金山金矿成矿年龄测定及华南加里东成金期的讨论

Metal logenic Age of the Jinshan Gold Deposit and Caledonian Gold Mineralization in South China

金山金矿是中国南方的一个重要金矿床,属于变质细碎屑岩型,产于中元古界双桥山群中。矿石由超糜棱岩型及石英脉型组成。对于其形成时代有晋宁期、燕山期、晋宁期—燕山期、晋宁期+加里东期—印支期—燕山期等多种观点。本文分别采取两种矿石测得其石英流体包裹体Rb-Sr等时线年龄为(406±25)Ma,属于加里东期成矿。根据研究,华南加里东期金矿床分布广泛,除产于华南加里东褶皱带外,也见于其北邻元古宙江南隆起中。产于隆起内的矿床围岩均为元古宙变质细碎屑岩,而产于褶皱带中除元古宙变质细碎屑岩外,还有寒武纪地层,澄江期及加里东期的岩体。华南加里东期金矿床与该区分布最广的燕山期金矿床在赋矿围岩时代、与燕山期岩浆活动的关系、元素组合、主要矿物及矿床类型等方面都有明显不同。研究结果表明华南是中国主要的加里东期成金区,它对研究其他早古生代褶皱带的加里东期成金作用具有启示意义。

The Jinshan gold deposit occurring in metamorphosed fine-clastic rocks of the Mesoprotero-zoic Shuangqiaoshan Group is an important gold deposit in South China. It consists of two types of orebodies, gold-bearing mylonite and gold-bearing quartz vein. Because of different under-standing of dating materials, many metallogenic epochs such as the Jinningian, Yanshanian, Jin-ningian + Yanshanian and Jinningian + Caledonian + Indochinese + Yanshanian, have been proposed. Rb-Sr isochronic dating of fluid inclusions in quartz from the Jinshan gold deposit gives an age of (406 ± 25) Ma, suggesting that the orebodies be formed in the Caledonian period. Many gold deposits were formed in the Caledonian period in south China, which are located not only in the south China Caledonian fold belt. but also in the Proterozoic Jiangnan uplift to ite north. The country rocks of the gold deposits occurring in the Jiangnan uplift differ from those of gold deposits in the Caledonian fold belt: the former is Proterozic metamorphosed fine-clastic rocks, and the latter include Proterozoic metamorphosed fine-clastic rocks, Cambrian formations and Chengjiangian and Caledonian intrusive rocks. Notable differences between the Caledonian and Yanshanian gold deposits in south China are manifested in their wall rocks, late magmatic ac-tivity, element associations, major minerals and gold deposits types. The Caledonian period is one of the most important epochs for the formation of gold deposits in South China. This conclu-sion is of suggestive significance for studying the Caledonian gold mineralization in other early Pa-leozoic fold belts of China.