2025年2月24日出版的《地球化学学报》发表了河北工程大学王开元小组的最新成果，他们报道了大庙矿中钛铁矿溶出物的地球化学、矿物学特征及其成矿意义。

大庙铁钛磷矿位于中国东北大庙斜长岩杂岩内，其铁钛氧化物矿石和镁铝榴辉石呈不规则倾斜的层状体、透镜体或脉状，与斜长岩和辉长岩有尖锐接触。该矿床以丰富的钛磁铁矿为特征，具有不同的钛铁矿溶出结构，包括块状、片状和布状。

本文对钛磁铁矿中钛铁矿溶出物的地球化学和矿物学进行了研究，以了解其形成机制及其对成矿过程的影响。详细的岩石学观察和电子探针分析表明，其外溶结构是由多种机制引起的——钛磁铁矿氧化引起的氧-外溶；铁、钛、铬、钴和镍的元素扩散导致磁铁矿和钛铁矿之间的再平衡；快速冷却导致晶格缺陷的析出。

热力学模型（Gibbs自由能计算）和QUILF程序表明，在高于或低于固溶体的温度下，块状、片层状和布状钛铁矿析出体在氧逸度降低的情况下形成。此外，他们的研究结果表明，钛铁矿晶界处锆石和杂石的析出，是由于钛磁铁矿氧化导致的Zr和Al等元素的饱和和沉淀，而不是钛铁矿与相邻斜辉石的相互作用。

冷却历史的重建表明，氧化磷灰石辉长岩的氧逸度明显高于铁钛磷矿石。这证实了岩浆演化过程中氧逸度的增加促进了非混溶性，导致了硅质熔体的形成，最终形成了Fe-Ti-P矿石。

附：英文原文

Title: Geochemistry and mineralogy of ilmenite exsolutions in titanomagnetite and their implications for the ore-forming process at the Damiao deposit

Author: Wang, Kaiyuan, He, Hongtao, Shi, Wenjie

Issue&Volume: 2025-02-24

Abstract: The Damiao Fe-Ti-P deposit, located within the Damiao anorthosite complex in northeastern China, features Fe-Ti oxide ores and nelsonites that occur as irregularly inclined stratiform-like bodies, lenses, or veins with sharp contacts against anorthosite and gabbronorite. This deposit is characterized by abundant titanomagnetite that hosts diverse ilmenite exsolution textures, including blocky, lamellar, and cloth-like forms. In this study, we investigate the geochemistry and mineralogy of ilmenite exsolutions in titanomagnetite to understand their formation mechanisms and implications for the ore-forming process. Detailed petrographic observations and electron microprobe analyses reveal that the exsolution textures result from multiple mechanisms: oxy-exsolution due to titanomagnetite oxidation; subsolidus re-equilibration between magnetite and ilmenite involving elemental diffusion of Fe, Ti, Cr, Co, and Ni; and exsolution related to lattice defects caused by rapid cooling. Thermodynamic modeling using Gibbs free energy calculations, and the QUILF program indicates that blocky, lamellar, and cloth-textured ilmenite exsolutions formed at temperatures above and below the solid-solution solvus under decreasing oxygen fugacity. Additionally, our results indicate that the exsolution of zircon and pleonaste at ilmenite grain boundaries is attributed to the saturation and precipitation of elements like Zr and Al, due to the oxidation of titanomagnetite, rather than interactions between ilmenite and adjacent clinopyroxene. Reconstruction of the cooling history suggests that the oxygen fugacity of oxide–apatite gabbronorites was significantly higher than that of Fe-Ti-P ores. This confirms that increasing oxygen fugacity during magma evolution promoted immiscibility, leading to the formation of nelsonitic melts and ultimately the development of Fe-Ti-P ores.

DOI: 10.1007/s11631-025-00766-x

Source: https://link.springer.com/article/10.1007/s11631-025-00766-x