首页 | 本学科首页   官方微博 | 高级检索  
     检索      


Stability of almandine in the system FeO-(Fe2O3)-Al2O3-SiO2-(H2O) at elevated pressures
Authors:I Keesmann  S Matthes  W Schreyer  F Seifert
Institution:(1) Université Lovanium, Rép. Dém. du Congo;(2) Mineralogisches Institut der Universität Würzburg, Germany;(3) Institut für Mineralogie der Ruhr-Universität Bochum, Germany
Abstract:Almandine, although decomposing in the presence of metallic iron into the anhydrous subsolidus assemblage fayalite + ferrocordierite + hercynite solid solution at low pressures, melts incongruently to hercynitess + quartz + liquid at 10 kb. At pressures between about 12 and 20 kb the products of incongruent melting are hercynitess + liquid only, and at still higher pressures almandine melts congruently. For the intermediate pressures between 2 and 10 kb not investigated a sequence of probable breakdown and melting relations involving the phases ferrocordierite, fayalite, hercynitess, quartz, and liquid is derived through Schreinemakers' analyses.The lower temperature stability limit of almandine in the presence of water at low oxygen fugacities and pressures of 15 to 20 kb lies between 550° and 600° C as at low pressures. It is marked, however, by the breakdown to a hydrous assemblage involving chloritoid and the new phase aluminous deerite. Since the anhydrous melting at these pressures occurs between 1300° and 1400° C, the thermal stability range of almandine increases drastically with pressure. Its upper breakdown limit shows in principle a similar behavior as those of other garnet end members.
Keywords:
本文献已被 SpringerLink 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号