Geochronology and Geochemistry of Early Paleozoic Granitic Plutons from Subei and Shibaocheng Areas, the Western Segment of
详细信息
- 责任者：Li Jianfeng (Key Laboratory of Orogenic Belts and Crustal Evolution ; MOE ; School of Earth and Space Sciences ; Peking University ; Beijing 100871 ; China) ; Zhang Zhicheng
- 刊名：Acta Petrologica Sinica
- 出版年：2010
- 卷期：26(8)
- 关键词：花岗岩 ; granite ; 铀—铅计时 ; U-Pb dating ; 祁连山 ; Qilian Mountains
- 页码：p.2431-2444
- 图表：11 illus., 4 tables, 51 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
SHRIMP zircon U-Pb ages of the granitic plutons from Subei and Shibaocheng areas emplaced during Early Paleozoic are 415 ± 3 Ma and 435 ± 4 Ma,respectively. The concentrations of TiO2,Al2O3,MgO,CaO,Fe2O3 and Mg# decrease with increasing SiO2 contents,implying magmatic differentiation model controlled by hornblende and plagioclase fractionation. Subei pluton is higher in ∑REE content,ranging from 118. 7 × 10 -6 ～ 202. 2 × 10 -6,with strong fractionation of LREE/ HREE,( La /Yb) N = 11. 1 ～ 16. 5,and has slightly δEu anomaly. Shibaocheng pluton is lower in ∑REE,ranging from 19. 7 × 10 -6 ～ 59. 0 × 10 -6,also with strong fractionation of LREE/HREE,( La /Yb) N = 6. 68 ～ 44. 8,but with δEu positive anomaly and inverse V shape. On chondrite-normalized REE fractional,the sub-parallel pattern indicates a co-genetic relation for all the samples. The concentrations of large ion lithophile elements ( LILE) ,such as Rb,K,Sr are enriched,whereas the high field strength elements ( HFSE) ( e. g. Nb and Ta) as well as P and Ti contents are depleted. On the Rb-Y+Nb diagrams,all plots from Subei pluton set in the area to island arc type,whereas Shibaocheng pluton in the area of island arc type. Subei pluton is the result of post-collision during Late Caledonian and Shibaocheng pluton formed in island arc tectonic environment.
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