Multiple metamorphic events revealed by zircons from the Diancang;Shan-Ailao Shan metamorphic complex, southeastern Tibetan Plateau

doi:10.1016/j.gr.2012.10.016

	Multiple metamorphic events revealed by zircons from the Diancang;Shan-Ailao Shan metamorphic complex, southeastern Tibetan Plateau
	Liu, Fulai 2; Wang, Fang ; Liu, Pinghua ; Liu, Chaohui
刊名	GONDWANA RESEARCH
	2013
卷号	24 期号:1;SI SI 页码:429-450
关键词	Multiple metamorphic events U-Pb and Ar-Ar dating Zircon P-T-t path Diancang Shan-Ailao Shan complex belt
ISSN号	1342-937X
DOI	10.1016/j.gr.2012.10.016
英文摘要	Analyses of mineral inclusions within complexly zoned zircons, combined with SIMS U-Pb ages for various domains within the zircons, provide evidence of the origin and multistage metamorphic evolution of the Diancang Shan-Ailao Shan metamorphic complex, southeastern Tibetan Plateau. Zircons separated from paragneisses, amphibolites, garnet pyroxenites, and marbles were subdivided into inherited (magmatic or detrital) and metamorphic zircons based on cathodoluminescence (CL) and Laser Raman spectroscopy. Weakly zoned, inherited detrital zircons from paragneisses yield ages of 700-540 Ma, 1000-800 Ma, similar to 1800 Ma, and 2550-2450 Ma, and contain inclusion assemblages of Qtz + Kfs + Pl + Ap, recording widespread geological events throughout the ancient Gondwana continent. In contrast, clearly zoned, inherited magmatic zircons in amphibolites and garnet pyroxenites yield ages of similar to 778-773 Ma and contain Cpx + Pl +/- Qtz + Ap inclusions, representing the crystallization age of the mafic protolith. Metamorphic zircons also record discrete Early-Middle Triassic and the Eocene-Oligocene thermal events. Homogeneous metamorphic zircons with low Th/U ratios (<0.1) contain high-pressure (HP)-diagnostic Grt + Ky + Phe/Mus + Kfs + Qtz + Ap, and Grt + Cpx + Pl +/- Qtz inclusions in paragneisses, and amphibolites and garnet pyroxenites, respectively, suggesting their formation at 650-720 degrees C and similar to 14 kb. These HP zircons yield Pb-206/U-238 ages of 249-230 Ma, indicating an Early-Middle Triassic HP metamorphic event in the Diancang Shan-Ailao Shan complex belt Two groups of Eocene-Oligocene metamorphic zircons are also present. One of the groups comprises homogenous zircons with low Th/U ratios (<0.1) that contain medium-pressure (MP) amphibolite-granulite fades Grt + Ky + St + Bt + Kfs + Qtz, Grt + Cpx + Hb + Pl, and Dol + Cal + Ap in paragneisses, amphibolites, and marbles. These assemblages are stable at peak pressure-temperature (P-T) conditions of 720 degrees C-760 degrees C and 8.0-9.6 kb, and yield consistent Eocene ages (44-36 Ma). The second group is homogeneous and all zircons have similar Th/U ratios, but contain distinct low-pressure (LP) Grt + Sil + Bt +Kfs + Qtz + Ap, Opx +/- Cpx +/- Grt + Hb + Pl, Cal +/- Cpx +Ap inclusions in paragneisses, amphibolites and garnet pyroxenites, and marbles, recording post-peak P-T conditions of 700 degrees C - 750 degrees C and 5.0-6.5 kb, and yielding younger Oligocene metamorphic ages (32-25 Ma). Ar-40/Ar-39 analyses of biotite, muscovite, and amphibole yield the youngest ages (25-14 Ma, Miocene) related to late cooling during retrogressive metamorphism under conditions of 520 degrees C-620 degrees C and 4.0-4.5 kb.;These new data suggest a clockwise P-T-t path for the Diancang Shan-Ailao Shan metamorphic complex belt, typical of continent-continent collision, indicating collision-subduction tectonism prior to the strong, left-lateral, ductile deformation along the Ailao Shan-Red River (ASRR) shear zone that started at similar to 32 Ma and lasted until 25 Ma, causing mid-crustal (18-25 km depth) high-temperature metamorphic conditions. Continued uplift, and a slowing of left-lateral ductile shearing occurred at similar to 25-14 Ma at a depth of 10-15 km and under relatively low-temperature conditions. This temporal and kinematic link between left-lateral shearing along the ASRR and the opening of the South China Sea supports the occurrence of the block extrusion of Indochina from Eurasia along lithospheric-scale strike-up faults. (C) 2012 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
学科主题	变质岩岩石学
WOS关键词	RIVER SHEAR ZONE ; ROCK-FORMING MINERALS ; INDIA-ASIA COLLISION ; U-TH-PB ; RED-RIVER ; TECTONIC EVOLUTION ; SE ASIA ; SOUTHERN TIBET ; LU-HF ; GEOCHRONOLOGICAL CONSTRAINTS
WOS研究方向	Geology
语种	英语
出版者	ELSEVIER SCIENCE BV
WOS记录号	WOS:000319635700027
内容类型	期刊论文
源URL	[http://119.78.100.197/handle/2HKVOGP0/40069]
专题	中国地质科学院地质研究所
作者单位	1.Chinese Acad Geol Sci, Inst Geol, Beijing 100037, Peoples R China. 2.中国地质科学院地质研究所
推荐引用方式 GB/T 7714	Liu, Fulai,Wang, Fang,Liu, Pinghua,et al. Multiple metamorphic events revealed by zircons from the Diancang;Shan-Ailao Shan metamorphic complex, southeastern Tibetan Plateau[J]. GONDWANA RESEARCH,2013,24(1;SI SI):429-450.
APA	Liu, Fulai,Wang, Fang,Liu, Pinghua,&Liu, Chaohui.(2013).Multiple metamorphic events revealed by zircons from the Diancang;Shan-Ailao Shan metamorphic complex, southeastern Tibetan Plateau.GONDWANA RESEARCH,24(1;SI SI),429-450.
MLA	Liu, Fulai,et al."Multiple metamorphic events revealed by zircons from the Diancang;Shan-Ailao Shan metamorphic complex, southeastern Tibetan Plateau".GONDWANA RESEARCH 24.1;SI SI(2013):429-450.