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Article: A Devonian arc–back-arc basin system in the southern Chinese Altai: Constraints from geochemical and Sr-Nd-Pb isotopic data for meta-basaltic rocks

TitleA Devonian arc–back-arc basin system in the southern Chinese Altai: Constraints from geochemical and Sr-Nd-Pb isotopic data for meta-basaltic rocks
Authors
KeywordsCentral Asian Orogenic Belt
Chinese Altai
Devonian
Meta-basalts
Accretionary geodynamics
Issue Date2020
PublisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/lithos
Citation
Lithos, 2020, v. 366-367, p. article no. 105540 How to Cite?
AbstractThe early to middle Paleozoic accretionary history of the Chinese Altai orogen remains controversial, especially along its southern margin facing the Paleo-Asian Ocean. This study conducts a systematic investigation on the Devonian meta-volcanic sequences from the Altay Formation in the southern Chinese Altai to constrain their petrogenesis and tectonic implications. LA-ICP-MS zircon Usingle bondPb dating for rocks from the bottom and top layers of the studied volcanic sequences indicates their eruption age at ca. 380 Ma. The basaltic rocks are low-K tholeiitic with high TiO2 (average = 1.98 wt%), and have rare-earth element (REE) patterns similar to the mid-ocean ridge basalt (MORB), in spite of a large variation in light REE (LREE). They also show enrichment in large ion lithophile elements (LILE; e.g. Ba, U, and Th) and depletion in high field strength elements (HFSE; e.g. Nb and Ta), which are hallmarks of supra-subduction zone basaltic magma. Thus, the elemental data indicate that these rocks are compositionally intermediate between MORB and island-arc tholeiite (IAT). The basaltic samples have positive εNd(t) values (+3.1 to +10.3) and elevated initial 87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb isotopic ratios. Whole-rock elemental and isotopic data suggest that the rocks were likely derived from a dominant N-MORB type depleted asthenosphere mantle, which was variably metasomatized by or interacted with the relatively enriched sub-arc mantle. In combination with the field relationship and regional geology, our study suggests that the meta-basaltic rocks from the middle Altay Formation formed in a mature back-arc spreading environment. We propose an evolving tectonic scenario from a magmatic arc to arc rifting, and finally back-arc opening in the southern Chinese Altai, which corresponds to an extensional regime and resultant asthenosphere upwelling event in this region during Devonian time, probably in response to a trench retreat.
Persistent Identifierhttp://hdl.handle.net/10722/289678
ISSN
2023 Impact Factor: 2.9
2023 SCImago Journal Rankings: 1.491
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorCui, X-
dc.contributor.authorSun, M-
dc.contributor.authorZhao, G-
dc.contributor.authorYao, J-
dc.contributor.authorZhang, Y-
dc.contributor.authorHan, Y-
dc.contributor.authorDai, LM-
dc.date.accessioned2020-10-22T08:15:54Z-
dc.date.available2020-10-22T08:15:54Z-
dc.date.issued2020-
dc.identifier.citationLithos, 2020, v. 366-367, p. article no. 105540-
dc.identifier.issn0024-4937-
dc.identifier.urihttp://hdl.handle.net/10722/289678-
dc.description.abstractThe early to middle Paleozoic accretionary history of the Chinese Altai orogen remains controversial, especially along its southern margin facing the Paleo-Asian Ocean. This study conducts a systematic investigation on the Devonian meta-volcanic sequences from the Altay Formation in the southern Chinese Altai to constrain their petrogenesis and tectonic implications. LA-ICP-MS zircon Usingle bondPb dating for rocks from the bottom and top layers of the studied volcanic sequences indicates their eruption age at ca. 380 Ma. The basaltic rocks are low-K tholeiitic with high TiO2 (average = 1.98 wt%), and have rare-earth element (REE) patterns similar to the mid-ocean ridge basalt (MORB), in spite of a large variation in light REE (LREE). They also show enrichment in large ion lithophile elements (LILE; e.g. Ba, U, and Th) and depletion in high field strength elements (HFSE; e.g. Nb and Ta), which are hallmarks of supra-subduction zone basaltic magma. Thus, the elemental data indicate that these rocks are compositionally intermediate between MORB and island-arc tholeiite (IAT). The basaltic samples have positive εNd(t) values (+3.1 to +10.3) and elevated initial 87Sr/86Sr, 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb isotopic ratios. Whole-rock elemental and isotopic data suggest that the rocks were likely derived from a dominant N-MORB type depleted asthenosphere mantle, which was variably metasomatized by or interacted with the relatively enriched sub-arc mantle. In combination with the field relationship and regional geology, our study suggests that the meta-basaltic rocks from the middle Altay Formation formed in a mature back-arc spreading environment. We propose an evolving tectonic scenario from a magmatic arc to arc rifting, and finally back-arc opening in the southern Chinese Altai, which corresponds to an extensional regime and resultant asthenosphere upwelling event in this region during Devonian time, probably in response to a trench retreat.-
dc.languageeng-
dc.publisherElsevier BV. The Journal's web site is located at http://www.elsevier.com/locate/lithos-
dc.relation.ispartofLithos-
dc.subjectCentral Asian Orogenic Belt-
dc.subjectChinese Altai-
dc.subjectDevonian-
dc.subjectMeta-basalts-
dc.subjectAccretionary geodynamics-
dc.titleA Devonian arc–back-arc basin system in the southern Chinese Altai: Constraints from geochemical and Sr-Nd-Pb isotopic data for meta-basaltic rocks-
dc.typeArticle-
dc.identifier.emailSun, M: minsun@hku.hk-
dc.identifier.emailZhao, G: gzhao@hku.hk-
dc.identifier.emailZhang, Y: zyy518@hku.hk-
dc.identifier.authoritySun, M=rp00780-
dc.identifier.authorityZhao, G=rp00842-
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1016/j.lithos.2020.105540-
dc.identifier.scopuseid_2-s2.0-85083723407-
dc.identifier.hkuros316238-
dc.identifier.volume366-367-
dc.identifier.spagearticle no. 105540-
dc.identifier.epagearticle no. 105540-
dc.identifier.isiWOS:000540493000005-
dc.publisher.placeNetherlands-
dc.identifier.issnl0024-4937-

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