Source to deposit tracing of metals in the lithosphere

岩石圈金属沉积物追踪来源

• 批准号: RGPIN-2017-06562
• 负责人: DeSouza, Stéphane
• 金额: $ 1.68万
• 依托单位: Université du Québec à Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=765312
• 关键词: Source; deposit; tracing; metals; lithosphere

Orogenic gold deposits form in a variety of host rocks with a complex history, and have the potential of forming large districts in which gold source and conditions leading to strong endowment of crustal sections are unresolved. The research program aims at the identification of crustal-scale gold concentration processes that lead to formation of world-class gold mining districts in terms of metallic heritage and geologic evolution. As part of this program, three crustal sections of different age and variable gold endowment are selected for a detailed tectonic and isotopic studies: the Archean Abitibi greenstone belt, and two Phanerozoic orogenic belts, i.e. the North American Cordillera and the Northern Appalachians. Short term objectives are 1) to initiate fieldwork and structural mapping necessary to interpret the geological evolution of the crust in areas of fluid generation to deposit formation, 2) define the radiogenic isotope (Pb-Pb and Re-Os) systematics of ore minerals and crustal host rocks, thus defining the isotopic metal signature of specific deposits and fluid pathways, and 3) use in-situ trace element, and S and Pb-Pb isotopic analyses (Laser ablation ICP-MS) of ore minerals in source rocks for a thorough investigation of gold preconcentration process. A similar scientific approach will be used for selected crustal sections and adjusted according to existing geological data and exposed mineralization. Thematic field work will be combined with detailed sampling of chosen sections for lithogeochemistry and isotope geochemistry. The research program will impact our understanding of crustal scale Archean to Mesozoic auriferous systems, and Precambrian vs Phanerozoic crustal architecture in terms of tectonic evolution and gold endowment. The integration of state-of-the art isotopic tracing (Re-Os; in-situ Pb and S isotopes), quantitative trace element mineral mapping (Laser ablation ICP-MS), and study of orogenic processes as conducted in my ongoing research, will allow to propose new models of gold concentration in the crust, and their influence on forming world-class vs poorly endowed gold belts. A detailed understanding of key components leading to formation of world-class gold districts is paramount when exploring in areas of limited geological knowledge (e.g. northern Canada), especially for highly sought low-grade bulk-tonnage deposits that generally have a discrete geological footprint. Identification of distinct isotopic signature of metals (e.g. provinciality) combined with documentation of favourable structural evolution and timing of fluid generation and circulation, will contribute to the definition of gold fertility assessment and exploration criteria for the industry.

造山型金矿床赋存于历史复杂的各种围岩中，具有形成大区域的潜力，在这些区域中，导致地壳剖面强烈赋存的金源和条件尚未得到解决。该研究方案旨在确定在金属遗产和地质演化方面导致世界级金矿区形成的地壳规模的金矿聚集过程。作为该计划的一部分，选择了三个不同时代和不同金矿资源的地壳剖面进行详细的构造和同位素研究：太古宙阿比提比绿岩带和两个显生宙造山带，即北美科迪莱拉和阿巴拉契亚北部。短期目标是1)启动必要的野外工作和构造填图，以解释流体形成区地壳的地质演化；2)确定矿石矿物和地壳容矿岩石的放射性成因同位素(铅-铅和Re-Os)体系，从而确定特定矿床和流体路径的同位素金属特征；以及3)利用矿源岩中矿石矿物的原位痕量元素、S和铅-铅同位素分析(激光烧蚀电感耦合等离子体质谱)，深入研究金的预富集过程。将对选定的地壳部分使用类似的科学方法，并根据现有的地质数据和暴露的矿化进行调整。专题实地工作将与岩石地球化学和同位素地球化学选定剖面的详细取样相结合。这一研究计划将影响我们对地壳尺度太古代至中生代含金系统，以及前寒武纪与显生宙地壳结构在构造演化和金矿赋存方面的理解。在我正在进行的研究中，将最先进的同位素示踪(Re-Os；原位铅和S同位素)、定量微量元素矿物填图(激光消融电感耦合等离子体质谱)和造山作用研究相结合，将能够提出新的地壳中金的聚集模式，以及它们对形成世界级与赋存较差的金矿带的影响。在地质知识有限的地区(如加拿大北部)进行勘探时，对导致形成世界级金矿区的关键成分的详细了解至关重要，特别是对那些通常具有离散地质足迹的高探索性低品位散装吨位矿床而言。确定不同的金属同位素特征(例如地域性)，再加上有利的构造演化和流体生成和循环时间的记录，将有助于确定该行业的黄金肥力评估和勘探标准。