宁夏贺兰山北段牛头沟金矿地质地球化学特征和矿床成因探讨

Geological and Geochemical Features and Ore Genesis of the Niutougou Gold Deposit in the Northern Helan Shan Mountains,Ningxia

牛头沟金矿位于华北陆块鄂尔多斯地块西缘贺兰山裂陷北段之基底杂岩带,赋矿地层为一套下元古界宗别立群第二亚群(Pt1z2)中的中-深程度变质岩系。矿体受深大断裂(正义关断裂)的次级主断裂(F1)控制;该控矿断裂构造(F1)形成于海西-印支期,经历早期逆冲挤压,晚期局部引张破裂的多期活动阶段,矿化作用主要形成于主断裂(F1)张性破裂阶段,矿化早期主要表现为强烈硅化,矿化晚期硅化岩破裂被主成矿流体充填-交代形成蚀变岩型金矿,为矿区主要成矿类型。石英脉型金矿形成于与主断裂有联系的次级张裂隙中。二者反映矿床类型不同,但成矿作用是一致的。即在动力作用下产生的变质热液在构造的有利部位或裂隙中交代-充填成矿。硫化物硫同位素组成和矿物流体包裹体研究表明,该蚀变岩型金矿成矿物质和成矿流体来源具多源性。

The Niutougou gold deposit lies in the basal complex belt,northern Helan Shan rift,the western margin of the Ordos block in North China.The ore-bearing strata are a set of intermedium-highly metamorphic rocks of the second subgroup（Pt1Z2）in the Lower Proterozoic Zongbieli Group.The ore body was controlled by the subsidiary fault（F1）of a deep and large fault（Zhengyiguan fault）,which was formed in the Hercynian-Indo-China period.This fault experienced early thrust extrusion and late local tensile rupture during multi-stage activities.The altered rock-type gold mineralization occurred in tensile rupture stage.The quartz vein-type gold body was formed in the secondary tensile fissures associated with the main fault.Both deposit types are different,but have same mineralization mechanism,i.e.the metamorphic hot fluid produced by dynamic effect caused replacement-filling mineralization at favorable positions or fissures.The study on sulfide sulfur isotopic composition and ore-fluid inclusions indicates that the altered rock-type gold mineralization and ore-forming fluids stemmed from a variety of sources.