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Curtis, D. B.

Publications and source records attributed to Curtis, D. B..

6 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Boron cosmochemistry

The abundances of boron, silicon, sulfur, and sodium were determined in 50 pieces of 28 chondritic meteorites. Boron abundances are found to define compositionally distinct domains within type C2M carbonaceous chondrites and petrologic type 5 and 6 ordinary chondrites. These domains may manifest the redistribution of boron within meteorites in response to low-temperature hydrous processes in C2M chondrites and high-temperature metamorphic processes in high petrologic type ordinary chondrites. Assuming that the redistribution was limited to regions comparable in size to the mass of the available meteorites, the boron abundance in unaltered material is determined. The depletion factors for boron in chondritic subgroups correlate with those for sulfur in the same subgroups. This correlation indicates that boron, like sulfur, is a moderately volatile element with a condensation temperature between 400 and 900 K.

Curtis, D. B.↗
NASA NTRS1984

Boron cosmochemistry

The assumption that boron is a moderately volatile element is examined. It was demonstrated that interior pieces of chondrites contain significantly less boron than had been thought to be indigenous to this type of meteorite. The mean and range of boron abundances in 16 internal pieces of 10 chondrites were significantly smaller than in 126 pieces of 40 chondrites with unknown terrestrial histories. A new value of the cosmic abundance of boron was determined using the geometric average of the results from interior pieces of 10 chondrites. Based upon the thermodynamic assessment of the cosmochemical properties of boron by Cameron, et al. Anders and Ebihara assumed that boron was a moderately volatile element. They renormalized the data of Curtis et al. to a chondrule free basis and thus inferred that the cosmic abundance of boron was about 3 times greater than that proposed by Curtis, et al. To resolve these differences in data, the relative abundances of several elements including boron were measured in 38 carefully prepared interior pieces of 26 different chondrites. Correlation between boron and sulfur abundances, indicate that, contrary to the conclusions of Cameron, et al., boron is not a moderately volatile element.

Curtis, D. B.↗
NASA NTRS1979

The petrogenesis of L-6 chondrites - Insights from the chemistry of minerals

Measurements of the major, minor and trace element abundances of the major minerals of the L-6 chondrites Alfianello, Colby (WI) and Leedey are used to investigate the formation mechanisms of L-6 chondrites. Electron microprobe analysis was performed on individual grains of each mineral, and separated minerals were analyzed by instrumental and radiochemical neutron activation analysis. The compositions of the three meteorites are observed to be generally uniform, however different abundances and distributions of rare earth elements and Co and Ni indicate that the meteorites have different petrogenetic histories. Alkali element distributions are found to be incompatible with internal equilibration of a closed system.

Curtis, D. B.↗
NASA NTRS1975

Apollo 17 neutron stratigraphy - Sedimentation and mixing in the lunar regolith

A report is presented concerning the Gd isotopic ratios in ten samples, representing nearly the entire depth of the drill stem which was recovered during the Apollo 17 mission. The lunar neutron energy spectrum is discussed along with questions regarding neutron fluence and neutron flux. The significance of the Apollo 17 deep drill stem is considered and attention is given to the statistical nature of the fluence in the lunar regolith. Vertical mixing models are also described.

Curtis, D. B.↗