The Estherville mesosiderite: U-Pb, Rb-Sr, and Sm-Nd isotopic study of a polymict breccia
- US Geological Survey, Denver, CO (USA)
A systematic U-Pb, Sm-Nd, and Rb-Sr isotopic study shows that the Estherville mesosiderite was formed between 4.56 and 4.43 Ga. Observed isotopic heterogeneity is in agreement with multiple generations of meteoritic impacts described in other mesosiderites. At least part of the Estherville silicate fraction was formed early in solar system history as indicated by the Pb-Pb (4555 {plus minus} 35 Ma), U-Pb (4560 {plus minus} 31 Ma), Rb-Sr (4542 {plus minus} 203 Ma), and Sm-Nd (4533 {plus minus} 94 Ma) ages. Mesosiderites therefore present not only petrological but also geochronological similarities with eucrites. The Pb isotopic composition of the metal phase plots on the same isochron as the silicates, indicating formation and subsequent mixing with silicates early in the history of the solar system. This is consistent with previous observations indicating that iron was reduced during the silicate-magmatic stage, most likely a consequence of mixing with metal. In addition to these more-ancient portions of the Estherville breccia, other parts were formed later as suggested by the Pb-Pb (4422 {plus minus} 50 Ma) and U-Pb (4437 {plus minus} 11 Ma) ages observed in a second group of leaches and residues. This age is similar to some cumulate eucrite ages and may represent the formation of a second mesosiderite component. The Sm-Nd and the Rb-Sr ages obtained on Estherville show large errors that may be a consequence of the mixing between the 4.56 and 4.43 Ga endmembers. Estherville, like most mesosiderites, was affected by a major heating event around 3.5-3.7 Ga as shown by the Ar-Ar ages. This heating event partially disturbed the Rb-Sr isotopic system (Rb-Sr metamorphic ages range between 3.81 and 4.08 Ga).
- OSTI ID:
- 5542540
- Journal Information:
- Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 55:4; ISSN GCACA; ISSN 0016-7037
- Country of Publication:
- United States
- Language:
- English
Similar Records
Determination of radiogenic isotopes (Rb/Sr, Sm/Nd and Pb/Pb) in fluid inclusion waters: An example from the Bluebell Pb-Zn deposit, British Columbia, Canada
A combined Sm-Nd, Rb-Sr, and U-Pb isotopic study of Mg-suite norite 78238: Further evidence for early differentiation of the Moon
Related Subjects
580000* -- Geosciences
ACTINIDE ISOTOPES
AGE ESTIMATION
ALKALI METAL ISOTOPES
ALKALINE EARTH ISOTOPES
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHEMISTRY
CHONDRITES
GEOCHEMISTRY
GEOLOGIC HISTORY
GEOLOGY
IRON CARBONATES
IRON COMPOUNDS
IRON ORES
ISOTOPE DATING
ISOTOPE RATIO
ISOTOPES
LEAD ISOTOPES
MAGMATISM
METAMORPHISM
METEORITES
MINERALS
NEODYMIUM ISOTOPES
ORES
OXYGEN COMPOUNDS
PETROGENESIS
PETROLOGY
RARE EARTH ISOTOPES
RUBIDIUM ISOTOPES
SAMARIUM ISOTOPES
SIDERITE
STONE METEORITES
STRONTIUM ISOTOPES
TRANSITION ELEMENT COMPOUNDS
URANIUM ISOTOPES