Chemical composition and petrogenesis of plagioclases in plagioclase-phyric basalts from the Southwest Indian Ridge(51°E)  

作　　者：Jie Li Jihao Zhu Fengyou Chu Xiaohu Li Zhimin Zhu Hao Wang 

机构地区：[1]Key Laboratory of Submarine Geosciences,Ministry of Natural Resources,Hangzhou 310012,China [2]Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310012,China

出　　处：《Acta Oceanologica Sinica》2020年第7期42-49,共8页海洋学报（英文版）

基　　金：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。

摘　　要：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.

关 键 词：plagioclase–phyric basalt plagioclase phenocrysts magmatic evolution SWIR 

分 类 号：P581[天文地球—岩石学] P575[天文地球—地质学]