Timing of metamorphism and deformation in the Swat valley, northern Pakistan:Insight into garnet-monazite HREE partitioning

查看全文 作　　者：Kyle [1]P.Larson;Asghar [1,2]Ali;Sudip [1]Shrestha;Mathieu [1]Soret;John [3]M.Cottle;Rafique [4]Ahmad

机构地区：[1]University of British Columbia, Okanagan, Earth, Environmental and Geographic Sciences;[2]University of Peshawar, Department of Geology;[3]University of Califomia, Santa Barbara, Department of Earth Sciences;[4]The Bacha Khan University,Department of Geology

出　　处：《Geoscience Frontiers》索引2019年第10卷第3期,共13页

基　　金：supported by a Higher Education Commission of Pakistan Post-Doctoral Scholarship to A. Ali, NSERC Discovery Grant and Canada Foundation for Innovation grants to K. Larson, and NSF grant NSF-EAR-1119380 to J. Cottle. D. Arkinstall is thanked for his assistance in the FiLTER 摘　　要：New metamorphic petrology and geochronology from the Loe Sar dome in the Swat region of northern Pakistan place refined constraints on the pressure, temperature and timing of metamorphism and deformation in that part of the Himalayan orogen. Thermodynamic modelling and monazite petrochronology indicate that metamorphism in the area followed a prograde evolution from ~525 ± 25 ℃and 6 士 0.5 kbar to ~610 ± 25 ℃ and 9 士 0.5 kbar, between ca. 39 Ma and 28 Ma. Partitioning of heavy rare earth elements between garnet rims and 30-28 Ma monazite are interpreted to indicate coeval crystallization at peak conditions. Microtextural relationships indicate that garnet rim growth post-dated the development of the main foliation in the area. The regional foliation is folded about large-scale N-S trending fold axes and overprinting E-W trending folds to form km-scale domal culminations. The textural relationships observed indicate that final dome development must be younger than the 30-28 Ma monazite that grew with garnet rims post-regional foliation development, but pre-doming-related deformation. This new timing constraint helps resolve discrepancy between previous interpretations,which have alternately suggested that N-S trending regional folds must be either pre-or post-early Oligocene. Finally, when combined with existing hornblende and white mica cooling ages, these new data indicate that the study area was exhumed rapidly following peak metamorphism. 关键词：Pakistan HIMALAYA MONAZITE petrochronology METAMORPHISM Phase EQUILIBRIA modelling Deformation

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Timing of metamorphism and deformation in the Swat valley, northern Pakistan:Insight into garnet-monazite HREE partitioning

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