Determination and Implication of the HP Pelitic Granulite from the Munabulake Area in the South Altyn Tagh
详细信息
- 责任者：Cao Yuting (State Key Laboratory of Continental Dynamics ; Department of Geology ; Northwest University ; Xi’an 710069 ; China) ; Liu Liang
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(5)
- 关键词：麻粒岩 ; granulite ; 高压变质作用 ; high pressure metamorphism ; 青藏高原 ; Qinghai-Tibetan Plateau
- 页码：p.1727-1739
- 图表：illus., 3 tables, 56 refs.
- 分类号：0802
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
A suit of high pressure ( HP) pelitic granulite was identified in the Munabulake area in the South Altyn Tagh. The peak mineral assemblage of the rock is Grt + Ky + Kfs + Qz + Ilm,and the peak P-T condition is estimated to be T > 850℃ and P > 11kbar according to the THERMOCALC 3. 33. Three stages of metamorphic evolutions are described by means of P-T pseudosections for the selected rock,showing a clockwise retrograde metamorphic P-T path with early decompression and late isobaric cooling. Zircon CL images show the internal structure of core-rim microstructure,the cores preserve residual detrital zircon,and the rims display metamorphic zircons with sector and planar structure. LA-ICP MS in situ trace element analyses and U-Pb dating yielded the toplimit protolith age of 579Ma and the peak metamorphic age of 486 ± 5Ma. The granulite has similar metamorphic evolution and peak metamorphic age with the high-pressure ( HP) granulite from Danshuiquan area,and has identical metamorphic age with the ultrahigh-pressure ( UHP) rock from other areas in the South Altyn,indicating the granulite in this study was a production of the South Altyn continental deep subduction. The coexistent of the contemporary UHP eclogite and the HP granulite might be accounted for by the crustal detachment of subducting continental lithosphere at different depths with different thermal conditions in subduction channels. Moreover,the protolith age of the granulite is in the Late Neoproterozoic Period,which is identical to those of the HP-UHP rocks from the South Altyn. Therefore,the rock should be a part of the South Altyn Tagh HP-UHP metamorphic belt rather than a lithostratigraphic unit belonging to"Changcheng System".
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