Metamorphic Evolution of Meta-Sedimentary Rocks within the Diancangshan-Ailaoshan Metamorphic Complex Belt
详细信息
- 责任者：Wang Fang (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(2)
- 关键词：变沉积岩 ; metasedimentary rocks ; 哀牢山 ; Ailao Mountains
- 页码：p.630-640
- 图表：illus., 3 tables, 36 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Meta-sedimentary rocks, characterized by intensive migmatization and/or mylonization, are widely distributed within the Diancang Shan-Ailao Shan metamorphic complex belt. On the basis of detailed mineralogical and petrographic observations, four metamorphic stages have been recognized, including early prograde metamorphic stage (M1), peak amphibolite-granulite facies metamorphic stage (M2), near isothermal decompression retrograde stage (M3), and late amphibolite facies retrograde stage (M4). Metamorphic P-T conditions for each stage were calculated by P-T pseudosection, and geothemobarometer (GB-GASP) and two-mica thermometer. The mineral assemblage for the early prograde assemblage (M1) is characterized by Pl+Ms+Qtz+St±Ky±Bt±Kfs, which as inclusions are preserved in the core of garnet, and formed at 560～590℃ and 5.5～6.3kb. The typical mineral assemblage for the peak amphibolite-granulite facies metamorphic stage (M2) assemblage is represented by Grt+Bt+Ky/Sil+Pl+Qtz or Grt+Bt+Pl+Qtz±Kfs±Sil, recording P-T conditions of 720～760℃ and 8.0～9.3kb. The near isothermal decompression retrograde stage (M3) is indicated by a mineral assemblage of Grt+Bt+Sil+Pl+Qtz, which were formed at P-T conditions of 640～760℃ and 5.0～7.3kb. Abundant retrogressive minerals, including fine-grained biotite and muscovite, together Pl+Qtz±Kfs±Grt were formed at the late amphibolite facies retrograde stage (M4), which occurred at P-T conditions of 521～648℃ and 4.0～5.0kb. The integrated clockwise P-T path revealed by the meta-sedimentary rocks indicates that the Diancang Shan-Ailao Shan metamorphic complex belt experienced a tectonic evolution of subduction-collision-exhumation, which was related to the amalgamation between the Indian and Eurasian plates.
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