Halogens (Cl, Br, I) are exceptional provenance tracers in crustal fluids because their ratios are not strongly altered during most fluid-rock interaction processes. The halogen systematics of metamorphic fluids are of particular interest because such fluids are key drivers of crustal-scale element fluxes and ore formation in orogenic belts, but they remain poorly studied due to analytical challenges. We present novel triple-halogen laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) fluid-inclusion data from metamorphic systems ranging in age from Archean to Phanerozoic. Our results show that the halogen signatures in Phanerozoic metamorphic fluids are controlled by variable degrees of organic-matter interaction in their source rocks, leading to increased I/Cl and decreased Br/I ratios relative to seawater. By contrast, Archean metamorphic fluids from organic matter–rich source rocks have low I/Cl and very high Br/I ratios, distinctly different from any known fluid source signature. We propose that these signatures nevertheless are consistent with organic-matter interaction because dominantly prokaryotic Archean lifeforms did not yet produce iodine-bearing metabolites. This prevented biosequestration and accumulation of iodine-rich organic matter in sediments and imposed halogen signatures onto Archean metamorphic fluids entirely unlike those in younger fluids.

中文翻译：

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随时间变化的地壳流体中的卤素比率——有氧生命出现的代理？

卤素（Cl、Br、I）是地壳流体中特殊的来源示踪剂，因为它们的比率在大多数流体-岩石相互作用过程中不会发生强烈变化。变质流体的卤素系统特别令人感兴趣，因为这些流体是地壳尺度元素通量和造山带成矿的关键驱动因素，但由于分析挑战，它们的研究仍然很少。我们提出了新的三卤素激光烧蚀-电感耦合等离子体-质谱 (LA-ICP-MS) 流体包裹体数据，这些数据来自从太古宙到显生宙的变质系统。我们的研究结果表明，显生宙变质流体中的卤素特征受其烃源岩中不同程度的有机物相互作用控制，导致相对于海水的 I/Cl 增加和 Br/I 比率降低。相比之下，来自富含有机质烃源岩的太古宙变质流体具有低 I/Cl 和非常高的 Br/I 比，与任何已知的流体源特征明显不同。我们认为这些特征仍然与有机物相互作用是一致的，因为主要的原核太古宙生命形式尚未产生含碘代谢物。这阻止了沉积物中富含碘的有机物的生物隔离和积累，并将卤素特征施加到太古宙变质流体上，这与年轻流体中的完全不同。我们认为这些特征仍然与有机物相互作用是一致的，因为主要的原核太古宙生命形式尚未产生含碘代谢物。这阻止了沉积物中富含碘的有机物的生物隔离和积累，并将卤素特征施加到太古宙变质流体上，这与年轻流体中的完全不同。我们认为这些特征仍然与有机物相互作用是一致的，因为主要的原核太古宙生命形式尚未产生含碘代谢物。这阻止了沉积物中富含碘的有机物的生物隔离和积累，并将卤素特征施加到太古宙变质流体上，这与年轻流体中的完全不同。