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: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633761
• 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.

造山型金矿床形成于多种赋矿岩石中，成矿历史复杂，具有形成大面积金矿床的潜力，但金的来源和地壳剖面的强赋矿条件尚不清楚。该研究计划旨在确定导致在金属遗产和地质演化方面形成世界级金矿区的地壳规模金富集过程。作为该计划的一部分，选择了三个不同时代和不同金丰度的地壳剖面进行详细的构造和同位素研究：太古代Abitibi绿岩带，以及两个中生代造山带，即北美科迪勒拉和北方阿巴拉契亚山脉。短期目标是：1）开展必要的野外工作和构造测绘，以解释流体生成至存款形成区域的地壳地质演化; 2）确定放射性同位素（Pb-Pb和Re-Os）系统学，从而确定特定矿床和流体通道的同位素金属特征; 3）使用原位微量元素，对源岩中的矿石矿物进行了S和Pb-Pb同位素分析（激光剥蚀ICP-MS），以深入研究金的富集过程。将对选定的地壳部分采用类似的科学方法，并根据现有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部分的详细取样相结合。该研究计划将影响我们对地壳规模的太古代至中生代含金系统，以及前寒武纪与中生代地壳结构的构造演化和黄金禀赋的理解。最先进的同位素示踪（Re-Os;原位Pb和S同位素），定量微量元素矿物测绘（激光消融ICP-MS）和造山过程的研究在我正在进行的研究中进行的整合，将允许提出新的地壳中的金浓度模型，以及它们对形成世界级与贫金带的影响。在地质知识有限的地区（如加拿大北方）进行勘探时，尤其是对于通常具有离散地质足迹的备受追捧的低品位大吨位矿床，详细了解导致世界级金矿区形成的关键组成部分至关重要。确定不同的金属同位素特征（如省性），结合有利的构造演化和流体生成和循环的时间记录，将有助于确定黄金肥力评估和行业勘探标准。