四川冕宁尤黑木地区两类前寒武纪斜长角闪岩比较研究

A COMPARATIVE STUDY FOR TWO PRECAMBRIAN PLAGIOCLASE AMPHIBOLITES IN YOUHEIMU AREA,MINNING,SICHUAN PROVINCE

四川冕宁尤黑木地区两类前寒武纪斜长角闪岩，分别归属为康定群和尤黑木群，具有相似的微量元素地球化学特征，大离子亲石元素（ＬＩＬＥ）明显富集，高场强部分相容元素（ＨＦＳＥ）稍有亏损。与尤黑木群斜长角闪岩相比，康定群斜长角闪岩富ＴｉＯ２，〈ＦｅＯ〉和Ｎａ２Ｏ，贫Ａｌ２Ｏ３，ＣａＯ和ＭｇＯ，具较高的ΣＲＥＥ和（Ｌａ／Ｙｂ）Ｎ值，具明显的负铕异常和弱的正铈异常，原岩为大洋岛弧钙碱性玄武质火山岩，与上地幔物质的部分熔融有关。尤黑木群斜长角闪岩具弱的正铕异常和明显的负铈异常，原岩为大陆岛弧钙碱性玄武质浅成侵入岩，原始岩浆起源于俯冲洋壳，与洋壳上部的海相沉积物及大洋拉斑玄武岩的部分熔融有关。

On the basis of systematical research on petrological geochemisity,two types of the precambrian plagioclase amphibolite in the Youheimu area have similar trace element geochemical characterists,and are remarkably enriched in LILE and weakly depleted in HFSE elements.The plagioclase amphibolite of Kangding Group contains more TiO 2,〈FeO〉 and Na 2O,but less MgO,CaO and Al 2O 3,and higher ΣREE and (La/Yb) N than that of Youheimu Group.Its original rock was the calc alkaline bascfic volcanic rock formed in the tectonic setting of oceanic island arc.It has obviously negative Eu anomacies and slightly positive Ce anomalies,and was related to partial mecting of the upper mantle.The original rock of plagioclase amphibolite from Youheimu Group was the calc ackaline basactic shallow seated intrusive rock formed in the tectonic setting of continental island arc.It has slightly positive Eu anomalies and obviously negative Ce anomalies.Its magma was originated from the subducted oceanic crust and was also related to partial melting of sea facies sediments of oceanic tholeiite spread on the oceanic crust.