Late-Eocene Dala
详细信息
- 责任者：Xie Kejia (Key Laboratory of Continental Collision and Plateau Uplift ; Institute of Tibetan Plateau Research ; Chinese Academy of Sciences ; Beijing 100085 ; China) ; Zeng Lingsen
- 刊名：Acta Petrologica Sinica
- 出版年：2010
- 卷期：26(4)
- 关键词：二云母花岗岩 ; two-mica granite ; 穹窿 ; domes ; 西藏 ; Tibet
- 页码：p.1016-1026
- 图表：illus., 2 tables, 73 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The Dala two-mica granite intruded into the Yardoi gneiss dome and is located to the southeastern of the Yardoi gneiss dome. It consists of quartz, plagioclase, and K-feldspar with subordinate biotite and muscovite and formed at～44.0Ma. Geochemical data show that the Dala granite has:1) high Al2O3(16.0%～17.0%), Na2O/K2O ratios(>1.20) and A/CNK(>1.05); 2) highly enriched in LREE((La/Yb)N=39.5～45.5) and depleted in HREE((Gd/Yb)N=5.5～6.4), slightly negative or no Eu anomalies; 3) relatively high Sr concentrations(355×10-6～416×10-6) and Sr/Y ratios(>59.0); 4) relatively radiogenic Sr (87Sr/86Sr(i)=0.717 54～0.717 85) and unradiogenic Nd(εNd(i)= -9.2～-12.4) isotope compositions, similar to those in the younger (～35Ma) leucogranites within the Yardoi gneiss dome. High Sr/Y and（La/Yb)N ratios, and Sr contents, but low Y and HREE concentrations in the Dala granite suggests it is of an adakitic composition. The data suggest that the Dala granite was derived from partial melting of mafic lower crustal materials in the overthickened Himalayan orogenic belt, and amphibolite melting was dominant in the early stages of Himalayan magmatism.