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Generation of Late Cretaceous Ji'an basalts through asthenosphere-slab interaction in south China

Wu Yangming, Guo Feng, Wang Xuance, Zhang Bo, Zhang Xiaobing, Melesse Alemayehu and Wang Guoqing
Generation of Late Cretaceous Ji'an basalts through asthenosphere-slab interaction in south China
Geological Society of America Bulletin (November 2019) 132 (5-6): 1316-1332

Abstract

Recycled crustal components have been widely identified in the source of continental basalts with geochemical features similar to oceanic island basalts (OIBs). However, the mechanism of how these recycled materials are involved remains highly debatable. Here we conduct comprehensive geochemical analyses (including whole-rock, olivine, and melt inclusion) and numerical modeling on Late Cretaceous Ji'an basalts from South China interior, aiming to investigate the possible role of recycled crustal components in basalt petrogenesis driven by the subducted paleo-Pacific oceanic plate. The Ji'an basalts show geochemical characteristics akin to OIBs and have depleted asthenospheric mantle-like Sr-Nd-Pb-Hf isotopic compositions with moderately radiogenic Os. Their olivine-hosted melt inclusions have low H (sub 2) O and highly negative delta D values and olivine phenocrysts are mainly characterized by depletion of (super 18) O with delta (super 18) O values lowering to 3.9 ppm. These features are consistent with positive Sr and Eu anomalies in some whole-rock samples. The combined geochemical data suggest that the primary magmas were derived from an asthenospheric mantle enriched by melts from an altered gabbroic oceanic crust, which had experienced intensive dehydration. Further numerical modeling shows that melting of the dehydrated oceanic crust can occur along the torn flank of the subducting lithosphere, in the case that the slab is strongly thinned and fractured. The low delta (super 18) O preserved in olivine and the estimated slab age (<300 Ma) from the radiogenic whole-rock Os and Pb compositions also require the involvement of a recently recycled slab, probably represented by the subducted paleo-Pacific oceanic plate. Rollback of the subducting paleo-Pacific slab might create a slab window, in which melt from the torn/fractured slab reacted with the upwelling asthenosphere to form an enriched mantle source for the Ji'an basalts and similar counterparts.


ISSN: 0016-7606
EISSN: 1943-2674
Coden: BUGMAF
Serial Title: Geological Society of America Bulletin
Serial Volume: 132
Serial Issue: 5-6
Title: Generation of Late Cretaceous Ji'an basalts through asthenosphere-slab interaction in south China
Affiliation: Chinese Academy of Sciences, Guangzhou Institute of Geochemistry, Laboratory of Isotope Geochemistry, Guangzhou, China
Pages: 1316-1332
Published: 20191101
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 148
Accession Number: 2020-006780
Categories: Isotope geochemistryIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2020012
Illustration Description: illus. incl. geol. sketch map
N22°00'00" - N28°00'00", E114°00'00" - E122°00'00"
Secondary Affiliation: Yunnan University, CHN, China
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 202006
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