CAREER: Investigating the source, transport and deposition of economically important metals in the lower continental crust

金属是现代社会的重要组成部分。除了回收之外，金属还可以从矿床中回收，例如岩浆硫化物系统，这些矿床通常在靠近地表的地方形成，因此相对容易获得镍和铜等金属。由于矿藏是不可再生的，我们必须为每一种枯竭的资源找到（至少）一个新的矿藏，以保证未来稳定的金属供应。目前，矿产勘探工作主要集中在上地壳，因为这种方法在过去的一个世纪里一直很有效。然而，最近新发现的矿藏数量下降，这意味着大多数地表附近的矿藏已经被发现。因此，为了保证稳定的金属供应，在地球深处开放搜索空间是必要的。该项目将通过研究意大利Ivrea-Verbano地区一系列可变交代岩浆硫化物矿床的形成来解决这一问题。这些矿床形成于地壳深处，并被构造抬升到可开采的水平。尽管这些矿床之前曾开采镍和铜，但令人惊讶的是，人们对它们（以及其他地方类似的矿床）最初是如何形成的知之甚少。该项目将利用Ivrea-Verbano带的矿床来更好地限制这些矿床的优先形成方式和位置，特别关注地幔交代作用在地壳深部成矿中的作用。这一发现将为在未来的勘探模型中纳入此类矿床提供重要的一步。这项研究将与教育组成部分相结合，将惠及K-12、本科生和研究生。与Project Lead The Way合作的一个高中拓展项目将使用这个项目中的例子来突出K-12学生最初可能不知道的地球科学职业道路，特别是在密苏里州的农村地区。该项目还将把拟议研究的各个方面纳入本科学生的暑期培训计划，帮助学生为本科毕业后的地球科学职业做准备。此外，两名研究生将积极参与研究部分。Ivrea-Verbano带是保存完好的次大陆岩石圈地幔和下大陆地壳的横截面，其亚垂直出露，因此可以对岩石圈深部质量传递进行全面的研究。以往对Ivrea-Verbano带的研究对我们对下大陆岩石圈的认识有重要贡献。然而，侧重于含金属的含水熔体/流体的来源及其在金属运输和局部沉积（即矿床）中的作用的研究很少。为了解决这一知识差距，该项目将调查Ivrea-Verbano带不同位置的不同交代和硫化物矿化程度：(1)强交代/高矿化管道，(2)未交代/中度矿化的岩/侵入体，(3)强交代/低硫化物的地幔橄榄岩。实地研究将结合岩石学观察、大块岩石、矿物和流体包裹体分析、同位素（Cu、Sm-Nd）和地质年代学研究。拟议的研究将为以下方面提供新的见解：(1)深层岩石圈中产生、运输和浓缩流体和金属的物理和化学过程；(2)这些过程的时空尺度。PI正在积极招募K-12教师，本科生和研究生参与该项目。K-12外展计划的目标是提高对地球科学学科的认识，并鼓励学生考虑地球科学或其他STEM职业道路。本科生和研究生项目将单独定制，为每个学生在学术界，联邦/州机构或私营部门选择的职业道路做好准备。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Metals are critical components of modern society. Aside from recycling, metals are recovered from ore deposits such as magmatic sulfide systems that often formed close to the surface and thus provide relatively easy access to metals like nickel and copper. Because ore deposits are non-renewable, we must find (at least) one new deposit for each exhausted resource to guarantee a steady metal supply in the future. Currently, mineral exploration efforts focus mostly on the upper crust because this approach has worked well over the past century. However, a recent decline in new discoveries implies that most of the deposits near the surface have already been found. Consequently, the opening of search space deeper in the Earth is necessary to guarantee a steady metal supply. This project will address this issue by investigating the formation of a series of variably metasomatized magmatic sulfide deposits in the Ivrea-Verbano Zone in Italy. These deposits formed in the deep crust and were tectonically uplifted to mineable levels. Although the deposits were previously mined for nickel and copper, surprisingly little is known about how they (and similar deposits elsewhere) originally formed. This project will use the deposits in the Ivrea-Verbano Zone to better constrain how and where such deposits preferentially form, particularly focusing on the role of mantle metasomatism in deep crustal ore formation. The findings will provide an important step toward including such deposits in future exploration models. The research will be integrated with an educational component that will reach K-12, undergraduate and graduate students. A high school outreach program in collaboration with Project Lead The Way will use examples from this project to highlight geoscience career paths that K-12 students may initially not be aware of, particularly in rural Missouri. The PI will also incorporate aspects of the proposed research into a summer training program for undergraduate students to help students prepare for a post-baccalaureate geoscience career. Furthermore, two graduate students will be actively involved in the research component. The Ivrea-Verbano Zone is a well-preserved cross section of the subcontinental lithospheric mantle and lower continental crust that outcrops subvertically and therefore allows for comprehensive studies of deep lithospheric mass transfer. Previous studies on the Ivrea-Verbano Zone have significantly contributed to our understanding of the lower continental lithosphere. However, research that focuses on the source of metalliferous hydrous melts/fluids, and their role in the transport and local deposition of metals (i.e., ore deposits) is rare. To address this knowledge gap, this project will investigate different localities in the Ivrea-Verbano Zone that represent variable degrees of metasomatism and sulfide mineralization: (1) strongly metasomatized / highly mineralized pipes, (2) un-metasomatized / moderately mineralized sills/intrusions, and (3) a strongly metasomatized / sulfide-poor mantle peridotite. Field studies will be integrated with petrographic observations, bulk rock, mineral and fluid inclusion analyses, isotopic (Cu, Sm-Nd) and geochronological studies. The proposed research will provide new insight into (1) the physical and chemical processes that produce, transport and concentrate fluids and metals in the deep lithosphere; and (2) the spatial and temporal scales of such processes. The PI is actively recruiting K-12 teachers, undergraduate and graduate students to be involved in this project. The goal of the K-12 outreach program is to raise awareness for geoscience disciplines and to encourage students to consider geoscience or other STEM career paths. Undergraduate and graduate student projects will be individually tailored to prepare each student for a career path of their choosing in academia, federal/state agencies, or the private sector.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.