中国蛇绿岩型铬铁矿的研究进展及思考

Petrogenesis of Ophiolite-type Chromite Deposits in China and Some New Perspectives

中国广泛分布有不同时期的蛇绿岩。相对于全球一些大型蛇绿岩铬铁矿床(如Kempirsai,Bulquiza,Guleman等),我国同期蛇绿岩中赋存的铬铁矿床规模都较小(如萨尔托海,东巧,罗布莎等)。近年来的研究认识到绝大多数成矿的蛇绿岩都形成于俯冲带上覆岩石圈。熔-岩反应是目前用来解释豆荚状铬铁矿成因的流行假说,但仍然不能解释铬元素的有效富集过程——即铬铁矿矿床的形成过程。高铬含量是岛弧玄武岩原始岩浆的特征,但与成矿要求的铬含量相差甚远;岛弧原始玄武岩浆结晶出富铬尖晶石,有利于成矿,但这个岩浆演化和相平衡过程仍然难以造就具有工业意义的矿体、矿床。那么存在形成富铬熔体的机制吗?又如何运移这些富铬熔体并集中结晶成矿?这些仍然是豆荚状铬铁矿成因的关键问题,有待于进一步思考研究。

Ophiolites of varying ages are widespread in China, some of which contain chromite deposites of industrial value. However, compared with some of the world＇s large ophiolite chromite deposites （e.g., Kempirsai, Bulquiza, Guleman）, the Chinese chromite deposits are small （e.g., Sartohay, Dongqiao, Luobusa）. Recent research recognizes that most ophiolites with significant chromite reserves are all formed in a surpasubduction zone environment. Melt-rock interaction is a popular interpretation for the origin of podiform chromite deposits, but the actual mechanism in this model for chromite enrichment remains unclear. It remains the primary task to understand process or processes of chromium enrichment towards the formation of chromite deposits. Is the formation of chromium-rich melts necessary？ If so, when, where, how, and under what conditions could this take place？ These are additional processes beyond the well-understood aspects of the petrogenesis that need to research towards an effective chromite mineralization model.