40Ar/39Ar ages of Northwest Africa 7034 and Northwest Africa 7533

The Martian breccias NWA 7034, NWA 7533, and paired meteorites record events ranging in age from 4.47 Ga to <200 Ma. Published ages indicate a period of major disturbance at similar to 1.4 Ga, examined in detail here through Ar-40/Ar-39 dating of handpicked grains and two small chips. Argon diffusion parameters were obtained for six samples. Also presented are He, Ne, Ar, Kr, and Xe contents of two small (<100 mu g), handpicked mineral separates, a felsic "Light" sample and a mafic/pyroxene-rich "Dark" sample. The Ar-40/Ar-39 ages of five samples, four containing >1 wt% K and thought to be rich in feldspar and one containing 更多