TY  - JOUR
AB  - Mars is seen as a basalt covered world that has been extensively altered through hydrothermal or near surface water-rock interactions. As a result, all the Fe/Mg-rich clay minerals detected from orbit so far have been interpreted as secondary, i.e. as products of aqueous alteration of pre-existing silicates by (sub)surface water. Based on the fine scale petrographic study of the evolved mesostasis of the Nakhla meteorite, we report here the presence of primary Fe/Mg-rich clay minerals that directly precipitated from a water-rich fluid exsolved from the Cl-rich parental melt of nakhlites during igneous differentiation. Such a tardi-magma tic precipitation of clay minerals requires much lower amounts of water compared to production via aqueous alteration. Although primary Fe/Mg-rich clay minerals are minor phases in Nakhla, the contribution of such a process to Martian clay formation may have been quite significant during the Noachian given that Noachian magmas were richer in H2O. In any case, the present discovery justifies a re-evaluation of the exact origin of the day minerals detected on Mars so far, with potential consequences for our vision of the early magmatic and climatic histories of Mars.
AU  - Viennet, J.-C.*
AU  - Bernard, S.*
AU  - Le Guillou, C.*
AU  - Sautter, V.*
AU  - Schmitt-Kopplin, P.
AU  - Beyssac, O.*
AU  - Pont, S.*
AU  - Zanda, B.*
AU  - Hewins, R.*
AU  - Remusat, L.*
C1  - 59900
C2  - 49642
CY  - Ipgp-gopel-bureau 566, 1 Rue Jussieu, Paris Cedex 05, 75238, France
SP  - 47-52
TI  - Tardi-magmatic precipitation of Martian Fe/Mg-rich clay minerals via igneous differentiation.
JO  - Geochem. Perspect. Lett.
VL  - 14
PB  - European Assoc Geochemistry
PY  - 2020
SN  - 2410-339X
ER  -