Micro-textural and geochemical constraints on fluid–rock interaction and fluid fluctuation in hydrothermal strategic metal mineralization systems

The formation of hydrothermal deposits of strategic metals such as gold and uranium involves complex, multi-stage processes coupling fluid–rock interaction, structural dynamics, and chemical evolution across scales. This study integrates structural and micro-textural analysis with multi-scale chemical kinetic investigations to elucidate the dynamics of element enrichment and ore formation. We focus on bridging the dynamic linkages between micro- to nano-scale textures and the larger-scale chemical evolutionary processes in complex natural systems, aiming to decode the kinetic mechanisms governing element migration and mineralization. Modern analytical approaches, including machine learning–assisted data interpretation, are explored for their potential to resolve the spatio-temporal evolution of mineralization.

Using representative hydrothermal gold deposits from the Jiaodong region and uranium deposits from the Bashibulake district (Xinjiang) in China as case studies, we investigate the micro-textures and in-situ trace element and oxygen isotopic compositions of hydrothermal quartz. Cathodoluminescence (CL) zoning and cross-cutting relationships reveal multiple generations of quartz, corresponding to discrete fluid infiltration events. The CL intensity correlates positively with Al content but not with δ¹⁸O, indicating differing controls on trace element incorporation versus isotopic fractionation. Elevated trace elements (e.g., Al) in quartz are attributed to intensified fluid–rock interaction, which mobilized lithophile elements. Seismically induced fluid fluctuations are shown to enhance compositional variability in quartz by affecting fluid chemistry and pH.

Oxygen isotope analyses of successive quartz generations yield distinct δ¹⁸O ranges. Calculated fluid δ¹⁸O values evolve from mantle-like signatures (≥7‰) in early stages toward progressively lower values, reflecting increasing meteoric water input in later stages. Water–rock reaction is identified as a key process modifying fluid O isotopic composition. Remarkably, mineral-scale near-constant δ¹⁸O values suggest effective isotopic buffering by the host rock despite episodic fluid fluctuations.

Our results demonstrate that micro-textural and geochemical signatures in quartz serve as effective tracers for quantifying water–rock interaction intensity and fluid fluctuation history. The study highlights the value of combining micro-analytical techniques (e.g., LA-ICP-MS, SIMS) with macro-structural analysis and emerging data-science methods to unravel the kinetic pathways of strategic metal mineralization in hydrothermal U-Au systems.

Keywords: Quartz geochemistry; Strategic metal deposits; Fluid–rock interaction; Multi-scale chemical kinetics