Identification and Petrogenesis of Potassic Volcanic Rocks with “Ultrapotassic” Characteristics from Maqiang Area in Lhasa
详细信息
- 责任者：Wang Baodi (Chengdu Institute of Geology and Mineral Resources ; Chengdu 610081 ; China) ; Chen Lingkang
- 刊名：Acta Petrologica Sinica
- 出版年：2011
- 卷期：27(6)
- 关键词：火山岩 ; volcanic rocks ; 氩—氩计时 ; Ar-Ar dating ; 西藏 ; Tibet
- 页码：p.1662-1674
- 图表：12 illus., 4 tables, 39 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
This paper has identified the potassic volcanic rocks from the Maqiang area in central of Lhasa block, which formed at ~21.3 Ma by 40Ar-39Ar dating. These potassic rocks are geochemical similar to ultrapotassic rocks, e.g., high in MgO (>3%) and K2O/Na2O (K2O/Na2O>2). Recognition of the potassic rocks in the Maqiang area imply that post-collisional potassic-ultrapotassic magmtism did not migrate from west to east in the Lhasa block. In other words, the post-collisional potassic and ultrapotassic lava in the Lhasa block were might erupted at the same time. And the authors suggest that the formation of the Miocene potassic-ultrapotassic volcanic rocks and N-S rifts in the Lhasa block were probably triggered by slab break-off of the India continent lithosphere during northern intra-continent subduction in early Miocene.