@article{fdi:010064094,
  title = {{H}ydrothermal alteration in basalts from {V}argeao impact structure, south {B}razil, and implications for recognition of impact-induced hydrothermalism on {M}ars},
  author = {{Y}okoyama, {E}. and {N}edelec, {A}. and {B}aratoux, {D}avid and {T}rindade, {R}. {I}. {F}. and {F}abre, {S}. and {B}erger, {G}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he 12-km-wide {V}argeao impact structure was formed 123 {M}yr ago in the {P}arana basaltic province (southern {B}razil). {A}t this time the province region had a dry climate, although a large brackish aquifer had been formed in the underlying sandstones. {I}t is therefore one of the best terrestrial analogs for studying impact-related products on a dry martian surface environment with preserved ice-rich ground. {T}he basalts within the impact structure display cm-sized breccia veins filled with lithic clasts, glassy remnants, newly formed {F}e-oxyhydroxides and secondary phases, such as calcite, phyllosilicates and, subordinately quartz and zeolite. {T}he textural and mineralogical study of these phases demonstrate their hydrothermal origin. {A}lthough the very center of the structure has experienced the highest pressures and temperatures, the most developed hydrothermal changes are recognized in an inner collar surrounding the central depression. {T}his inner collar is also the location of major modifications of the rock magnetic properties. {T}hese magnetic signatures are related to the distribution of impact-related faults and to the formation of new iron oxides. {G}eochemical modeling indicate that hydrothermal phases formation required low water/rock ratios. {O}ur observations therefore suggest that hydrothermal alteration took place following the perturbation of the aquifer by the impact, but evidence for hydrothermal circulation is limited in comparison with other impact-related hydrothermal systems. {T}his situation may be explained by the presence of the aquifer below the heat source, such a setting being exceptional for the {E}arth, but common on {M}ars. {H}owever, the spectroscopic signatures in visible/near infrared images suggest that this kind of impact-related hydrothermal alteration may be still indentified in large impact craters on {M}ars by orbital instruments. {T}hese results does not exclude the possibility that more developed alteration took place in breccias that are today eroded.},
  keywords = {{I}mpact processes ; {E}arth ; {M}ars, surface ; {I}nfrared observations ; {BRESIL} ; {MARS} {PLANETE}},
  booktitle = {},
  journal = {{I}carus},
  volume = {252},
  numero = {},
  pages = {347--365},
  ISSN = {0019-1035},
  year = {2015},
  DOI = {10.1016/j.icarus.2015.02.001},
  URL = {https://www.documentation.ird.fr/hor/fdi:010064094},
}