¹Y. Wu,^1,2Z. Xiao,³Y. Wu,⁴L. Pan,¹P. Yan,^2,6S. Liao,¹Q. Pan,⁷S. Li,^2,6Y. Li,^2,6W. Hsu
Journal of Geophysical Research (Planets) (In Press) Link to Article [https://doi.org/10.1029/2024JE008412]
¹Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, China
²CAS Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei, China
³Analysis and Test Center, Guangdong University of Technology, Guangzhou, China
⁴School of Earth Sciences and Engineering, Sun Yat-sen University, Zhuhai, China
⁵Planetary Environmental and Astrobiological Research Laboratory, School of Atmospheric Sciences, Sun Yat-sen University, Zhuhai, China
⁶Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
⁷Astronomical Research Center, Shanghai Science & Technology Museum, Shanghai, China
Published by arrangement with John Wiley & Sons

Apatites record crucial information on the origin, composition, and chemical evolution of volatiles on terrestrial planets. As a martian intrusive rock, the gabbroic shergottite Northwest Africa (NWA) 13581 provides key information on the volatile evolution related to magmatic processes in the interior, shedding light on the intricate volatile circulation on Mars. The textural and chemical characteristics of the phosphates in NWA 13581 indicate a complex formation history involving fractional crystallization, degassing, and fluid interaction. Degassing of the NWA 13581 parent melt is capable of exsolving chlorine-rich fluids, resulting in the formation of notably fluorine-rich apatite with a high x-site occupancy of fluorine up to 90%. The degassed/exsolved volatile-rich fluids could subsequently continue to migrate and interact with surrounding magmatic suites, leading to highly heterogeneous compositions of active fluids. The crystallization of apatite is initiated by the interaction of fluids with merrillite at the late stage of the magmatic process, leading to the formation of phosphate intergrowths. Influenced by the composition and chemical evolution of volatiles in fluids and melts, apatite exhibits notable variability in chlorine compositions both within individual grains and among different grains. Moreover, the presence of magnetite associated with phosphate intergrowth highlights the transportation of metallic components in addition to volatiles from deep layers to shallower depths or to the surface of Mars. This process, which is observed in young shergottites, indicates the persistent presence of hydrothermal systems until recent geological periods, contributing to the generation and circulation of volatiles within the martian interior and on the surface.

¹Juulia-Gabrielle Moreau,¹Argo Jõeleht,²Aleksandra N. Stojic,³Christopher Hamann,³Felix E. D. Kaufmann,¹Peeter Somelar,¹Jüri Plado,⁴Satu Hietala,^5,6Tomas Kohout
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.14274]
¹Department of Geology, Institute of Ecology and Earth Science, University of Tartu, Tartu, Estonia
²Institut für Planetologie, Westfälische Wilhelms Universität Münster, Münster, Germany
³Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science, Berlin, Germany
⁴Geological Survey of Finland, Kuopio, Finland
⁵School of Electrical Engineering, Aalto University, Espoo, Finland
⁶Institute of Geology of the Czech Academy of Sciences, Prague 6, Czech Republic
Published by arrangement with John Wiley & Sons

Iron sulfide and metal melt veins in chondritic materials are associated with advanced stages of dynamic shock. The shock-induced residual temperatures liquefy the sulfide component and enable melt distribution. However, the distribution mechanism is not yet fully understood. Capillary forces are proposed as agents of melt distribution; yet, no laboratory experiments were conducted to assess the role that capillary forces play in the redistribution of iron sulfide in post-shock conditions. To investigate this further, we conducted thermal experiments under reducing conditions (N2(g)) using dunitic fragments, suitable chondritic analog materials that were doped with synthesized troilite (stoichiometric exact FeS). We observed extensive iron sulfide (troilite) migration that partially resembles that of ordinary chondrites, without the additional influence of shock pressure-induced fracturing. The iron sulfide melt infiltrated grain boundaries and pre-existing fractures that darkened the analog material pervasively. We also observed that the iron sulfide melt, which mobilized into grain boundaries, got systematically enriched in Ni from the surrounding host olivine. Consequently, FeNi metal fractionated from the melt in several places. Our results indicate that capillary forces majorly contribute to melt migration in the heated post-shock environment.