摘要
通过对安徽铜陵地区冬瓜山大型铜矿床详细的野外观察和室内分析对比 ,笔者认为 ,冬瓜山矿床是一个海西期同生沉积的块状硫化物被燕山期岩浆成矿作用叠加而形成的大型铜矿床。经过岩浆叠加改造 ,底部的纹层状含燧石富水高镁碳酸盐岩变为蛇纹石 (滑石 )岩 ;胶黄铁矿、黄铁矿大部分变为磁黄铁矿。这种变质过程是在一种近于封闭的等化学条件下完成的 ,类似角岩化。在有岩浆加入的条件下形成交代夕卡岩 ,这类夕卡岩明显地晚于封闭条件下形成的层状“夕卡岩”。通过岩浆的叠加改造 ,在温度场作用下产生的排金效应使金向上部温度较低的场所富集 ,使矿床中金品位由下而上显著增大 (下部 0 .15× 10 - 6 ,上部 16 .4 7× 10 - 6 ) ,岩浆叠加改造过程中 ,排金效应是金矿床形成的机制之一。同时 ,海西期沉积喷流型块状硫化物矿床与燕山期岩浆成矿作用的叠加是形成大型—超大型铜 (金 )矿床的前提条件之一。也是铜陵地区夕卡岩能形成大型铜矿床的内在原因之一。
Based on detailed field observation and analysis on the large-sized Dongguashan copper deposit in the Tongling area, Anhui Province, it is suggested that the Dongguashan deposit is a large copper deposit formed by superimposition of the Yanshanian magmatic mineralization on the Hercynian synsedimentary massive sulfides. After superimposition of magmatic mineralization, chert-bearing water-rich carbonates, such as dolomite, ankerite and/or calcite were turned into serpentitite-talcite; greite and pyrite into pyrrhotite. This kind of metamorphic process is similar to hornfelsic alteration under a nearly closed isochemical condition. If magma is involved, metasomatic skarn can be formed, but this kind of skarn is obviously later than the stratified skarn formed under a closed circumstance. Furthermore, through superimposition and reformation of magmas, the “gold-driven effect” can happen under the temperature field, making gold enriched upwards to places with relative low temperature, and thus the average gold grade increases upwards from 0.15×10 -6 at the bottom to 16.47×10 -6 at the top. The “gold-driven effect” is one of the ore-forming mechanisms for gold deposits. Meanwhile, the superposition of Hercynian Sedex-type massive sulfide deposits with Yanshanian magmatic ore formation is a necessary process for the formation of large or superlarge copper (gold) deposits in the Tongling area and also one of the interior causes for the formation of special large skarn-type copper deposits in this area.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2005年第1期106-113,共8页
Acta Geologica Sinica
基金
国土资源部科技司专项研究计划 (编号 B0 0 0 2 -3 )
地质调查项目 (编号 2 0 0 10 0 0 0 0 0 4)资助的成果
关键词
叠加改造
岩浆
夕卡岩
铜矿床
矿集区
燕山期
成矿作用
磁黄铁矿
品位
角岩
sedex-type deposit
magmatic ore-formation
superimposition-reformation
large-superlarge ore deposit
Dongguashan copper deposit, Tongling, Anhui
