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<p>Deep fluid convection within the upper crust is pivotal in transferring heat and mass between geological environments. However, a comprehensive understanding of how hydrothermal systems influence geological processes such as metasomatism and mineral deposit formation is lacking due to poor constraints on their temporal longevity. In this study, we use laser ablation U-Pb carbonate geochronology to analyze well-characterized ore stage calcite veins from the Osiris Carlin-type gold deposit to investigate the timing of fluid flow circulation in the deposit. Our results suggest the veins formed during episodic fluid flow events spanning millions of years between ~ 73 and 11&#xa0;Ma. We propose a model where sustained high crustal heat flow coupled with intermittent fault rupture induces episodic free-convection of meteoric fluids without a magmatic thermal driver. The fluids infiltrate downward, liberate metals, acidity, and ligands from sedimentary rocks, and ascend to the deposit site when heated by a high geothermal gradient. Our findings underscore the potential significance of amagmatic free-convection in the Carlin-type gold deposit genetic model. However, it does not preclude magmatism from being a salient process for forming large and well-endowed deposits. The longevity of amagmatic free-convection hydrothermal systems means they have substantial potential for distributing heat and mass throughout the crust over extended geological timeframes.</p>

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U-Pb calcite geochronology indicates episodic amagmatic free-convection over tens of millions of years in Carlin-type gold deposits

  • 期刊论文

  • 发表日期：

    2025年6月30日

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  • Andrew P. Steiner,
  • Kenneth A. Hickey,
  • Dominique Weis,
  • Marghaleray Amini

摘要

Deep fluid convection within the upper crust is pivotal in transferring heat and mass between geological environments. However, a comprehensive understanding of how hydrothermal systems influence geological processes such as metasomatism and mineral deposit formation is lacking due to poor constraints on their temporal longevity. In this study, we use laser ablation U-Pb carbonate geochronology to analyze well-characterized ore stage calcite veins from the Osiris Carlin-type gold deposit to investigate the timing of fluid flow circulation in the deposit. Our results suggest the veins formed during episodic fluid flow events spanning millions of years between ~ 73 and 11 Ma. We propose a model where sustained high crustal heat flow coupled with intermittent fault rupture induces episodic free-convection of meteoric fluids without a magmatic thermal driver. The fluids infiltrate downward, liberate metals, acidity, and ligands from sedimentary rocks, and ascend to the deposit site when heated by a high geothermal gradient. Our findings underscore the potential significance of amagmatic free-convection in the Carlin-type gold deposit genetic model. However, it does not preclude magmatism from being a salient process for forming large and well-endowed deposits. The longevity of amagmatic free-convection hydrothermal systems means they have substantial potential for distributing heat and mass throughout the crust over extended geological timeframes.