Intrusion-related critical metal deposits throughout the Appalachian orogen: constraining melt fertility and the magmatic-hydrothermal transition

加拿大的东部边缘是由地质堆积物组成的，这些地质堆积物是在4.8亿年前开始的造山运动（阿巴拉契亚造山运动）中“增生”（添加到构造板块一侧的物质）。这些岩浆岩中含有主要由地壳在增生过程中熔融而形成的火成岩侵入体。这些侵入体中有一些是金属矿床的所在地（例如，锡、钨、锂、铯、铟、稀土元素），这些元素对加拿大继续向低碳数字化经济转型至关重要。在新斯科舍省和新玩法，过去对与侵入有关的矿床的研究历来侧重于使用化学和同位素分析的整体（整个岩石）方法来限制岩浆的金属“肥力”（特定年龄和成分的岩浆形成金属矿床的可能性）。然而，从大量分析中得到的信息往往是模糊的，因为大块火成岩是多种地质过程的最终产物，这些地质过程可以消除或减少岩浆和相关流体在其演化的不同阶段的原始化学特征。因此，阿巴拉契亚造山带中与侵入相关的矿床的当前地质模型需要修订。熔体和流体包裹体（以前熔融的岩石和热液溶液的显微样品，在整个地质时期运输和浓缩金属，捕获在矿物中）的分析是直接测量古代岩浆和相关挥发物金属含量的最可靠方法。 建议的研究计划将通过熔体和流体包裹体的调查约束阿巴拉契亚造山运动中的矿化火成岩的演化。这些包裹体被捕获在相对物理和化学坚固的矿物中（例如，锆石）将使用各种微量分析方法进行分析。个别项目将通过调查不同年龄和不同金属禀赋的火成岩环境的岩浆历史来推进整体研究计划目标。目的是更好地理解主要控制的相对重要性（例如，岩浆源区成分、结晶作用、混染作用、流体脱气作用等）对岩浆金属资源和经济潜力的影响。参与拟议研究的受训人员将获得宝贵的技能和知识，这些技能和知识将转移到学术界、政府和私营部门的职业生涯中，并产生一系列适合各种最终用户的数据产品和新知识。该计划将提供重要的更新成矿模型，不仅在研究领域，但在其他类似的矿床全球范围内，更广泛地说，将解决有关岩浆过程在阿巴拉契亚造山带的基本问题，测试以前的研究的有效性。拟议的研究显然适用于自然资源领域，旨在提供对加拿大具有社会经济效益的勘探标准。

The eastern margin of Canada is comprised of geological terranes that were "accreted" (material added to the side of a tectonic plate) during mountain building events (the Appalachian Orogeny) beginning more than 480 million years ago. These terranes contain igneous intrusions formed mainly by melting of the crust during accretion. Some of these intrusions host deposits of metals (e.g., tin, tungsten, lithium, cesium, indium, rare-earth elements) that are critical for Canada's continuing transition to a low-carbon, digitized economy. In Nova Scotia and New Brunswick, past research on intrusion-related deposits has historically focused on using bulk (the whole rock) methods of chemical and isotopic analyses to constrain the metal "fertility" of magmas (the likelihood that magmas of specific ages and compositions could form metal deposits). However, information yielded from bulk analyses is often ambiguous because bulk igneous rocks are end-products of multiple geological processes that can erase, or diminish, the original chemical signature of magmas and related fluids at different stages in their evolution. Consequently, current geological models for intrusion-related deposits in the Appalachian orogen require revision. The analysis of melt and fluid inclusions (microscopic samples of formerly molten rock and hydrothermal solutions that transported and concentrated metals, trapped in minerals throughout geological time) is the most robust approach to directly measure the metal content of ancient magmas and related volatiles. The proposed research program will constrain the evolution of variably mineralized igneous rocks in the Appalachian Orogeny through the investigation of melt and fluid inclusions. These inclusions, trapped in relatively physically and chemically robust minerals (e.g., zircon) will be analyzed using a variety of microanalytical methods. Individual projects will advance overall research program objectives by investigating the magmatic history of igneous settings of different ages and varying metal endowments. The objective will be to better understand the relative importance of primary controls (e.g., the magma source composition, crystallization, contamination, fluid degassing) on magma metal endowment and economic potential. Trainees involved in the proposed research will gain valuable skills and knowledge that will be transferable to careers in academia, government and the private sector and generate a range of data products and new knowledge suitable for a variety of end-users. The program will provide important updates to metallogenic models not only in the study areas, but in other similar terranes globally, and more broadly, will address fundamental questions about magmatic processes in the Appalachian orogen, testing the validity of previous studies. The research proposed has clear application to the natural resource field, aiming to provide exploration criteria that will have socio-economic benefit to Canada.