Melt inclusions in olivine and plagioclase phenocrysts from Antarctic-Phoenix Ridge basalts: Implications for origins of N- and E-type MORB parent magmas

• Published in: Journal of Volcanology and Geothermal Research
• Main Authors: Hi Choi, Sung, Schiano, Pierre, Chen, Yang, Devidal, Jean-Luc, Kyung Choo, Mi, Lee, Jong-Ik
• Other Authors: Department of Geology and Earth Environmental Sciences Daejeon, Chungnam National University (CNU), Laboratoire Magmas et Volcans (LMV), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Department of Science Education, EWHA Womans University (EWHA), Korea Polar Research Institute (KOPRI)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2013
• Subjects: Melt inclusion; Olivine phenocryst; Plagioclase phenocryst; N-MORB; E-MORB; Antarctic-Phoenix ridge; [SDU.STU.PE]Sciences of the Universe [physics]/Earth Sciences/Petrography; Antarctic; Antarctic Ocean; Drake Passage; The Antarctic; Antarc*
• Online Access: https://hal.science/hal-00996552; https://doi.org/10.1016/j.jvolgeores.2012.12.008

International audience The Antarctic-Phoenix Ridge (APR) is a fossil spreading center in the Drake Passage, Antarctic Ocean. Spreading ceased in chron C2A (ca. 3.3 Ma). Although the APR is a normal ridge that is not influenced by a hotspot, enriched (E-type) mid-ocean ridge basalt (MORB) coexists with normal (N-type) MORB in the ridge's axial region. The E-type APR basalt is relatively young (< 3.1 Ma) compared to the N-type basalt (> 3.5 Ma). The E-type basalt is characterized by elevated K2O/TiO2 (= 0.4-0.8) and (La/Sm)N (= 2.2-3.4) ratios, relative to the N-type basalt (K2O/TiO2 = 0.1-0.3; (La/Sm)N = 0.7-0.8). To better understand the compositional variation in the APR basalts and their mantle source regions through time, silicate melt inclusions in primitive olivine (Fo87-89) and plagioclase (An85-89) phenocrysts from the N-type APR basalt were studied. Rehomogenized melt inclusions were analyzed by electron microprobe and LA-ICPMS for major and trace elements. The melt inclusions are more primitive than the host basalt, with Mg#s from 67.5 to 74.1. All inclusions exhibit patterns that are depleted in the light rare earth elements. The inclusions have K2O/TiO2 from 0.1 to 0.3 and (La/Sm)N ratios from 0.4 to 0.9; these values overlap with those of the N-type APR basalt. Furthermore, the melt inclusions have elevated (Lu/Hf)N and (Sm/Nd)N ratios compared to the E-type basalts. The N-type APR basalts do not contain any melt inclusions that are enriched in incompatible elements. The E-type basalt was generated by a low degree of partial melting of a relatively incompatible-element-enriched mantle source. In contrast, chemistries of melt inclusions and N-type basalts are compatible with high degrees of partial melting of an increasingly depleted mantle source. Assuming a veined or otherwise heterogeneous mantle, the absence of E-type inclusions from the N-type host has implications for cyclic magmatic activity beneath the APR. Multi-stage mantle melting and melt extraction from a composite source with ...