云南中甸峨眉山玄武岩中超基性-基性岩包体元素地球化学分析

Geochemistry and Petrogenesis of Ultrabasic-Basic Xenoliths from Emeishan Basalt in Zhongdian,Yunnan

峨眉山大火成岩省于滇西地区广泛发育有一系列的镁铁-超镁铁质岩体,但对于其中地幔包体的报道还相对较少。本次研究在云南中甸地区峨眉山玄武岩中发现了岩性表现为由纯橄岩→辉橄岩→橄辉岩→苦橄岩→辉长岩→辉绿辉长岩→辉绿岩变化系列的超基性-基性岩包体。通过对包体岩石开展元素地球化学分析研究,结果表明:形成包体的原始超基性岩浆属于峨眉山地幔柱活动产物,且与主岩形成背景相似,其岩浆源区位于难熔的方辉橄榄岩区与石榴二辉橄榄岩区的过渡部位,受岩石圈地壳混染程度较低。结合丽江苦橄岩性质,认为滇西地区上地幔存在早阶段峨眉山地幔柱活动。

Emeishan large igneous province widely developed inaseriesofmafic-ultramaficpluton inwestern Yunnan.However,reports about mantle xenoliths of Emeishan large igneous province still relatively few. We found a series of ultrabasic-basic xenoliths that have variation of dunite→lherzolite→ olivinepyroxenite→picrites→ gabbro→diabase-gabbro→diabase in Emeishan Basalt from Zhongdian Yunnan.Based on the research of element geochemistry and mineral geochemistry of ultrabasic-basic xenoliths.The results show that ultrabasic magma derived from the mantle plume activity,also have a similar background with the host rock;ultrabasic magma source region has the characteristics of the pomegranate lherzolite zone transition to the harzburgite area,has not been affected by lithospheric mantle and crustal material contamination.And combine the characteristics of the Lijiangpicrites,we draw that the upper mantle of this area exist Emeishan large igneous provinces mantle plume activity,and may represent the early stages of the mantle plume activity.