Mineralogical Characteristics of the Sodium- and Potassic-Rich Alkaline Volcanic Rocks at Tangra Yumco, SE Tibet： Implications for Petrogenesis

详细信息   

• 责任者：Yu Lifang (Instrumental Analysis and Research Center ; Sun Yat-Sen University ; Guangzhou 510275 ; China) ; Zhao Wenxia
• 刊名：Geotectonica et Metallogenia
• 出版年：2012
• 卷期：36(2)
• 关键词：碱性岩 ; alkali rocks ; 火山岩 ; volcanic rocks ; 矿物学 ; mineralogy ; 西藏 ; Tibet
• 页码：p.274-283
• 图表：4 illus., 27 tables, 6 refs.
• 分类号：0801
• issnNo：ISSN1001-1552
• isbnNo：CN44-1595/P

摘要

The Miocene sodium-rich analcime （nepheline） phonolite and coexisting ultrahigh-potassium trachytes at Tangra Yumco area in southwestern Qinghai-Tibetan Plateau show distinct petrological and mineralogical characteristics. The magmatic inclusions within olivine phenocrysts in the sodium analcime （nepheline） phonolite are compositionally similar to the ultrapotassic volcanic rocks, indicating that the potassium magma was formed prior to the sodium magma. Because of the different whole rock components, mineral assemblages, mineral compositions and Ti-Al ratios in the clinopyroxene cores, the sodium analcime （nepheline） phonolites were likely derived from different mantle magmatic sources rather than fractional results of a potassic trachytic magma.