Study of Rb-Sr and Sm-Nd Isotopic Systems in Chondrules of the Sierra Gorda 009 and 013 Chondrites and Possible Mechanisms of Their Disturbance

M. A. Ivanova, A. V. Somsikova, C. A. Lorenz & Yu. A. Kostitsyn

Geochemistry International
Published: 24 April 2023


“We conducted a first investigation of the Rb-Sr and Sm-Nd isotopic systems of chondrules from rare metal-rich chondrites: the G chondrite Sierra Gorda 009 (SG 009) and the CBa-like chondrite Sierra Gorda 013 (SG 013). Isotopic data were obtained by isotopic dilution methods using multi-collector TIMS spectrometer. Chondrules from both meteorites have low and variable Rb/Sr and Sm/Nd ratios relative to CI. The isotopic data do not produce obvious isochrons due to the heterogeneity of isotopic composition of the chondrule precursors and disturbance of the Rb-Sr and Sm-Nd isotopic systems in chondrules of both meteorites due to inheritance of isotopic heterogeneity in the colliding bodies (chondritic and differentiated) in high-temperature impact plume processes. Shock events and metamorphism after accretion of the SG 013 parent bodies did not result in homogenization of strontium and neodymium isotopes. In general, our data indicate that the Rb-Sr and Sm-Nd isotopic systems probably are not reliable enough to use them for dating of chondrules from the unique chondrites such as SG 009 and SG 013.”