云南南涧各救母岩体地球化学特征及其构造背景

Geochemical Characteristics and Tectonic Setting of Gejiumu Lithosome in Nanjian County,Yunnan

各救母岩体位于滇西富碱斑岩带中,属于金沙江—红河富碱侵入岩带的南段。对岩体进行了地球化学特征分析。样品主量元素的分析表明,各救母岩体属中酸性岩,具有高钾、高碱的特征,属于高钾钙碱性或钾玄岩系列;微量和稀土元素的分析表明,该岩体LREE/HREE值和（La/Yb）N值分别为12.60～19.25和17.02～34.87,属于轻稀土富集型,δEu为0.73~0.98,Eu具轻微的负异常,形成各救母岩体的岩浆应来自于高压环境的上地幔-下地壳,经历了地幔交代作用,并与富碱岩浆进行了混合。各救母斑岩体锆石U-Pb定年（LA-MC-ICPMS）加权平均年龄为（37.91±0.35）Ma（n=27,MSWD=0.99）。研究表明各救母岩体处于印度—欧亚大陆的晚碰撞构造转换阶段,亦为后碰撞的早期阶段。

Gejiumu Lithosome located in the western Yunnan alkali-rich porphyry band,which belongs to the southern section of Jinshajiang-Red River alkali-rich intrusive lithosome.An analysis is conducted to figure out the geochemical characteristics of the rock mass.The result shows that Gejiumu Lithosome is characterized by high potassium,alkali,and belongs to a high potassium calc-alkali or potassium basalt series.The trace and lanthanon elements analysis show that the ratios of LREE/HREE and（La/Yb）Nare 12.60-19.25 and 17.02-34.87 respectively,belonging to the light lanthanon enrichment type,with the delta Eu of 0.73-0.98,a slight negative Eu anomaly.The magma of Gejiumu Lithosome should come from a high-pressure environment of the upper mantle or the lower crust,withmantle metasomatism experienced and alkali-rich magma mixed.The weighted average age of the zircon U-Pb dating（LA-MC-ICPMS）is（37.91±0.35）Ma（n=27 MSWD=0.99）.The studies show that Gejiumu Lithosome formed in the late India-Eurasia collision of tectonic transformation stage,also known as the early stage of the post collision.