¹A.R.Russell et al. (>10)
Journal of Geophysical Reserac (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009244]
¹Arizona State University, Tempe, AZ, USA
Published by arrangement with John Wiley & Sons

The Martian surface preserves evidence of a global climate transition from wetter to drier conditions, but the nature of the fluids involved in this evolution remains poorly constrained. In Gale crater, the clay-sulfate transition and presence of evaporite mineral assemblages can provide insights into the properties of these fluids and the timing of environmental change. While traversing through the Chenapau member of the sulfate-bearing unit in Gale crater, the Curiosity rover encountered a set of dark-toned veins enriched in Na and Cl, suggestive of halite. However, previous halite detections in Gale crater have been limited to occurrences along the edges of Ca-sulfate veins or nodules, suggesting a unique origin for this set of veins. Here, we hypothesize that these veins formed through the infiltration of saline fluids along pre-existing hydraulically induced fractures. These fluids permeated into the host rock beyond the primary fractures, precipitating halite and cementing the fractures. Using Mastcam and ChemCam spectra, we found that the veins displayed a downturn in the near-infrared wavelengths, consistent with the presence of ferrous iron. Furthermore, textural analysis of the veins reveals host rock material preserved within the veins. ChemCam laser-induced breakdown spectroscopy observations also support the presence of a minor Fe component in the veins and halite concentrated along the center of the fractures. Our results demonstrate that these veins represent a distinct class of diagenetic features in Curiosity’s mission that record an important transition in near-surface fluid chemistry consistent with a transition to a drier environment.

¹Lars E. Borg, ¹Thomas S. Kruijer, ¹Ming-Chang Liu, ^1,2Autumn G. Roberts, ¹Josh Wimpenny, ¹Ouyanatu N.Z. Maina, ¹Joseph Boro, ¹Charles K. Shearer, ^1,4Kyle M. Samperton
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2025.10.028]
¹Cosmochemical & Isotopic Signatures Group, Lawrence Livermore National Laboratory, 7000 East Avenue L-231, Livermore, CA 94550, USA
²Geological Sciences, University of Colorado, Boulder, CO 80309, USA
³Department of Earth and Planetary Science, Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131, USA
⁴Trace Nuclear Measurement Technology Group, Savannah River National Laboratory, Aiken SC 29802 USA
Copyright Elsevier

Temporal relationships among the three most common suites of lunar crustal rocks have been investigated by obtaining new high precision ages on Felsic/Alkali-suite Quartz monzodiorite Clast B from breccia 15405 and Magnesian-suite norite 78235/6/8/55/56 and comparing them to previously dated ferroan anorthosite sample 60025. The weighted average age of 4337.19 ± 0.49 Ma of 15405 Clast B is defined by zircon U-Pb and Pb-Pb ages as well as mineral isochron Sm-Nd and Nd-Nd ages. It is identical to the weighted average age for Apollo 17 norite 78235/6/8/55/56 of 4334.1 ± 3.5 Ma which is defined by Pb-Pb ages measured on baddeleyites in this investigation and less precise Pb-Pb and Sm-Nd ages reported in the literature. Both ages are ∼ 25 Ma younger than the weighted average of Sm-Nd and Pb-Pb ages reported in the literature on ferroan anorthosite 60025 of 4359.3 ± 2.3 Ma. The fact that ages of all three samples are defined by multiple U-Pb, Pb-Pb, Sm-Nd, and 142Nd-143Nd chronometers provide confidence that they record the igneous crystallization history of the samples and do not represent disturbances or mixing lines with no temporal significance.
The extent to which these three ages represent broader scale magmatism is difficult to evaluate. Nevertheless, the age defined for 15405 Clast B, 78235/6/8/55/56, and 60025 are contemporaneous with the peak of ages observed in detrital zircons from the Apollo 12, 14, 15, and 17 landing sites (4340 ± 20 Ma), a Mg-suite Sm-Nd whole rock isochron defined by samples from Apollo 14, 15, 16, and 17 landing sites (4348 ± 25 Ma), and a Ferroan Anorthosite-suite Sm-Nd whole rock isochron defined by samples from the Apollo 15 and 16 landing sites (4354 ± 29 Ma). This implies that Ferroan Anorthosite-suite magmatism is temporally distinct and earlier than magmatism associated with the Mg-suite and the Felsic/Alkali-suite, as predicted by the lunar magma ocean model of lunar differentiation. The short 35 ± 10 Ma interval between primary ferroan anorthosite magmatism and secondary magmatism suggests that the lunar crust formed over a limited period of time. Although heat from decay of long-lived isotopes, large impacts, tidal heating associated with interactions between the Earth and Moon, and density driven overturn of the magma ocean have all been invoked to explain production of ancient secondary crustal magmatism, only tidal heating and cumulate overturn are consistent with the apparent short duration of secondary crustal magmatism and the great depth of crystallization implied for some Mg-suite samples.
The initial ε143Nd values derived from the 15405 Clast B and 78238 Mg-suite norite isochrons, as well as a Mg-suite whole rock isochron are −0.23 ± 0.11, −0.27 ± 0.74, and −0.25 ± 0.09, respectively. They are identical within uncertainty indicating that Mg-suite and Felsic/Alkali-suite magmas were derived from materials that had the same time averaged Sm/Nd ratios since the formation of the solar system. This, combined with the contemporaneous nature of 15405 Clast B and 78235/6/8/55/56 Mg-suite norite, is consistent with evolution of both samples, and likely both magma suites, from a common source through closed system fractional crystallization or partial melting processes.