¹Connor A. Diaz, ¹Rebecca M. Flowers, ¹Carolyn A. Crow, ¹James R. Metcalf, ²Rita Economos
Earth and Planetary Science Letters 679, 119826 Link to Article [https://doi.org/10.1016/j.epsl.2026.119826]
¹Department of Geological Sciences, University of Colorado Boulder, 2200 Colorado Avenue, UCB 399, Boulder, CO 80309-0399, USA
²Hawaiʻi Institute of Geophysics and Planetology, University of Hawaiʻi at Mānoa, Honolulu HI 96822, USA
Copyright Elsevier

Understanding the shock conditions of shergottites during their ejection from the Martian surface is important for deconvolving the pre-ejection thermal and geological history from the ejection overprint in Martian meteorite samples. Here, we investigate Martian meteorite Northwest Africa (NWA) 12241 to better quantify absolute temperatures and local variability in shock-induced thermal events and implications for deciphering the Martian meteorite record. NWA 12241 is classified petrologically as low-shock based on its limited shock features. However, new Raman identification of tuite, a high-pressure phosphate polymorph, demonstrates that minimum temperatures of 1100 °C were achieved in some regions of the sample during ejection. (U-Th)/He dating of merrillite yields a wide range of dates from 2.0 ± 0.3 Ma to 191.7 ± 2.7 Ma, interpreted as the ejection and crystallization ages of NWA 12241, respectively. Thermal history modeling suggests that heterogeneous shock heating is required to explain the merrillite data distribution, with local shock temperatures of ≤570 °C necessary to account for preservation of the older dates. Together, the tuite occurrence and (U-Th)/He data support at least 530 °C (and up to 1730 °C) of variability in the peak shock temperature across this small (7.21 g, ∼4 cm) sample. These findings highlight intense thermal heterogeneity and localized high-temperature microenvironments in an otherwise low-shock meteorite, illustrating the value of (U-Th)/He thermochronology for refining interpretations of localized shock effects in Martian meteorites.