Petrogenesis, zircon U–Pb age, and geochemistry of the A-type Mogou syenite, western Henan province: implications for mesozoic tectono-magmatic evolution of the Qinling Orogen

He, Xinyu, Wang, Jionghui, Wang, Changming, Carranza, Emmanuel John M., Chen, Liang, and Wu, Bin (2016) Petrogenesis, zircon U–Pb age, and geochemistry of the A-type Mogou syenite, western Henan province: implications for mesozoic tectono-magmatic evolution of the Qinling Orogen. Journal of Earth System Science, 125 (3). pp. 585-603.

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Abstract

The Mogou syenite intruded into the Mesoproterozoic Xiong’er Group is the main lithostratigraphic unit, along the southern margin of the North China Craton (NCC). This paper reports zircon LAICP- MS data, whole-rock major and trace element compositions of late Triassic magmatic rocks in the Mogou syenite, in order to constrain the formation age of the Mogou syenite, research the origin and evolution of the magma and analyse the geodynamic setting of the Qinling Orogen (QO) in Late Triassic. These rocks consist of medium- to coarse-grained syenite and fine-grained quartz syenite. Zircon U–Pb dating yields a crystallization age of 226.5±2.7 Ma. The syenites are characterized by high SiO2 (63.49–72.17%), alkali (K2O+Na2O of 11.18–15.38%) and potassium (K2O/Na2O of 2.88–28.11), are peralkaline or metaluminous (molar A/CNK of 0.87–1.02) and belong to shoshonite series. The syenites have ΣREE of 33.01–191.30 ppm, LREE/HREE of 14–20, (La/Yb) N of 11–24, with LREE-rich distribution pattern and obvious differentiation between HREE and LREE. Eu anomalies are positive for the medium- to coarse-grained syenite and weakly negative for the fine-grained quartz syenite. In addition, the syenites are enriched in large-ion lithophile elements (Ba, K, Sr, and Pb) but depleted in high strength field elements (Ti, Ta, Nb, Zr, and Hf), and have high differentiation indices of 91.69– 97.06. These geochemical features indicate that the primary magma of the Mogou syenite most likely originated from a mantle source with minor crustal component, and underwent a fractional crystallization process during its emplacement. The late Triassic A-type Moguo syenite along the southern margin of the NCC was generated in the late stage of the syn-collision event of QO, recording a transition period from compression to extension at around 227 Ma.

Item ID: 49274
Item Type: Article (Research - C1)
ISSN: 0973-774X
Keywords: zircon U–Pb dating, syn-collision, post-collision, syenite, Mogou, Qinling orogen
Funders: National Natural Science Foundation of China (NNSFC), CSC-Sponsored Scholarship Program (CSC), National Basic Research Program (NBRP), Fundamental Research Funds for the Central Universities (FRFCU), China Minmetals Corporation (CMC), 111 Project (111)
Projects and Grants: NNSFC grant No. 41230311, CSC No. 201406405006, NBRP No. 2015CB452600, FRFCU No. 2652013034, FRFCU No. 2652015314, FRFCU No. 2652015315, FRFCU No. 2652015430, CMC No. 2013KC0201, 111 Project No. B07011
Date Deposited: 09 Jun 2017 00:32
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040202 Inorganic Geochemistry @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
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