Vanadium mineralization at Los Chihuidos sediment-hosted Cu-V deposit Neuquén Basin, Argentina: an approach to vanadium ore forming processes

RAINOLDI A. L.; BAUFORT D.; FRANCHINI M.B.; GIUSIANO A.; PETIT SABINE ; PATRIER P. ; PONS, MARÍA JOSEFINA

Geoscience Frontiers

Elseiver

Lugar: Beijing; Año: 2023 p. 1 - 68

1674-9871

Vanadium mineralization at Los Chihuidos deposit of the Neuquén Basin is linked tothe development of a redox front system related to the inflow of hydrocarbons into thered sandstone of the Huincul Formation. Interaction of hydrocarbons with oxidized redbeds and connate water generated redox reactions where hematite was dissolved dueto iron reduction resulting in the discoloration of the red strata. At the contact betweenoxidized red sandstone and reduced white sandstone, precipitation of specific mineralphases resulted in the V ore with Cu subordinated. With the implementation of theredox interface, abundant V-montmorillonite and V-hematite precipitated at the mostoxidizing and Cu-V-corrensite-like at the most reducing conditions of the redox front.As the redox front advanced with fluids constantly migrating into the reservoir, morereducing conditions were stablished, promoting chloritization and subordinatedillitization with V-Cu incorporation and continuous upgrading of the ore. Main oremineralogy consists of clay minerals including V-bearing montmorillonite, Cu-Vcorrensite-like, V-di-trioctahedral chlorite and Cu-tri-trioctahedral chlorite with minor Villite-smectite mixed-layer minerals and associated secondary V-hematite.Chloritization over illitization was favored due to high amounts of Fe and Mg in detritalclasts and in connate fluids and by low K availability related to low amounts of detritalK-feldspar. The spatial transition of V and /or Cu bearing clay minerals observedthrough the mineralized redox fronts at Los Chihuidos deposit (kaolinite→ smectite→illite/smectite→ corrensite-like→ di- trioctahedral -chlorite→ tri- trioctahedral -chlorite)and the related variation of V-Cu concentrations in bulk rock are indicative ofincreasing pH and decreasing Eh of resident solutions from red to white sandstonesduring the hypogene mineralization process. Late incoming of Cu-rich oxidized basinalbrines precipitated main copper ore with Cu-sulfides in the white sandstone up to thecontact with the redox front in contact with hydrocarbons. During uplift and exhumation,percolation of meteoric water promoted mobilization of V and Cu and the precipitationof oxidized V-Cu ore.