The shocking state of apatite and merrillite in shergottite Northwest Africa 5298 and extreme nanoscale chlorine isotope variability revealed by atom probe tomography

The elemental and chlorine isotope compositions of calcium-phosphate minerals are key recorders the volatile inventory Mars, as well planet’s endogenous magmatic hydrothermal history. Most martian meteorites have clear evidence for exogenous impact-generated deformation metamorphism, yet effects these shock metamorphic processes on isotopic records contained within calcium phosphates not been evaluated. Here we test a single cycle systematics in apatite from highly shocked, enriched shergottite Northwest Africa (NWA) 5298. Detailed nanostructural (EBSD, Raman TEM) data reveals wide range distributed features. These principally result intensive plastic deformation, recrystallization and/or impact melting. features directly linked with chemical heterogeneities, including crosscutting microscale chlorine-enriched that associated melt iron-rich veins. NanoSIMS measurements NWA 5298 reveal ?37Cl values (?3 to 1‰; 2? uncertainties <0.9‰) is almost large all previous basaltic shergottites, measured can be readily different states targeted apatite. High spatial resolution atom probe tomography (APT) defect-rich nanoscale boundaries negative (mean ?15 ± 8‰). Our results show metamorphism significant phosphates, mobilization during melting recrystallization. Despite this, low-strain domains identified by EBSD, yield mean value ?0.3 0.6‰ taken best estimate primary composition combined nanostructural, microscale-chemical APT approach gives ability better isolate identify volatile-element near-surface exogenous, shock-related effects.