Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area, Daqingshan-Wulashan Metamorphic Complex Belt
详细信息
- 责任者：Cai Jia (Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Liu Fulai
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(7)
- 关键词：黑云母片麻岩 ; biotite gneiss ; 杂岩 ; complexes ; 大青山 ; Daqing Mountains
- 页码：p.2313-2328
- 图表：10 illus., 4 tables, 79 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Danangou garnet-spinel-biotite-bearing paragneiss occurs as interlayers or various lenses within garnet-bearing quartzofeldspathic rocks and garnet-cordierite-sillimanite-bearing paragneisses,Daqingshan-Wulashan metamorphic complex belt,North China Craton.The combined studies of petrography,metamorphic reaction,genetic mineralogy,and quantitative phase modeling provide insight into the origin of the garnet-spinel-biotite-bearing paragneiss.This typical silica-undersaturated metamorphic rock mainly consists of garnet,spinel,biotite,sillimanite,K-feldspar with secondary minerals of magnetite,apatite,quartz,etc.Thereinto,spinel has extremely low gahnite content with X Zn ratio < 0.006 (X Zn=Zn /(Fe 2 + + Mg + Zn).Spinel-bearing mineral assemblages within the same microdomain were formed at the late re-equilibration stage corresponding to the decompression or cooling evolution.The symplectite of K-feldspar + spinel ± plagioclase around relic garnet is attributed to the reaction Grt + Sil + Melt→Kfs + Spl + Pl during the early retrogression.Whereas the fine-grained retrogressive mineral assemblage of spinel + corundum + magnetite was formed by the reaction of Spl ss + O 2 →Spl + Mag + Crn related to the late cooling process and oxidation state of spinel solid solution.The P-T relationships from phase modeling for garnet-spinel-biotite-bearing paragneiss reveal a granulite facies mineral assemblage of Bt + Grt + Spl + Mag + Sil + Kfs + Pl + Liq which records a peak metamorphic P-T condition of around 830 ～ 870℃ and 8.3 ～ 8.6kb.
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