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：奥威希山脉岩浆作用与成矿作用：以中中新世金银矿石与黄石热点地区的出现为例。大量的哥伦比亚河-斯汀洪水玄武岩火山活动发生在俄勒冈州东部和华盛顿州，爱达荷州西南部和内华达州北部，这些活动发生在为新生的黄石热点提出的~16.7 Ma起始轨道期间。该岩浆事件与影响洪水玄武岩省南部（如俄勒冈高原）的三个现象相吻合：伸展构造集中带在全区范围内的发育±洪水玄武岩岩浆的喷发（如北内华达裂谷和俄勒冈-爱达荷地堑）；大量以硅质为主的岩浆体系（如McDermitt和Santa Rosa- Calico火山田）的bb0发育；和[3]丰富的浅成热液型金银矿化（如Buckskin-National、Sleeper、DeLamar）。最近的研究表明，以双峰玄武岩-流纹岩为主的岩浆作用和集中伸展作用的结合，导致了岩浆系统不仅仅是火山口形成，而是具有多个离散的喷发位点，喷发产物和样式的多样性。推测其局部喷发产物和喷发样式包括与基性岩浆一起从地幔运来并局部侵位于浅成热液体系中的金银矿石。该模型的有效性将在Owyhee山脉（ID）和Jarbidge地区（Jarbidge Mountains， NV）两个重点地区进行验证，在这些地区有中中新世洪水玄武岩熔岩流和浅层侵入体，硅质火山和浅成岩产物，以及具有经济和历史意义的金银矿。野外、岩石学、地球化学、同位素和地质年代学资料将用于评价浅成热液型金银矿化与伴生岩浆活动的关系。提出的研究将具体检查局部矿化和硅岩浆的产生是否受到增强的基性岩浆活动时期的刺激。野外、地球化学和地质年代学结果将对中新世中期俄勒冈高原火山活动的时空格局和风格提供额外的限制，这是充分了解这次岩浆事件如何影响北美岩石圈所必需的。更广泛的影响。这个项目解决了一个基本问题，即贵金属起源于地球的哪个储层？浅成热液型贵金属成矿作用与基性岩浆作用（特别是洪泛玄武岩）密切相关的假设具有世界范围的经济意义，并可以指导全球贵金属勘探工作。拟议的研究将使两个EPSCoR机构的学生接触到基本的地质野外工作以及详细的、基于实验室的分析工作。此外，这项工作将为Owyhee油田地区的动态数字地图提供基础，该地图将用于本科和研究生课程，以及一系列关于火山学、岩石学和矿床形成的实验室练习。最后，该项目将为一位年轻科学家（首席PI）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).