陕西省略阳县徐家沟铜矿床地质、地球化学特征及成矿模式

Geological,Geochemical Characteristics and Metallogenic Model of the Xujiagou Cu Deposit in Lueyang County,Shaanxi Province

徐家沟铜矿床位于“勉-略-宁”矿集区内铜厂铜矿西侧,矿体主要赋存于中新元古界碧口岩群郭家沟组中岩段片理化细碧岩中,多呈似层状、透镜状产出,与片理化细碧岩产状一致,或斜切交代细碧岩产出,呈现出明显的构造-热液改造特征。对微量元素及S同位素分析,表明徐家沟铜矿床中Cu、Ni、Co等成矿元素主要来自细碧岩,而S主要来自岩浆。流体包裹体研究也指出,成矿流体属中-高温为主（166-412℃）、中-低盐度（2.6%-10.9%NaCleq）的NaCl-H_2O体系流体,为混合的岩浆水、变质水或建造水,但以岩浆水为主。综合矿床地质、地球化学、稳定同位素和测年结果,徐家沟铜矿床形成于中生代,属于火山沉积-构造-岩浆改造型矿床。

The Xujiagou Cu deposit lies in the west side of the Tongchang Cu deposit in ＂Mianxian-Lueyang-Ningqiang＂ mineralization concentrated area. The orebodies are hosted in the schis tose spilitein the Guojiagou formation of Upper Proterozoic Bikou Group, and they are occurred as stratiformed, lentoid shape, which have similar occurrence with schistose spilite or have replaced the spilite, with obvious hydrothermal replacement texture and deformation features. Trace elements and S isotope compositions of host rocks and ores show that ore-forming materials （Cu, Ni and Co elements） were mainly derived from spilite and magma, respectively. Fluid inclusions of the ores suggest that ore-forming fluids mainly belong to medium-high temperature （166-412℃） and moderate-low salinity （2.6%-10.9% NaCleq） NaC1-H2O series, which were mainly sourced from magmatic water, combined with few metamorphic water or formation water. According to the geological characteristics, geochemistry compositions, stable isotopes and dating results, it＇ s considered that the Xujiagou Cu deposit was formed in Mesozoic and was formed by volcanic-exhalation, regional metamorphism and magmatic metallogenesis.