- 责任者：Wei Xun (State Key Laboratory of Isotope Geochemistry ; Guangzhou Institute of Geochemistry ; Chinese Academy of Sciences ; Guangzhou 510640 ; China) ; Xu Yigang
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(10)
- 关键词：大火成岩省 ; large igneous provinces ; 辉绿岩 ; diabase ; 塔里木盆地 ; Tarim Basin
- 页码：p.3323-3335
- 图表：10 illus., 2 tables, 88 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
The Early Permian Tarim large igneous province （TLIP） in Northwest China consists of two main magmatic phases： the earlier one （ ～ 290Ma） represented by basahs in Keping, and the later one （ ～ 280Ma） by uhramafic-mafic-felsic intrusions and mafic dykes in Bachu. In order to identify mantle and crustal components involved in the genesis of the TLIP and to understand the plumelithosphere interaction, we performed zircon U-Pb dating, geochemical analyses on the Bachu dykes. Zircons from sample XHZ-10 are all inherited in origin, thus yielding no constraints on eruption age. Field relationship, however, suggests that the Bachu dykes were emplaced during the second episode of TLIP magmatism. The Bachu dykes experienced fractionation of olivine, clinopyroxene and magnetite. Correlations among εNd and SiO2 and La/Nb, as well as the age spectrum of inherited zircons （2480 ～717Ma, with a peak at ～800Ma） suggest that some dykes with low εNd may have been assimilated by Neoproterozoic basements en route to the surface. Nevertheless, the least-contaminated samples show OIB-like trace element compositions and high εNO （ ±5 ）, consistent with a derivation from a convective mantle source. This is in contrast with the earlier phase of magmatism （～ 290Ma）, which was mainly derived from an enriched sub-continental lithospheric mantle （SCLM）. We propose here a model involving plume lateral deflection to account for these two discrete magmatic phases in the TLIP. The earlier phase formed as a response of impact of a mantle plume at the base of the SCLM. Partial melting of the enriched lithospheric mantle was triggered by conductive heating of the impregnating plume. The later phase was generated by decompression melting of the mantle plume, as a result of deflection of the plume towards the margins of the Tarim craton where the lithosphere is relatively thin.