Tectonomagmatic history and ore-forming triggers at the Titiribi and La Mina porphyry-epithermal deposits, Colombia

哥伦比亚蒂蒂里比和拉米纳斑岩-浅成热液矿床的构造岩浆历史和成矿触发因素

• 批准号: 523133-2017
• 负责人: Richards, Jeremy
• 金额: $ 2.89万
• 依托单位: Laurentian University of Sudbury
• 依托单位国家: 加拿大
• 项目类别: Collaborative Research and Development Grants
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=663326
• 关键词: Tectonomagmatic; history; ore; forming; triggers

Porphyry copper deposits are major global sources of copper (as well as gold and molybdenum) to industry and society, and are premier targets for exploration by mining companies. The general mode of formation and occurrence of these deposits is now well understood by geologists, and involves the exsolution of hot metalliferous fluids from crystallizing magma in the upper crust (magmatic-hydrothermal fluids); the "fertile" magma that releases these fluids is typically formed above subduction zones at convergent plate boundaries, such as the Andes of South America, and the Cordillera of western North America. However, the ultimate controls on whether an economic deposit of metals is formed (as opposed to a low-grade deposit or barren system) are not well constrained, and indeed may be stochastic (inasmuch as they may not be predictable except in a probabilistic sense). It is noticeable that ore formation in porphyry systems occurs over short and singular periods of time (~100,000 years) in the overall history of the source magmatic system (1 to 5 million years), and commonly involves explosive brecciation and shallow magma emplacement, and yet many magmatic systems to not show evidence of such events. This suggests that a dramatic, perhaps catastrophic change occasionally affects otherwise passively crystallizing arc magmatic systems, leading to ore-formation. The nature of large ore deposits is that they display extensive overprinting and alteration, such that early textures that might reveal these triggering processes are destroyed. Therefore, we plan to study the relatively small Titiribi and La Mina porphyry deposits in Colombia, where the degree of overprinting is less, and early breccia and magmatic textures are well preserved. This will enable us to tightly constrain the interplay between magma emplacement, hydrothermal fluid release, and ore deposition, with the objective of identifying the underlying triggers for these processes. Although, ore formation may still be stochastic, understanding the key controls will improve predictability, thereby improving the ability to target exploration.

斑岩铜矿是全球工业和社会铜（以及金和钼）的主要来源，也是矿业公司勘探的首要目标。这些矿床的形成和产出的一般模式现在已为地质学家所熟知，其中包括热金属流体从上地壳结晶岩浆（岩浆-热液流体）中的出溶作用;释放这些流体的“肥沃”岩浆通常形成于板块会聚边界的俯冲带上方，如南美洲的安第斯山脉和北美洲西部的科迪勒拉山脉。然而，对是否形成经济的金属存款（相对于低品位存款或贫瘠系统）的最终控制没有很好的约束，实际上可能是随机的（因为它们可能无法预测，除非在概率意义上）。值得注意的是，斑岩系统中的成矿作用发生在源岩浆系统的整个历史（100万至500万年）中的短时间内（约10万年），通常涉及爆炸角砾岩和浅岩浆侵位，但许多岩浆系统没有显示出此类事件的证据。这表明，一个戏剧性的，也许是灾难性的变化偶尔会影响，否则被动结晶弧岩浆系统，导致成矿。大型矿床的性质是，它们显示出广泛的叠印和蚀变，从而可能揭示这些触发过程的早期结构被破坏。因此，我们计划对哥伦比亚规模相对较小的Titiribi和La Mina斑岩矿床进行研究，那里的叠加程度较小，早期角砾岩和岩浆结构保存较好。这将使我们能够严格限制岩浆侵位，热液流体释放和矿石沉积之间的相互作用，目的是确定这些过程的潜在触发因素。尽管成矿可能仍然是随机的，但了解关键控制因素将提高可预测性，从而提高目标勘探能力。