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传质

• 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: 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=669530
• 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成矿元素和挥发性元素在地球固体地壳中的质量传递的理解，从而导致矿床的形成。几种类型的矿床的成因与岩浆作用有关，这里提出的研究重点是理解导致所谓的“岩浆-热液”矿床形成的过程。这一矿化亚类是我们主要或主要的元素来源，如铜、钼、金、锡、钨、稀土、银、铅和锌。这种矿床的形成与减压和结晶作用下岩浆中的挥发性相释放有关，这与驱动火山爆发活动的过程相同。这是成矿过程中必不可少的一步，因为这种溶出的挥发性相可以有效地从岩浆中提取金属，然后使它们沉淀，从而导致特定矿石金属的局部浓缩。这种溶出的岩浆挥发相通常以水和少量的二氧化碳为主，但也含有明显浓度的S、氯和各种金属。矿体中S和氯的浓度和形态对岩浆中金属的提取效率起主要控制作用，也影响矿化部位的迁移和沉淀。*这里提出的综合研究计划涉及从岩浆中提取金属的这一关键过程，以及那些在岩浆挥发相外溶之前控制岩浆初始金属赋存的过程。我们将把直接对自然样品进行的观测与在高压和高温下模拟地质系统中的物理化学条件进行的实验调查结合起来。实验研究将首先利用一系列创新方法，重点研究S和氯的挥发/熔融分配，以及铜和金的溶解和分配行为。最终目标是利用这个实验数据集和以前公布的数据来构建一个热力学模型，该模型可以准确地预测这些元素的挥发/熔体分配系数作为压力、温度和熔体组成的函数。对天然样品的研究将跟踪不同岩浆-热液成矿系统中挥发性元素和成矿金属浓度在整个岩浆和/或热液演化过程中的协同变化。大部分数据将通过分析矿物中的硅酸盐熔体、硫化物和流体包裹体获得。这些是这些相(约10至100微米)的微小液滴，在这些系统的演化过程中被捕获在结晶矿物中，保存了它们成分变化的时间分辨记录。对这些包裹体的分析带来了分析上的挑战；然而，多伦多大学将为此设立一个最先进的实验室。这将使某些元素的浓度检测到最优样品的十亿分之几的水平。所有这些数据将被整合起来，以构建改进的岩浆-热液成矿模型。*改进的成矿成因模型将允许为采矿业制定更严格的勘探标准，并为发现新的矿藏奠定基础。确保矿产资源的持续供应对经济增长、人类舒适生活和全球和平至关重要。由于拥有丰富的矿藏资源，加拿大可能在满足社会快速增长的资源需求方面发挥战略作用。因此，高效的矿产勘探可能会促进加拿大经济的增长，为加拿大人创造财富，并增加加拿大在世界政治中的影响力。