Genesis of the Megacryst Orthoamphibole Rock from Hengshan Mts., Shanxi Province: Evidence from Geochemistry and Sm-Nd Isotopic Data
详细信息
- 责任者：Qian Jiahui (Key Laboratory of Orogenic Belts and Crustal Evolution ; Ministry of Education ; School of Earth and Space Sciences ; Peking University ; Beijing 100871 ; China) ; Wei ChunJing
- 刊名：Acta Petrologica Sinica
- 出版年：2012
- 卷期：28(9)
- 关键词：直闪石 ; anthophyllite ; 岩石地球化学 ; lithogeochemistry ; 变质岩 ; metamorphic rocks ; 恒山 ; Hengshan Mountains
- 页码：p.2819-2830
- 图表：6 illus., 3 tables, 58 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
normal; DISPLAY: inline !important; FONT: 12px/15px ����,verdana; WHITE-SPACE: normal; ORPHANS: 2; FLOAT: none; COLOR: rgb(0,0,0); WORD-SPACING: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px">The megacryst orthoamphibole rocks from Hengshan Mts, Shanxi Province are comprised of orthoamphibole, kyanite, staurolite, cordierite, quartz, rutile, ilmenite and a small amount of plagioclase and calcic amphibole. Anormal; DISPLAY: inline !important; FONT: 12px/15px ����,verdana; WHITE-SPACE: normal; ORPHANS: 2; FLOAT: none; COLOR: rgb(0,0,0); WORD-SPACING: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px">ccording to the petrography and geochemistry, the authors infer that protolith of the orthoamphibole rocks may have been originated from hydrothermal alteration of basic volcanics equivalent to the mafic rocks in Wutai Complex. This hydrothermal alteration caused the depletion of Ca, Na and K and relative enrichment of Mg (Fe), and probably resulted in formation of large amount of hydrous minerals such as chlorite. The present mineral assemblages in the orthoamphibole rocks were formed due to a high-pressure amphibolite facies metamorphism with a subsequent isothermal decompression. The megacrysts may have been resulted from prograde dehydrations of the extremely fluid-rich rocks during the pre-peak stages, and metamorphic differentiation related to these prograde dehydrations may have led to a further modification of the bulk rock compositions.