沉积与特提斯地质2018，Vol.38Issue(1)：23-36,14.
滇西双江县勐库地区临沧花岗岩中暗色包体锆石U-Pb年代学及其地质意义
U-Pb dating of the detrital zircons in the dark diorite enclaves from the Lincang granites in Mengku, Shuangjiang, western Yunnan and its geological significance
摘要
Abstract
The Lincang granites in Mengku,Shuangjiang,western Yunnan consist,lithologically,of biotite monzogranite,biotite granodiorite and alkali feldspar granite. The dark mafic microgranular diorite enclaves (MME)were discovered in biotite monzogranite near Reshuitang,Mengku during our field geological survey. The present paper focuses on petrographic observation,LA-ICP-MS zircon U-Pb dating and whole-rock major elemental analysis of the dark diorite enclaves. The LA-ICP-MS zircon U-Pb age of 230. 9 ± 1. 2 Ma for the dark diorite enclaves is roughly consistent with that of 229. 2 ± 0. 8 Ma for the medium- to fine-grained biotite monzogranite. Geochemically,the biotite monzogranite is characterized by the enrichment of K 2 O and Na2 O contents (Na 2 O >K2 O)and Al 2 O3 ,and an average A/ CNK ratio of 1. 17,while the dark diorite has moderate contents of K 2 O and Na2 O (Na 2 O > K2 O),enrichment of Al 2 O3 and MgO,and an average A/ CNK ratio of 0. 77. Both the biotite monzogranite and dark diorite display the right-leaning LREE distribution patterns. They are all enriched in large ion lithophile elements (LILE)and depleted in the high field strength elements (HFSE)Na and Ta,and show relatively higher Mg# values (30. 50 to 61. 41 for biotite monzogranite and 58. 58 to 67. 34 for dark diorite, respectively). The Cr and Ni contents in biotite monzogranite range in 46. 96 × 10-6 and 11. 21 × 10-6 ,respectively, which are lower than those in dark diorite (an average ranging in 197. 62 × 10-6 and 75. 68 × 10-6 ,respectively). The formation of the granitic magmas in the study area may well be closely related with the partial crustal melting caused by mantle fluid action and crust-mantle magmatic mixing in the continental-continental collision to post-collisional tectonic settings,implying that the Baoshan and Simao blocks were in the continental-continental collision to post-collisional periods at the age of 230 Ma.关键词
锆石U-Pb年代学/岩石地球化学特征/暗色包体/临沧花岗岩/滇西双江县勐库Key words
zircon U-Pb dating/geochemical signature/dark enclaves/Lincang granite/Mengku in Shuangjiang/western Yunnan分类
天文与地球科学引用本文复制引用
曾文涛,孙载波,周坤,吴嘉林,黄亮,赵江泰..滇西双江县勐库地区临沧花岗岩中暗色包体锆石U-Pb年代学及其地质意义[J].沉积与特提斯地质,2018,38(1):23-36,14.基金项目
中国地质调查局地质调查项目(121201010000150007)和云南省科技领军人才培养计划项目(2013HA001) （121201010000150007）
