Late Cretaceous Adakites in the Eastern Segment of the Gangdese Belt,
详细信息
- 责任者：Guan Qi (State Key Laboratory of Geological Processes and Mineral Resources ; School of Earth Sciences and Resources ; China University of Geosciences ; Beijing 100083 ; China) ; Zhu Dicheng
- 刊名：Acta Petrologica Sinica
- 出版年：2010
- 卷期：26(7)
- 关键词：埃达克岩 ; adakite ; 冈底斯山 ; Gangdise Range
- 页码：p.2165-2179
- 图表：8 illus., 3 tables, 68 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Contrasting views remain exist so far for the nature and geodynamic mechanism of the Late Cretaceous magmatism in the southern Gangdise Belt,southern Tibet.To further constrain the tectonomagmatic evolution of southern Tibet during the Late Cretaceous,the authors present zircon LA-ICPMS U-Pb data,geochemical and Hf isotopic data for the granitoids from the eastern segment of the southern Gangdise Belt,southern Tibet.New age data indicate that the granitoids were emplaced at 84~78 Ma.These rocks are characterized by high Al2O3（15.69%~17.65%）,low MgO（0.47%~1.24%）,very low abundances of compatible elements（Cr=1.34×10-6~3.27×10-6、Ni=0.69×10-6~3.32×10-6）,high Sr（542×10-6~774×10-6）and high Sr/Y ratios（48~397）,similar to those of adakite.The rocks are medium-K calc-alkaline,metaluminous（A/CNK=0.95~1.04）,and are enriched in LILE,depleted in HFSE,and are heterogeneous in zircon εHf（t）values（+0.2~+15.1）.Some of they show distinct positive Eu anomalies（δEu=1.16~2.26）and middle REE depletion.The Late Cretaceous adakites are interpreted as the products of partial melting of newly underplated mafic lower crust under hydrous amphibolite facies conditions.Compared with the zonal magmatic flare-up events at about 110Ma documented in the middle-northern Gangdise and at about 50 Ma documented in the southern Gangdise,the authors argue that the Neo-Tethyan ridge subduction is the most probable mechanism to trigger the generation of the widespread zonal magmatism in the southern Gangdise during Late Cretaceous.