滇西新生代富碱斑岩及其深源包体的岩石学和地球化学特征  

PETROLOGICAL AND GEOCHEMICAL CHARACTERISTICS OF CENOZOIC ALKALI-RICH PORPHYRIES AND XENOLITHS HOSTED IN WESTERN YUNNAN PROVINCE

作　　者：赵欣[1] 喻学惠[1] 莫宣学[1] 张瑾[2] 吕伯西 

机构地区：[1]中国地质大学"岩石圈构造,深部过程及探测技术"教育部重点实验室,北京100083 [2]中国科学院地质与地球物理研究所,北京100029 [3]云南地质科学研究所,云南昆明650011

出　　处：《现代地质》2004年第2期217-228,共12页Geoscience

基　　金：国家自然科学基金项目 (4 0 172 0 2 5 ) ;国土资源部青藏高原专项计划项目 (2 0 0 10 10 2 0 40 1) ;国家重点基础研究发展规划项目 (2 0 0 2CB412 60 0 )。

摘　　要：滇西地区沿金沙江—哀牢山断裂带产出了一套第三纪富碱斑岩 ,其中包含有多种类型的深源包体 ,它们对于了解滇西地区的地幔组成与演化及壳幔相互作用有重要意义。介绍了鹤庆六合、剑川新华、甸心和石鼓小桥头等地的富碱斑岩及其深源包体的岩石类型和岩相学特征 ;通过对寄主岩及其包体的主量元素、微量元素、稀土元素和Pb、Sr、Nd同位素的分析 ,运用多种地球化学判别图解并结合实验岩石学和相平衡的研究结果 ,认为研究区的富碱斑岩属于钾玄岩系列的岩石 ,主要形成于后碰撞弧环境 ;富碱斑岩起源于滇西加厚地壳的下部 (约 5 5km处 ) ,源区岩石应是榴辉岩相的岩石 ;富碱斑岩的源区具有EMⅡ型富集地幔的地球化学特征 。A set of Tertiary alkali-rich porphyries occurs in the Jinshajiang River-Ailao Mountain fault belt, western Yunnan Province. And many types of deep-derived xenoliths have been discovered in some of the alkali -rich porphyries. Research on the porphyries and xenoliths is very important for understanding the composition and evolution of the mantle and the interaction between the mantle and the crust in western Yunnan. In this paper, rock types and petrographic characteristics of the porphyries and xenoliths in Liuhe, Xinhua, Dianxin and Xiaoqiaotou are introduced and the analysis results of major elements, trace elements, rare earth elements and Pb-Sr-Nd isotopes are presented. Based on these analyses, geochemical discrimination diagrams and studies of experimental petrology and phase equilibrium, the following conclusions have been reached: Most of the alkali-rich porphyries are shoshonitic and formed in post-collision arc settings; magmas of alkali-rich porphyries originated near the bottom (about 55 km in depth) of the thickened crust in western Yunnan;the source rocks may be those of eclogite phase; the geochemical characteristics of EMⅡenriched mantle in the source region is likely related to the mixing of the lower crust and the mantle with fingerprints of subducted ocean crust.

关 键 词：滇西 富碱斑岩 深源包体 钾玄岩 地球化学 壳幔相互作用 岩石成因 

分 类 号：P588.1[天文地球—岩石学]