The Chromite Crisis in the Evolution of Continental Magmas and the Initial High delta Mg-26 Reservoir
文献类型：期刊论文
| 作者 | Xiao, Yan1; Yuan, Meng1,7; Su, Ben-Xun6,7; Chen, Chen5; Bai, Yang4; Ke, Shan2; Sun, Yang3; Robinson, Paul T.1 |
| 刊名 | JOURNAL OF PETROLOGY
 |
| 出版日期 | 2023-04-01 |
| 卷号 | 64期号:4页码:18 |
| 关键词 | intra-continental magmatism isotope fractionation chromite segregation fractional crystallization magnesium isotopes |
| ISSN号 | 0022-3530 |
| DOI | 10.1093/petrology/egad019 |
| 英文摘要 | Fractional crystallization of Fe-Ti oxides can induce detectable Mg isotopic changes during late-stage basalt differentiation. Because chromite and olivine are early crystallizing phases during basaltic melt differentiation, the effect of chromite crystallization on the fractionation of Mg isotopes during early-stage basalt differentiation is still poorly understood. Here, we examine the possibility of chromite induced Mg isotope fractionation with a Mg isotopic study of chromite-olivine pairs in dunites and chromitites collected from major types of basaltic intrusive rock suites formed by fractional crystallization in different tectonic settings. The chromite delta Mg-26 (= [(Mg-26/Mg-24)(sample) / (Mg-26/Mg-24)(DSM3)-1] x 1000) values range from -0.19 parts per thousand to 0.30 parts per thousand in the Luobusa ophiolite, -0.09 parts per thousand to 0.78 parts per thousand in the Kizildag ophiolite, -0.04 to 0.42 parts per thousand in the Gaositai Alaskan-type complex, similar to those previously reported from the Stillwater layered intrusion (-0.05 to 0.84 parts per thousand; ). They are significantly higher than those of coexisting olivine (delta Mg-26 = -0.48 to -0.10 parts per thousand). The Delta Mg-26(Chr-Ol) (= delta Mg-26(Chr) - delta Mg-26(Ol)) values in the rock suites investigated here fall largely between equilibrium fractionation lines of spinel-olivine pairs and magnesioferrite-olivine pairs, indicating equilibrium Mg isotopic fractionation. Furthermore, the Delta Mg-26(Chr-Ol) values increase with decreasing Cr content of chromite in the dunites and chromitites, showing that high Mg-26 has a greater affinity to Al-rich chromite than Cr-rich chromite. Fractional crystallization of such isotopically high chromite is expected to progressively lower the Mg isotope values of the in the remaining magma. Furthermore, continental basaltic magmas typically experience early crystallization of olivine and Al-rich chromite. Their delta Mg-26 values correlate positively with MgO (FeO, Cr,) and CaO/Al2O3 ratios and negatively with total alkali contents (Na2O + K2O). This indicates that detectable Mg isotopic fractionation occurred in intra-continental basalt magmas, probably by fractional crystallization of olivine and chromite. The observed low-delta Mg-26 intra-continental basalts can be accurately modeled by olivine + chromite fractionation with fractionation factors (Delta Mg-26(Chr-Melt)) of 0.20 parts per thousand, 0.60 parts per thousand, and 1.18 parts per thousand as observed in the chromitites investigated during this study. Therefore, the early-stage basaltic melt differentiation involving separation of olivine and chromite may induce resolvable Mg isotopic fractionation, and the delta Mg-26 values of continental basalts should be used with caution in petrogenetic studies. |
| WOS研究方向 | Geochemistry & Geophysics |
| 语种 | 英语 |
| WOS记录号 | WOS:001008020400001 |
| 源URL | [http://ir.gig.ac.cn/handle/344008/74404]  |
| 专题 | 中国科学院矿物学与成矿学重点实验室 |
| 通讯作者 | Xiao, Yan |
| 作者单位 | 1.Chinese Acad Sci, Inst Geol & Geophys, State Key Lab Lithospher Evolut, Beijing 100029, Peoples R China 2.China Univ Geosci, State Key Lab Geol Proc & Mineral Resources, Beijing 100083, Peoples R China 3.Southern Univ Sci & Technol, Dept Earth & Space Sci, Shenzhen 518055, Guangdong, Peoples R China 4.Taiyuan Univ Technol, Coll Min Engn, Taiyuan 030024, Peoples R China 5.Chinese Acad Sci, Guangzhou Inst Geochem, Key Lab Mineral & Metallogeny, Guangzhou 510640, Peoples R China 6.Chinese Acad Sci, Inst Geol & Geophys, Key Lab Mineral Resources, Beijing 100029, Peoples R China 7.Univ Chinese Acad Sci, Beijing 100049, Peoples R China |
| 推荐引用方式 GB/T 7714 | Xiao, Yan,Yuan, Meng,Su, Ben-Xun,et al. The Chromite Crisis in the Evolution of Continental Magmas and the Initial High delta Mg-26 Reservoir[J]. JOURNAL OF PETROLOGY,2023,64(4):18. |
| APA | Xiao, Yan.,Yuan, Meng.,Su, Ben-Xun.,Chen, Chen.,Bai, Yang.,...&Robinson, Paul T..(2023).The Chromite Crisis in the Evolution of Continental Magmas and the Initial High delta Mg-26 Reservoir.JOURNAL OF PETROLOGY,64(4),18. |
| MLA | Xiao, Yan,et al."The Chromite Crisis in the Evolution of Continental Magmas and the Initial High delta Mg-26 Reservoir".JOURNAL OF PETROLOGY 64.4(2023):18. |
入库方式： OAI收割
来源：广州地球化学研究所
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