Geology, mineralogy and possible origin of the copper mineralization in marble near Saldán, Córdoba (Argentina)

Abstract

; refractive indices are e = 1.707(3), ω = 1.656(3), with an anomalous small 2V. Magnesium (up to 0.15 wt. % MgO) is the only significant substituent. Yellow barite crystals tabular on {001} contain traces of Sr. Quartz occurs rarely, as drusy linings. A few cases of botryoidal, opal-like quartz crusts are known. Tenorite forms dark brown masses and stringers included in marble. Very scarce grains of copper sulfides (anilite altering to spionkopite and covellite along rims and cracks) are found scattered in the marble. Copper is partially replaced by Bi (≤ 0.15 wt. % Bi) and Pb (≤ 0.16 wt. % Pb). Malachite and brochantite are alteration products of sulfides. Fluid inclusion studies indicate that the minerals precipitated from a single-phase fluid initially at a temperature above 300 oC that cooled to c. 220 oC. Salinity was very low, 0 to 2 wt. % NaCl eq. Isotopic analyses of calcite give δ 13