Collaborative Research: Magmatism and Mineralization in the Owyhee Mountains, ID: A Case Study of Mid-Miocene Au-Ag Ores and the Emergence of the Yellowstone Hotspot

合作研究：俄维希山脉的岩浆作用和成矿作用：中中新世金银矿石和黄石热点出现的案例研究。大量的哥伦比亚河Steens洪水玄武岩火山活动在东部俄勒冈州和华盛顿，西南部爱达荷州，和北方内华达州发生在拟议的16.7马初始的轨道新生黄石热点。这一岩浆事件与影响泛滥玄武岩区南部的三种现象相吻合（例如俄勒冈州高原）：[1]区域范围内伸展构造作用集中区的发展±泛滥玄武岩岩浆的喷发（例如北方内华达州裂谷和俄勒冈-爱达荷地堑）;[2]发育多个以岩浆活动为主的岩浆系统（如McDermitt和圣罗莎- Calico火山岩区）;[3]丰富的低温热液金银矿化（如Buckskin-National、Sleeper、DeLamar）。最近的研究表明，主要是双峰玄武岩流纹岩岩浆活动和集中的扩展相结合，导致岩浆系统，不只是破火山口形成，而是具有多个离散的喷发地点和多样性的喷发产品和风格。据推测，喷发产物和样式局部包括金，银矿石从地幔与镁铁质岩浆搬运和局部侵位在低温热液系统。该模型的有效性将在两个重点区域进行测试，Owyhee山脉（ID）和Jarbidge地区（Jarbidge山脉，NV），其中有良好的暴露中中新世洪水玄武岩熔岩流和浅侵入体，火山和浅成产物，以及具有经济和历史意义的Au-Ag矿。将获得野外、岩相学、地球化学、同位素和年代学数据，以评价浅成低温热液金银矿化与相关岩浆活动的关系。拟议中的研究将专门研究当地的矿化和岩浆生产是否受到增强的镁铁质岩浆作用时期的刺激。现场，地球化学和地质年代学的结果将提供额外的限制了解的时空模式（S）和风格的中新世中期俄勒冈州高原火山活动，这是需要充分了解这一岩浆事件如何影响北美岩石圈。该项目解决了一个基本问题，即贵金属起源于什么样的地球水库？浅成热液贵金属成矿作用与镁铁质岩浆作用（特别是泛滥玄武岩）密切相关的假设具有全球经济影响，并可以指导全球贵金属勘探工作。拟议的研究将使来自两个EPSCoR机构的学生接触基本的地质实地工作以及详细的实验室分析工作。此外，这项工作将提供一个动态的Owyhee领域的数字地图，将用于本科生和研究生课程，以及一系列的实验室练习有关火山学，岩石学和矿石成因的基础。最后，该项目将为一名年轻科学家（主要研究者）提供宝贵的指导。

Collaborative Research: Magmatism and mineralization in the Owyhee Mountains, ID: A case study of mid-Miocene Au-Ag ores and the emergence of the Yellowstone HotspotIntellectual Merit. Voluminous Columbia River-Steens flood basalt volcanism in eastern Oregon and Washington, southwestern Idaho, and northern Nevada occurred during the proposed ~16.7 Ma initiation of the track for the nascent Yellowstone hotspot. This magmatic event coincided with three phenomena that affected the southern portion of the flood basalt province (e.g. the Oregon Plateau): [1] region-wide development of focused zones of extensional tectonism ± eruption of flood basalt magmas (e.g. the northern Nevada rift and Oregon-Idaho graben); [2] development of numerous silicic dominated magmatic systems (e.g. the McDermitt and Santa Rosa- Calico volcanic fields); and [3] abundant epithermal Au-Ag mineralization, (e.g. Buckskin-National, Sleeper, DeLamar). Recent work by the lead PI suggests that the combination of dominantly bimodal basalt-rhyolite magmatism and focused extension resulted in magmatic systems that were not just caldera-forming, but instead were characterized by multiple discrete eruptive loci and a diversity of eruptive products and styles. It is hypothesized that the eruptive products and styles locally included Au-Ag ores that were transported from the mantle with mafic magmas and emplaced locally in epithermal systems. The validity of this model will be tested in two focus regions, the Owyhee Mountains (ID) and the Jarbidge district (Jarbidge Mountains, NV), where there are excellent exposures of mid-Miocene flood basalt lava flows and shallow intrusive bodies, silicic volcanic and hypabyssal products, and Au-Ag mines that are economically and historically significant. Field, petrographic, geochemical, isotopic, and geochronologic data will be obtained to evaluate the relation of epithermal Au-Ag mineralization to the associated magmatic activity. The proposed research will specifically examine whether local mineralization and silicic magma production was stimulated by periods of enhanced mafic magmatism. The field, geochemical, and geochronologic results will provide additional constraints on the poorly understood spatial-temporal pattern(s) and styles of mid-Miocene Oregon Plateau volcanism, which are needed to fully understand how this magmatic event affected the North American lithosphere.Broader Impacts. This project addresses a fundamental question, namely, in what Earth reservoir do precious metals originate? The hypothesis that epithermal precious metal mineralization is intimately related to mafic magmatism (specifically, flood basalts) has worldwide economic implications, and could guide global precious metal exploration efforts. The proposed research will expose students from two EPSCoR institutions to basic geologic field work as well as detailed, laboratory-based analytical work. Additionally, this work will provide the basis for a dynamic digital map of the Owyhee field area that will be used in undergraduate and graduate courses, as well as a series of laboratory exercises regarding volcanology, petrology, and ore genesis. Finally, this project will provide invaluable mentoring aspects to a young scientist (lead PI).