威海北部古元古代岩石地层──荆山岩群

PALEOPROTEROZOIC LITHOSTRATA IN THE NORTH WEIHAI-JINSHAN GROUP

摘要:

出露于威海北部的古元古界荆山岩群，呈包体状零散分布在新元古代晋宁期荣成超单元中，经过区域对比，可将其划分为3个岩组共6个岩段。麻粒岩、石榴夕线黑云片岩、堇青石榴夕线黑云片岩、方镁石镁橄榄石大理岩及透辉石镁橄榄石大理岩等是荆山岩群经历过麻粒岩相变质作用形成的指示性岩石（组合）。麻粒岩相变质作用分为3个阶段：早期阶段T=550～600℃，P=0．2～0．55GPa，地热梯度平均38℃／km；峰期阶段T=700～820℃，P=0．71～1．0GPa，地热梯度平均26℃／km；晚期阶段T＜700℃，P=0．65GPa，地热梯度30℃／km。属低压区域变质相系。PT轨迹总体呈逆时针形式，表明本区麻粒岩相变质作用发生的大地构造环境靠近大陆边缘的岛弧区。

Abstract:

Paleoproterozoic Jinshan group overcropped in the north Weihai distributes sporadically in the Rongcheng intrusive superunit in the Jinning period of Neoproterozoic. According tothe regional comparasion, it can be divided into three rock formations, including six rocksections altogether. Granulite,Garnet and sillimanite biotite gneiss, periclase and forsteritemarble and diopside forsterite are indicative rock formations of Jinshan group to show itsforming history of granulite facies. The granulite facies me...