Ureilites: trace element clues to their origin

Journal Article · Tue Sep 01 04:00:00 EDT 1987 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(87)90280-8· OSTI ID:5128083

Janssens, M J; Hertogen, J; Wolf, R; Ebihara, M; Anders, E

Carbonaceous vein separates from Kenna and Haveroe, as well as bulk Kenna, were analyzed by RNAA for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Pd, Os, Rb, Re, Sb, Se, Te, Tl, U, and Zn. The data are reviewed together with four earlier Chicago analyses of bulk ureiltes. Linear regressions confirm the presence of two metal components, with the following Cl-normalized ratios: Ir/Ni = 14.6, less than or equal to 1; Ge/Ni = 5.4, 2.4; Au/Ni = 2.3, 0.9. The high-Ir component is enriched in vein separates and hence belongs to veins; the low-Ir component belongs to the ultramafic rock. Vein material is enriched in all elements analyzed by us except Zn, and accounts for most of the C, noble gases, and presumably siderophiles in the meteorite. Most of the properties of ureilites apparently can be explained by the cumulate model of Berkley et al. (1980), with certain modifications. Comparison of ureilites with three other ultramafic rocks from different planets suggest that the ureilite parent body had a primitive chondritic composition, similar to C3V chondrites but richer in metal and carbon. It melted, causing depletion of incompatibles to a mean abundance of approx. 0.02X Cl and incomplete segregation of metal, FeS, and C. Fractional crystallization or melting of metal in the presence of S and C apparently can explain the fractionations of Ir, Re, Ni, Au, and perhaps Ge, obviating the need for extraneous sources of vein metal or unusual parent-body compositions. Noble gases from the parent material may have been retrapped in carbon during magmatism, provided the system was closed.

• Research Organization: Univ. of Chicago, IL (USA)
• OSTI ID: 5128083
• Journal Information: Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 51:9; ISSN GCACA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
ACHONDRITES
ALKALINE EARTH METAL COMPOUNDS
CARBON
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
CHEMISTRY
COSMOLOGICAL MODELS
ELEMENTS
GEOCHEMISTRY
GERMANIUM
GOLD
IGNEOUS ROCKS
IRIDIUM
IRON COMPOUNDS
IRON SILICATES
IRON SULFIDES
MAGMA
MAGMATISM
MAGNESIUM COMPOUNDS
MAGNESIUM SILICATES
MATHEMATICAL MODELS
METALS
METEORITES
MINERALOGY
MINERALS
NICKEL
NONMETALS
OLIVINE
ORIGIN
OXYGEN COMPOUNDS
PETROGENESIS
PLATINUM METALS
PYROXENES
QUANTITY RATIO
RHENIUM
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
STONE METEORITES
SULFIDES
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS