Magmatic volatiles and ore metals released from intraoceanic arc magmas: constraints from high pressure experiments and melt inclusions for Brothers volcano, Kermadec arc

洋内弧岩浆释放的岩浆挥发物和矿石金属：来自克马德克弧兄弟火山高压实验和熔融包裹体的限制

• 批准号: 429243206
• 负责人: Professor Dr. Francois Holtz, Ph.D.
• 金额: --
• 依托单位: Institut für Mineralogie
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/429243206?language=en
• 关键词: Magmatic; volatiles; ore; metals; released

The main goal of IODP Expedition 376 (conducted in 2018) was the understanding of the magmatic-hydrothermal system and associated metal ore deposits (e.g., Cu+Au) at intraoceanic volcanic arcs. The expedition focused on the sampling of Brothers volcano of the Kermadec arc, that produces evolved dacitic to rhyolitic melts, in contrast to several other volcanic systems along the Kermadec arc. Brothers volcano has also the particularity to be extremely Cl-rich with a large compositional variability (e.g., alkali and alumina content, Mg#) and the aim of this proposal is to unravel the nature and composition of magma chamber-derived volatile phases (e.g., single-phase fluid or two-phase brine and vapor) as well as their effect on fractionation trends and metal enrichment during differentiation.This objective will be achieved with three complementary analytical and experimental tasks: 1) the origin of the felsic magmas, the fractionation and differentiation processes will be investigated based on the major element analysis of matrix glasses and glass inclusions, 2) the magma storage conditions and the role of volatiles, especially Cl and H2O, on the fractionation of magmas will be constrained from high pressure crystallization experiments and 3) the role of volatiles and oxygen fugacity for ore metals (e.g., Fe, Cu, Zn, W, Au) enrichment will be estimated based on trace element analysis of glass inclusions in plagioclase and clinopyroxene. Most glass inclusions contain quench crystals and bubbles and need to be re-homogenized at high pressure. The combination of the three work packages will allow us to track the evolution of metal concentrations in Cl-rich magmatic systems during differentiation and at the magmatic-hydrothermal stage.

IODP Expedition 376（2018年进行）的主要目标是了解岩浆热液系统和相关的金属矿床（例如，Cu+Au）。考察的重点是对克马德克弧兄弟火山的取样，该火山产生演化的英安岩到流纹岩熔体，与克马德克弧沿着的其他几个火山系统形成对比。兄弟火山也有特殊性，是非常丰富的氯与一个大的组成变化（例如，碱和氧化铝含量，Mg#），并且该提议的目的是揭示岩浆室衍生的挥发相的性质和组成（例如，单相流体或两相盐水和蒸汽）以及它们对分馏趋势和分异过程中金属富集的影响。这一目标将通过三项补充分析和实验任务来实现：1）通过对基质玻璃和玻璃包裹体的主量元素分析，探讨长英质岩浆的成因、分异作用和分异过程，2）岩浆的储存条件和挥发分，特别是Cl和H_2O对岩浆分馏的作用将受到高压结晶实验的制约; 3）挥发分和氧逸度对矿石金属的作用（例如，通过对斜长石和单斜辉石中玻璃包裹体的微量元素分析，估算了斜长石和单斜辉石中Fe、Cu、Zn、W、Au的富集程度。大多数玻璃夹杂物含有淬火晶体和气泡，需要在高压下重新均匀化。这三个工作包的结合将使我们能够跟踪金属浓度的演变过程中，富氯岩浆系统在分化和岩浆热液阶段。