高加索Eldjurti花岗岩体的生成环境及岩浆演化特征

Ｅｌｄｊｕｒｔｉ岩体是俄罗斯内高加索地区阿尔卑斯造山活动晚期形成的花岗岩体。笔者研究了岩体中部由钻孔构成深达５０００ｍ的垂直剖面中岩石的岩石化学特征及岩体的生成环境和岩浆演化特征，结果表明Ｅｌｄｊｕｒｔｉ花岗岩体分异成两个岩石化学特征不同的单元，相对偏在性，岩浆分异程度较左的浅部和偏酸性，岩浆分异程度较高的深部。浆结晶分异作用使熔体中Ａｌ，Ｍｇ，Ｆｅ，Ｃａ，Ｎａ不断被消耗，Ｓｉ，Ｋ相对富集于残余熔

THE FORMATION CONDITIONS AND MAGMATIC EVOLUTION OF THE ELDJURTI GRANITE,CAUCASUS,RUSSIA

The Eldjurti granite massif is sited in the Alpine magmato-tectonic belt inCaucasus, Russia. It is one of the youngest granite massifs in the world. It hasbeen drilled from its top to a depth of hearly 5000m. So it is a good sample tostudy magmatic evolution and rock-forming processes in vertical section. Thiswork discusses the granite formation conditions and magmatic evolution. (1) Eldjurti granite was differentiated into two parts with different petro-chemical properties: the relatively basic and poorly differentiated rock body,located in the upper part of the massif and the more acid, highly differentiatedrock body, located at depths. Such difference shows that the chanacteristics ofelement migration are different in granitic magma: Al, Ca, Na, Mg and Fe go up,while Si and K are concentrated at depths. (2) Crystallization differentiaton leads to depletion of Al, Ca, Na, Mg andFe and concentration of Si and K in residual magma. Becauce of the buoyantuplift of volatiles and plagioclase crystals, petrochemically the Eldjurti granitedisplays layering. In the magma chamber the contents of fluids and elementsare not homogeneous. (3) The crystallization conditions of rock-forming minerals change greatlyin veitical section. In the upper part minerals crystallized under dry and high-temperature conditions, while in the deep part under low-temperature and wetconditions.