Controls on the fertility of magmas for the genesis of associated hydrothermal ore deposits

控制伴生热液矿床成因的岩浆肥力

• 批准号: RGPIN-2019-05244
• 负责人: Zajacz, Zoltan
• 金额: $ 2.61万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=686498
• 关键词: Controls; fertility; magmas; genesis; associated

Magmatic-hydrothermal ore deposits are our major resources of metals such as Cu, Mo, Au, Ag, Re, Sn and W. Most large ore deposits near the surface have already been discovered and the finding of new major deposits to cover the increasing metal demand of society requires exploration at depth at greatly increased cost. Therefore, the identification of the most prospective regions for ore genesis to focus mineral exploration efforts on is essential. The outcomes of the proposed research will help to identify ore-fertile segments of continental arcs based on geochemical criteria, which may be particularly useful when applied to accreted composite arc terrains with complicated magmatic history and tectonic evolution such as the Canadian Cordillera.***To achieve this goal, I will combine experimental and field-based studies to investigate the fate of sulfur and ore metals during all main stages of magma evolution leading up to ore genesis, including 1) the generation of magmas in the Earth's upper mantle over subducting oceanic plates; 2) the transport of magmas through the Earth's lithosphere, and 3) ore fluid generation by magma degassing at upper crustal depths. Particular attention will be paid to the evolution of the redox state of magmas as this defines the geochemical behavior of sulfur and many ore metals. For example, the presence of sulfur in reduced state may lead to magmatic sulfide saturation, which may greatly affect metal transfer into later exsolving fluids. On the other hand, the presence of abundant oxidized sulfur species in the magmatic fluid phase is a pre-requisite for efficient ore mineral precipitation in porphyry and high-sulfidation epithermal ore deposits. We will therefore: 1) Investigate how subducted slab-derived fluids influence the oxidation state and ore metal budget of arc magmas by using high pressure-temperature experiments and by studying volcanic rocks in the Trans-Mexican Volcanic Belt, a unique continental arc with a great diversity of primitive mantle-derived magmas; 2) Conduct a field-based study in the Andes to constrain how the concentration of ore metals, S and Cl vary during magma differentiation in the crust in tectonic settings particularly favorable for ore genesis, and compare this to arc segments with moderate mineralization potential; 3) Experimentally develop new methods to constrain the evolution of the redox state of magmas and apply these to rock samples collected in the field; 4) Experimentally constrain how silicate melt composition, pressure and temperature affect the efficiency of ore metal and sulfur transfer into exsolving magmatic fluids and use this information to help interpret data obtained from natural samples. The proposed research will take advantage of numerous recent successful experimental and analytical method developments in my group, which will allow us to obtain very powerful and previously inaccessible information to facilitate better understanding of the above processes.**

岩浆 - 水热矿石沉积物是我们的主要资源，例如Cu，Mo，Au，Ag，Re，Sn和W。已经发现了地表附近的大多数大型矿床，并且发现了新的主要沉积物以覆盖社会的日益增长的社会需求，需要以大大增加的成本以深度勘探。因此，对矿石创世纪最具前瞻性区域的识别至关重要。拟议的研究的结果将有助于根据地球化学标准识别大陆弧的矿石领域，当应用于具有复杂的岩浆历史和构造性进化的增值复合弧形地形时，这可能是特别有用的。导致矿石起源的进化，包括1）地球上地幔中岩浆的产生； 2）岩浆穿过地球岩石圈的运输，以及3）岩浆在上皮深度下脱气。特别关注岩浆的氧化还原状态，因为这定义了硫和许多矿石金属的地球化学行为。例如，在降低的状态下硫的存在可能导致岩浆硫化物饱和度，这可能会极大地影响金属转移到后来的溶液中。另一方面，在岩浆液相中存在丰富的氧化硫种类是在斑岩和高硫化表皮沉积中有效的矿石矿物沉淀的先决条件。因此，我们将：1）研究俯冲板衍生的流体如何通过使用高压温度实验以及研究跨墨西哥火山带中的火山岩来影响电弧岩浆的氧化状态和矿石金属预算，这是一种独特的大陆弧，具有独特的大陆弧。 2）在安第斯山脉中进行基于现场的研究，以限制矿石金属，s和cl在岩浆分化过程中的浓度如何在构造环境中的岩浆分化过程中如何变化，并将其与具有中等矿化潜力的电弧段进行比较； 3）实验开发新​​方法来限制岩浆的氧化还原状态的演化，并将其应用于在田间收集的岩石样品中； 4）在实验上限制了硅质熔体成分，压力和温度如何影响矿石金属和硫的效率转移到岩浆流体中，并使用此信息来解释从天然样品获得的数据。拟议的研究将利用我小组中众多成功的实验和分析方法的发展，这将使我们能够获得非常强大且以前无法访问的信息，以促进对上述过程的更好理解。**