Silicate liquid immiscibility and the formation of Fe (±Ti ±P ±F ±REE) ore deposits

硅酸盐液体不混溶性与Fe(±Ti±P±F±REE)矿床的形成

基本信息

批准号：
268008671
负责人：
Professor Dr. Jürgen Koepke
金额：
--
依托单位：
Institut für Mineralogie
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/268008671?language=en
关键词：
Silicate liquid immiscibility formation Fe

项目摘要

The role of immiscibility between two silicate melts (ferrobasalt-rhyolite) on differentiation and ore-forming processes is under debate since decades. Clear evidence for the separation of two silicate melts in natural systems is rarely recorded in rocks because of the transient nature of immiscibility during cooling and solidification. Thus, experimental approaches are crucial to test the importance of melt immiscibility in magmatic and associated ore-forming processes. In this study, we propose to use a twofold approach to understand the role of silicate liquid immiscibility in the formation of Fe (±Ti ±P ±F ±REE) ore deposits: (1) we will study melt inclusions trapped in apatite of some major iron deposits which will give us direct constraints on the equilibrium liquid compositions and (2) we will perform a detailed experimental approach to understand the conditions for the onset of immiscibility (magma compositions, temperature, pressure, oxygen fugacity and fluid content), and the partitioning of major elements between paired melts. The role of melt immiscibility will be tested for three well known natural examples, all containing Fe- and P-rich associations and covering a broad compositional range: tholeiitic basaltic system (Bushveld complex), ferropicritic/high-Ti basaltic system (Emeishan large igneous province), and Kiruna-type systems (Vergenoeg deposit). In selected experiments, we will also study the effect of immiscibility on trace elements fractionation between Fe-rich and Fe-poor silicate melts. The results will provide crucial data allowing us to discuss quantitatively the role of melt immiscibility on differentiation processes in basaltic systems, on the formation of some economically important Fe ore deposits and on enrichment mechanisms of trace elements (especially REE).

几十年来，两种硅酸盐熔体（玄武岩-流纹岩）之间的不混溶性对分异和成矿过程的作用一直存在争议，因为岩石中很少记录自然系统中两种硅酸盐熔体分离的明确证据，因为不混溶性具有短暂性。因此，实验方法对于测试熔体不混溶性在岩浆和相关成矿过程中的重要性至关重要。采用双重方法来了解硅酸盐液体不混溶性在 Fe (±Ti ±P ±F ±REE) 矿床形成中的作用：(1) 我们将研究一些主要铁矿床中磷灰石中捕获的熔体包裹体，这将给我们带来直接约束（2）我们将进行详细的实验方法来了解不混溶发生的条件（岩浆成分、温度、压力、氧逸度和流体含量）以及主要元素的分配熔体不混溶性的作用将在三个众所周知的自然实例中进行测试，所有实例都含有富铁和富磷的缔合体，并涵盖广泛的成分范围：拉斑玄武岩体系（布什维尔德杂岩）、铁黄铁矿/高钛玄武岩体系。（峨眉山大型火成岩省）和基律纳型系统（Vergenoeg 矿床）在选定的实验中，我们还将研究不混溶性对微量元素分馏的影响。富铁和贫铁硅酸盐熔体的研究结果将为我们定量讨论熔体不混溶性对玄武岩系统分异过程、一些重要经济铁矿床的形成以及微量元素富集机制的作用提供重要数据。（特别是稀土元素）。