本文对虎跳峡苦橄岩和玄武岩及金安玄武岩的地球化学特征进行了研究.结果表明其微量元素原始地幔标准化曲线、Sr-Nd-Pb同位素比值与OIB、丽江苦橄岩相似,表现为其大离子亲石元素相对高场强元素富集,并且不存在Nb、Ta和Ti的负异常,表明岩浆在上升过程中很少受到岩石圈地幔或地壳物质的混染.利用Klein and Langmuir(1987)的方法得出虎跳峡熔岩和金安玄武岩原始岩浆MgO含量分别为15.81％～20.89％和8.06％～13.84％,其相应的地幔温度分别为1493～1611℃和1055 ～ 1474℃.所得温度略高于正常软流圈地幔温度,低于丽江仕满苦橄岩的熔融温度(1630 ～ 1680℃),推测丽江地区可能是峨眉山地幔柱的中心部位.
Geochemical characteristics of Permian basalt from Hutiaoxia and Jin'an area of the Emeishan Large Igneous Province and constraints on their source region
The geochemical characteristics of picrite and basalt that we discovered recently in Hutiaoxia and Jin'an area show that the primitive-mantle normalized incompatible element diagrams and Sr,Nd-Pb isotopic ratios are similar to those of OIB and Lijiang picrite,all of which display an enrichment of lithophile element (LILE) and relative depletion of high field strength element (HFSE)associated with an absence of Nb,Ta and Ti negative anomalies.All these observations suggest little lithosphere or crustal material contamination of uplifting magma.With the Klein and Langmuir method (1987),the MgO content of the Hutiaoxia's and Jin'an's primary magma are 15.81％ ～ 20.89％ and 8.06％ ～ 13.84％ respectively.Mantle temperature of both are 1493 ～ 1611 ℃ and 1055 ～ 1474℃ respectively.These mantle temperatures are lower than Shiman picritic melting temperature (1630 ～ 1680℃),and a little higher than mantle temperature of normal asthenosphere.Thus,the axis of the Emeishan mantle plume should be located beneath the Lijiang County Town,Yunnan Province.
Emeishan Large Igneous ProvincePermian basaltPicriteTail of Mantle plumeLijiang area
NETL
NSTL
万方数据
维普
