Manganese-Chromium Isotope Systematics of Ivuna, Kainsaz and Other Carbonaceous Chondrites

We have shown earlier that the bulk samples of carbonaceous chondrites [CC] reveal excesses in both Cr-53 (Cr-53*) and Cr-54 (Cr-54*) as compared to the terrestrial standard value. The Cr-53/52 ratios in bulk samples of Orgueil (CI), Murray (CM), Allende (CV), and the Bencubbin/CH-like meteorite Hammadah Al Hambra 237 (HH237) are correlated with the respective Mn/Cr ratios. In contrast to CC, HH237 is characterized by a deficit of Cr-53 (-0.15 +/- 0.10(epsilon)) at a low Mn/Cr ratio of 0.07. The HH237 data point, however, falls on the CC line. Here we report new Mn-53 - Cr-53 results for the CC Kainsaz (CO) and Ivuna (CI).