地质力学学报2017，Vol.23Issue(5)：673-685,13.
西藏狮泉河地区晚侏罗世中性侵入岩锆石U-Pb年龄、地球化学特征及构造意义
ZIRCON U-PB AGES, GEOCHEMICAL CHARACTERISTICS AND TECTONICS IMPLICATIONS OF LATE JURASSIC INTERMEDIATE INTRUSIVE ROCKS IN SHIQUANHE AREA, WESTERN TIBET
摘要
Abstract
A set of intermediate intrusive rocks have been identified from a late Cretaceous pluton which intruded into the Paleozoic stratigraphy along the south of Shiquanhe belt, during the 1:50000 geological survey in the Gaer area. The intrusive rocks are exhibited as stock and apophyse, with the types of quartz diorite, tonalite and granodiorite. The zircon from quartz diorites and tonalites yield U-Pb ages of 157. 3 ± 1. 5 ( MSWD=0. 96 ) and 159. 3 ± 3. 7 Ma ( MSWD =2. 30 ) with LA-ICP-MS method, indicating late Jurassic magmatic activities. These intermediate-acid intrusive rocks have a SiO2 content of 59. 65% ~64. 57%, K2 O of 1. 95% ~2. 54%, Na2 O of 1. 97% ~2. 54%, K2 O/Na2 O of 0. 77% ~1. 29%, P2 O5 of 0. 085% ~0. 139%, Al2 O3 of 13. 63% ~15. 68%and A/CNK value of 0. 89~1. 04, which could belong to meta-aluminous rocks. The REE content of these rocks range from 107. 37 × 10 -6 to 148. 33 × 10 -6 with high grade fractionation of LREE/HREE (6. 77~9. 67) and some negative anomaly of Eu (0. 63~0. 84). Compared with the primitive mantle, all rocks are enriched in large ion lithophile elements ( Rb and Th et al) and depleted in high field strength elements ( Nb, Ta, Ti and P et al) with geochemical characteristics of the island arc calcalkaline magma. Petrological and geochemical characteristics indicate that the rocks have acidic rule of evolution, with the features of comagmatic evolution and typical I-type granite, and they were formed in the island arc environment with plate subduction. This research also indicates that subduction-type granite already existed in the Shiquanhe area during late Jurassic, and the magmatic activities were likely the product of subducted southward from Northern subzone in Shiquanhe area.关键词
狮泉河地区/中性侵入岩/LA-ICP-MS锆石U-Pb/晚侏罗世Key words
Shiquanhe area/intermediate intrusive rocks/LA-ICP-MS zircon U-Pb/late Jurassic分类
天文与地球科学引用本文复制引用
尼玛次仁,达娃,王国灿,顿都,普尺,次仁央宗,焦文龙,李开云,叶强,洛桑朗杰..西藏狮泉河地区晚侏罗世中性侵入岩锆石U-Pb年龄、地球化学特征及构造意义[J].地质力学学报,2017,23(5):673-685,13.基金项目
中国地质调查局青藏专项《西藏1:5万噶尔地区6幅区域地质调查》(1212011121232,1212011221057) （1212011121232,1212011221057）
