Geochronology and geochemistry of the Bashikaogong S-type granitic rocks: a record of Early Paleozoic subduction and collision in North Altun, Northwestern China

Autor: Fenghui Zou, Cailai Wu, Kun Zheng, Di Wu, Hongjie Chen, Dong Gao
Rok vydání: 2021
Předmět:
Zdroj: Arabian Journal of Geosciences. 14
ISSN: 1866-7538
1866-7511
DOI: 10.1007/s12517-021-07658-3
Popis: The Altun orogenic belt (AOB) was the site of complex subduction of oceanic crust and continental collision during the Paleozoic. The North Altun ophiolitic melange belt (NAB) is a one of the key tectonic units of the AOB and contains abundant subduction- and collision-related rocks. In this paper, we report the petrography, zircon U–Pb ages, geochemistry, and zircon Hf isotopes of the Bashikaogong S-type granitic rocks from the North Altun ophiolitic melange belt (NAB) to constrain their petrogenesis and tectonic setting. The granitic rocks consist of three types of granites, i.e., (1) gray, medium- to coarse-grained porphyritic granite; (2) gray, medium-grained granite; and (3) pink, medium- to coarse-grained granite. Zircon U–Pb dating yielded ages of 483–477, 458–453, and 447–445 Ma for type 1, type 2, and type s3 granites, respectively. All the three types of granites share similar strongly peraluminous (A/CNK > 1.1), contain muscovite mineral, have K2O/ Na2O ratios of > 1, and display negative zircon eHf(t) values, which are similar to typical S-type granites. On the basis of our data and results of previous studies, we infer that type 1 granites (483–477 Ma) are related to subduction of North Altun oceanic lithosphere, type 2 granites (458–453 Ma) are syn-collision granites related to continental collision between the Central Altun and Dunhuang Blocks, and type 3 granites (447–445 Ma) are from the late-collision stage. The Bashikaogong S-type granitic rocks recorded early Paleozoic subduction and collision in the North Altun region and were generated by the partial melting of the protolith of the metasedimentary Paleoproterozoic–Mesoproterozoic basement in the CAB due to the collapse of the overthickened subduction orogen.
Databáze: OpenAIRE
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