Mass transfer of volatile and ore-forming elements in the Earth’s lithosphere

地球岩石圈中挥发性元素和成矿元素的质量转移

• 批准号: RGPIN-2014-04805
• 负责人: Zajacz, Zoltan
• 金额: $ 2.7万
• 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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=611252
• 关键词: Mass; transfer; volatile; ore; forming

The major goal of this research program is to improve our understanding of the mass transfer of ore-forming and volatile elements in the Earth’s solid crust, leading to the formation of ore deposits. The genesis of several types of mineral deposits is linked to magmatism, and the research proposed here focuses on the understanding of processes leading to the formation of so called “magmatic-hydrothermal” ore deposits. This subclass of mineralizations serves as our primary or major resource of elements such as Cu, Mo, Au, Sn, W, Re, Ag, Pb and Zn. The formation of such deposits relates to the exsolution of a volatile phase from magmas in response to decompression and crystallization, the same process which drives explosive volcanic activity. This is an essential step in ore formation, because this exsolving volatile phase may efficiently extract metals from magmas, and later precipitate them leading to local enrichment of specific ore metals. This exsolving magmatic volatile phase (MVP) is usually dominated by water and smaller amounts of CO2, but also contains S, Cl and various metals in significant concentrations. The concentration and speciation of S and Cl in the MVP exert primary control on the efficiency of ore metal extraction from magmas, and also affect the transfer to, and precipitation at the site of mineralization. The comprehensive research program proposed here addresses this key process of metal extraction from magmas, and also those that control the initial metal endowment of the magmas before the exsolution of a magmatic volatile phase. We will combine observations made directly on natural samples with experimental investigations conducted at high pressures and temperatures simulating the physical-chemical conditions in geologic systems. The experimental studies will first focus on the volatile/melt partitioning of S and Cl, and the solubility and partitioning behavior of Cu and Au, using a range of innovative methodologies. The ultimate goal is to use this experimental dataset along with previously published data to construct a thermodynamic model which can accurately predict the volatile/melt partition coefficients of these elements as a function of pressure, temperature and melt composition. The studies on natural samples will track the co-variation of the concentration of volatile elements and ore forming metals in various magmatic-hydrothermal ore forming systems throughout the magmatic and/or hydrothermal evolution. Most data will be obtained by analyzing silicate melt-, sulfide- and fluid inclusions in minerals. These are tiny droplets of these phases (~10 to 100 µm), which are trapped in crystallizing minerals during the evolution of these systems, preserving a time resolved record of their compositional variation. The analysis of these inclusions poses an analytical challenge; however, a state of the art laboratory will be set up at the University of Toronto for this purpose. This will allow the detection of some element concentrations down to the parts per billion level for optimal samples. All these data will be integrated to construct improved models of magmatic-hydrothermal ore genesis. Improved genetic models of ore formation will allow developing more rigorous exploration criteria for the mining industry and serve as a foundation for the discovery of new ore deposits. Securing the constant supply of mineral resources is essential for economic growth, comfortable human life and global peace. Due to its natural endowment of ore deposits, Canada may play a strategic role in covering the rapidly growing resource demands of society. Therefore, efficient mineral exploration may boost the growth of the Canadian economy, generate wealth for Canadians and increase Canada’s influence in world politics.

这项研究计划的主要目标是提高我们对地球固体地壳中成矿和挥发性元素的质量传递的理解，从而导致矿床的形成。几种类型矿床的成因与岩浆作用有关，这里提出的研究重点是了解导致所谓“岩浆-热液”矿床形成的过程。这类矿化是铜、钼、金、锡、钨、稀土、银、铅和锌等元素的主要或主要来源。这种矿床的形成与岩浆在减压和结晶过程中挥发相的析出有关，这一过程与火山爆发活动的成因相同。这是成矿过程中必不可少的一步，因为这种溶解挥发相可以有效地从岩浆中提取金属，然后使其沉淀，从而导致特定矿石金属的局部富集。这种溶出性岩浆挥发相（MVP）通常以水和少量的CO2为主，但也含有大量的S、Cl和各种金属。MVP中S和Cl的浓度和形态对岩浆中矿石金属的提取效率起主要控制作用，同时也影响矿化部位的转移和沉淀。