Dissected hydrologic system at the Grand Canyon: Interaction between deeply derived fluids and plateau aquifer waters in modern springs and travertine
Dissected hydrologic system at the Grand Canyon: Interaction between deeply derived fluids and plateau aquifer waters in modern springs and travertine
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DOI：
10.1130/g22057.1
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发表时间：
2006-01-01
期刊：
影响因子：
5.8
通讯作者：
de Leeuw, GAM
中科院分区：
文献类型：
--
作者：
Crossey, LJ;Fischer, TP;de Leeuw, GAM
地球化学研究的水和气体排放的深切含水层系统在大峡谷，亚利桑那州，提供了一个范例，了解复杂的地下水混合现象，和第四纪沉积从冷泉提供了这种混合的古水文记录。地球化学数据表明，弹簧有显着的成分变化：那些与活跃的古生物积累（深源内生沃茨）更咸，更丰富的CO2，和升高的Sr-87/Sr-86相对于主要来自高原含水层的地表补给（表生沃茨）的弹簧。内生沃茨和伴生水优先沿沿着基底断裂分布。我们提出了一个模型，即深源流体通过岩浆活动和地震活动向上输送。我们的模型得到以下方面的支持：（1）高He/Ar、He/N-2和He-3/He-4比值的沃茨的气体分析表明存在幔源He;（2）泉水中大量富含碳酸盐和CO2的气体记录了高CO2通量;（3）这些泉水中的Sr-87/Sr-86表明沃茨通过前寒武纪基底循环。地球化学趋势的解释混合后生沃茨的科罗拉多高原含水层与不同的内生端员沃茨在不同的构造分区。内生沃茨体积较小，但对水化学有重大影响。它们是美国西南部水文地球化学和新构造学的一个重要组成部分，但在很大程度上未被认识。
Geochemical study of water and gas discharging from the deeply incised aquifer system at the Grand Canyon, Arizona, provides a paradigm for understanding complex groundwater mixing phenomena, and Quaternary travertines deposited from cool springs provide a paleohydrologic record of this mixing. Geochemical data show that springs have marked compositional variability: those associated with active travertine accumulations (deeply derived endogenic waters) are more saline, richer in CO2, and elevated in Sr-87/Sr-86 relative to springs derived dominantly from surface recharge of plateau aquifers (epigenic waters). Endogenic waters and associated travertine are preferentially located along basement-penetrating faults. We propose a model whereby deeply derived fluids are conveyed upward via both magmatism and seismicity. Our model is supported by: (1) gas analyses from spring waters with high He/Ar and He/N-2 and He-3/He-4 ratios indicating the presence of mantle-derived He; (2) large volumes of travertine and CO2-rich gases in springs recording high CO2 fluxes; and (3) Sr-87/Sr-86 in these springs that indicate circulation of waters through Precambrian basement. Geochemical trends are explained by mixing of epigenic waters of the Colorado Plateau aquifers with different endogenic end-member waters in different tectonic sub-provinces. Endogenic waters are volumetrically minor but have significant effects on water chemistry. They are an important and largely unrecognized component of the hydrogeochemistry and neotectonics of the southwestern United States.