Origin of lavas from the Ninetyeast Ridge, Eastern Indian Ocean: An evaluation of fractional crystallization models

Journal Article · Sun Aug 10 04:00:00 EDT 1980 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB085iB08p04405· OSTI ID:5192121

Ludden, J N; Thompson, G; Bryan, W B; Frey, F A

Ferrobasalts from DSDP sites 214 and 216 on the Ninetyeast Ridge are characterized by high absolute iron (FeO>12.9 wt %), FeO/MgO>1.9, and TiO/sub 2/>2.0 wt %. Their trace element abundances indicate a tholeiitic affinity; however, they are distinct from midocean ridge incompatible element-depleted tholeiites owing to higher contents of Ba, Zr, and Sr and flat to slightly light-REE-enriched, chondrite-normalized REE patterns. Calculations using major and trace element abundances and phase compositions are generally consistent with a model relating most major elements and phase compositions in site 214 and 216 ferrobasalts by fractionation of clinopyroxene and plagio-class. However, some incompatible element abundances for site 216 basalts are not consistent with the fractional crystallization models. Baslats from site 214 can be related to andesitic rocks from the same site by fractionating clinopyroxene, plagioclase and titanomagnetite. Site 254 basalts, at the southern end of the Ninetyeast Ridge, and island tholeiites in the southern Indian Ocean (Amsterdam-St. Paul or Kerguelen-Heard volcanic provinces) possibly represent the most recent activity associated with a hot spot forming the Ninetyeast Ridge. These incompatible-element-enriched tholeiites have major element compositions consistent with those expected for a parental liquid for the site 214 and 216 ferrobasalts. However, differences in the trace element contents of the basalts from the Ninetyeast Ridge sites are not consistent with simple fractional crystallization derivation but require either a complex melting model or a heterogeneous mantle source.

• Research Organization: Department of Chemistry, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
• OSTI ID: 5192121
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 85:B8; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580500* -- Oceanography-- (1980-1989)
BASALT
CHEMISTRY
EARTH CRUST
FRACTIONATION
GEOCHEMISTRY
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
GEOLOGY
IGNEOUS ROCKS
INDIAN OCEAN
LAVA
OCEANIC CRUST
PETROLOGY
PLATE TECTONICS
RIFT ZONES
ROCKS
SEAS
SEPARATION PROCESSES
SURFACE WATERS
TECTONICS
VOLCANIC ROCKS