摘要
本文从岩相学、地球化学和同位素地质研究角度出发,详细论证了哈达庙含金侵入杂岩体的地质地球化学特征、成因机制及其与金矿化的关系。研究认为:侵入杂岩体内的闪长玢岩、石英闪长岩、花岗闪长岩、花岗斑岩和隐爆火山角砾岩是同源岩浆不同演化阶段的产物,成岩成矿物质来源与含基性岩成分较多的陆壳岩石深熔作用有关。从杂岩体边缘到核部,随着岩体从中基性到酸性方向的演化,碱质组分、成矿元素(Au、Ag)和挥发份的不断聚集,不仅形成了一系列隐爆火山角砾岩脉,同时也促进了金的沉淀富集。对比研究表明:流纹岩脉与侵入杂岩体是异源岩浆不同演化阶段的产物。
The Hadamiao gold-bearing intrusive complex occurs in the Xianghuangqi synclinorium of the late Hercynian Tianshan-Nei Mongol fold belt. Its country rocks are mainly Lower Permian sedimentary rocks.The complex, controlled by an EW- or NE-trending tectonic line consists of diorite porphyrite, quartz diorite, granodiorite, granite porphyry and a cryptoexplosion volcanic breccia zone. Chemically, it belongs to calc-alkaline rock series and exhibits some features of Ⅰ-type or anatectic granitoids.Incompatible elements (K, Th, Ta, Nb, La and Ce), Au and Ag and the Rb/Sr ratio increase while compatible elements (Ti, V, Cr, Mn, Sc, Fe and Sin) decrease with the evolution of the petrochemical composition from basic to acidic. As compared with gold-bearing granite porphyry in the complex, the gold-barren porphyry is characterized by enrichment in silica and alkalis and obvious depletion in trace elements, which might be taken as indicators for evaluation of gold-bearing porphyry in this area. Studies show that the rhyolite dike swarm has different geochemical characteristics (especialy the trace element abundance)from the complex. The main cayuse for this might be due to the difference in trace element between their original rocks. Whole-rock lead isotopic ratios of the complex vary to a certain extent: ^(206)Pb/^(204)Pb= 19.5863—18.7771, ^(207)Pb/^(204)Pb=15.6731—15.6286 and ^(208)Pb/^(204)Pb=39.9690—39.3214, showing the features of anomalous lead. The ^(232)Th/^(238)U, Th/U, slope of the anomalous lead line and t, are 2.88, 2.78, 0.054 and 1300 Ma respectively.Based on these geochemical and isotopic characteristics combined with the geological setting of the complex, it has been suggested that the rock-forming material originated mainly by anatexis of Proterozoic basement rocks (1300 Ma B. P.). The authors have concluded that the intrusive complex resulted from different stages of evolution of the comagmas whereas gold mineralization was only a special event during rock-forming processes.
出处
《地质论评》
CAS
CSCD
北大核心
1989年第4期297-306,共10页
Geological Review
