中国前寒武纪层控铜矿的矿石组构特征及其成因分析

THE CHARACTER AND GENESIS OF THE FABRICS OF THE PRECAMBRIAN STRATA-BOUND COPPER ORE DEPOSIT IN CHINA

本文是研究中国前寒武纪层控铜矿矿石组构特征的初步总结。所研究的层控铜矿床既有早前寒武纪的,也有属于晚前寒武纪的。虽然早、晚前寒武纪层控铜矿床在地质特征方面有显著的区别(张秋生,1981),但是这些矿床的矿石组构特征往往有许多相似之处。早、晚雨寒武纪层控铜矿床的对比研究有利于查明矿石组构的演化特征。

This paper consistes of four sections.The first section, discusses the conception of strata-bound deposits.The second section gives the classification of the strata-bound copper ore deposits in China.The third section outlines the main geologycal features of the pracambrian strata-bound copper ore deposits in China.The fourth section describes the fabrics of strata-bound copper ore deposits.The ore structure can be divided into two types; the stratified and the veined.The stratified structures consist of stratiform structure, rhythmic stracture, current erosion structure, synsedimentary deformation and concretion structue.The vein structures consist of synsedimentary vein structue, syndiagenetic vein structure, metamorphic hydrothermal vein structure and post-metamorphic hydrothermal vein structure.The author thinks that the coexistence of the stratified structures and the vein structuresis a main feature of the precambrian strata-bound copper ore deposits in China.The ore texture also can be divided into two types: synge tie and metamorphic.The syngenetic ore texture includes synsedimentary texture and syndiagenetic texture; the metamorphic texture includes metamorphic recrystallizatibn texture, metamorphic hydro-thermal texture, ex-solution texture and remelting texture.The author thinks that the coexistence of the syngenetic texture and metamorphic texture is characte ristic of the ore texture of precambrian strata-bound copper ore deposits in China.The ores show clear evidence of post-depositional deformation and recrystallization. It is now more clear through mineralogical, textural and structural studies, that such ores have been affected to a greater or a lesser degree, by the regional metamorphism.The precambrian strata-bound copper ore deposits in China are especially switable for the study of the effect of metamorphism on textures and structures. The metamorphic grade varies considerably from district to district, from lower greenchist to granulite fades. It is thus possible to study texture and structure of copper ores in areas of very different metamorphic conditions and then to build up a fairly complete picture of the effects of increasing regional metamorphism on the fabrics of copper ore deposits in China.The ideas expressed in this paper came from the author's observations.