胶东威海—乳山麻粒岩相岩石的发现及初步研究

THE DISCOVERY AND PRELIMINARY STUDY OF GRANULITE FACIES ROCKS IN THE WEIHAI RUSHAN REGION,EASTERN SHANDONG

摘要: 威海—乳山麻粒岩带是苏北—胶南构造混杂岩带北东段的北西边缘带。麻粒岩体呈无根的透镜状。典型的共生矿物组合为Ｃｐｘ＋Ｇｒ＋Ｐｌ±Ｑ、Ｃｐｘ＋Ｏｐｘ＋Ｇｒ＋Ｐｌ和Ｏｐｘ＋Ｇｒ＋Ｃｐｘ。单斜辉石含Ｊｄ２．５０％—８．７９％，石榴石含Ｐｙｒ１４．４７％—３５．３６％。该麻粒岩形成条件：Ｐ为７．９１—１０．７０×１０８Ｐａ，Ｔ为７１７—８０７℃，地热梯度约２１—２５℃／ｋｍ，埋藏深度约２９—３９ｋｍ，属中压麻粒岩相。其变质作用峰期的年龄约（１９１３±９）Ｍａ。

Abstract: The Weihai Rushan granulite belt is the northwestern marginal zone of the northeastern section of the Subei Jiaonan tectonic melange zone.The granulite bodies have no roots and occur mainly as lenses.The typical mineral assemblages are Cpx+Gr+Pl+Q,Cpx+Opx+Gr+Pl and Opx+Gr+Cpx.The clinopyroxenes contain 2.50% 8.79% jadeite and the garnets contain 14.47% 35.36% pyrope.The granulite facies rocks were formed at P=7.91 10.70×10 8Pa,T=717 807℃,a geothermal gradient of approximately 21 25℃/km and burial depths of roughly 29 39 km;so the rocks belong to middle pressure granulite facies.The age of the peak metamorphism is about （1913±9）Ma.