赛马-柏林川碱性杂岩常量组分变异的分离结晶制约

FRACTIONAL CRYSTALLIZATTION CONSTRAIN IN INVARIABLE ELEMEHT VARIATION OF SAIMA- BAILINCHUAN ALKALI IGNEOUS COMPLEX

赛马－柏林川碱性杂岩体为侵位于古元古宙与新元古宙之间的缓倾斜岩席状岩体，缓倾的张裂隙制约了分异岩浆的侵位和含矿溶液的流通，交代富集的上地幔产生的富碱岩浆与富集的地壳产生的岩浆以不同比例混合，形成了正长质岩浆和霞石正长质岩浆。含地壳组分较高的正长质岩浆，受富钙辉石、角闪石和镁质较高黑云母的结晶分离制约向硅酸过饱和方向演化；霞石正长质岩浆受富钙辉石—霓辉石、白榴石、含Ｆｅ较高黑云母、黑榴石的分离结晶制约发生分异。稀土元素矿床是霞石正长质岩浆分异残余熔体的产物，侵位于岩体最高层位。

Saima-Bailinchuan alkali igneous complex having intruded between the lower Proterozoic group and the lower Proterozoic group is a slightly inclined sheet-like body. The intrusion of differentiation magma and the flowage of ore solution would be constrained by the slightly inclined extension fracture. The syenite magma and the nepheline syenite magma would be formed from the mixing of magma produced from the metasomatised upper mantle with the magma produced from the metasomatized crust in different ratio. The syenite magma with more component of crust was evolved to the silica-oversaturated magma constrained by the fractional crystallization of calcium-rich pyroxene, hornblende and magnisium-rich biotite. The nepheline syenite magma would be evoluted in the form of fractional crystallization constrained by the fractionation of calcium-rich pyroxene, aegirine-augite,leucite, Fe-rich biotite, and melanite. The REE enriched residual melt penetrated into the top of intrusion would be the products of nepheline syenite magma produced in the process of differentiation.