Renbiao Tao*, Jiaxin Zhang, Yuhang Lu, Yurun Wu
1Center for High Pressure Science & Technology Advanced Research (HPSTAR), Beijing 100094, China
Abstract: Natural hydrogen (H₂) is an emerging low-carbon energy resource, and serpentinization of ultramafic rocks in subduction zones and orogenic belts has long been regarded as the dominant abiotic mechanism for H₂ generation. However, intraplate sedimentary basins generally lack ultramafic rocks in their basement, so serpentinization is not developed, and the sources of natural hydrogen in such basins remain poorly constrained. Here, we propose a new concept of chloritization-driven hydrogen generation: the hydration and oxidation of Fe²⁺- bearing silicates in basement rocks release H₂. We validate this concept using drill-hole samples from the basement of the Ordos and Chuxiong Basins through petrological observation and geochemical analysis, combined with high-pressure/high-temperature experiments and thermodynamic modeling. Notably, the two basins represent two distinct end-members of chloritization-driven hydrogen generation in intraplate settings. In the Ordos Basin, H₂ is generated by hydration of the metamorphic basement rocks (e.g., biotite-, amphibole-, and garnet-bearing gneisses), which constitutes the metamorphic-basement water-rock reaction end-member. In the Chuxiong Basin, in contrast, H₂ generation is dominated by chloritization of intrusive diabase (dolerite) bodies, in which pyroxene and feldspar are hydrated andFe²⁺) is oxidized to FFe³⁺during chloritization, representing the mafic-intrusion hydration end-member. Although the two end-members share a similar chloritization mechanism, their modes of occurrence differ markedly, and both are important sources of natural hydrogen in intraplate basins. We finally compare the conditions of hydrogen generation between chloritization and serpentinization, including tectonic setting, protolith composition, Fe²⁺+ reservoir, P-T conditions, and H₂ yield, providing new constraints for natural hydrogen exploration.
Keywords: Natural hydrogen; Chloritization; Serpentinization; Metamorphic basement; Diabase (dolerite); Intraplate basins; Ordos Basin; Chuxiong Basin
Author Profile (corresponding author):
Tao R, Male, PhD, Staff Scientist, mainly engaged in deep volatile (C-H-O-N-S) cycling and natural abiotic hydrogen and methane generation research.
E-mail: renbiao.tao@hpstar.ac.cn
