EAGER: Collaborative Research: Dating mineralization in a Carlin-type gold deposit: A test of the Fe-oxide (U-Th)/He chronometer

EAGER：合作研究：卡林型金矿床中的矿化年代测定：铁氧化物 (U-Th)/He 天文计的测试

• 批准号: 1641142
• 负责人: Elizabeth Holley
• 金额: $ 2.93万
• 依托单位: Colorado School of Mines
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1641142&HistoricalAwards=false
• 关键词: EAGER; Collaborative; Research; Dating; mineralization

The Carlin-type gold deposits (CTGDs) of northern Nevada are the source of most of the gold production in the United States and are thus of major economic importance; however, their geologic origin is uncertain. Various models for deposit formation relate the gold mineralization to different geologic events which likely occurred at different times, including magmatic activity, or circulation of groundwater-derived fluids through deeper gold-bearing units in the crust. Because of the lack of easily dateable minerals in CTGDs, it has historically been challenging to determine when gold mineralization occurred. The result is that effective exploration is hampered by the lack of knowledge about how and when these deposits formed. In this study, a new method of dating these deposits will be refined and tested. If the ages of CTGD formation could be more definitively known, gold mineralization could be correlated to broader geologic processes that were occurring at the same time. This knowledge would enable scientists and explorers to more easily discover new deposits.Available geochronological data suggest that Carlin-type mineralization broadly overlapped in space and time with the southwest sweep of Eocene magmatism through Nevada. Geo- and thermochronologic datasets are critical to identify direct evidence that magmatism and ore formation overlapped at individual deposits. Indeed, new chronometric tools could greatly expand knowledge of the genetic processes that lead to CTGD formation. No straightforward method currently exists to date CTDG mineralization. Recent studies have explored the use of the (U-Th)/He chronometer for Fe-oxides, but this chronometer has not been systematically tested in ore deposits. The proposed research has two major goals: to test feasibility of the Fe-oxide (U-Th)/He chronometer to date hydrothermal fluid flow, and to use this method to determine the age of hydrothermal activity in a CTGD in Nevada.

内华达州北方的卡林型金矿（CTGD）是美国大部分黄金生产的来源，因此具有重要的经济意义;然而，其地质成因尚不确定。不同的存款形成模型将金矿化与可能发生在不同时间的不同地质事件联系起来，包括岩浆活动或地下水衍生流体通过地壳中更深的含金单元的循环。由于CTGD中缺乏容易确定年代的矿物，因此历史上确定金矿化发生的时间一直具有挑战性。其结果是，由于缺乏关于这些矿床如何以及何时形成的知识，有效的勘探受到阻碍。在这项研究中，将改进和测试一种测定这些矿床年龄的新方法。如果CTGD形成的年龄可以更确切地知道，金矿化可以与更广泛的地质过程，发生在同一时间。这一知识将使科学家和探险家更容易发现新的矿床。现有的地质年代学数据表明，卡林型矿化在空间和时间上与贯穿内华达州的始新世岩浆活动的西南方向大致重叠。地质和热年代学数据集是至关重要的，以确定直接的证据，岩浆作用和成矿作用在个别矿床重叠。事实上，新的计时工具可以大大扩展导致CTGD形成的遗传过程的知识。目前还没有直接的方法来确定CTDG矿化的日期。最近的研究探索了使用（U-Th）/He计时器的铁氧化物，但这种计时器还没有系统地测试矿床。该研究有两个主要目标：测试铁氧化物（U-Th）/He计时器的可行性，以确定热液流体流动，并使用这种方法来确定热液活动的年龄在内华达州的CTGD。