宝坛地区透闪石化镁铁质岩石成因的地质地球化学证据  

Geological and geochemical evidence for the genesis of tremolitized mafic rocks from Baotan in northern Guangxi

作　　者：葛文春[1] 李献华[1] 李正祥[2] 王剑成 周汉文[1] 李寄嵎[4] 

机构地区：[1]中国科学院广州地球化学研究所,广东广州510640 [2]西澳大学地质和地球物理系 [3]都地质矿产研究所,四川成都610082 [4]台湾大学地质系,台北10770

出　　处：《地球化学》2000年第3期253-258,共6页Geochimica

基　　金：国家杰出青年科学基金!(49725309);中国科学院重大项目 B项目!(KZ951-B1-413)

摘　　要：宝坛地区呈岩脉状或岩席状侵入于四堡群变质地层之中的透闪石化镁铁质岩石包括堆积的超镁铁质岩和分异的闪长岩，其岩石类型为透闪石化辉石岩、辉橄岩、辉长岩、辉绿岩及门长岩等。该镁铁质－间长质岩石以富集轻稀土和大离子亲石元素、亏损高场强元素（Ｎｂ、Ｔａ）为特征；除堆积成因的超镁铁质岩石外，透闪石化镁铁质岩石及其分异的闪长岩的ＭｇＯ为４．４５％～７．９６％，是镁铁质岩浆经结晶分异（辉石、橄榄石）作用的产物。Tremolitized mafic rocks emplaced as vein or sheet in metamorphic strata of Sibao Group consist of ultramafic rocks and differentiated diorite, such as tremolitized pyroxenite, pyroxene-peridotite, gabbro, diabase and diorite, etc. This suite of mafic and dioritic rocks is characterized by enriched LREE, LILE and depleted HFSE (Nb, Ta), suggesting that mafic magma had ever been contaminated by crustal material. The poikilitic structure of tremolitized ultramafic rocks and its transitional relationships with mafic rocks imply that it is a cumulus phase of mafic magma, not komatiite; tremolitized mafic rocks and its differentiated diorite, with the MgO content ranging from 4. 45% to 7. 96%, are the products of mafic magma through crystal fractionation (pyroxene, olive). Mafic rocks, together with the synchronous granites in this region, constitute a kind of similarly bimodal rock association, which is related to the breakup of Rodinia supercontinent.

关 键 词：镁铁质岩石 岩石成因 透闪石 地质地球化学 

分 类 号：P588.242[天文地球—岩石学] P578.955[天文地球—地质学]