Fig. 3: Representative zoning patterns in olivine, DIPRA results, and estimated thickness of the lava flow.

a The BSE image of olivine. The arrow marks the positions of the electron microprobe line scan. Inset is an equal-area pole figure of the crystal showing the orientation of the main crystallographic axes (blue points) relative to the profile (shown as a red point). Abbreviations: Ol olivine, Cpx clinopyroxene, ilm ilmenite, Spl spinel, Tro troilite. b, c Fo, Al, and Mn contents and modeled profiles for sample Z0303-002, 007. The orange curves show the modeled fit for Fo and Mn calculated using the DIPRA software (see Methods for more details). Note that this profile contains a “coupled” and an “uncoupled” part, suggesting a two-stage crystallization history. We have only calculated the timescale of the “uncoupled” part here, as the growth time of the “coupled” part is generally negligible. The initial concentrations for the modeling are given in Supplementary Data 3. The error bar represents 1 standard deviation for each point, which are given in Supplementary Data 1. Abbreviations: Fo forsterite, Mn Manganese, Al Aluminum. d Simple one-dimensional modeling of conductive cooling of a basaltic flow. Depth and initial parameters for the underlying cold basalt and overlying high-temperature lava flow (T temperature, ρ density, k thermal conductivity, cp heat capacity) are shown. e Graph of temperature versus depth showing cooling curves at different depths after different times. The green curves are the modeling results for sample Z0303-002, 007. Assuming that the soil clasts are from the slowest cooling location, we obtain a minimum value for the thickness of the lava flow when the time period for the sample to cool from the olivine Fo core temperature to the rim temperature is equal to the timescale estimated for the same olivine grain.