Formation of monomineralic Fe-Ti oxide ores in the high-Ti ferrobasaltic system: A case study in Emeishan, China

来自层状侵入体的岩浆铁矿是工业过程中使用的铁、钛和钒金属的主要来源之一。Fe-Ti-V富氧化层的起源仍不清楚，可能涉及不同的过程，这取决于自然案例研究。在这项研究中，我们将结合对自然样品的地球化学研究(由北京的中方合作伙伴负责)和实验方法(由德国合作伙伴负责)来了解峨眉山大火成岩省(ELIP)近单矿物磁铁矿层的形成，中国。这种单矿物矿床并不常见，就峨眉山省而言，地球化学和自然观察表明，熔体不混溶在矿石形成过程中并不起主要作用。该研究计划旨在了解ELIP形成的磁铁矿层，并将解决以下问题：-在最原始的高钛铁玄武岩的演化过程中，哪些因素对Fe-Ti氧化物的稳定性起到主要控制作用，以及在岩浆分异过程中，最富Fe-Ti的熔体成分是什么？-玄武岩岩浆与石灰岩(作为寄主岩石)之间的相互作用能在多大程度上影响岩浆分异和含铁、钛矿物的结晶行为？-岩浆补充，即演化和原始岩浆之间的混合，在多大程度上，增加Fe-Ti氧化物的稳定场或影响Fe-Ti氧化物是唯一稳定固相的条件？岩石和矿物(主量元素和微量元素)的地球化学特征和高压实验所获得的约束条件的互补性将对峨眉山层状侵入体的岩浆演化史提供定量的制约。

Magmatic iron ore from layered intrusions is one of the major sources for Fe, Ti and V metals used in industrial processes. The origin of the Fe-Ti-V oxide-rich layers is still poorly understood and may involve different processes, depending on the natural case studies. In this study we will combine the geochemical study of natural samples (under the responsibility of Chinese partners of Beijing) and an experimental approach (under the responsibility of the German partners) to understand the formation of the nearly monomineralic magnetite layers in the Emeishan Large igneous Province (ELIP), China. Such monomineralic deposits are uncommon and, in the case of the Emeishan Province, geochemical and natural observations indicate that melt immiscibility does not play a major role during the formation of the ores. The research program aims at understanding the formation of magnetite-layers from ELIP and will tackle the following questions:- Which factors do exert a major control on the stability of Fe-Ti oxides during the evolution of the most primitive high-Ti ferrobasalt and what is the most Fe-Ti-rich melt composition during magma differentiation? - To which extent can interaction between basaltic magmas and limestone (occurring as host-rock) affect magma differentiation and the crystallization behavior of Fe- and Ti-bearing minerals?- To which extent can magma replenishment, i.e. mixing between evolved and primitive magmas, increase the stability field of Fe-Ti-oxides or affect the conditions at which Fe-Ti-oxides are the only stable solid phases?The complementarity of the geochemical characterization of rocks and minerals (major and trace elements) and of the constraints gained from high pressure experiments will provide quantitative constraints on the magma evolution history in the layered intrusions of Emeishan province.