Solidus of carbonated fertile peridotite under fluid-saturated conditions
- Univ. of Tasmania, Hobart (Australia)
The solidus for a fertile peridotite composition (Hawaiian pyrolite) in the presence of a CO{sub 2}-H{sub 2}O fluid phase has been determined from 10 to 35 kbar. The intersection of the decarbonation reaction (olivine + diopside + CO{sub 2} {l reversible} orthopyroxene + dolomite) with the pyrolite solidus defines the point Q{prime}, located at 22 kbar and 940 C. At pressures less than Q{prime}, the solidus passes through a temperature maximum at kbar, 1060 C. The solidus is coincident with amphibole breakdown at pressures less than 16 kbar. At pressures above Q{prime}, the solidus is defined by the dissolution of crystalline carbonate into a sodic, dolomitic carbonatite melt. The solidus is at a temperature of 925 C at {approximately} 28 kbar. The solidus temperature above the point Q{prime} is similar to the solidus determined for Hawaiian pyrolite-H{sub 2}O-CO{sub 2} for small contents of H{sub 2}O (<0.3 wt%) and CO{sub 2} (<5 wt%), thus indicating that the primary sodic dolomitic carbonatite melt at both solidi has a very low and limited H{sub 2}O solubility. The new data clarify the roles of carbonatite melt, carbonated silicate melt, and H{sub 2}O-rich fluid in mantle conditions that are relatively oxidized (f{sub O{sub 2}} {approximately} MW to FMQ). In particular, a carbonatite melt + garnet lherzolite region is intersected by continental shield geothermal gradients, but such geotherms only intersect regions with carbonated silicate melt if perturbed to higher temperatures (kinked geotherm).
- OSTI ID:
- 6140657
- Journal Information:
- Geology; (USA), Journal Name: Geology; (USA) Vol. 18:3; ISSN GLGYB; ISSN 0091-7613
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580000* -- Geosciences
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBONATE MINERALS
CARBONATE ROCKS
CARBONATES
CHALCOGENIDES
DIAGRAMS
DIOPSIDE
DISSOLUTION
DOLOMITE
EARTH MANTLE
ELEMENTS
FLUIDS
GEOTHERMAL GRADIENTS
HYDROGEN COMPOUNDS
IGNEOUS ROCKS
IRON COMPOUNDS
IRON SILICATES
MAGNESIUM CARBONATES
MAGNESIUM COMPOUNDS
MAGNESIUM SILICATES
MELTING
MINERALS
NONMETALS
OLIVINE
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PERIDOTITES
PHASE DIAGRAMS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
PLUTONIC ROCKS
PYROXENES
RESERVOIR FLUIDS
ROCKS
SEDIMENTARY ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
SOLUBILITY
TEMPERATURE GRADIENTS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
VAPOR PRESSURE
VERY HIGH PRESSURE
VERY HIGH TEMPERATURE
WATER