info:eu-repo/semantics/article
Stable isotope and fluid inclusion study of sediment-hosted stratiform copper deposits from the Neuquén Basin, Argentina
Fecha
2019-03Registro en:
Rainoldi, Ana Laura; Franchini, Marta Beatriz; Boyce, Adrian; Giusiano, Adolfo Eugenio; Cesaretti, Nora Noemi; et al.; Stable isotope and fluid inclusion study of sediment-hosted stratiform copper deposits from the Neuquén Basin, Argentina; Springer; Mineralium Deposita; 54; 3; 3-2019; 415-436
0026-4598
CONICET Digital
CONICET
Autor
Rainoldi, Ana Laura
Franchini, Marta Beatriz
Boyce, Adrian
Giusiano, Adolfo Eugenio
Cesaretti, Nora Noemi
Pons, María Josefina
Ríos, Francisco Javier
Resumen
The Los Chihuidos and El Porvenir deposits of the Neuquén Basin are examples of sediment-hosted stratiform Cu deposits generated by interaction of hydrocarbons and formation water with host red beds and metal-charged basinal brines. During early diagenesis of red beds precipitated hematite, kaolinite at 60 °C from meteoric water followed by calcite 1 (δ 13 C − 8 to − 3.3‰) and barite (δ 34 S + 4.1‰) with increasing temperature (75–85 °C) from an evolved surface fluid (δ 18 O fluids + 0.9 to + 2.7‰). During the Tertiary Andean orogeny, hydrocarbons and formation water migrated and reacted with the red beds resulting in bleaching of the sandstone. Smectite (fluid δ 18 O − 2.2‰ and δD − 73.7‰), chlorite-smectite mixed-layer minerals (fluid δ 18 O − 6.9‰ and δD − 84‰), pyrite (δ 34 S + 10.2‰), and calcite 2 (δ 13 C − 12.9 to − 6.8‰) formed as by-product of the redox reactions. Calcite 2 formed from low-salinity fluids (0.4 to 5.9 wt% NaCl equiv.) at slightly higher temperatures (125–145 °C) at El Porvenir and at Los Chihuidos deposit (80–105 °C). During subsequent uplift, metal-charged basinal brines flowed into the bleached sandstone and precipitated chalcopyrite-bornite (δ 34 S + 12.3‰) followed by chalcocite-spionkopite (δ 34 S − 64 to + 4.1‰). Calcites 3a (δ 13 C − 19 to − 10.1‰) and 3b (δ 13 C − 31.4 to − 9.5‰) that accompanied Fe-Cu and Cu sulfides, respectively, formed from saline fluids (up to 21.3 wt% NaCl equiv.) at temperatures of 159–70 °C. The δ 18 O values (+ 5.6 to + 11.4‰) of fluids in equilibrium with calcite 3a are similar to oilfield and basinal brines. Fluids in equilibrium with calcite 3 in Los Chihuidos and calcite 3b in El Porvenir show much lighter δ 18 O values (− 7.3 to − 4.6‰ and − 0.6 to + 2.3‰, respectively), which suggests the involvement of methane as the main reductant and possibly meteoric water interaction.