Engineering topics

Brett, Robin

Publications and source records attributed to Brett, Robin.

3 records

NASA NTRS1988

Oxidation state in chondrites

An evaluation is made of extant data on chondrite oxidation states and intrinsic O fugacities. A variety of oxidation states are exhibited by the chondritic meteorites; petrologic and chemical data may be used to arrange the major chondrite groups in order of oxidation state. The intrinsic O fugacity measurements on chondrite whole-rock samples are noted to display a corresponding ordering of oxidation states. Metamorphosed chondrites and igneous meteorites that were substantially altered by metamorphic reactions, outgassing, and igneous processes may preserve information on the oxidation state and size of their parent bodies.

Rubin, Alan E.↗

NASA NTRS1987

Mineralogical studies of sulfide samples and volatile concentrations of basalt glasses from the southern Juan de Fuca Ridge

Sulfide samples obtained from Alvin dives on the southern Juan de Fuca Ridge were examined, showing the presence of two previously undiscovered minerals, both formed at low temperatures. The first detection of lizardite, starkeyite, and anatase in such an environment is also reported. Sulfide geothermometry involving the Cu-Fe-S system shows a vent temperature of less than 328 C for one sample. Ice-melting temperatures on inclusions from this sample are about -2.8 C, and fluid inclusion studies on crystals near this sample show pressure-corrected homogenization temperatures of 268 and 285 C. Volatile concentrations from vesicle-free basalt glass from the vent field are found to be about 0.0013 wt pct CO2 and 0.16 wt pct H2O.

Brett, Robin↗

NASA NTRS1986

Enstatite chondrites and enstatite achondrites (aubrites) were not derived from the same parent body

Enstatite achondrites (aubrites) were not derived from known enstatite chondrites by melting and fractionation on one and the same parent body, for these and other reasons: (1) There is no satisfactory mechanism for fractionating metal plus troilite in enstatite chondrites to form these phases in different proportions and with different Ti contents in aubrites. (2) Many enstatite chondrites and aubrites are regolith or fragmental breccias, but clasts of one within the other have not been found. (3) Cosmic ray exposure ages of the two groups are difficult to explain if they are from the same parent body, but are easy to explain if they are from different parent bodies. Siderophile element abundances in metal from the Mt. Egerton meteorite, which consists of enstatite and metallic Fe, Ni, preclude it from being a complementary differentiate of the aubrites. Rather, it appears that Mt. Egerton was formed from the same source material as enstatite chondrites, but the components were mixed in different proportions.

Brett, Robin↗