Knowledge Management System Of Guangzhou Institute of Geochemistry，CAS
| Wang, Mengxi1,2; Zhang, Buqian1; Li, Zhongzhou1; Wang, Jie2,3; Wang, Jiangze2,3 | |
| In situ crystallization of Fe-Ti oxides in the Bijigou layered intrusion: Insights from crystal size distributions and compositions of magnetite and ilmenite | |
| Source Publication | JOURNAL OF ASIAN EARTH SCIENCES
 |
| ISSN | 1367-9120 |
| 2023-10-01 | |
| Volume | 255Pages:17 |
| DOI | 10.1016/j.jseaes.2023.105773 |
| Language | 英语 |
| WOS Research Area | Geology |
| Abstract | The formation of Fe-Ti oxide ore bodies in layered intrusions is attributed to in situ crystallization of basaltic magmas or accumulation after crystal settling regardless of their thicknesses and occurrences in the intrusion. These two key processes are difficult to be distinguished in terms of chemical compositions of minerals or cumulates. However, the crystal size distributions (CSDs) of Fe-Ti oxides in the rocks can be remarkably distinct in these two processes. In this study, we collected samples from a drill core profile across the major Fe-Ti oxide-rich segment of the Bijigou intrusion, a large and differentiated layered intrusion in Central China, and carried out a detailed study on the CSDs and in situ major and trace elements of magnetite and ilmenite to examine how Fe-Ti oxides are accumulated to form Fe-Ti oxide ore bodies in the intrusion. The major Fe-Ti oxide-rich segment of the intrusion consists of, from the base upward, a Fe-Ti oxide ore layer (-80 m), a troctolite unit (-105 m), an oxide gabbro unit (-153 m) and an apatite-oxide gabbronorite unit (-165 m). Large grains of magnetite and ilmenite in the Fe-Ti oxide ore layer show logarithmic-linear CSD curves, similar to those yielded by in situ crystallization of Fe-Ti oxides. The modes of Fe-Ti oxides in the oxide gabbro unit and apatite-oxide gabbronorite unit fluctuate along the profile, which cannot be attributed to accumulation after crystal settling. In addition, the magnetite of the Fe-Ti oxide ore layer, oxide gabbro unit and apatite-oxide gabbronorite unit shows a gentle increase trend of Cr concentration from the base upward in each unit, inconsistent with the trend for an accumulation after crystal settling. The magnetite grains enclosed within silicates have similar compositions to those interstitial to silicates, indicating that they all crystallized from similarly interstitial Fe-rich melt. The in situ crystallization of Fe-Ti oxides is likely triggered by increasing oxygen fugacity due to dissociation of H2O in highly evolved interstitial liquid that was expelled from underlying crystal mush. The crystallization of low-Cr magnetite at the base of each unit is attributed to suppressed eddy currents by dramatic increase of latent heat of crystallization in the magmas at the base. The eddy currents may gradually become efficient toward the top of the magmas due to rapid dissipation of latent heat of crystallization in the magmas, leading to crystallization of high-Cr magnetite by ion diffusion on the top of each unit. This study also demonstrates that analysis of CSDs for Fe-Ti oxides is applicable to examine the accumulation mechanism of Fe-Ti oxide ore bodies in layered intrusions. |
| Keyword | In situ crystallization Oxygen fugacity Chromium concentration Fe-Ti oxides Layered intrusions |
| WOS ID | WOS:001036292600001 |
| Indexed By | SCI |
| Citation statistics | |
| Document Type | 期刊论文 |
| Identifier | http://ir.gig.ac.cn/handle/344008/74569 |
| Collection | 中国科学院矿物学与成矿学重点实验室 |
| Corresponding Author | Wang, Mengxi |
| Affiliation | 1.Changan Univ, Sch Earth Sci & Resources, Xian 710054, Peoples R China 2.Guangzhou Inst Geochem, CAS Key Lab Mineral & Metallogeny, Guangzhou 510640, Peoples R China 3.Univ Chinese Acad Sci, Beijing 100049, Peoples R China |
| Recommended Citation GB/T 7714 | Wang, Mengxi,Zhang, Buqian,Li, Zhongzhou,et al. In situ crystallization of Fe-Ti oxides in the Bijigou layered intrusion: Insights from crystal size distributions and compositions of magnetite and ilmenite[J]. JOURNAL OF ASIAN EARTH SCIENCES,2023,255:17. |
| APA | Wang, Mengxi,Zhang, Buqian,Li, Zhongzhou,Wang, Jie,&Wang, Jiangze.(2023).In situ crystallization of Fe-Ti oxides in the Bijigou layered intrusion: Insights from crystal size distributions and compositions of magnetite and ilmenite.JOURNAL OF ASIAN EARTH SCIENCES,255,17. |
| MLA | Wang, Mengxi,et al."In situ crystallization of Fe-Ti oxides in the Bijigou layered intrusion: Insights from crystal size distributions and compositions of magnetite and ilmenite".JOURNAL OF ASIAN EARTH SCIENCES 255(2023):17. |
| Files in This Item: | There are no files associated with this item. | |||||
Items in the repository are protected by copyright, with all rights reserved, unless otherwise indicated.
Edit Comment