| Abstract: | The CB chondrites are metal‐rich meteorites with characteristics that sharply distinguish them from other chondrite groups. Their unusual chemical and petrologic features and a young formation age of bulk chondrules dated from the CBa chondrite Gujba are interpreted to reflect a single‐stage impact origin. Here, we report high‐precision internal isochrons for four individual chondrules of the Gujba chondrite to probe the formation history of CB chondrites and evaluate the concordancy of relevant short‐lived radionuclide chronometers. All four chondrules define a brief formation interval with a weighted mean age of 4562.49 ± 0.21 Myr, consistent with its origin from the vapor‐melt impact plume generated by colliding planetesimals. Formation in a debris disk mostly devoid of nebular gas and dust sets an upper limit for the solar protoplanetary disk lifetime at 4.8 ± 0.3 Myr. Finally, given the well‐behaved Pb‐Pb systematics of all four chondrules, a precise formation age and the concordancy of the Mn‐Cr, Hf‐W, and I‐Xe short‐lived radionuclide relative chronometers, we propose that Gujba may serve as a suitable time anchor for these systems. |
