Anticlockwise metamorphic paths at ca.890–790 Ma from the NE Baidrag block,Mongolia,indicate back-arc compression at the Rodinia periphery  

作　　者：PavlaŠtípská Vít Peresty Igor Soejono Karel Schulmann RCAndrew Kylander-Clark Carmen Aguilar Stephen Collett Martin Racek Jitka Míková Otgonbaatar Dorjsuren Nikol Novotná 

机构地区：[1]Czech Geological Survey,11821 Praha 1,Czech Republic [2]Institute of Petrology and Structural Geology,Charles University in Prague,Albertov 6,Praha 212800,Czech Republic [3]Institut Terre et Environnement de Strasbourg,UMR 7063 Universitéde Strasbourg-CNRS,1 Rue Blessig,67084 Strasbourg,Cedex,France [4]Department of Earth Science,University of California,Santa Barbara,CA 93106,United States [5]Department of Mineralogy,Petrology and Applied Geology,Faculty of Earth Science,University of Barcelona,08028 Barcelona,Spain [6]Institute of Geology,Mongolian Academy of Sciences,Labor Union Street,Songinokhairkhan District,Ulaanbaatar 18080,Mongolia

出　　处：《Geoscience Frontiers》2023年第2期154-181,共28页地学前缘（英文版）

基　　金：supported by the Czech Science Foundation,Czechia(grant number 19-27682X to K.S.)。

摘　　要：The processes leading to the assembly of the Rodinia supercontinent through Grenvillian collisional orogeny are relatively well known.In contrast,accretionary orogenic processes occurring at the supercontinent periphery following Rodinia assembly are poorly understood.To fill this gap,we have identified metamorphic rocks in the Mongolia collage of the Central Asian Orogenic Belt,where numerous data testify for Meso-to Neoproterozoic magmatic reworking.The tectono-metamorphic evolution of the periSiberian tract of the Central Asian Orogenic Belt is mainly characterized by the late Proterozoic–early Cambrian(Baikalian)cycle.However,we document here a Tonian age metamorphism at the northern part of the Precambrian Baidrag block,previously considered as a typical example of the Baikalian metamorphic belt.This study incorporates zircon and in-situ monazite geochronology linked to P-T modelling of Grt-Sil-Ky migmatite gneiss and Grt-St micaschist.Grt-Sil-Ky gneiss records initial burial to the sillimanite stability field at 720℃ and 6.0 kbar followed by further burial to the kyanite stability field at 750℃ and 9 kbar and decompression to 650℃ and 8 kbar.The Grt-St schist records initial burial to the staurolite stability field at 620℃ and 6 kbar,followed by further burial to 590℃ and 8.5 kbar.The monazite data yield a continuum of ^(207)Pb-corrected ^(238)U/^(206)Pb dates of ca.926–768 Ma in the Grt-Sil-Ky gneiss,and ca.937–754 Ma in the Grt-St schist.Based on monazite textural positon,internal zoning,and REE patterns,the time of prograde burial to 6.0 kbar under a thermal gradient of 27–32℃/km is estimated at ca.890–853 Ma.It is not clear whether such high-grade conditions prevailed until a phase of further burial under a geothermal gradient of 18–22℃/km dated at ca.835–815 Ma.The late monazite recrystallization at ca.790 Ma is related to decompression.Additionally,monazite with dates of ca.568–515 Ma occur as whole grains or as rims with sharp boundaries on Tonian monazite in Grt-St schi

关 键 词：Central Asian Orogenic Belt Grenvillian-age metamorphism Monazite in-situ U-Pb dating Monazite REE composition Zircon U-Pb dating Thermodynamic modelling 

分 类 号：P588.3[天文地球—岩石学]