| 大别造山带前陆阳新盆地古近纪玄武岩地球化学特征与成因研究 |
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| 关键词:Paleogene basalt lithospheric mantle lower mantle Yangxin basin |
| 基金项目:国家“973”项目(TG1999075505)和(2003CB716502)，地质调查项目“湖北红安地区构造和年代格架与高压-超高压变质带的演化”(200013000169) |
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| 摘要: |
| Geochemistry and Genesis of Paleogene Bsalts in the Yangxin Basin,Foreland of the Dabie Orogen |
| The Paleogene basalts in the Yangxin basin on the foreland of the Dabie orogen are from quartz tholeiitic basalt to olivine-tholeiitic basalt in composition, characterized by relative richness of large ion lithophile (LIL) elements (Rb, Ba,K,Th,U),and slight to medium degree depletion of high field strength (HFS) elements (Nb,Ta).The rocks are generally similar to the initial rifting tholeiitic basalt in geochemical features but distinctly different from continental tholeiitic basalt, which is characterized by strong depletion of HFS (Nb, Ta) elements. The tholeiitic basaltic magma had undergone fractional crystallization of minerals (mainly olivine) by about 4.5 percent before extrusion,and the primary magma was formed by about 15 percent partial melting of source materials, which might have included two components, i.e., the FOZO from the lower mantle and the enriched continental lithospheric mantle. Geochemical characteristics of the Eogene tholeiitic basalts in different parts of the orogen have affinity. This suggests that, with the delamination of the mountain root, the FOZO magma from the lower mantle (probably as mantle plume) migrated upward and reformed the continental lithospheric mantle extensively, causing the indistinctness of two large blocks of lithospheric mantle (Yangtze and North China) near the subduction zone. Except for those within the orogen, the basalts formed have more FOZO characteristics but preserve different degrees of lithospheric mantle features. |
| XUE Huai-min,DONG Shu-wen,LIU Xiao-chun,LI San-zhong.2004.Geochemistry and Genesis of Paleogene Bsalts in the Yangxin Basin,Foreland of the Dabie Orogen[J].Acta Geoscientica Sinica,25(1):25-32. |
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