滇西梁河—潞西地区新生代英安岩的源区及成因——来自地球化学的证据

The source and origin of Cenozoic dacites in Lianghe-Luxi area, western Yunnan Province: geochemical evidence

摘要: 报道了滇西梁河—潞西地区新生代英安岩的主量、微量、稀土元素和Nd同位素地球化学研究成果。英安岩富集轻稀土元素、大离子亲石元素(Rb、Th、U、K)，相对亏损重稀土元素和Nb、Ta、Sr、P、Ti，具有Eu负异常和Pb正异常。火山岩的εNd(0)为-10.3~-8.72，Nd同位素模式年龄(tDM)为1.2~1.4Ga。这些地球化学特征表明，研究区英安岩源于区域基底岩系的部分熔融，并与该地区同期幔源玄武质岩浆发生了不同程度的混合。

Abstract: Major elements, trace elements, REE and Nd isotopic geochemistry of the Cenozoic dacites from Lianghe-Luxi area, western Yunnan Province, were studied in this paper, and the results show that the dacites are enriched in light REE, large-ion lithophile elements and Pb and depleted in Nb, Ta, Sr, P, Ti and heavy REE, with negative Eu anomaly and positive Pb anomaly. These rocks have εNd(0) values from -10.3 to -8.72 and Nd isotopic model ages (tDM) from1.2 to 1.4Ga. It is suggested that the Lianghe-Luxi Cenozoic dacites were derived dominantly by partial melting of crystalline basement rock mixed in different degrees with melts of coeval mantle-derived basaltic magma.