Subsolidus equilibria between pyroxenes in the CaO--MgO--SiO/sub 2/ system at high pressures and temperatures

Journal Article · Thu Jan 01 04:00:00 EST 1976 · Am. Mineral.; (United States)

OSTI ID:6771618

Mori, T; Green, D H

The extent of pyroxene solid solutions was experimentally determined in the CaO--MgO--SiO/sub 2/ system at 30 kbar and 1500/sup 0/C. The results show the enstatite and diopside mutual solid solutions and also define the limited solid solutions towards olivine and quartz. Although the enstatite--diopside solvus is wider when olivine rather than quartz is a coexisting phase, the difference does not seriously affect the pyroxene solvus as a geothermometer. Thus, this geothermometer can be used without taking the coexisting phases other than pyroxenes into account. The study of the enstatite--diopside solvus in the Mg/sub 2/Si/sub 2/O/sub 6/--CaMgSi/sub 2/O/sub 6/ system was extended above 1500/sup 0/C at 20 and 30 kbar. These pyroxenes show almost complete solid solution at solidus temperatures. The iron-free pigeonite--diopside solvus which was previously found at 20 kbar and inferred to be stable at 30 kbar did not appear at these pressures. The phase equilibrium data in this paper are combined with those in the literature to make a compilation of the enstatite--diopside solvus over a wide temperature-pressure range. Some difficulties in use of the pyroxene solvus geothermometer are discussed, taking the garnet lherzolite nodules from Lesotho kimberlites as examples.

• Research Organization: Australian National Univ., Canberra
• OSTI ID: 6771618
• Journal Information: Am. Mineral.; (United States), Journal Name: Am. Mineral.; (United States) Vol. 61:7/8; ISSN AMMIA
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
152004* -- Geothermal Data & Theory-- Isotope & Trace Element Studies
ALKALINE EARTH METAL COMPOUNDS
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
DIAGRAMS
DIOPSIDE
DISPERSIONS
ENSTATITE
EQUILIBRIUM
GEOTHERMOMETRY
HIGH TEMPERATURE
IRON COMPOUNDS
IRON SILICATES
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MAGNESIUM SILICATES
MINERALS
MIXTURES
OLIVINES
OXIDES
OXYGEN COMPOUNDS
PHASE DIAGRAMS
PHASE STUDIES
PYROXENES
QUARTZ
SILICA
SILICATES
SILICON COMPOUNDS
SILICON OXIDES
SOLID SOLUTIONS
SOLUTIONS
TRANSITION ELEMENT COMPOUNDS
VERY HIGH PRESSURE