Oxygen isotope ratios of garnet provide well-established means to investigate crustal fluid histories. Traditionally, δ18O values from skarn garnets have been used to track the hydrothermal evolution of an individual skarn body through time. We, however, use garnet from 14 skarns from the Jurassic (ca. 175 to ca. 148 Ma) Cordilleran margin arc (southwestern United States) to provide regional tectonic context to arc magmatism and hydrothermal activity. We document arc-wide garnet δ18O variability of ~19‰ (−8.9‰ to +10.3‰, n = 159), providing a record of contrasting meteoric fluid ingress between northern (Sierra Nevada) and southern (Mojave Desert) arc segments. Strongly negative garnet δ18O values (≤−3‰) are limited to the Mojave Desert arc segment and can only form in the presence of meteoric fluid, requiring shallow formation in subaerial crust. When combined with U-Pb garnet ages, the δ18O data provide a minimum radiometric age of local subaerial arc emergence and temporal constraint on the migration of the Jurassic paleoshoreline in the Mojave Desert section of the arc.

中文翻译：

---

矽卡岩流体源作为美国西南部科迪勒拉弧出现时间和古地理的指标

石榴石的氧同位素比率为研究地壳流体历史提供了成熟的方法。传统上，矽卡岩石榴石的 δ18O 值已被用于跟踪单个矽卡岩体随时间的热液演化。然而，我们使用来自侏罗纪（约 175 至约 148 Ma）科迪勒拉边缘弧（美国西南部）的 14 个矽卡岩中的石榴石为弧岩浆活动和热液活动提供区域构造背景。我们记录了约 19‰（-8.9‰ 至 +10.3‰，n = 159）的弧宽石榴石 δ18O 变异性，提供了北部（内华达山脉）和南部（莫哈韦沙漠）弧段之间对比大气流体进入的记录。强负石榴石δ18O值（≤-3‰）仅限于莫哈韦沙漠弧段，只能在大气流体存在下形成，需要在地壳浅层形成。