The cycling of sulfur (S) to the upper crust and surface via thermal springs at convergent margins has not been explored outside areas with active arc volcanism, even though subduction plays a key role in the Earth's long-term S cycle. To address this knowledge gap, we analyzed stable sulfur and oxygen isotope compositions (δS and δO values) of dissolved sulfate (SO) in 55 thermal springs from five distinct settings in the Andean orogen. These regions are the Peruvian flat slab and backarc, transition between these two, Argentinian backarc, and Chilean forearc. Although the flat-slab settings had lower SO concentrations (<2000 mg/L) compared to the steep-slab settings (<12,700 mg/L), there was no significant relationship between isotope composition of SO and slab geometry. The δS and δO values of SO varied widely across the studied areas (+0.2 to +23.5 ‰ and − 3.3 to +16.0 ‰, respectively) and reflected the isotope compositions of local bedrock endmembers from dissolution of marine evaporites (+5 to +25 ‰ and + 10 to +20 ‰, respectively) and oxidation of magmatic and/or hydrothermal S and ore sulfide minerals with variable δS (0 to +16 ‰). The δO and δH values of thermal spring water (−18.5 to −3.3 ‰ and − 141.1 to −23.7 ‰, respectively) were consistent with meteoric precipitation, and in most cases decreased with increasing altitude following precipitation in the Andes. Generally, our isotope results do not support the direct transfer of slab-derived S/SO to thermal springs in the investigated settings. Rather, the δS and δO of SO in the thermal springs are a sensitive indicator of local water-rock interactions that remobilize bedrock S originating from a complex orogenic cycle reflecting tectonic uplift, erosion, weathering, and exhumation history across the duration of Andean Mountain building.

中文翻译：

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利用温泉中溶解硫酸盐的稳定同位素组成追踪安第斯山脉的造山硫循环


尽管俯冲作用在地球的长期硫循环中发挥着关键作用，但在弧火山活动活跃的区域之外，尚未探索过硫（S）通过汇聚边缘的热泉循环到上地壳和地表的情况。为了解决这一知识差距，我们分析了安第斯造山带五个不同环境中 55 个温泉中溶解的硫酸盐 (SO) 的稳定硫和氧同位素组成（δS 和 δO 值）。这些区域是秘鲁平板和弧后、两者之间的过渡区、阿根廷弧后和智利弧前。尽管与陡板设置 (<12,700 mg/L) 相比，平板设置的 SO 浓度 (<2000 mg/L) 较低，但 SO 的同位素组成与板几何形状之间没有显着关系。 SO 的 δS 和 δ18O 值在整个研究区域变化很大（分别为 +0.2 至 +23.5 ‰ 和 − 3.3 至 +16.0 ‰），反映了海洋蒸发岩溶解产生的当地基岩端元的同位素组成（+5 至 +25分别为 ‰ 和 + 10 至 +20 ‰）以及具有可变 δS（0 至 +16 ‰）的岩浆和/或热液 S 和矿石硫化物矿物的氧化。温泉水的δO和δH值（分别为-18.5至-3.3‰和-141.1至-23.7‰）与大气降水一致，并且在大多数情况下随着安第斯山脉降水后海拔的升高而降低。一般来说，我们的同位素结果不支持在研究环境中将板片衍生的 S/SO 直接转移到温泉中。 相反，温泉中 SO 的 δS 和 δ18O 是当地水-岩石相互作用的敏感指标，它重新激活了源自复杂造山旋回的基岩 S，反映了安第斯山脉建造过程中的构造隆升、侵蚀、风化和折返历史。 。