千里山钨锡金属矿床物质运移模式与成岩成矿关系——小岩体成大矿的一个实例
The Explanation of the Metallogeny about Qianlishan Tungsten-tin by the Theory of Small Magmatic Intrusion Mineralization
-
摘要: 千里山岩体位于湖南省郴州市,处于南岭成矿带中段,出露面积约10km2.作为出露面积不大的小岩体,形成了世界罕见的柿竹园超大型多金属矿床,引发国内外学者对小岩体成大矿机制的广泛关注.千里山岩体由三期花岗岩以及后期脉岩组成,分别为第一期似斑状黑云母花岗岩,第二期中粒黑云母花岗岩,第三期细粒黑云母花岗岩及岩浆近固结时侵入的石英斑岩、花岗斑岩和辉绿岩脉.总结分析前人的地球化学数据后可得出,成分相近的前三期花岗岩与后期花岗斑岩源区不同,反应二者为两次独立的岩浆事件.岩体F含量极高,甚至高于世界花岗岩的平均值几倍以上.含F的流体有助于萃取熔浆中的W、Sn金属,升高金属离子价态并增加流体的饱和度.另外,F的富集可以降低岩浆的固结温度,有效地延长了物质运移的时间.多期次的脉动式的岩浆作用使得流体不断地得到补充.然而,前期近固结的千里山似斑状花岗岩作为圈闭层出现在成矿物质运移的终端,阻碍了流体的扩散,对成矿物质的收敛起了至关重要的作用.结合透岩浆流体理论,以成矿流体为切入点分析讨论物质在流体中的运移过程及卸载方式.Abstract: Qianlishan magmatic intrusion is located on Chenzhou Hunan,and composes 3 periods of granite and late stage dykes,as known as pseudoporphyritic biotite granite,medium-grain biotite granite,short-grain biotite granite and with granite-porphyry and diabase dyke intruding when magma was almost concretionary.The geochemistry data show that early stage granite and the late stage granite-porphyry share the similar component but differ in source region,therefore they are considered two independent magmatic activities.Shizhuyuan,forms large-scale deposits as small magmatic intrusion,arises extensive study of "large deposit in small intrusion" among the pundit around the world.The emphasis of this paper is to analyzing the migration processes of the elements which are dissolved in fluid through the transmagmatic fluid theory.The fluid within F contributes to extracting tungsten-tin metal,and increasing the saturation of the it by rising the valence of metal ion.On the other hand,the enrichment of F could to reduce the crystallizing point of magma,and promote the migration of elements.The fluid is supplemented by impulse magmatic activities repeatedly,and yet blocke its diffusion by concretionary pseudoporphyritic biotite granite that exist in the terminal of the migration of mineralizing material as a shield layer,which plays a vital role in the mineralization.