Abstract: Eldjurti granite is a small intrusion roughly 2.0 Ma.y.old, which is located in the Caucasus in the South-East part of Russia. The intrusion is structurally simple with a nearly homogeneous porphyritic biotite granite from centre to margin. Throughout the pluton there are randomly distributed mafic microgranular enclaves. Both in this enclave and granite exist a kind of plagioclase phenocryst, which has a parthy core. ln such plagioclase there are two composition surfaces, which divided the plagioclase phenocryst into three parts: parthy core, inner rim, and outer rim. The composition surface between parchy core and inner rim is coincident with a resorption surface, which implies that the core has been fused. Plagioclase phenocryst from enclave has a wide inner rim and a narrow, discontinuous outer rim, in contrast, plagioclase from granite has a wide outer rim, but a narrow, discontinuousinner rim. Such characteristics allows us to propose a model which give a reasonable explanation for the formation and the characteristics of the mafic microgranuclar enclaves in Eldjurti granite.

Key words: plagioclase phenocryst, porphyritic granite, mafic microgra-nular enclave, liquid immiscibility

摘要： 位于俄罗斯境内高加索地区的埃提哲尔花岗岩体中广泛分布暗色微粒包体，花岗岩体由黑云母花岗斑岩及暗色微粒包体组成，这两种岩石均含有一种具斑点状结构核的斜长石斑晶。在这类斜长石斑晶内部可分辨出两个成分变异面，这两个界面把斜长石斑晶分割成３部分：具斑点状结构的核部；偏基性且富含细小矿物（磷灰石，黑云母等）包裹体的内环带和具正环带结构的酸性外环带。虽然花岗斑岩和包体中斜长石斑晶的核部特征完全相同，但它们的内外环带差别很大，包体中的斜长石斑晶具有宽的内环带和窄且不连续的外环带，而花岗斑岩中的斜长石斑晶具有窄且不连续的内环带及宽的外环带。依斜长石的这些特征我们建立了其形成模式，并对暗色文粒包体及寄主花岗斑岩的同源性作了合理的解释。

关键词: 长石斑晶, 花岗斑岩, 暗色微粒包体, 岩浆液态不混溶