南秦岭汉阴北部金矿田长沟金矿区控矿构造解析

Analysis of ore-controlling structure in the Changgou gold deposit of the northern Hanyin gold orefield,southern Qinling Mountains

南秦岭汉阴北部金矿田含矿岩系主要是志留系梅子垭岩组中浅变质岩层,该套地层经历了中生代的构造变形,复杂多样,其中发育的脆-韧性剪切带成为梅子垭岩组发育蚀变岩型金矿富集的良好场所。通过对汉阴北部金矿田近年新发现的长沟金矿区及周邻区带成矿地质背景、控矿构造特征等进行解析研究,结合以往资料,总结汉阴北部金矿田该类型金矿床的控矿构造特征和成矿规律,初步探讨长沟金矿床的热液成因类型。研究发现汉阴北部金矿田区发育有五条脆-韧性剪切带,其构造样式、变质作用具多样性和多期性,其中第二期变形与金成矿作用关系密切;长沟金矿区受区域DSZ3(≈RF5)脆-韧性剪切带及多期构造置换中的S2面理控制,控矿构造样式具有斜列排布特征。含矿流体包裹体研究认为其在低—中温热液环境形成,主要是在退变质作用下易于在局部两种岩性差异界面附近、片理面之间薄弱变形带、密集剪切节理带或劈理化带等有利构造部位含金热液发生富集成矿。因此,脆-韧性剪切带及其多期面理置换与密集片理、剪切节理带及热液蚀变岩是主要的控矿构造类型。进一步的找矿预测工作主要应该紧抓其脆-韧性剪切带的走向延伸和倾向延深,更应重视侧向斜列富集规律。

The ore-bearing rock series in the northern Hanyin gold orefield of the southern Qinling mountains mainly consists of the shallow metamorphic rocks in the Silurian Meiziya formation,which underwent complex tectonic deformation in Mesozoic,and the brittle-ductile shear zone is a good place for the enrichment of altered rock type gold deposits in the Meiziya formation.Based on the comprehensive analysis of the metallogenic geological background and ore-controlling tectonic characteristics of the newly discovered Changgou gold deposit and its adjacent areas in the northern Hanyin gold orefield in recent years,the ore-controlling tectonic characteristics and ore-forming rules of this type of gold deposits in the northern Hanyin gold orefield are summarizes,and the hydrothermal genetic type of the Changgou gold deposit is preliminarily discussed.It is found that there are five brittle-ductile shear zones developed in the northern Hanyin gold orefield,and their tectonic patterns and metamorphism are diverse and multistage,among which the second deformation is closely related to gold mineralization.The Changgou gold mining area is controlled by the regional brittlle-ductile shear zone DSZ3(≈RF5)and S2 bedding in multi-stage tectonic replacement,and the ore-controlling structure is characterized by oblique arrangement.The study of ore-bearing fluid inclusions shows that the formation of ore-bearing fluid inclusions in low-medium-temperature hydrothermal environment is mainly due to the accumulation and mineralization of gold-bearing hydrothermal fluids in favorable tectonic areas such as the weak deformation zone,dense shear joint zone or cleavage zone near the interface of two local lithologic differences and between foliation planes.Therefore,the brittlle-ductile shear zone and its multi-phase plane displacement and dense foliation,shear joint zone and hydrothermal altered rock are the main ore-controlling structural types.Further prospecting and prediction work should focus on the trend extension and dip extension of the brittle-ductile shear zone,and more attention should be paid to the law of lateral oblique accumulation.