兰坪盆地及邻区岩浆岩的微量元素地球化学研究

采用中子活化分析方法系统研究了云南省兰坪盆地内永平卓潘、云龙皂角场及邻区二龙山、剑川、甸南、马登、北衙、老君山等岩体的稀土元素及微量元素组成 ,探讨了岩浆岩系的稀土元素特征、成岩物质来源、成岩方式、构造环境。该区岩浆岩系的稀土元素地球化学特征表现为 :(1)稀土元素组成特征相似 ,配分型式为轻稀土富集向右倾型 ;(2 ) (L a/Yb) n 较高 ,轻重稀土元素分异明显 ;(3) Eu负异常不明显 ,无 Ce负异常或略显正 Ce异常。该区岩浆岩系的微量元素以富集 Rb,Ba,Sr,Th,U ;而亏损 Ta为特征。稀土元素、微量元素结合同位素地球化学研究表明 ,该区岩浆岩系成岩物质主要来源于富集地幔并有地壳混染 ,成岩方式以地幔部分熔融为主 ,成岩环境为大陆裂谷。

TRACE ELEMENT CHARACTERISTICS OF MAGMATIC ROCK SERIES IN LANP ING BASIN AND ITS NEIGHBORING AREAS

Using NAA method, the authors studied REE and trace elements geochemistry of the magmatic rock series from Yongping Zhuopan, Yunlong Zaojiaochang, Erlongshan, Diannan, Madeng, Beiya, and Laojunshan in Lanping basin and its neighboring regions. At the same time, the authors discussed REE geochemistry characteristics, diagenesis style, tectonic environment of the magmatic rock series. The results show: (1) REE patterns of magmatic rock series are similar, and they are rich in LREE; (2) they have high La/Yb ratio, so the separation between HREE and LREE is significant; (3) Eu and Ce amormaly is not obvious. The magmatic rock series has high Rb, Ba, Sr, Th, U and low Ta. Combining the studies of REE, Trace elements geochemistry with that of isotope geochemistry, the authors think that the diagenetic source mainly comes from enriched mantle and partly from the crust, the diagenetic process is batch partial melting, and the diagenetic environment is continental rifting.