摘要
本文根据盐源-丽江岩区和攀西岩区峨眉山玄武岩的地球化学组成,包括各种氧化物之间的关系、微量元素标准化曲线、Th/Yb与Ta/Yb、Ce/Nb与Th/Nb,以及^(87)Sr/^(86)Sr与^(143)Nd/^(144)Nd值的相互关系,重点对峨眉山玄武岩地幔源的地球化学特点、上扬子地区岩石圈地幔的地球化学特征及成因、地幔热柱与岩石圈地幔的相互作用,以及峨眉山玄武岩的喷发时限进行了初步探讨。
Features of the correlations between MgO and CaO, SiO2 and A12O3, trace element concentrations normalized to the primitive mantle and the Sr anormaly indicated that the evolution of the Emeishan Basalts was controlled mainly by the fractional crystallization of Ol + Cpx,and crustal contamination was less. The main geo-chemical characteristics of source mantle were remained. The primitive-mantle-normalized patterns and the correlation between Th/Yb-Ta/Yb imply that the Emishan Basalts were originated from enriched mantle. The concentrations of LILE and HFSE are slightly lower than the EM-1 and EM-2 OIB. With the lower ratios of 87 Sr/86Sr 和143Nd/144Nd and the relationship between Ce/Nb-Th/Nb, it is implied that the mantle source of the Emishan Basalts had been contaminated by subducting sediment. The subduction of the Old Qingzang Oceanic plate toward the Yangtze Block along the western margin during the Jinning-Chen Jiang Period (Neo-protero-zoic) caused the oceanic sediment contamination of the lithospheric mantle, and the enrichment features of the Emishan Basalts were closely related to the heavy contamination during the partial melting of the mantle plume in this enriched lithospheric mantle. So, the studies of the Emishan Basalts are significant for the researches of the crust-mantle reaction and the recycling crustal materials in the western margin before the Late Palaeozoic. Stratigraphic and palaeomagnetic studies and the zircon uranium/lead age indicate that the Emishan Basalts erupted during the middle/late Permian (259-257 Ma) and were closely related to the extinction of 258 Ma.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2001年第4期498-506,共9页
Acta Geologica Sinica
基金
国家自然科学基金(编号40072037)
