北苏鲁荣成地区超高压变质带大理岩中石榴辉石岩的退变质过程  

Retrograde Reactions of Garnet Pyroxenite Inclusion within Marble from Rongcheng,Northern Sulu UHPM Terrane

作　　者：蔡志慧[1] 唐哲民[1] 梁凤华[1] 陈方远[1] 张丽军[2] 

机构地区：[1]中国地质科学院地质研究所大陆动力学重点实验室,北京100037 [2]河北工程技术高等专科学校水利系,河北沧州065001

出　　处：《现代地质》2010年第1期175-186,共12页Geoscience

基　　金：国家自然科学基金重大项目(40399141);中国地质调查局地质大调查项目(121201056606)

摘　　要：北苏鲁荣成地区超高压变质带大理岩中的退变质石榴辉石岩包裹体具有"核-幔-边"结构,核部主要由石榴子石与单斜辉石组成,幔部含有由细小角闪石与绿帘石组成的后成合晶以及颗粒较大的角闪石与单斜辉石,通过详细的岩相学分析以及矿物成分分析,认为这些后成合晶是由石榴子石、单斜辉石以及来自围岩的流体共同反应而产生,大颗粒的角闪石主要是由辉石转变而来的,在幔部这个转变并不彻底,仍有一些残余辉石颗粒。边部主要由角闪石和绿帘石组成。该石榴辉石岩曾经历榴辉岩相超高压变质阶段。没有柯石英超高压代表性矿物(采样处的其他类型岩石都含有柯石英)的原因是石榴辉石岩的原岩为超基性岩。Garnet pyroxenite inclusions within marble,from Rongcheng,northern Sulu ultrahigh-pressure metamorphic（UHPM） terrane are studied in detail.The garnet pyroxenite samples are divided into three parts（core,mantle and rim） according to their petrographic characteristics.The core of the retrograded garnet pyroxenite is composed of garnet and clinopyroxene.In the mantle,fine grained symplectites of hornblende and epidote occur along the garnet and clinopyrocene grains.It is suggested that these symplectites are developed from garnet and clinopyroxene reacted with fluids from the wall rock.The reaction was not completed which is evidenced by the larger hornblende and clinopyroxene relics remained in the retrograded garnet pyroxenite mantle.The larger hornblende came from the clinopyroxene.The rim of the retrograded garnet pyroxenite is composed of hornblende and epidote.The results of Laser Raman experiments indicate no coesite existed in the retrograded garnet pyroxenite,whereas coesites are found in all other type of rocks near these sample sites.It is likely that the garnet pyroxenite also proceeded the ultrahigh pressure metamorphic condition.The reason of absence of coesite in the rock is merely that the primary rocks are ultramafic.

关 键 词：石榴辉石岩 退变质过程 苏鲁 超高压变质带 

分 类 号：P588.31[天文地球—岩石学]