Mineral compositions of MORB from the Australian Antarctic discordance (AAD); implications for mantle source characteristics

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doi: 10.2973/odp.proc.sr.187.202.2004
Author(s): Sato, Hiroshi
Ocean Drilling Program, Leg 187, Shipboard Scientific Party, College Station, TX
Author Affiliation(s): Primary:
University of Tokyo, Ocean Research Institute, Tokyo, Japan
Other:
Oregon State University, United States
Ocean Drilling Program, United States
Laboratoire de Mesures en Forage, France
University of London, United Kingdom
Christian-Albrechts-Universität zu Kiel, Federal Republic of Germany
Isotope Geosciences Laboratory, United Kingdom
Academia Sinica, Taiwan
University of Bergen, Norway
Centre de Recherches Pétrographiques et Géochimiques, France
University of Tokyo, Japan
Volume Title: Proceedings of the Ocean Drilling Program; scientific results; mantle reservoirs and migration associated with Australian Antarctic rifting; covering Leg 187 of the cruises of the drilling vessel JOIDES Resolution; Fremantle, Australia, to Fremantle, Australia, Sites 1152-1164; 16 November 1999-10 January 2000
Volume Author(s): Pedersen, Rolf B.; Christie, David M.; Miller, D. Jay; Balzer, Vaughn G.; Einaudi, Florence; Gee, M. A. Mary; Hauff, Folkmar; Kempton, Pamela D.; Liang, Wen-Tzong; Lysnes, Kristine; Meyzen, Christine M.; Pyle, Douglas G.; Russo, Christopher J.; Sato, Hiroshi; Thorseth, Ingunn H.
Source: Proceedings of the Ocean Drilling Program; scientific results; mantle reservoirs and migration associated with Australian Antarctic rifting; covering Leg 187 of the cruises of the drilling vessel JOIDES Resolution; Fremantle, Australia, to Fremantle, Australia, Sites 1152-1164; 16 November 1999-10 January 2000, Rolf B. Pedersen, David M. Christie, D. Jay Miller, Vaughn G. Balzer, Florence Einaudi, M. A. Mary Gee, Folkmar Hauff, Pamela D. Kempton, Wen-Tzong Liang, Kristine Lysnes, Christine M. Meyzen, Douglas G. Pyle, Christopher J. Russo, Hiroshi Sato and Ingunn H. Thorseth; Ocean Drilling Program, Leg 187, Shipboard Scientific Party, College Station, TX. Proceedings of the Ocean Drilling Program, Scientific Results (CD ROM), Vol.187, 26p. Publisher: Texas A&M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 1096-2514
Note: In English. Available only on CD-ROM in PDF format and on the Web in PDF or HTML. 26 refs.CD-ROM format, ISSN 1096-2514; WWW format, ISSN 1096-7451; illus., incl. 3 tables, geol. sketch maps
Summary: The chemical compositions of olivine, plagioclase, pyroxene, and spinel in lavas collected during Ocean Drilling Program Leg 187 in the Australian Antarctic Discordance, Southeast Indian Ridge (41°-46°S, 126°-135°E) were analyzed, and modeling of the theoretical equilibrium petrogenetic conditions between olivine and melt was conducted. The cores of larger olivine phenocrysts, particularly in the isotopic Indian-type mid-ocean-ridge basalt (MORB), are not equilibrated with melt compositions and are considered to be xenocrystic. Larger plagioclase phenocrysts with compositionally reversed zonation are also xenocrystic. The compositions of primary magma were calculated using a "maximum olivine fractionation" model for primitive MORB that should fractionate only olivine. Olivine compositions equilibrated with calculated primary magma and compositions of calculated primary magma suggest that (1) isotopic Pacific-type MORB is more fractionated than Indian-type MORB, (2) Pacific-type MORB was produced by higher degrees of partial melting than Indian-type MORB, and (3) primary magma for Indian-type MORB was segregated from mantle at 10 kbar (∼30 km depth), whereas that for Pacific-type MORB was segregated at 15 kbar (∼45 km depth).
Year of Publication: 2004
Research Program: ODP Ocean Drilling Program
Key Words: 05 Petrology, Igneous and Metamorphic; Australian-Antarctic discordance; Basalts; Chain silicates; Feldspar group; Framework silicates; Genesis; Geochemistry; Igneous rocks; Indian Ocean; Leg 187; Magmas; Mantle; Mid-Indian Ridge; Mid-ocean ridge basalts; Mineral composition; Nesosilicates; Ocean Drilling Program; Olivine; Olivine group; Orthosilicates; Partial melting; Phenocrysts; Plagioclase; Pyroxene group; Silicates; Southeast Indian Ridge; Volcanic rocks; Whole rock; Xenocrysts
Coordinates: S460000 S411500 E1350000 E1260000
Record ID: 2005011566
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