关键词: 长石斑晶, 花岗斑岩, 暗色微粒包体, 岩浆液态不混溶

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