Geochronology, geochemistry, and Hf isotopes of mafic rocks from Dalabute ophiolitic mélange in West Junggar, Xinjiang (NW China): Implications for the magmatic source and tectonic setting

2020 ◽  
Vol 55 (3) ◽  
pp. 2342-2362 ◽  
Author(s):  
Hai Li ◽  
Yongjun Li ◽  
Gaoxue Yang ◽  
Zuopeng Wang ◽  
Pengfei Ren ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Hf Isotopes ◽  
Mafic Rocks ◽  
Nw China ◽  
Magmatic Source ◽  
Ophiolitic Mélange ◽  
West Junggar

A Neoproterozoic seamount in the Paleoasian Ocean: Evidence from zircon U–Pb geochronology and geochemistry of the Mayile ophiolitic mélange in West Junggar, NW China

Lithos ◽  
2012 ◽  
Vol 140-141 ◽  
pp. 53-65 ◽  
Author(s):  
Gaoxue Yang ◽  
Yongjun Li ◽  
M. Santosh ◽  
Pingyang Gu ◽  
Baokai Yang ◽  
...  
Keyword(s):  
Paleoasian Ocean ◽  
Nw China ◽  
Ophiolitic Mélange ◽  
West Junggar

Geochronological and geochemical studies of the OIB-type Baiyanghe dolerites: implications for the existence of a mantle plume in northern West Junggar (NW China)

2018 ◽  
Vol 156 (4) ◽  
pp. 702-724 ◽  
Author(s):  
XIU-QUAN MIAO ◽  
XIN ZHANG ◽  
HUI ZHANG ◽  
JIN-RONG WANG ◽  
ZHENG LIU ◽  
...  
Keyword(s):  
Mantle Plume ◽  
Isotope Geochemistry ◽  
Tectonic Setting ◽  
Major And Trace Elements ◽  
Nd Isotope ◽  
Nw China ◽  
Tholeiite Basalt ◽  
West Junggar ◽  
Geochemical Studies ◽  
T Values

AbstractIn this paper, zircon U–Pb geochronology, major and trace elements, and Sr–Nd isotope geochemistry of the Baiyanghe dolerites in northern West Junggar of NW China are presented. The U–Pb dating of zircons from the dolerites yielded ages of 272.2±4 Ma and 276.7±6.2 Ma, which indicate the emplacement times. The dolerites are characterized by minor variations in SiO2(46.89 to 49.07 wt%), high contents of Al2O3(13.60 to 13.92 wt%) and total Fe2O3(11.14 to 11.70 wt%), and low contents of MgO (2.67 to 3.64 wt%) and total alkalis (Na2O+K2O, 5.1 to 5.97 wt%, K2O/Na2O = 0.37–0.94), which indicate affinities to metaluminous tholeiite basalt. The REE pattern ((La/Sm)N= 2.25–2.34, (La/Yb)N= 7.42–8.36), V–Ti/1000 and 50*Zr–Ti/50–Sm discrimination diagrams show that these rocks are OIB-type. The high contents of Zr and Ti indicate a within-plate tectonic setting, and samples plot in the ‘plume source’ field shown on the Dy/Yb(N)versus Ce/Yb(N)diagram. The positive εNd(t) values (+7.09 to +7.48), high initial87Sr/86Sr ratios (0.70442 to 0.70682) and depletions of Nb and Ta elements in the samples can be explained by the involvement of subducted sediments. In summary, it is possible that the Baiyanghe dolerites were derived from an OIB-like mantle source and associated with a mantle plume tectonic setting. Therefore, our samples provide the youngest evidence for the existence of a mantle plume, which may provide new insights into the Late Palaeozoic tectonic setting of West Junggar.

The Liuyuan complex in the Beishan, NW China: a Carboniferous–Permian ophiolitic fore-arc sliver in the southern Altaids

2011 ◽  
Vol 149 (3) ◽  
pp. 483-506 ◽  
Author(s):  
QIGUI MAO ◽  
WENJIAO XIAO ◽  
BRIAN F. WINDLEY ◽  
CHUNMING HAN ◽  
JUNFENG QU ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Weighted Average ◽  
Geochemical Data ◽  
Current Debate ◽  
Mafic Rocks ◽  
Nw China ◽  
Tectonic History ◽  
Icp Ms ◽  
Ocean Ridge ◽  
Basic Rocks

AbstractThe tectonic history and time of closure of the Palaeo-Asian ocean of the Altaids are issues of lively current debate. To address these issues, this paper presents detailed geological, petrological and geochemical data of the Liuyuan complex (LC) in the Beishan region in NW China, located in the southernmost Altaids, in order to constrain its age, origin and tectonic setting. The LC mainly comprises massive basalts, pillow basalts, basaltic breccias, gabbros and ultramafic rocks together with cherts and tuffs. Most prominent are gabbros and large volumes of basaltic lavas. These mafic rocks have high TiO2 contents, flat rare earth element (REE) patterns and show high-field-strength elements (HFSEs) similar to those of mid-ocean ridge basalts (MORB). The mafic rocks exhibit positive εNd(t) (6.6–9.0) values, representing magmas derived from the mantle. But these basic rocks are also enriched in Th relative to REEs, and are systematically depleted in Nb–Ta–(Ti) relative to REEs. There is also a large range in initial 87Sr/86Sr (0.7037–0.7093). All these variables indicate that mantle-derived magma was contaminated by fluids and/or melts from a subducting lithospheric slab, and formed in a supra-subduction zone (SSZ) setting. A gabbro intruded in the complex was dated by LA-ICP-MS on 20 zircons that yielded a 206Pb–238U weighted average age of 286 ± 2 Ma. Considering the fact that all these basalts are imbricated against Permian tuffaceous sediments and limestone, we propose that the LC formed as an ophiolite in a fore-arc in Carboniferous–Permian time. This indicates that the Palaeo-Asian ocean still existed at 286 ± 2 Ma in early Permian time, and thus the time of closure of the Palaeo-Asian ocean was in or after the late Permian.

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