Stable isotope geochemistry of carbonates from the Apuane Alps mining district, northern Tuscany, Italy

Depending on their location in the geological framework, carbonate rocks of this area interacted with metamorphic fluids to a quite different extent, their original delta (super 18) O values being either lowered or preserved. The delta (super 18) O variations are particularly pronounced for the rocks at the contact with schists or orebodies. The water in the fluids was probably driven out of the schists (estimated delta (super 18) O +11.6 +- 1.0 per mille for such water). Vein dolomite from fissure fillings in the dolostones is a metamorphic product and is depleted in both (super 13) C and (super 18) O relative to host dolomite. At Buca della Vena, T of 310 +- 40 degrees C and delta (super 18) O of +15 +- 2 per mille are estimated for vein-forming solutions. According to their delta (super 13) C values, gangue calcites from the stratiform ore deposits at Pollone and Monte Arsiccio should be sedimentary-diagenetic products, essentially produced from organic CO (sub 2) generated by sulphate-reducing bacteria. Their delta (super 18) O values may be due to recrystallization from late diagenetic fluids or alternatively from metamorphic fluids.