Institutional Repository of Key Laboratory of Mineral Resources, Chinese Academy of Sciences
| Silicate mineral inclusions in chromite from the Eastern Bushveld complex: Implications for the origin and evolution of hydrous melt during chromite mineralization in the Critical Zone | |
| Tang, Dongmei1,2; Qin, Kezhang1,2,3; Fang, Linru1,2,3; Evans, Noreen J.4 | |
| 2023-02-01 | |
| Source Publication | LITHOS
 |
| ISSN | 0024-4937 |
| Volume | 438Pages:16 |
| Abstract | In this work, we systematically describe silicate mineral inclusion morphology and genesis in chromite from UG3, MG2 and LG6 chromitite layers of the Eastern Limb of the Bushveld Complex. Rounded to subhedral in-clusions of phlogopite, amphibole and, to a lesser extent, olivine and orthopyroxene, are concentrated at or near the center of chromite grains. The most common occurrences are tabular amphibole forming planar contact with orthopyroxene, phlogopite, and phlogopite surrounding amphibole and olivine. Several features indicate re-equilibration reactions between the host chromite and the inclusions including high Mg# values in orthopyr-oxene inclusions (81.9 to 88.4; average of 85.0), low MgO (5.16 to 8.15 wt%) and high FeO (28.66 to 32.54 wt%) contents in the host chromite, and higher Cr2O3 content in amphibole (0.32 to 3.60 wt%) and phlogopite (0.29 to 2.29 wt%) inclusions relative to cumulus orthopyroxene, amphibole and phlogopite in the silicate rocks. Furthermore, the high H2O (4.16 to 4.45 wt%) and Na2O (0.07 to 6.12 wt%) contents in phlogopite inclusions, low transition element (V, Ni, Co and Zn) contents in the orthopyroxene from chromitite seams, and the devi-ation from mantle 818O values (5.7 to 6.7 %o) in inclusions, indicates alteration by or reaction with, hydrous melt. In addition, the similar orthopyroxene 818O (5.7-6.8 %o) in the MG2 and LG6 hanging wall and footwall, and in amphibole inclusions (818O = 5.9-6.7 %o) from the LG6, MG2 and UG3 chromitite seams, suggest that the hy-drous melt which formed hydrous mineral inclusions in chromite, and in the hanging wall and footwall silicate minerals, had a similar origin. The high 818O values, LG6 olivine inclusions, and the lower H2O and Li contents in Critical Zone (CZ) orthopyroxene from chromitite compared to orthopyroxene from the overlying and underlying rocks, as well as previous experiments and chemical data, all indicated that a pyroxene remelted hydrous alkali-melt was probably the main source of the trapped melt in chromite. Compatible transition metal element (Ni and Co) contents in orthopyroxene from chromitite seams are lower than those in orthopyroxene from mafic rocks, indicating the former intensely reacted with interstitial liquid. Conversely, there is a low but narrow range in H2O content (8.7 ppm to 28.1 ppm) in orthopyroxene from the CZ chromitite relative to orthopyroxene from norite in the overlying and underlying rocks (3.0 ppm to 46.1 ppm), and a lower Li content in orthopyroxene from chromitite (2.4 ppm to 4.2 ppm) relative to the overlying and underlying norite rocks (2.5 ppm to 8.7 ppm). Coupled low H2O-Li contents in the orthopyroxene from chro-mitite seams and reaction with interstitial liquid suggest that chromite selectively captured hydrous silicate melt during grain formation. Capture of hydrous melt related to remelted pyroxene is a likely mechanism of inclusion formation, and was a common phenomenon in chromite from the Eastern Limb of the Bushveld Complex. |
| Keyword | Chromitite Silicate mineral inclusion H 2 O content Hydrous melt Bushveld |
| DOI | 10.1016/j.lithos.2022.106997 |
| Funding Organization | National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China |
| WOS Keyword | PLATINUM-GROUP ELEMENT ; OXYGEN-ISOTOPE ; QUANTITATIVE-ANALYSIS ; STILLWATER COMPLEX ; TRACE-ELEMENTS ; UG2 CHROMITITE ; ORTHO-PYROXENE ; MERENSKY REEF ; MARGINAL ROCKS ; SOUTH-AFRICA |
| Language | 英语 |
| Funding Project | National Natural Science Foundation of China[42073039] |
| Funding Organization | National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; National Natural Science Foundation of China |
| WOS Research Area | Geochemistry & Geophysics ; Mineralogy |
| WOS Subject | Geochemistry & Geophysics ; Mineralogy |
| WOS ID | WOS:000916026900001 |
| Publisher | ELSEVIER |
| Citation statistics | |
| Document Type | 期刊论文 |
| Identifier | http://ir.iggcas.ac.cn/handle/132A11/106818 |
| Collection | 矿产资源研究院重点实验室 |
| Corresponding Author | Tang, Dongmei |
| Affiliation | 1.Chinese Acad Sci, Inst Geol & Geophys, Key Lab Mineral Resources, Beijing 100029, Peoples R China 2.Chinese Acad Sci, Inst Earth Sci, Beijing 100029, Peoples R China 3.Univ Chinese Acad Sci, Beijing 100049, Peoples R China 4.Curtin Univ, John De Laeter Ctr, Perth, WA 6845, Australia |
| First Author Affilication | Key Laboratory of Mineral Resources, Chinese Academy of Sciences; Institute of Geology and Geophysics, Chinese Academy of Sciences |
| Corresponding Author Affilication | Key Laboratory of Mineral Resources, Chinese Academy of Sciences; Institute of Geology and Geophysics, Chinese Academy of Sciences |
| Recommended Citation GB/T 7714 | Tang, Dongmei,Qin, Kezhang,Fang, Linru,et al. Silicate mineral inclusions in chromite from the Eastern Bushveld complex: Implications for the origin and evolution of hydrous melt during chromite mineralization in the Critical Zone[J]. LITHOS,2023,438:16. |
| APA | Tang, Dongmei,Qin, Kezhang,Fang, Linru,&Evans, Noreen J..(2023).Silicate mineral inclusions in chromite from the Eastern Bushveld complex: Implications for the origin and evolution of hydrous melt during chromite mineralization in the Critical Zone.LITHOS,438,16. |
| MLA | Tang, Dongmei,et al."Silicate mineral inclusions in chromite from the Eastern Bushveld complex: Implications for the origin and evolution of hydrous melt during chromite mineralization in the Critical Zone".LITHOS 438(2023):16. |
| 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