa型)以及次生富液相气液两相包裹体(IIIb型).其中与成矿密切相关的为原生富液相气液两相包裹体(IIIa型).该类包裹体的均一温度集中在100~260 ℃,盐度在0.18%~9.98%(NaCleq),密度为0.75~1.0 g/cm3;激光拉曼探针分析表明,液相成分以H2O为主,气相成分以H2、N2以及CH4为主.成矿流体具有中低温、低盐度以及低密度的流体特征.斑岩的上升侵位为矿床的形成奠定了物质基础——Cu、S.斑岩分异出成矿流体沿早期断裂系统向上运移发生减压沸腾导致相态分离,从而造成Cu发生沉淀.因此,减压沸腾可能是导致流体中金属卸载的主要原因.
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关键词:
- 矿床地质 /
- 流体包裹体,公婆泉铜矿 /
- 甘肃北山
Abstract: Gongpoquan copper deposit is a typical porphyry copper deposit located in the Gongpoquan island arc zone of Gansu-Mongolia-Beishan porphyry copper metallogenic belt. The host rocks are characterized by dacite porphyry, granodiorite porphyry and quartz diorite porphyrite. The ore minerals mainly consist of chalcopyrites and bornites, with few pyrites, sphalerites, galenas and digenites etc. The study of fluid inclusions in the ore-bearing vein-quartz concludes four types of fluid inclusions namely pure vapor inclusions (I-type), pure aqueous inclusions (II-type), nature aqueous-rich gas-liquid two phase inclusions (IIIa-type) and secondary aqueous-rich gas-liquid two phase inclusions (IIIb-type). The mineralization is closely related to nature aqueous-rich gas-liquid two phase inclusions, i.e. IIIa-type. This kind of fluid inclusions have homogenization temperature of 103-250℃, salinity of 0.18%-9.98%(NaCleq), and density of 0.75-1.0g/cm3, which shows that the ore-forming fluid is mesothermal, with low salinity and low density. Laser-Raman microspectroscopy analyses reveal that the liquid phase is mainly composed of H2O, and the vapor phase of H2, N2 and CO2. The rising and emplacement of porphyry provided ore-forming materials such as Cu and S for the formation of the copper deposit. Due to late tectonic activity, the porphyry became mobilized and generated ore-forming fluid through differentiation, the decompressing boiling of which resulted in separation of phases whilemigrating upward, and then Cu precipitated. Therefore, the decompressing boiling might be mainly responsible for the precipitation of metal in fluid.-
Keywords:
- ore geology /
- fluid inclusions /
- Gongpoquan copper deposit
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