Geochemical Characteristics and Petrogenesis of Two Types of Acid Volcanic Rocks from Yingcheng Formation in Songliao Basin
详细信息
- 责任者：Meng Fanchao (School of Geosciences ; China University of Petroleum ; Qingdao 266580 ; China) ; Lu Yulin
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(8)
- 关键词：火山岩 ; volcanic rocks ; 松辽平原 ; Songliao Plain
- 页码：p.2731-2745
- 图表：12 illus., 3 tables, 71 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The thick volcanic rocks are widely distributed in Yingcheng Formation of Songliao Basin. Core and thin section identification exhibit that volcanic rocks are mainly composed of rhyolite,dacite,rhyolitic tuff,ignimbrite and so on. Major,trace elements and isotopic geochemistry studies indicate that acid rocks are obviously classified as two types: high Ti acid volcanic rocks (HTAVR) and low Ti acid volcanic rocks (LTAVR). Many conclusions can be draw from the results of geochemical elements: (1) HTAVR have higher TiO 2 (TiO2 > 0. 45%) but lower SiO2 (64. 87% ～68. 79%) . LTAVR have lower TiO2 (TiO2 < 0. 4%) but higher SiO2 ( 68. 93% ～76. 69%). (2) Major and trace elements express continuous variation between HTAVR and sub-alkaline intermediate-basic rocks. They also have similar Sr-Nd isotopic elements. LTAVR are the main components in Yingcheng Formation with wide initial 87Sr/86Sr ratios. (3) The two types of acid rocks were probably associated with the lithospheric thinning and asthenospheric mantle upwelling by subduction of the Pacific plate beneath eastern China. However,there are many different geochemical characteristics between the two types of acid rocks because of different magmas source,geochemistry process and crustal contamination. The magmas of HTAVR were generated partial melting of the depleted mantle which has been enriched but undergoing fractional crystallization. The generation of LTAVR origined from mixed melting of juvenile crust and low crust components with contaminated by supracrust.
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