Migration and tectonic implications of Late Jurassic mafic magmatism in South China

Author:

Liu Zi1,Qian Xin12ORCID,Gan Chengshi12,Cui Xiang1,Zhang Yuzhi12,Wang Yang12,Wang Yuejun12

Affiliation:

1. Guangdong Provincial Key Laboratory of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Zhuhai 519082, China

2. Southern Marine Science and Engineering Guangdong Laboratory, Zhuhai 519082, China

Abstract

The Jurassic magmatism in the southeastern South China Block has been interpreted as extension-related, yet its tectonic drivers remain unclear. Tectonic models vary between two end-members: (1) Palaeopacific subduction-related; and (2) intracontinental extension-related. This study presents new geochronological and geochemical data for the Late Jurassic mafic rocks in the southeastern South China Block that allow us to differentiate between these tectonic models. The Late Jurassic mafic rocks yielded crystallization ages of 162–157 Ma. Our new geochemical data, together with previously published data, can be divided into three groups: group A with variable ε Nd ( t ) (+0.1 to +3.4) and zircon ε Hf ( t ) (−4.1 to +15.9) values has slightly negative Nb–Ta anomalies; group B is characterized by negative Nb–Ta anomalies with varying ε Nd ( t ) (+1.4 to +1.5) and ε Hf ( t ) (–3.0 to +2.6) values; and group C displays significant Nb–Ta anomalies with high ε Nd ( t ) (+4.5 to +6.6) and ε Hf ( t ) (+6.4 to +14.4) values. The geochemical characteristics suggest that groups A and B are mainly the products of asthenosphere–lithosphere interactions and group C was derived from the asthenosphere. Our new data, together with geological observations, suggest that the Late Jurassic magmatism in the southeastern South China Block probably resulted from asthenospheric upwelling in an intracontinental extension setting due to the far-field effects of the subduction of the Palaeopacific Ocean. Supplementary material: Tables of geochronological data, geochemical data, and additional figures are available at https://doi.org/10.6084/m9.figshare.c.6080871

Funder

National Natural Science Foundation of China

Guangdong Basic and Applied Basic Research Foundation

Fundamental Research Funds for the Central Universities to SYSU.

Publisher

Geological Society of London

Subject

Geology

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