Thermal Structure Beneath the Tarim Craton and Its Tectonic Implications

Xi Xu,Xuezhong Yu,Shengqing Xiong,Xiaoying Zhu,Jianhua Wan,Qiang Zheng,Baodi Wang,Qifang Zheng,Xingtao Kuang,Daoqing Zhou,Akiko Tanaka

doi:10.3389/feart.2021.700114

Abstract

The lateral distribution of the magnetic layer beneath the Tarim Craton and its environs was estimated from spectral analysis using the newest high-resolution aeromagnetic dataset of mainland China, which is enlarged by EMAG2. As a proxy, the Curie point depth (CPD) provides a comprehensive view of a crust-scale thermal regime, accounted for the depth at which magnetite becomes paramagnetic, and the correspondence of the CPD with the tectonic regime indicates that the CPD is useful for delineating the regional crustal thermal structure. Furthermore, lateral variations in CPD provide useful insights into the lithospheric thermal state of the Tarim Craton and its surrounding areas and can be related to ancient and active tectonics, such as geothermal activity, seismicity, and mineral-petroleum generation. In the Tarim interior, the NW domain covering the Bachu Uplift and its surrounding areas corresponds to the minimum magnetic CPD signature geometry of this area, which is most likely linked to the Permian Tarim plume-lithosphere interaction. In contrast, the other domains are characterized by large CPD values (up to 50 km), which are floored by a Precambrian basement without the Permian magmatism modification. Moreover, the estimated CPD values are consistent with surface heat flow measurements with an inverse correlation, which can assist in identifying the potential area for mineral deposits and hydrocarbon fields. Earthquakes are mostly concentrated in the gradient and transition zones of the Curie surface, suggesting that these abrupt variation domains in the crustal thermal structure act as a secondary mechanism for earthquake generation.

Highlights

The Earth’s crustal thermal structure is related to ancient and active tectonics such as volcanism, intrusion, mountain uplift and earthquakes (e.g., Turcotte and Schubert, 2002a; Li et al, 2009; Li et al, 2012a; Correa et al, 2016; Wang et al, 2018), and constrains the lithospheric tectonic processes in response to the dynamics of the Earth, as the mechanical/physical properties of the crust and lithosphere are temperature-dependent (Afonso et al, 2005)
Northwestward of the western Tarim Basin, shallow values ranging from 34 km up to 20 km extend over the western Tian Shan and its environs, with the exception of the Issyk-Kul Lake domain characterized by high Curie point depth (CPD) values
The newest high-resolution aeromagnetic dataset of the Chinese mainland acquired over the past 60 decades was used, and the no-data area corresponding to the abroad domain was enlarged by the EMAG2

Summary

Introduction

The Earth’s crustal thermal structure is related to ancient and active tectonics such as volcanism, intrusion, mountain uplift and earthquakes (e.g., Turcotte and Schubert, 2002a; Li et al, 2009; Li et al, 2012a; Correa et al, 2016; Wang et al, 2018), and constrains the lithospheric tectonic processes in response to the dynamics of the Earth, as the mechanical/physical properties of the crust and lithosphere are temperature-dependent (Afonso et al, 2005). It is widely accepted that the CPD may be interpreted as the isotherm surface where ferromagnetic magnetized minerals, which are responsible for the magnetization of crustal rocks, Thermal Structure of Tarim Craton become paramagnetic due to the temperature (CPD), generally approximated at 580°C (Bhattacharyya and Leu, 1975; Frost and Shive, 1986; Lorwrie, 2007). The depth of this surface depending on temperature can be accurately used to infer the regional thermal structure within the lithosphere. Considering the influence of irregularly distributed measurements, shallow geothermal circulation, and local tectonic activity (e.g., Davies, 2013; Li and Wang, 2016; Andrés et al, 2018), the thermal regime can be better constrained overall via the CPD, which is derived from magnetic anomalies; the CPD is viewed as an alternative to circumvent the thermal configuration of crust and lithosphere (e.g., Tanaka, 2007)

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