Low-temperature alteration of submarine basalts from the Ontong Java Plateau

Author(s): Banerjee, Neil R.; Honnorez, José; Muehlenbachs, Karlis
Author Affiliation(s): Primary:
University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada
Other:
University of Hawaii, United States
University of Oregon, United States
University of Leicester, United Kingdom
Université Louis Pasteur, France
Volume Title: Origin and evolution of the Ontong Java Plateau
Volume Author(s): Fitton, J. Godfrey, editor; Mahoney, John J.; Wallace, Paul J.; Saunders, Andrew D.
Source: Origin and evolution of the Ontong Java Plateau, edited by J. Godfrey Fitton, John J. Mahoney, Paul J. Wallace and Andrew D. Saunders. Geological Society Special Publications, Vol.229, p.259-273. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0305-8719. ISBN: 1-86239-157-2 CODEN: GSLSBW
Note: In English. 23 refs.; illus.
Summary: We present a detailed mineralogical and petrological description of the low-temperature alteration patterns in basalts from four new sites drilled during ODP Leg 192 on the Early Cretaceous Ontong Java Plateau. Three main alteration types have been identified: pervasively altered dark grey basalt; black or dusky green halos; and brown halos. Dark grey basalts are the most common and represent the least intensive, but most pervasive, alteration phase. Early interaction of the basalt with low-temperature sea-water-derived hydrothermal fluids lead to the development of black and dusky green halos characterized by the replacement of groundmass and olivine phenocrysts by celadonitic phyllosilicates and smectite. Later interaction of basalts with cold oxidizing sea water produced brown halos characterized by replacement of primary phases and mesostasis by smectite and iron oxyhydroxides. Secondary minerals in order of decreasing abundance include phyllosilicates, calcite, iron oxyhydroxides, pyrite, chalcedony, quartz and zeolites. Veins, resulting from symmetrical infilling of open cracks, commonly contain phyllosilicates, iron oxyhydroxide or pyrite, and late calcite. Carbonate veins cross-cut all other alteration features and stable isotope analyses of vein carbonates indicate formation from marine bicarbonate below about 40°C. A positive correlation between vein density and overall degree of alteration is observed resulting in pervasive development of brown alteration halos in highly fractured rocks. Overall, alteration of basalts from the Ontong Java Plateau is similar to that observed from other DSDP/ODP sites throughout the oceans.
Year of Publication: 2004
Research Program: ODP Ocean Drilling Program
Key Words: 05 Petrology, Igneous and Metamorphic; 18 Geophysics, Solid-Earth; Alteration; Basalts; C-13/C-12; Carbon; Crust; Geochemistry; Igneous rocks; Isotope ratios; Isotopes; Leg 130; Leg 192; Low temperature; Nesosilicates; O-18/O-16; ODP Site 1183; ODP Site 1185; ODP Site 1186; ODP Site 1187; ODP Site 807; Ocean Drilling Program; Oceanic crust; Olivine; Olivine group; Ontong Java Plateau; Orthosilicates; Oxygen; Pacific Ocean; Petrography; Sampling; Sea-floor spreading; Secondary minerals; Silicates; Stable isotopes; Temperature; Veins; Volcanic rocks; West Pacific
Coordinates: S050000 N050000 E1650000 E1550000
N033622 N033626 E1563730 E1563728
N005600 N005600 E1612700 E1612700
S004100 S004100 E1595100 E1595100
Record ID: 2006012381
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