The Rb‐Sr isotopic data for mineral separates from a rock of the Manicouagan impact melt sheet define an isochron of age T = 214 ± 5 (2σ) m.y. and an initial Sr 87 /sr 86 ratio I = 0.70991 ± 0.00007 (2σ). This age is in excellent agreement with the K‐Ar age of 210 ± 8 (2σ) m.y. of Wolfe [1971] and represents the time of crystallization of the melt sheet. Four whole rock samples yield age‐corrected I values ranging from 0.70965 to 0.71006. These high I values are consistent with geological and geochemical arguments that the melt sheet was derived by total melting of Grenville basement rocks during the impact event 214 m.y. ago.
No takes yet. Share an insight, caveat, or question.
Jahn et al. (1978) studied this question.
Synapse has enriched 2 closely related papers on similar clinical questions. Consider them for comparative context: