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Fig. 5 | Earth, Planets and Space

Fig. 5

From: 40Ar/39Ar and cosmic ray exposure ages of plagioclase-rich lithic fragments from Apollo 17 regolith, 78461

Fig. 5

The cosmic ray exposure ages along with 38Ar production rates for plagioclase-rich lithic fragments. Cosmic ray exposure (CRE) ages (left y-axis) and 38Ar production rates (right y-axis) for individual plagioclase-rich lithic fragments from 78461 regolith sample. The CRE ages and production rates are determined assuming that fragments were exposed either on lunar surface (i.e., T38 sf, P38 sf, a) or at depth between surface to 10 g/cm2 (i.e., T38 avg, P38 avg, b). P38 avg is the average of production rates at 2, 5, and 10 g/cm2. The production rates are calculated using the major elemental compositions following production rates given by Hohenberg et al. (1978). Since plagioclase-rich lithic fragments have similar chemical compositions (as shown in Table 1), the production rates are also similar for the fragments. The variation in cosmic ray exposure ages is interpreted to result from the variation in abundances of cosmogenic 38Ar. Dashed line indicates the average of 38Ar production rates

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