Contributions of basaltic underplating to crustal growth in island arc and extensional tectonic settings in the Chinese Tianshan Orogenic Belt, NW China

Chen, Baoyun1,2; Yu, Jinjie1; Liu, Shuaijie1,3

2019-05

10.1016/j.gr.2019.01.004

GONDWANA RESEARCH   影响因子和分区

1342-937X

1878-0571

A mafic-ultramafic intrusive belt comprising Silurian arc gabbroic rocks and Early Permian mafic-ultramafic intrusions was recently identified in the western part of the East Tianshan, NW China. This paper discusses the petrogenesis of the mafic-ultramafic rocks in this belt and intends to understand Phanerozoic crust growth through basaltic magmatism occurring in an island arc and intraplate extensional tectonic setting in the Chinese Tianshan Orogenic Belt (CTOB). The Silurian gabbroic rocks comprise troctolite, olivine gabbro, and leucogabbro enclosed by Early Permian diorites. SHRIMP II U-Pb zircon dating yields a 427 +/- 7.3 Ma age for the Silurian gabbroic rocks and a 280.9 +/- 3.1 Ma age for the surrounding diorite. These gabbroic rocks are direct products of mantle basaltic magmas generated by flux melting of the hydrous mantle wedge over subduction zone during Silurian subduction in the CTOB. The arc signature of the basaltic magmas receives support from incompatible trace elements in olivine gabbro and leucogabbro, which display enrichment in large ion lithophile elements and prominent depletion in Nb and Ta with higher U/Th and lower Ce/Pb and Nb/Ta ratios than MORBs and OIBs. The hydrous nature of the arc magmas are corroborated by the Silurian gabbroic rocks with a cumulate texture comprising hornblende cumulates and extremely calcic plagiodase (An up to 99 mol%). Troctolite is a hybrid rock, and its formation is related to the reaction of the hydrous basaltic magmas with a former arc olivine-diallage matrix which suggests multiple arc basaltic magmatism in the Early Paleozoic. The Early Permian mafic-ultramafic intrusions in this belt comprise ultramafic rocks and evolved hornblende gabbro resulting from differentiation of a basaltic magma underplated in an intraplate extensional tectonic setting, and this model would apply to coeval maficultramafic intrusions in the CTOB. Presence of Silurian gabbroic rocks as well as pervasively distributed arc felsic plutons in the CTOB suggest active crust-mantle magmatism in the Silurian, which has contributed to crustal growth by (1) serving as heat sources that remelted former arc crust to generate arc plutons, (2) addition of a mantle component to the arc plutons by magma mixing, and (3) transport of mantle materials to form new lower or middle crust. Mafic-ultramafic intrusions and their spatiotemporal A-type granites during Early Permian to Triassic intraplate extension are intrusive counterparts of the contemporaneous bimodal volcanic rocks in the CTOB. Basaltic underplating in this temporal interval contributed to crustal growth in a vertical form, including adding mantle materials to lower or middle crust by intracrustal differentiation and remelting Early-Paleozoic formed arc crust in the CTOB. (C) 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

Mafic-ultramafic rocks Basaltic underplating Arc accretion intraplate extension Crustal growth

SCI

英语

其他

State Key Fundamental Program Project[2012CB416803]

Geology

Geosciences, Multidisciplinary

WOS:000486979400007

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GEOSCIENCES

Web of Science

1.CAGS, Inst Mineral Resources, MNR Key Lab Metallogeny & Mineral Assessment, Beijing 100037, Peoples R China
2.Changan Univ, Sch Earth Sci & Resources, Xian 710054, Shaanxi, Peoples R China
3.Southern Univ Sci & Technol, Dept Earth & Space Sci, Shenzhen 518055, Guangdong, Peoples R China

Chen, Baoyun,Yu, Jinjie,Liu, Shuaijie. Contributions of basaltic underplating to crustal growth in island arc and extensional tectonic settings in the Chinese Tianshan Orogenic Belt, NW China[J]. GONDWANA RESEARCH,2019,69:106-121.

Chen, Baoyun,Yu, Jinjie,&Liu, Shuaijie.(2019).Contributions of basaltic underplating to crustal growth in island arc and extensional tectonic settings in the Chinese Tianshan Orogenic Belt, NW China.GONDWANA RESEARCH,69,106-121.

Chen, Baoyun,et al."Contributions of basaltic underplating to crustal growth in island arc and extensional tectonic settings in the Chinese Tianshan Orogenic Belt, NW China".GONDWANA RESEARCH 69(2019):106-121.