首页|期刊导航|中国地球化学学报(英文版)|Deep-derived enclaves (belonging to middle-lower crust metamorphic rocks) in the Liuhe-Xiangduo area,eastern Tibet: Evidence from petrogeochemistry
中国地球化学学报(英文版)2006，Vol.25Issue(3)：245-254,10.
Deep-derived enclaves (belonging to middle-lower crust metamorphic rocks) in the Liuhe-Xiangduo area,eastern Tibet: Evidence from petrogeochemistry
Deep-derived enclaves (belonging to middle-lower crust metamorphic rocks) in the Liuhe-Xiangduo area,eastern Tibet: Evidence from petrogeochemistry
摘要
Abstract
Petrological and geochemical studies of deep-derived enclaves from the Liuhe-Xiangduo area, eastern Tibet, showed that the enclaves involve five types of rocks, i. e. , garnet diopsidite, garnet amphibolite, garnet hornblendite, amphibolite and hornblendite, whose main mineral assemblages are Grt+Di + Hbl, Grt+ Pl + Hbl + Di, Grt + Hbl + Pl, Pl + Hbl, and Hbl + Bt, respectively. The enclaves exhibit typical crystalloblastic texture, and growth zones are well developed in garnet (Grt) in the enclaves. In view of major element geochemistry, the deep-derived enclaves are characterized by high MgO and FeO * ,ranging from 12.00% to 12.30% and 8.15% to 10.94%, respectively. The protolith restoration of metamorphic rocks revealed that the enclaves belong to ortho-metamorphic rocks. The REE abundances vary over a wide range, and ∑ REE ranges from 53.39 to 129.04 μg/g. The REE patterns slightly incline toward the HREE side with weak LREE enrichment. The contents of Rb, Sr, and Ba range from 8.34 to 101μg/g, 165 to 1485 μg/g, and 105 to 721 μg/g, respectively. The primitive mantle-normalized spider diagrams of trace elements show obvious negative Nb, Ta, Zr and Hf anomalies. Sr-Nd isotopic compositions of the enclaves indicated that the potential source of deep-derived enclaves is similar to the depletedmantle, and their (87Sr/86Sr) i ratios vary from 0.706314 to 0.707198, (147Nd/144Nd)i ratios from 0.512947 to 0.513046, and εNd(T) values from + 7.0 to +9.0, respectively. The potential source of the enclaves is obviously different from the EM2-type mantle from which high-K igneous rocks stemmed(the host rocks), i.e. , there is no direct genetic relationship between the enclaves and the host rocks.Deep-derived enclaves in the host rocks belong to mafic xenoliths, and those in the Liuhe-Xiangduo area,eastern Tibet, are some middle-lower crust ortho-metamorphic rocks which were accidentally captured at20-50 km level by rapidly entrained high-temperature high-K magma, whose source is considered to be located at 50-km depth or so.关键词
eastern Tibet/Liuhe-Xiangduo area/deep-derived enclave/middle-lower ortho-metamorphic rock/petrology/geochemistryKey words
eastern Tibet/Liuhe-Xiangduo area/deep-derived enclave/middle-lower ortho-metamorphic rock/petrology/geochemistry分类
天文与地球科学引用本文复制引用
WEI Qirong,LI Dewei,ZHENG Jianping,WANG Jianghai..Deep-derived enclaves (belonging to middle-lower crust metamorphic rocks) in the Liuhe-Xiangduo area,eastern Tibet: Evidence from petrogeochemistry[J].中国地球化学学报(英文版),2006,25(3):245-254,10.基金项目
The study was supported jointly by the Innovation Scientific Group Project of the China University of Geosciences,Wuhan ( Continental Dynamics and Metallogeny on the Qinghai-Tibet Plateau),the National Natural Science Foundation of China for Distinguished Young Scholars(No.404225002),the State Key Projects for Basic Research(No.G1998040807),and the China Geological Survey Project(No.200313000005). （ Continental Dynamics and Metallogeny on the Qinghai-Tibet Plateau）
