Collaborative Research: CO2 Springs and Travertines of the Southwestern US: Hydrologic Pathways Linking Tectonism to Water Quality

该项目调查了一个新的假设，即美国西部的第四纪火山岩和富含二氧化碳的泉水是构造活动（岩浆活动和地震活动）和水文之间相互作用的结果。 以前的研究表明，美国西部的冷泉和热泉具有指示地幔脱气的3He/4He比值，因此是地幔输入的地表表现。深源流体含盐量高，含有砷和铀等有害微量元素，可能会自然混入科罗拉多高原和格兰德河裂谷的含水层系统。 对活跃泉水的水和气的地球化学进行观察，结合地下水建模，将有助于了解深源和浅源水文输入之间的联系。 我们将检查水和气体在科罗拉多高原和周围的构造省份，以：1）评估内生水文端员，可能对应于地幔输入的异质性和接近年轻的玄武岩火山作用; 2）通过水文模拟量化深源和浅源地下水之间的混合参数; 3）对第四纪断裂、古岩溶、古岩溶泉和CO2场进行新构造研究，建立构造作用与水质的联系。我们正在使用天然地球化学示踪剂（水中的主要和微量元素，包括Sr，Cl/Br，As和C，H和O的稳定同位素）与气体化学（3He/4He，CO2，% He，N2/He，N2/CO2，CO2/3He）相结合。拟议的研究的空间尺度是从地方到区域;时间尺度范围从现代到晚第三纪地质记录的CO2出气在古陆沉积物编码。该项目包括在研究生和本科生一级开展教育和推广工作，将研究和教学结合起来，通过在大峡谷的"时间之路"项目开展非正式公共教育，以及让包括美洲土著人在内的少数民族参与。我们正在与国家公园管理局和各种美洲原住民部落（Hualapai，Havasupai和Navajo）密切合作，这些部落的沃茨直接受到深源污染物的影响。

This project investigates the novel hypothesis that the Quaternary travertines and CO2-rich springs of the western US are a consequence of the interplay between tectonic activity (magmatism and seismicity) and hydrology. Previous work has shown that travertine-depositing cool springs and hydrothermal springs of the western U.S. have 3He/4He ratios indicative of mantle out-gassing and hence are surface manifestations of mantle inputs. Deeply-sourced fluids include high salt contents and deleterious trace elements such as arsenic and uranium, and may naturally mix into aquifer systems on the Colorado Plateau and the Rio Grande Rift. Observation of the geochemistry of water and gas from active springs, combined with groundwater modeling, will assist in understanding the connections between deep-sourced and shallow-sourced hydrologic inputs. We will examine water and gases in the Colorado Plateau and surrounding tectonic provinces to; 1) evaluate endogenic hydrologic end members that may correspond to heterogeneity in mantle inputs and proximity to young basaltic volcanism; 2) quantify mixing parameters between deeply-sourced and shallow-sourced groundwaters via hydrologic modeling; 3) conduct neotectonic studies on Quaternary faults, travertines, travertine-depositing springs, and CO2 fields to establish the link between tectonism and water quality. We are using natural geochemical tracers (major and trace elements in water including Sr, Cl/Br, As, and stable isotopes of C, H and O) integrated with gas chemistry (3He/4He, CO2, % He, N2/He, N2/CO2, CO2/3He). The spatial scale of the proposed study is from local to regional; the temporal scale ranges from modern to the late Neogene geologic record of CO2 outgassing encoded in travertine deposits. This project includes education and outreach effort at the graduate and undergraduate levels, an integration of research and teaching, informal public education through the Trail of Time project at Grand Canyon, and involvement of minority populations, including Native American. We are working closely with the National Park Service and with various Native American tribes (Hualapai, Havasupai, and Navajo) whose waters are directly impacted by deeply sourced contaminants.