云南金顶铅锌矿区赋矿角砾岩成因分析

Genesis analysis of ore-forming brecciaed rocks in Jinding Pb-Zn deposit,Yunnan

云南兰坪金顶铅锌矿床矿体沿推覆构造、次级断裂旁侧的构造——溶蚀角砾岩带分布,有两种岩性的矿化角砾,一种为砂岩,另一种为灰岩。有关角砾成因的争议较多,有"滑塌成因""溶蚀成因"等。随着地质调查工作的深入,越来越多的证据表明这些角砾与推覆构造伴生,空间上定位分布,角砾岩性均一,角砾间无碎屑物支撑,角砾破碎程度分布和所受应力具有明显的分带性,角砾与表面蚀变物界线截然,无蚀变退色现象,伴随流体的包裹体均一温度较低等,这些特殊的地质特征说明角砾是构造成因,非"滑塌成因"和"溶蚀成因"。

The Jindin lead-zinc ore bodies are usually distributed in the tectonic-dissoluted breccia belt near the nappe structure and second fault.There are two kinds of mineralized breccias, i.e.,sandstone and limestone. There is still argument about the formation of the “tectonie-dissoluted breccia”. Someone thought that the teetonic-dissoluted breccia was formed due to collapsed stratums located at the edge of the basin. Another thought that the teetonic-dissoluted breccia was formed due to the broken stratas which located on the fault-fracture surface, and then were dissolved and accumulated by underground rich salt-bearing water. With the deep study and investigation, more evidences show that formation of breccias were associated with the nappe structure, such as spatial orientation distribution of these breccias nearby the nappe structure, homogeneous lithology, without support and filling of debris among breecias, obvious zonation of fragmentation and stress intensity, clear boundary beween the breccias and alteration located breccias surface, etc..