摘要
碳酸岩是出露相对较少的幔源岩石,其中Sr与Nd是研究地幔物质组成的主要对象之一。本文统计了世界上主要碳酸岩的锶、钕、铅同位素组成特征;研究显示,碳酸岩源区主要是洋岛玄武岩高U Pb的HIMU端员和富集端员(EM1或EM2)的混合作用;此外大部分碳酸岩的锶、钕同位素落在大洋玄武岩范围内;这些均表明其成因与地幔柱有密切联系。碳酸岩及与之共生的硅酸岩的同源或独立源区模式都很难充分解释两者同位素组成特征,这反映碳酸岩的演化模式涉及更复杂的过程。可能是俯冲作用使碳酸岩源区经历不同时间和程度的富集、亏损过程导致地幔源区成分不均一。
Carbonatites are rare mantle-derived magmatic rocks. They have very high Sr and Nd concentrations and can provide valuable information on the composition of the mantle. Based on the Sr, Nd, Pb isotopic geochemistry of carbonatites worldwide, it shows that the source of carbonatites was generated by mixture of HIMU (high U/Pb ratios in OIB) with enrichment mantle end-members (EM1 or EM2). In addition, Sr and Nd isotopes of most carbonatites lie in range of the oceanic basalts. Those facts suggest that the source of carbonatites is related with plume. The genetic models (same or single source) of carbonatites and associated rocks don't sufficiently decipher the characteristics of their Sr, Nd and Pb isotopes. This shows that the source of carbonatites underwent complex evolutional processes. Crustal material subducted into the source of carbonatites. This was followed by enrichment and depletion processes at different time and degrees, and resulted in inhomogeneity of the mantle source.
出处
《矿物岩石地球化学通报》
CAS
CSCD
2004年第4期336-343,共8页
Bulletin of Mineralogy, Petrology and Geochemistry
基金
国家自然科学基金(40303004)
中国科学院地球化学研究所创新项目资助
