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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。
Through the detailed field observation and indoor analysis of the Dongguashan large copper deposit in Tongling area, Anhui Province, the authors believe that the Dongguashan deposit is a superposition of massive sulphide deposited during the Hercynian period by Yanshanian magmatic mineralization Large copper deposits. After magmatic superimposition and transformation, the laminar chevron-rich water-rich high-Mg carbonate rocks at the bottom become serpentine (talc) rocks; pyrite and pyrite are mostly pyrrhotite. This metamorphism is done in a nearly isochronal, isochronal, similar to lithicization. The metamorphic skarn was formed under magmatic conditions. Such skarns were significantly later than the layered “skarn” formed under confined conditions. Through the magmatic superimposition and transformation, the gold emission effect produced by the temperature field causes the gold to be enriched toward the lower temperature, and the gold grade in the deposit increases significantly from the bottom up (0 · 15 × 10 -6, Upper 16.47 × 10 - 6). During the process of magmatic superimposition and reformation, the gold-releasing effect is one of the mechanisms for the formation of gold deposits. At the same time, the superimposition of Hercynian sedimentary jet-stream massive sulphide deposits and Yanshanian magmatic mineralization is one of the prerequisites for the formation of large-super-large copper (Au) deposits. It is also one of the intrinsic reasons why skarn can form large copper deposits in Tongling area.