桂北元宝山宝坛地区约825Ma镁铁-超镁铁岩的地球化学及其地质意义  

Geochemistry and geological implications of mafic- ultramafic rocks with the age of～ 825 Ma in Yuanbaoshan- Baotan area of northern Guangxi

作　　者：葛文春[1] 李献华[1] 梁细荣[1] 王汝成[2] 李正祥[3] 周汉文[1] 

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]南京大学地球科学系,江苏南京210093 [3]西澳大利亚大学地质和地球物理系

出　　处：《地球化学》2001年第2期123-130,共8页Geochimica

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

摘　　要：镁铁-超镁铁岩的岩石学和地球化学特征表明 ,元宝山超镁铁岩中橄榄石的 Fo为 78～ 83，岩石具有明显的包橄结构，具有 LREE亏损、低 Th/Nb和 La/Nb比值以及高ε Nd(t)值 (约＋ 5)，是来源于亏损地幔低程度部分熔融的岩浆堆晶的产物；宝坛地区镁铁-超镁铁岩富集 LREE，具有高的 Th/Nb、 La/Nb比值和低的ε Nd(t)值（－ 0.45～ － 7.01），是镁铁质岩浆上升、结晶过程中与地壳物质混染 (AFC)的结果。超镁铁岩与澳大利亚 Gairdner岩脉群具有相似的不相容元素分布型式和ε Nd(t)值，是导致新元古代 Rodinia超大陆裂解的地幔柱熔融的产物。Petrological and geochemical characteristics show that mafic- ultramafic rocks in Yuanbaoshan area have remarked olivine peritectic texture with Fo values of 78～ 83 in olivines, depletion of LREE, low ratios of Th/Nb, La/Nb and highε Nd(t) values (about＋ 5), implying they are magmatic cumulus derived from partial melting at lower degree of depleted mantle; while the mafic- ultramafic rocks in Baotan area have enrichment of LREE, high ratios of Th/Nb, La/Nb and lowε Nd(t) values (－ 0.45～－ 7.01), indicating they are the result of contamination with crustal material during the ascending and crystallization process of mafic magma, similar to a process of AFC. The ultramafic rocks in this area have similar incompatible elements distribution pattern andε Nd(t) values with Gairdner dyke swarm of Australia, which is the melting product of mantle plume which led to the breakup of late Proterozoic Rodinia Supercontinent.

关 键 词：镁铁-超镁铁岩 地球化学 地幔柱 广西壮族自治区 稀土元素 微量元素 钐-钕同位素 

分 类 号：P588.12[天文地球—岩石学] P595[天文地球—地质学]