摘要
苏鲁造山带中胡家林超镁铁质岩地块主要由两部分组成:南部滑石山以蛇纹岩和蛇纹石化橄榄岩为主,夹薄层状石榴橄辉岩-(石榴)单斜辉石岩;北部胡家林主要由(石榴)单斜辉石岩组成,夹厚层状蛇纹岩。蛇纹岩-蛇纹石化橄榄岩低Al2O3、低Ca O和高Mg O,REE含量低,但LREE稍富集。石榴橄辉岩和(石榴)单斜辉石岩低Mg O和Ca O,高REE含量高,其稀土配分曲线均表现出单斜辉石单矿物的配分特征。这些超镁铁岩块中不同岩石的微量元素均具有Pb的正异常,弱的Nb、Ta的负异常,显示地壳流体交代信息。Nd、Sr、Pb同位素特征显示存在亏损地幔与地壳之间的混合作用。亲石元素含量最低的蛇纹石化石榴橄辉岩的Sr、Nd、Pb同位素组成受交代流体控制明显,而石榴橄辉岩和(石榴)单斜辉石岩不明显。胡家林和滑石山超镁铁岩中所含的交代地壳成分不同,胡家林样品受到含水熔体和富水流体的双重交代,滑石山样品主要受富水流体的交代。
The ultramafic body at Hujialin consists of two parts. The southern part,which is the Huashishan body,consists mainly of serpentinite and serpentinized peridotite with thin layers of garnet olivine pyroxenite and（ garnet） clinopyroxenite. The northern part consists mainly of clinopyroxenite with thick layer of serpentinite. Serpentinite and serpentinized peridotite are low in Al2O3 and Ca O and high in Mg O. These rocks are low in REE,but slightly enrich in LREE. The garnet olivine pyroxenite and（ garnet） clinopyroxenite are low in Mg O and high in Ca O and total REE contents. Primitive mantle-normalized trace element patterns for all types of mafic-ultramafic rocks show positive Pb anomaly and weak negative Nb and Ta anomalies,suggesting metasomatism of crustally derived fluid/melt. The Sr,Nd and Pb isotopic compositions of these ultramafic rocks can be explained by mixing between the depleted mantle and the crust at216 Ma. The serpentinized garnet olivine pyroxenite exhibits the lowest concentrations of lithophile elements,suggesting significant contributions from the metasomatic fluid/melt. The garnet olivine pyroxenite and（ garnet） clinopyroxenite were metasomatised by hydrous melt. Therefore,the ultramafic rocks were metasomatised by different compositions of crustal material.
出处
《矿物岩石地球化学通报》
CAS
CSCD
北大核心
2015年第3期601-618,共18页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
国家重点基础研究发展计划项目(G1999075503)
中国地质调查局项目(12120114039001)
关键词
元素地球化学
放射成因同位素
超镁铁质岩
苏鲁造山带
element geochemistry
radiogenic isotopes
mafic-ultramafic rock
Sulu metamorphic zone
