Linking deeply-sourced volatile emissions to plateau growth dynamics in southeastern Tibetan Plateau

Abstract

The episodic growth of high-elevation orogenic plateaux is controlled by a series of geodynamic processes. However, determining the underlying mechanisms that drive plateau growth dynamics over geological history and constraining the depths at which growth originates, remains challenging. Here we present He-CO2-N2 systematics of hydrothermal fluids that reveal the existence of a lithospheric-scale fault system in the southeastern Tibetan Plateau, whereby multi-stage plateau growth occurred in the geological past and continues to the present. He isotopes provide unambiguous evidence for the involvement of mantle-scale dynamics in lateral expansion and localized surface uplift of the Tibetan Plateau. The excellent correlation between 3He/4He values and strain rates, along the strike of Indian indentation into Asia, suggests non-uniform distribution of stresses between the plateau boundary and interior, which modulate southeastward growth of the Tibetan Plateau within the context of India-Asia convergence. Our results demonstrate that deeply-sourced volatile geochemistry can be used to constrain deep dynamic processes involved in orogenic plateau growth.

Geochemical Characteristics of Hydrothermal Volatiles From Southeast China and Their Implications on the Tectonic Structure Controlling Heat Convection

“…For the southwest part, the Qinghai-Tibet Plateau has attracted the attention of many researchers to conduct studies on how tectonic structures control hot spring distributions (Guo, 2012;Hochstein and Regenauer-Lieb, 1998;Liao and Zhao, 1999). Studies on hydrothermal volatiles were critical in identifying the influence of tectonic structures on geothermal exhibitions (Tian et al, 2021;Zhang et al, 2021;Zhou et al, 2017). The southeast Chinese mainland is characterized by widespread Jurassic-Cretaceous granitic magmatism (Figures 1B,C) associated with more than 500 hot springs exposed along a series of NE-trending faults, with temperatures of 50 °C-100 °C (Pei and Hong, 1995;Jiang et al, 2019).…”

“…Specifically, isotopic and elemental compositions of He, CO 2 , and N 2 in the gases are sensitive tracers of crustal and mantle components in the overall volatile inventory (Hilton et al, 2002;Smith et al, 2005;Sano et al, 2017). Furthermore, the melting and stress-induced dilatancy of deep-seated rocks can cause detectable changes in volatile geochemistry (Zhang et al, 2021). Thus, geothermal volatiles have been used as an effective tool for understanding tectonic structures (Hoke et al, 2000;Newell et al, 2008).…”

Hydrogeochemical Characteristics of Hot Springs and Their Short-Term Seismic Precursor Anomalies along the Xiaojiang Fault Zone, Southeast Tibet Plateau

“…This suggests the potential relationship between hydrochemical composition anomaly and regional stress field, which influences the fault permeability in terms of strain partitioning across active faults. Precursory anomalies for the Shuangbai M L 5.1 earthquake in the spring S9 confirmed the anisotropic character of the stress/strain transmission through the tectonic discontinuities between the focal zone and the measurement site [35].…”

“…The lower crust is broadly characterized by enhanced conductivity and likely associated with partial melting at high temperatures [18,72,88,89]. Additionally, the XJF is characterized by moderately high total strain rates and low 3 He/ 4 He values (mostly <0.10 RA), suggesting that crustal He degassing dominates such fault regions [35]. Thus, we inferred that the XJF acted as a tunnel of these groundwaters in the crust which could be heated by hot material in this region.…”

“…We discussed the coupling mechanism of fluids from deep and shallow parts inside the fault zone and the association between the changes of geochemical characteristics of hot spring fluids and the earthquakes. These studies were then followed by geochemical modeling and statistical studies to explain and verify previous interpretations [35].…”