Hydrothermally altered basalts at high water-to-rock ratio at Skouriotissa VMS (Cyprus): an analog site to constrain condition formations of Fe-Mg-Al phyllosilicates on Noachian Mars
Claire Ramboz  1, 2, 3, *@  , Nicolas Bost  4, 5  , Claude Fontaine  6  , Frances Westall  7@  
1 : Bureau de recherches géologiques et minières  (BRGM)  -  Website
Bureau de Recherches Géologiques et Minières (BRGM)
BRGM, Institut des Sciences de la Terre d'Orléans, UMR 7327, BP 36009, 45060 Orléans, France -  France
2 : Centre National de la Recherche Scientifique  (CNRS)  -  Website
CNRS : UMR7327
CNRS, Institut des Sciences de la Terre d'Orléans, UMR 7327, 45071 Orléans, France -  France
3 : Université d'Orléans  (Univ. Orléans)  -  Website
Université d'Orléans
Univ Orleans, Institut des Sciences de la Terre d'Orléans, UMR 7327, 45071, Orléans, France -  France
4 : Institut des Sciences de la Terre d'Orléans  (ISTO)  -  Website
Université d'Orléans, CNRS : UMR7327, INSU, Bureau de Recherches Géologiques et Minières (BRGM)
Campus Géosciences 1A, rue de la Férollerie 45071 Orléans cedex 2 -  France
5 : Centre de biophysique moléculaire
Centre National de la Recherche Scientifique : UPR4301
Rue Charles Sadron 45071 ORLEANS CEDEX 2 -  France
6 : Institut de Chimie des Milieux et Matériaux de Poitiers
Université de Poitiers, Centre National de la Recherche Scientifique : UMR7285
4 RUE MICHEL BRUNET BAT B27 - CHIMIE 86022 POITIERS CEDEX -  France
7 : Centre de biophysique moléculaire  (CBM)  -  Website
CNRS : UPR4301
Rue Charles Sadron 45071 ORLEANS CEDEX 2 -  France
* : Corresponding author

The Skouriotissa (SK) massive sulfide deposit (VMS) formed on top of the extrusive sequence of a fossil spreading ridge at Cyprus. At SK mine, we have sampled outcropping metabasalts along a 200 m-long cross section ranging from the fossil seaflloor to the VMS envelop.

- Quartz-chlorite rocks of metasomatic origin outcrop at the seafloor. They formed from deep hot fluids which reacted in situ with extrusive basalts and mixed with seawater. The NIR spectrum of SK Fe-Mg clinochlore has a higher reflectance than that of FRT000033C Nili Fossae chlorite (Carter et al., 2013); 0.35- 0.7 compare to 0.12-0.25, respectively). By its overall reflectance and spectral properties in the 2-2.6 µm range, the Martian chlorite is closer to the Al-poor Fe-Mg-Ti prochlorite SMR14 (Clark et al., 2007).

- Pyrite-bearing quartz-smectite and corrensite (ordered S/C mixed layer) rocks characterize the VMS envelop. They are deeply leached and metasomatic.

-Saponite zeolite metabasalts are found inbetween the fossil seafloor and the VMS. Bulk rock analyses and advanced DRX studies allow discrimination of two groups among these metabasalts. A former group, still showing primary basaltic minerals, is less argilllized and less affected by medium temperature zeolitization (analcime stage). It shows limited growth of a C/Sm saponite with dominant chlorite over Ca-rich smectite. Group 2 saponite metabasalts have undergone both advanced argillization and long lived zeolitization from medium to low temperature (analcime-philipsite association). Group 2 saponite contains Sm/c mixed layer with Mg-rich smectite and subordinate chlorite. The IR spectrum of a Group 1 metabasalt, interpreted in terms of 80% Mg-chlorite-20% Ca-Fe smectite, is similar to that of Tyrrhena Terra CRISM 1 phyllo (Loizeau et al., 2012).

- SK basalts are presently altered to illlite-smectite-bearing rocks due to the flow of acidic drainage waters (17°


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