Geochronology and Geochemistry of the Gerizhuotuo Diorites from the Buqingshan Tectonic Mélange Belt in the Southern Margin of East Kunlun and Their Geologic Implications
详细信息
- 责任者：Li Zuochen (Key Laboratory of Western China’s Mineral Resources and Geological Engineering ; Ministry of Education ; Faculty of Earth Science and Resources ; Chang’an University ; Xi’an 710054 ; China) ; Pei Xianzhi
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(8)
- 关键词：闪长岩 ; diorites ; 昆仑山 ; Kunlun Mountains
- 页码：p.1089-1103
- 图表：12 illus., 2 tables, 81 refs.
- 分类号：0801
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
This paper studies the Gerizhuotuo diorite of Buqingshan tectonic mélange belt in the southern margin of East Kunlun using zircon U-Pb geochronology and geochemical methods so as to constrain its formation and origin.The results shows that the zircons have high ratios of Th/U (0.63-1.28) and internal oscillatory zoning on CL imagines of the Gerizhuotuo diorites,suggesting a magmatic origin.LA-ICP-MS zircon geochronological age of 225.8±1.5Ma (MSWD=0.53) implies the diorite formed at the early period of Late Triassic.Geochemically,the rock is characterized by medium contents of SiO2(53.07%-58.74%),and relatively high Al2O3 (14.66%～16.17%),low alkaline (4.76%～6.04%),high K2O(1.60%～2.90%)and Rittmann index σ from 1.69 to 2.66,suggesting that the diorite belongs to the high-K calc-alkaline series.The average value of ΣREE is 158.36×10-6 ～211.50×10-6,with δEu= 0.85～0.97.The chondrite normalized REE pattern curve shows right-sloping type,with weak negative Eu anomalies.The primitive mantle standardized trace elements diagram show that HFSE(Nb,Ta,P,etc.) and LILE(Ba、Sr,Ti,etc.) has remarkable negative anomalies,while Rb,U,La,Hf,Nd,etc.) has remarkable positive anomalies.Our study indicates that the Gerizhuotuo diorite formed in the high temperature environment (800 ℃ ±),and its post-collisional magmatism characteristic suggests the diorite was the product of crustal partial melting after the collision of the East Kunlun block and Bayan Har block.