| Li Jie,Zhu Jihao,Chu Fengyou,Li Xiaohu,Zhu Zhimin,Wang Hao. 2020. Chemical composition and petrogenesis of plagioclases in plagioclase-phyric basalts from the Southwest Indian Ridge (51°E). Acta Oceanologica Sinica, 39(7):42－49 |
| Chemical composition and petrogenesis of plagioclases in plagioclase-phyric basalts from the Southwest Indian Ridge (51°E) |
| 西南印度洋中脊（51°E）斜斑玄武岩中斜长石的成分特征及其指示意义 |
| Received:December 15, 2019 |
| DOI：10.1007/s13131-020-1613-1 |
| Key words:plagioclase-phyric basalt plagioclase phenocrysts magmatic evolution SWIR |
| 中文关键词: 斜斑玄武岩 斜长石斑晶 岩浆演化 西南印度洋洋中脊 |
| 基金项目:The National Natural Science Foundation of China under contract Nos 41606041 and 41903046; the Scientific Research Fund of the Second Institute of Oceanography, MNR under contract Nos JG1604 and JT1504; China Ocean Mineral R&D Association (COMRA) Project under contract Nos DY135-G2-1-03 and DY135-N2-1-04. |
| Author Name | Affiliation | E-mail | | Li Jie | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | lijie@sio.org.cn | | Zhu Jihao | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | | | Chu Fengyou | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | | | Li Xiaohu | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | | | Zhu Zhimin | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | | | Wang Hao | Key Laboratory of Submarine Geosciences, Ministry of Natural Resources, Hangzhou 310012, China
Second Institute of Oceanography, Ministry of Natural Resources, Hangzhou 310012, China | |
|
| Hits: 1062 |
| Download times: 774 |
| Abstract: |
| Electron microprobe analysis was conducted on plagioclase from the plagioclase ultraphyric basalts (PUBs) erupted on the Southwest Indian Ridge (SWIR) (51°E) to investigate the geochemical changes in order to better understand the magmatic processes occurring under ultraslow spreading ridges and to provide insights into the thermal and dynamic regimes of the magmatic reservoirs and conduit systems. The phenocryst cores are generally calcic (An74-82) and are depleted in FeO and MgO. Whereas the phenocryst rims (An67-71) and the plagioclase in the groundmass (An58-63) are more sodic and have higher FeO and MgO contents than the phenocryst cores. The crystallization temperatures of the phenocryst cores and the calculation of the equilibrium between the phenocrysts and the matrix suggest that the plagioclase cores are unlikely to have crystallized from the host basaltic melt, but are likely to have crystallized from a more calcic melt. The enrichment in incompatible elements (FeO and MgO), as well as the higher FeO/MgO ratios of the outermost phenocryst rims and the groundmass, are the result of plagioclase-melt disequilibrium diffusion during the short residence time in which the plagioclase crystallized. Our results indicate that an evolved melt replenishing under the SWIR (51°E) drives the eruption over a short period of time. |
| 中文摘要: |
| 本文利用电子探针对来自西南印度洋洋中脊（51°E）的斜斑玄武岩（PUB）中斜长石开展了微区成分分析，通过斜长石化学成分变化研究了超慢速扩张洋中脊下的岩浆演化过程，进而为探讨岩浆在源区和运移通道中热力学及动力学变化提供制约。结果表明，样品中斜长石斑晶核部通常具有富钙（An74-82）贫FeO、MgO的特征，而边部(An67-71)和基质(An58-63)中的斜长石一般更富钠,且具有更高的FeO和MgO含量。斜长石地质温度计计算结果显示，斜长石斑晶核部具有较高的结晶温度（1273℃），结合斜长石斑晶核部与熔体间Ca/Na比值不平衡的特征，说明PUB中斜长石斑晶核部可能不是从寄主玄武质岩浆中结晶出来，而更可能来源于更为富钙的岩浆。斜长石斑晶边部及基质中斜长石富集不相容元素FeO和MgO，并具有更高的FeO/MgO比值，可能是由于这些斜长石在结晶过程中岩浆驻留时间较短所致。我们的研究结果表明演化程度相对较高的岩浆与先存岩浆混合可能是导致西南印度洋洋中脊（51°E）岩浆突然喷发的重要原因。 |
|
HTML
View Full Text
View/Add Comment Download reader |
| Close |
|
|
|
