粤西-桂东四套成矿系统地质特征、成因类型及构造启示

Geological characteristics and genetic types of four series of ore-forming systems at West Guangdong and East Guangxi and their implication for the tectonic evolution of Qinzhou-Hangzhou Joint Belt

粤西-桂东地区是我国重要的矿产资源基地,是研究区域成矿作用和大地构造演化耦合关系的理想地区。本文基于粤西-桂东地区四套主要成矿系统的地质特征的研究,结合区域内矿床精确定年和构造演化的研究成果,探讨四套主要成矿系统的成因类型、成矿构造背景及其对钦杭结合带构造演化的启示。其中,广东云浮硫铁矿产于震旦系大绀山组,块状和条带状矿石呈层状产于火山沉积岩系中,是一套与海底热液活动密切相关的VMS成矿系统,形成于新元古代俯冲相关的弧后(间)拉张盆地;盘龙铅锌矿产于泥盆系上伦组,角砾状和胶状矿石产于浅海相白云质碎屑岩中,是一套加里东期被动大陆边缘的SEDEX型铅锌成矿系统;河台金矿田赋存于震旦系乐昌组,脉状矿体严格受断裂和蚀变带控制,是一套变质热液主导的造山型金矿成矿系统,形成于印支-燕山期陆内走滑或陆陆碰撞背景;圆珠顶铜钼矿床形成与燕山期(155Ma)二长花岗斑岩密切相关,细脉浸染状矿石赋存于岩体的内外接触带,是一套陆内伸展背景的斑岩铜钼成矿系统。总体而言,粤西-桂东地区经历了新元古代俯冲、加里东期被动大陆边缘、印支期陆内走滑(或陆陆碰撞)和燕山期陆内伸展四个重要的构造事件,这与钦杭结合带总体构造演化过程一致。

The area of West Guangdong-East Guangxi is one of the important base providing large amounts of gold,silver,copper,molybdenum,lead,zinc and pyrite,etc. Four main series of ore-forming systems in this area are distinguished. The Dajiangping pyrite deposit,hosted in the Daganshan Formation,is consisted of massive and banded ores,which possibly represent a VMS mineralization system form in a Neoproterozoic back-arc basin. The Panlong sedimentary exhalative（ SEDEX） Pb-Zn deposit is hosted in the marine calcite of Devonian Shanglun Formation,interpreted to be formed in a passive continental margin. The Hetai gold deposit in hosted in silicified fracture zones of Sinian metamorphic rocks,which is a typical orogenic gold deposit formed in the Indosinian to Yanshanian collisional or strike-slipping setting. The Yuanzhuding Cu-Mo deposit is related to porphyry granite and formed at 155 Ma intracontinental extensive setting. Combining with the published tectonic evolution and geochronological data,the area of West Guangdong and East Guangxi have experienced Neoproterozoic subduction,Devonian passive continental margin,Indosinian-Yanshanian collision（or strike-slip） and Late Yanshanian intra-continental extension,which maybe code the Qinzhou-Hangzhou joint belt also experiencing the similar tectonic evolution.