Recycling of elements in subduction zones and formation of mineral deposits in magmatic arcs

俯冲带元素的循环和岩浆弧矿床的形成

• 批准号: RGPIN-2022-05452
• 负责人: Hattori, Keiko
• 金额: $ 3.13万
• 依托单位: University of Ottawa
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=751208
• 关键词: Recycling; elements; subduction; zones; formation

Volcanoes in magmatic arcs discharge large quantities of volatile elements. These magmas produce hydrothermal activity that can concentrate metallic minerals, such as porphyry copper deposits and precious metal veins. The association of these metallic deposits with arc magmas indicate a genetic link for the two. The constituents of deposits (metals, volatiles including water) are abundant near the surface, but extremely low in the mantle where these magmas originate. Continuous discharges of volatile elements from volcanoes, as well as the formation of mineral deposits in magmatic arcs, require these components to be supplied from the surface to the mantle via subduction processes where slabs descend from the surface into the mantle and transfer these elements to the mantle. The general concept is well accepted, but the mechanism of this chemical transfer is not well understood. Our earlier work showed that parental magmas of igneous rocks that host copper deposits are oxidized and sulphur-rich. Some volcanic arcs, such as Luzon, Philippines, contain abundant porphyry copper deposits, whereas there are no porphyry copper deposits in Japan. The causes of this uneven distribution of various types of metal deposits are not understood. I plan to examine two types of rocks; primitive mafic rocks that reflect the conditions of the source mantle, and igneous rocks contemporaneous with epithermal precious vein deposits. Questions to address include: 1. What controls the conditions of subarc mantle? What controls the mobility of metals to transfer metals from slabs to the mantle, and to arc magmas? 2. What characterizes magmas associated with precious metal deposits? How are they different from normal arc magmas and those responsible for porphyry copper deposits? In the first phase of the project, I propose to study active subduction zones in the western Pacific, since the configuration of the subduction zones is well understood, based on seismic activity and tomographic images. In addition, ocean drilling programs in the areas show the compositions of subducting slabs and sediments. Then, I plan to apply the information from these young arcs to old terranes in Yukon and Newfoundland, which contain many precious metal deposits similar to active arcs. My proposal addresses fundamental scientific questions: how are elements recycled from the surface to the mantle, then to arc magmas? In addition to these academic questions, the proposed project contributes to securing our living standards. Metals from magmatic arcs are vital for our society, such as copper for electric transmission. In addition, a low-carbon society calls for alternative energy sources. Clean energy requires many metals, such as indium and silver for solar panels, which are extracted from deposits in magmatic arcs. The proposed research can assist the efficient exploration and discovery of such metal deposits by targeting favourable magmatic arcs and regions

岩浆弧中的火山排放大量挥发性元件。这些岩浆产生的水热活性可以浓缩金属矿物质，例如斑岩铜沉积物和贵金属静脉。这些金属沉积物与弧岩浆的关联表示两者的遗传联系。沉积物（金属，包括水在内的挥发物）的成分在表面附近丰富，但在这些岩浆起源的地幔中极低。连续排放来自火山的挥发性元件，以及岩浆弧中的矿物沉积物的形成，需要通过俯冲过程从表面到地幔提供这些成分，在这些过程中，平板从表面从表面下降到地幔中并将这些元素传递到地幔。一般概念已被公认，但是这种化学转移的机制尚不清楚。我们较早的工作表明，托管铜沉积物的火成岩的父母岩浆被氧化且富含硫的岩石。一些火山弧，例如吕宋，菲律宾，含有丰富的斑岩铜矿，而日本没有斑岩铜矿。不了解各种类型金属沉积物的这种不均匀分布的原因。我计划检查两种类型的岩石。原始的镁铁质岩石反映了源地幔的条件，火成岩岩石与表皮珍贵的静脉沉积物同时发生。要解决的问题包括：1。是什么控制了Subarc Mantle的条件？是什么控制金属将金属从平板转移到地幔的迁移率以及弧形岩浆？ 2。与贵金属沉积物相关的岩浆的特征是什么？它们与正常的弧岩浆和负责斑岩铜沉积物的人有何不同？ 在该项目的第一阶段，我建议研究西太平洋的主动俯冲带，因为俯冲带的构型基于地震活动和层析成像图像可以很好地理解。此外，该地区的海洋钻井程序显示了俯冲板和沉积物的组成。然后，我计划将这些年轻弧线的信息应用于育空地区和纽芬兰的旧地形，其中包含许多类似于活跃弧的贵金属沉积物。我的提议解决了基本科学问题：如何从表面回收到地幔，然后再回到弧岩石？除了这些学术问题外，拟议的项目还有助于确保我们的生活水平。来自岩浆弧的金属对我们的社会至关重要，例如电动传输的铜。此外，低碳社会需要替代能源。清洁能需要许多金属，例如太阳能电池板的粘合和银，这些金属是从岩浆弧中的沉积物中提取的。拟议的研究可以通过瞄准有利的岩浆弧和区域来帮助有效探索和发现此类金属沉积物