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

大庙铁钛磷矿床位于中国东北大庙斜长岩杂岩中，其特征是铁钛氧化物矿石和钛铁磷灰岩，以不规则倾斜的层状体、透镜体或脉状的形式出现，与斜长岩和辉长岩有尖锐的接触。该矿床以丰富的钛磁铁矿为特征，具有多种钛铁矿溶出结构，包括块状、片状和布状。

研究组探索了钛磁铁矿中钛铁矿溶出物的地球化学和矿物学，以了解其形成机制和对成矿过程的影响。详细的岩相观察和电子探针分析表明，溶出结构是由多种机制引起的：钛磁铁矿氧化引起的氧溶出；磁铁矿和钛铁矿之间的亚固体再平衡，涉及铁、钛、铬、钴和镍的元素扩散；以及与快速冷却引起的晶格缺陷相关的析出。使用吉布斯自由能计算和QUILF程序的热力学建模表明，在氧逸度降低的情况下，在高于和低于固溶体固溶线的温度下形成块状、层状和布状结构的钛铁矿析出体。

此外，研究结果表明，锆石和磷榴石在钛铁矿晶界的析出归因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之间的相互作用。冷却历史的重建表明，氧化物磷灰石辉长岩的氧逸度明显高于Fe-Ti-P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，导致了镍黄铁矿熔体的形成，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