辽宁朝阳南部蛇纹石石棉矿床成因探讨

本区蛇纹石石棉矿床,前人多认为属岩浆期后中一低温热液交代矿床。笔者通过实地考察,室内分析、鉴定,认为本区蛇纹石石棉矿床属改造型层控矿床。一、成矿地质条件及矿(化)带基本特征本区位于朝阳市西南部,北起灵山庙—谢家杖子,南至上柳树杖子,东起吴大成沟一大柏山,西至波针沟,面积约45km~2。其大地构造位置处于华北地台燕山台褶带北段,朝阳—建昌复背斜中段西翼。区域构造由苏家店—柳树杖子背斜及长茂河子—马家店向斜组成,总体方向北东;主要断层方向与褶皱构造线方向一致。

An Investigation Into The Genesis Of Chrysotile Asbestos Deposits In Southern Chaoyang, Liaoning Province

The study area is noted for wide-spread mineralization of cnrysotile asbestos with numerous ore deposits and occurrences characterized by long mining history. In contrast to the post-magmatic origin hold by most of previous workers, the author considers that these deposits are genetically of reformation type stratabound deposits. The elongation of the chrysotile asbestos mineralization zone is strictly controlled by regional structural lineament with its sphtial distribution closely related to basic intrusive bodies. The asbestos veins, have filled into the host rocks along the minute or thin stratification, mainly as composite veins with lesser dendritic veins and stockworks; pinching out and reappearance as well as branching and compounding are characteristic of the composite veins. The carbonate rocks of the Middle Sinian Wumishan Formation make the ore-bearing strata with mineralization zone possessing fixed horizon. The stratification type and chemical composition of the near-ore country rocks have a decisive bearing on asbestos mineralization. Petrochemicaily, the near-ore country rocks are of the type of siliceous dolomite or siliceous calcareous dolomite. The predeccessor mineral prior to the formation of asbestos-chrysotile is produced by autochthonous reformation of chemical composition of country rocks. These facts indicate that structures, magmatic rocks and country rocks are all factors governing the formation of asbestos. The country rocks serve as material sources while structures and magmatic rocks make up the ore-forming condition, i. e., with the prerequisite of ore-forming materials, a slowly ascending magmatic body in a metastable structural environment provides a relatively stable physical (thermodynamic) condition for alteration and mineralization during its emplacement and diagenetic evolution. The regional structures, stratification of wall rocks and interformational fissures supply space for activity of media, distribution of mineralized zone as well as the formation of asbestos veins. In spite of their miscellaneous shapes and diverse modes of occurrence, the asbestos veins are all restricted to fixed horizon. Consequently, the chrysotile asbestos deposits of siliceous magnesian carbolate rock type are reformation type stratabound ones.