Extended Data Fig. 6: Sensitivity of 130Xe and 128Xe/130Xe to model parameters. | Nature

Extended Data Fig. 6: Sensitivity of 130Xe and 128Xe/130Xe to model parameters.

From: Xenon isotopic constraints on the history of volatile recycling into the mantle

Extended Data Fig. 6

Present-day mantle 130Xe concentration and the ratio of two primordial stable isotopes, 128Xe and 130Xe are shown for different model parameter combinations. Four parameters are explored: those affecting the mantle processing-rate history (Mres and Nres), LV (initial 130Xe concentrations corresponding to a late veneer fraction between 0.1% and 1%) and CC (Extended Data Fig. 3). In each panel, three of these parameters are held constant and the other is varied to illustrate model sensitivity to the varied parameter. Each cloud of points represents the range of present-day 130Xe and 128Xe/130Xe generated by different regassing histories for the specified Nres, Mres, LV and CC. The red rectangle indicates the estimated present-day mantle 130Xe concentration and 128Xe/130Xe range. Dots that fall within the red rectangle represent the family of regassing histories that successfully reproduce the present-day mantle composition for each parameter combination. The reference case shown in Figs. 3, 4 (Mres = 90%, Nres = 8, LV = 1%, CC = 1) is shown as a cloud of black points in all panels. a, A higher mantle processing rate (Nres = 10) results in low 130Xe concentrations for successful 128Xe/130Xe ratios, and 128Xe/130Xe ratios that are too low for successful 130Xe concentrations. b, Higher late-veneer fractions correspond to higher initial 130Xe concentrations in the mantle. For the same mantle processing-rate history, LV = 0.1% yields present-day mantle 130Xe concentrations that are too low given successful 128Xe/130Xe ratios. The effect of low LV can be offset by lowering Nres and thus decreasing the total amount of degassing over Earth history; thus, Nres and LV can be co-varied to find solutions. c, The effect of Mres is minimal because degassing is parameterized through the number of reservoir masses processed over Earth history. Some difference is evident at high present-day mantle 130Xe abundances because the same 130Xed regassing rate parameter space is explored against different absolute degassing rates. d, The continental crust model has no effect on budgets of primordial Xe isotopes.

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