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Development of new oxybarometers for silicic magmas

新型硅岩浆氧压计的研制

基本信息

批准号：
261400976
负责人：
Dr. Andreas Audétat
金额：
--
依托单位：
Bayerisches Forschungsinstitut für Experimentelle Geochemie und Geophysik (BGI)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2017-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/261400976?language=en
关键词：
Development new oxybarometers silicic magmas

项目摘要

The oxygen fugacity of intermediate to silicic magmas is most commonly reconstructed by Fe-Ti two-oxide thermobarometry. However, many silicic igneous rocks lack coexisting magnetite and ilmenite or other mafic minerals that could be used to constrain fO2. Furthermore, in many samples in which such phases originally were present they subsequently were destroyed or reset during subsolidus processes. The aim of this project is to develop three new mineral-melt partitioning oxybarometers that can be applied to both volcanic and slowly-cooled, intrusive rocks. The project is divided into three independent subprojects that deal with the mineral-melt partitioning of three different multivalent elements: (1) vanadium partitioning between magnetite and silicate melt, (2) uranium partitioning between zircon (or apatite) and silicate melt, and (3) iron partitioning between feldspar and silicate melt. Each of these equilibria will be investigated experimentally under controlled temperature and fO2 conditions, and the resulting calibrations will be tested on natural samples that formed at known T-fO2 conditions. The latter will be done via laser ablation ICP-MS analysis of silicate melt inclusions and solid inclusions within magmatic quartz phenocrysts, which has the advantage that the trapped phases were protected from alteration by hydrothermal fluids, and that re-equilibration processes that occurred within the inclusions during magma cooling are "reversed" during the analysis of entire, unexposed inclusions.

中硅质岩浆的氧逸度最常通过铁钛二氧化物温压法重建。然而，许多硅质火成岩缺乏共存的磁铁矿和钛铁矿或其他可用于限制 fO2 的镁铁质矿物。此外，在许多最初存在此类相的样品中，它们随后在亚固相线过程中被破坏或重置。该项目的目的是开发三种新型矿物熔体分配氧压计，可应用于火山岩和缓慢冷却的侵入岩。该项目分为三个独立的子项目，分别处理三种不同多价元素的矿物熔体分配：（1）磁铁矿和硅酸盐熔体之间的钒分配，（2）锆石（或磷灰石）和硅酸盐熔体之间的铀分配，以及（3）长石和硅酸盐熔体之间的铁分配。这些平衡中的每一个都将在受控温度和 fO2 条件下进行实验研究，并将在已知 T-fO2 条件下形成的天然样品上测试所得校准结果。后者将通过对岩浆石英斑晶内的硅酸盐熔体包裹体和固体包裹体进行激光烧蚀ICP-MS分析来完成，其优点是保护被捕获的相免受热液的改变，并且在分析整个未暴露的包裹体期间，在岩浆冷却期间包裹体内发生的重新平衡过程被“逆转”。