秦岭群中花岗质正片麻岩的确认及其意义

THECONFIRMATION OFGRANITIC ORTHOGENEISSES IN THE QINLING GROUP AND THEIR SIGNIFICANCE

野外填图及室内分析表明，原秦岭群中存在一种花岗质片麻岩，表现为眼球状、条带状黑云斜长片麻岩及二长片麻岩。本文以产状、成分、所含包体、残留的变余结构及侵入关系为依据，论证了它们是以片麻岩形式存在的古老花岗质深成岩体。这一确认对原秦岭群组成的认识及其早期地壳演化的探讨等方面具有重要意义。

Field geological mapping and indoor analysis indicate that there exist granitic gneisses in theQinling Group. These gneisses are represented by augen and banded biotiteplagioclase gneiss andmonzonitic gneiss. Their occurrence,composition,enclaves,palimpsest structure and intrusive con-tact relationships prove that they are ancient granitic plutons which now occur in the form ofgneisss. This confiramtion has significance for the understanding of the composition of the origi-nal Qinling Group and study of the early evolution of the crust.