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.

该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转移的理解，从而形成矿床。几种类型的矿床的成因与岩浆活动有关，这里提出的研究重点是了解导致形成所谓的“岩浆热液”矿床的过程。这类矿化是我们的主要或主要的元素资源，如Cu、Mo、Au、Sn、W、Re、Ag、Pb和Zn。这类矿床的形成与岩浆中的挥发相因减压和结晶而出溶有关，这一过程也是火山爆发活动的驱动力。这是成矿过程中必不可少的一步，因为这种出溶挥发相可以有效地从岩浆中提取金属，然后沉淀，导致特定矿石金属的局部富集。这种出溶的岩浆挥发相（MVP）通常由水和少量的CO2占主导地位，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提取矿石金属的效率起主要控制作用，并且还影响向成矿部位的转移和沉淀。* 这里提出的综合研究计划解决了从岩浆中提取金属的关键过程，以及在岩浆挥发相出溶之前控制岩浆初始金属禀赋的过程。我们将把直接对天然样品进行的联合收割机观察与在高压和高温下进行的模拟地质系统物理化学条件的实验研究相结合。实验研究将首先集中在挥发/熔融分配的S和Cl，和溶解度和分配行为的Cu和Au，使用一系列的创新方法。最终的目标是使用这个实验数据集沿着与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在整个岩浆和/或热液演化过程中各种岩浆-热液成矿系统中挥发性元素和成矿金属浓度的共变。大多数数据将通过分析矿物中的硅酸盐熔体包裹体、硫化物包裹体和流体包裹体获得。这些是这些相的微小液滴（~10至100 µm），在这些系统的演化过程中被捕获在结晶矿物中，保留了其成分变化的时间分辨记录。这些夹杂物的分析提出了一个分析挑战;然而，一个最先进的实验室将建立在多伦多大学为此目的。这将允许检测一些元素浓度低至十亿分之一水平的最佳样品。将综合所有这些数据，以建立改进的岩浆热液成矿模型。改进的成矿成因模型将使采矿业能够制定更严格的勘探标准，并作为发现新矿床的基础。确保矿物资源的持续供应对经济增长、舒适的人类生活和全球和平至关重要。由于其自然禀赋的矿床，加拿大可以发挥战略作用，以满足社会迅速增长的资源需求。因此，有效的矿产勘探可以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。