A Comparative Study of Emeishan Basalt and Gangdagai Formation Basalt in Northwest Yunnan Provinceoft-com:office:office" />
详细信息
- 责任者：Lü Jingsong (Chengdu University of Technology ; Sichuan 610059 ; China) ; Xiao Yuanfu
- 刊名：Acta Petrologica et Mineralogica
- 出版年：2013
- 卷期：32(1)
- 页码：p.73-89
- issnNo：ISSN1000-6524
- isbnNo：CN11-1966/P
摘要
The Jiulong Emeishan basalt is distributed on the western margin of Yangtze block,and the Gangdagai Formation baslat is distributed in Zhongza massif in the neighborhood of Yangtze block.They both have rich alkali,high titanium characteristics,thus mostly belonging to the alkaline basalt series.On the whole,Gangdagai Formation basalt exhibits richer Ti,higher FeO*,lower MgO,lower SiO2 and lower Mg#(0.34~0.43).Jiulong Emeishan basalt exhibits higher Mg#(0.31~0.70),thus belonging to the moderate evolution magma.The two groups of basalt are both characterized by strong enrichment of light rare earth elements,and enrichment of LILE and HFSE(Th,Ta,Nb,Hf),partly with Sr,Zr negative anomalies,hence belonging to the plate basalts derived from the enriched mantle under the influence of mantle plume.Rb,Ba in Jiulong Emeishan basalt show obvious fluctuation,probably influenced by source area contamination;the trace element ratios show features of EM1-OIB and EM2-OIB mixture,suggesting the origination from garnet lherzolite,with molten degree being 4%~7%.The element ratios of lower Gangdagai Formation basalt are stable,and EM1-OIB shows great similarities,suggesting that its formation depth was deeper than that of Jiulong Emeishan basalt,that its origination was from an garnet stable region with low molten degree(2%~5%),and that it was produced at the mantle plume edge.The source area materials of basalt distributed in Zhongza massif and the western margin of Yangzi landmass were influenced by Emeishan mantle plume,with obvious familiarity,and the activities of Emeishan mantle plume provided power for plate splitting.