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Geochronology and geochemistry of basalts from the Karamay ophiolitic melange in West Junggar (NW China): Implications for Devonian-Carboniferous intra-oceanic accretionary tectonics of the southern Altaids

2012; Geological Society of America; Volume: 125; Issue: 3-4 Linguagem: Inglês

10.1130/b30650.1

1943-2674

Gui‐Peng Yang, Li Yin, M. Santosh, B. Yang, Bo Zhang, Lili Tong,

High-pressure geophysics and materials

Research Article| March 01, 2013 Geochronology and geochemistry of basalts from the Karamay ophiolitic mélange in West Junggar (NW China): Implications for Devonian–Carboniferous intra-oceanic accretionary tectonics of the southern Altaids Gaoxue Yang; Gaoxue Yang † 1Ministry of Education, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Xi'an 710054, China2School of Earth Science & Resources, Chang'an University, Xi'an 710054, China †E-mail: mllygx@126.com Search for other works by this author on: GSW Google Scholar Yongjun Li; Yongjun Li 1Ministry of Education, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Xi'an 710054, China2School of Earth Science & Resources, Chang'an University, Xi'an 710054, China Search for other works by this author on: GSW Google Scholar M. Santosh; M. Santosh 3Department of Natural Environmental Science, Kochi University, Kochi 7808520, Japan Search for other works by this author on: GSW Google Scholar Baokai Yang; Baokai Yang 2School of Earth Science & Resources, Chang'an University, Xi'an 710054, China4The Qingdao Geological Engineering Investigation Institute, Qingdao 266071, China Search for other works by this author on: GSW Google Scholar Bing Zhang; Bing Zhang 5No. 7 Geological Survey Team, Xinjiang Bureau of Geology and Mineral Resource Exploration, Wusu 833000, China Search for other works by this author on: GSW Google Scholar Lili Tong Lili Tong 1Ministry of Education, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Xi'an 710054, China2School of Earth Science & Resources, Chang'an University, Xi'an 710054, China Search for other works by this author on: GSW Google Scholar Author and Article Information Gaoxue Yang † 1Ministry of Education, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Xi'an 710054, China2School of Earth Science & Resources, Chang'an University, Xi'an 710054, China Yongjun Li 1Ministry of Education, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Xi'an 710054, China2School of Earth Science & Resources, Chang'an University, Xi'an 710054, China M. Santosh 3Department of Natural Environmental Science, Kochi University, Kochi 7808520, Japan Baokai Yang 2School of Earth Science & Resources, Chang'an University, Xi'an 710054, China4The Qingdao Geological Engineering Investigation Institute, Qingdao 266071, China Bing Zhang 5No. 7 Geological Survey Team, Xinjiang Bureau of Geology and Mineral Resource Exploration, Wusu 833000, China Lili Tong 1Ministry of Education, Key Laboratory of Western China's Mineral Resources and Geological Engineering, Xi'an 710054, China2School of Earth Science & Resources, Chang'an University, Xi'an 710054, China †E-mail: mllygx@126.com Publisher: Geological Society of America Received: 08 Dec 2011 Revision Received: 07 Aug 2012 Accepted: 26 Sep 2012 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2013 Geological Society of America GSA Bulletin (2013) 125 (3-4): 401–419. https://doi.org/10.1130/B30650.1 Article history Received: 08 Dec 2011 Revision Received: 07 Aug 2012 Accepted: 26 Sep 2012 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Gaoxue Yang, Yongjun Li, M. Santosh, Baokai Yang, Bing Zhang, Lili Tong; Geochronology and geochemistry of basalts from the Karamay ophiolitic mélange in West Junggar (NW China): Implications for Devonian–Carboniferous intra-oceanic accretionary tectonics of the southern Altaids. GSA Bulletin 2013;; 125 (3-4): 401–419. doi: https://doi.org/10.1130/B30650.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract New laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb zircon ages and geochemical data are reported for the Karamay ophiolitic mélange in the West Junggar area at the southwestern margin of the Altaids (or Central Asian orogenic belt), northwestern China. The data were used to identify the petrogenesis of the mélange, and to evaluate its tectonic significance. In addition, this study aimed to assess the possible presence of Devonian mantle plume in the region. The Karamay ophiolitic mélange crops out at the boundary of the Junggar Basin but is partly hidden by Mesozoic sediments, with an exposure area of ∼40 km2. The site contains ultramafic rocks, cumulates, gabbros, pillow lavas, abyssal radiolarian cherts, turbidites, and tuffs, which show typical block-in-matrix structures. Zircon U-Pb analyses from the basalt and gabbro by LA-ICP-MS yielded weighted mean ages of 395 ± 3 Ma and 387 ± 8 Ma, respectively. These ages suggest a Middle Devonian emplacement. All basalts bear the signature of ocean-island basalt (OIB) and are characterized by alkaline compositions with high concentrations of Na2O + K2O (3.7–8.5 wt%) and TiO2 (1.5–3.1 wt%); large ion lithophile element and light rare earth element enrichment and heavy rare earth element depletion; very weak or no Eu anomalies (Eu/Eu* = 0.9–1.0); and no obvious Nb, Ta, or Ti negative anomalies. We propose that these basaltic rocks were derived from mantle plume–related magmatism associated with the evolution of the Paleoasian oceanic system. The enriched mantle source could have contained 2%–5% garnet and ∼3% spinel. The rocks also display strong geochemical similarities with the Xigaze seamount basalts, which formed in intra-oceanic settings. Compared to the basalts, the gabbros display mid-ocean-ridge-basalt–type tholeiitic basalt features, derived from a depleted mantle source with the addition of fluids from a subducted slab within a suprasubduction-zone environment. These observations are supported by previous work, and they indicate Devonian mantle plume–related magmatism within the Paleoasian Ocean. However, as these rocks are mainly parts of accretionary complexes, whether the Karamay and Darbut ophiolitic mélange formed in a single belt remains equivocal, and further work is required to resolve this issue. Thus, there was a complex evolution by subduction-accretion processes from the Devonian to the Carboniferous before final amalgamation and docking to the northern Siberian block. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.