Alkaline basalts in the Karamay ophiolitic mélange, NW China: a geological, geochemical and geochronological study and implications for geodynamic setting

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dc.contributor.authorYang, G.
dc.contributor.authorLi, Y.
dc.contributor.authorSantosh, M.
dc.contributor.authorXiao, W.
dc.contributor.authorYang, B.
dc.contributor.authorTong, L.
dc.contributor.authorZhang, S.
dc.date.issued2015
dc.description.abstractAlkaline basalts are common constituents in many ophiolite belts and accretionary complexes. Here we report geological, geochronological, geochemical, and whole-rock Sr–Nd isotopic data for alkaline basalts from the Karamay ophiolitic mélange of West Junggar, southern Central Asian Orogenic Belt (CAOB). In the ophiolitic mélange, imbricate thrusts, duplexes, “web” structures, pinch-and-swell structures, tilted structures in pillow metabasalts, and shear band cleavages are widely developed. U–Pb analyses of zircon grains from a representative basalt by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) yielded crystallization age of ca. 395 ± 3 Ma, suggesting formation during the Middle Devonian. Geochemically, all the samples bear the signature of ocean island basalt (OIB), and are characterized by alkaline affinity with high concentrations of Na₂O + K₂O (4.22–7.28 wt.%) and TiO₂ (1.72–2.89 wt.%), LILE and LREE enrichment and HREE depletion ((La/Yb)N = 8.4–15.6), with very strong or no Eu anomalies (Eu/Eu* = 0.6–1.1), and no obvious Nb, Ta or Ti negative anomalies. The rocks display consistent Sr–Nd isotopic compositions (initial ⁸⁷Sr/⁸⁶Sr ratios = 0.70326–0.70453, εNd(t) = + 3.1–+7.6). The results suggest that all the alkaline basalts were derived from a mantle plume-related source in an intra-oceanic setting with ca. 1–3% degree partial melting of garnet lherzolite. These observations, in combination with previous work, indicate that the alkaline basalts from Karamay ophiolitic mélange can be correlated to a Middle Devonian mantle plume-related magmatism within Paleo-Asian Ocean. We further suggest that the plume-related activity in the CAOB was generally continuous during the development of the Paleo-Asian Ocean.
dc.description.statementofresponsibilityGaoxue Yang, Yongjun Li, M. Santosh, Wenjiao Xiao, Baokai Yang, Lili Tong, Shenglong Zhang
dc.identifier.citationJournal of Asian Earth Sciences, 2015; 113(1):110-125
dc.identifier.doi10.1016/j.jseaes.2014.08.017
dc.identifier.issn1367-9120
dc.identifier.issn1878-5786
dc.identifier.orcidSantosh, M. [0000-0002-1073-8477]
dc.identifier.urihttp://hdl.handle.net/2440/116219
dc.language.isoen
dc.publisherElsevier
dc.relation.grant41303027
dc.relation.grant41230207
dc.relation.grant41390441
dc.relation.grant41190075
dc.rights© 2014 Elsevier Ltd. All rights reserved.
dc.source.urihttps://doi.org/10.1016/j.jseaes.2014.08.017
dc.subjectOphiolitic mélange; mantle plume; zircon geochronology; geochemistry; West Junggar; Central Asian Orogenic Belt
dc.titleAlkaline basalts in the Karamay ophiolitic mélange, NW China: a geological, geochemical and geochronological study and implications for geodynamic setting
dc.typeJournal article
pubs.publication-statusPublished

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