Petrographic and Micro-Textural Features of the Yellow Pumice at Tianwen Peak of Changbaishan Tianchi Volcano
详细信息
- 责任者：Xu Jiandong (Key Laboratory of Active Tectonics and Volcano ; Institute of Geology ; China Earthquake Administration ; Beijing 100029 ; China) ; Yu Hongmei
- 刊名：Seismology and Geology
- 出版年：2013
- 卷期：35(2)
- 关键词：喷发作用 ; eruptive processes ; 浮岩 ; pumice ; 长白山 ; Changbai Mountains
- 页码：p.363-370
- 图表：illus., 2 tables, 17 refs.
- 分类号：0801
- issnNo：ISSN0253-4967
- isbnNo：CN11-2192/P
摘要
A series of deposits with tens of meters in thickness and in black,grey and yellow colors,from explosive eruptions in the Holocene,are developed at Tianwen peak,the north summit of Tianchi caldera of Changbaishan volcano. Among the deposits,a relatively large scale unit in yellow color,socalled" yellow pumice"by the previous studies,is characterized by coarse tephra and well-developed pores with large-sized trachyte blocks. In this study,we analyzed the petrographic and micro-textural features of the yellow pumice,as well as the grey pumice which is believed to be produced by the millennium eruption in 946 AD. Our results indicate that: 1) the yellow pumice can be classified into alkaline rhyolite as like the grey pumice,but is slightly more basaltic than the grey pumice,suggesting that they all are probably from the identical magma source; 2) remarkably similar as the grey pumice in texture,the yellow deposits are pumiceous with abundant pores in various sizes and few phenocrysts around which moniliform pores are well developed with typical flowing features; 3 ) parameters of feldspar of the yellow pumice from SEM and X - ray diffraction by predecessors are distinguishable from that of the other pumice,indicating that the yellow pumice is presumably produced by the isolated explosive eruption event. In all,our findings provide strongly petrographic evidences to support the conclusion that the yellow pumice deposits at Tianwen peak of the volcano summit are the product of an explosive eruption prior to the millennium eruption of Changbaishan volcano.
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