Fluid Inclusion Evidence for the Development of Zn-Pb-Cu-F Skarn Mineralization in SW Sardinia, Italy

M. Boni, A. H. Rankin and M. Salvadori
Dipartimento di Scienze della Terra, Universitá di Napoli, Largo S. Marcellino, 10 80138 Naples, Italy
Department of Geology, Royal School of Mines, Imperial College of Science, Technology and Medicine, London SW7 2BP, U.K.

Abstract: New microthermometric data are presented for fluid inclusions in epidote, garnet, hedenbergite, armenite, quartz, fluorite, calcite and baryte associated with skarn-related base metal mineralization in the Iglesiente and Sulcis mining districts of SW Sardinia. Based on a comparison of these data with published results for vein and palaeokarst mineralization a ‘two fluid’ model is proposed for the mineralization in the area. An early fluid, responsible for skarn-associated sulphide mineralization, developed above 350–400°C with a salinity generally less than about 10 eq. wt.% NaCl, and on cooling was also responsible for some of the vein and palaeokarst mineralization. The origin of this fluid is, at this stage, speculative (meteoric/magmatic?). A separate fluid regime, characterized by lower temperatures and much higher salinities (Th < 140°C and >20 eq. wt. % NaCl) was mainly responsible for the bulk of the Permo-Triassic vein and palaeokarst mineralization, and some late-stage skarn mineralization. This low-temperature, saline (basinal or evaporitic?) brine appears to have mixed with more dilute groundwaters during this stage of mineralization. The existence of two (or more) mineralizing fluids with different characteristics at the end of Hercynian tectonic/magmatic events appears to be widespread throughout the whole of Europe.

Keywords: fluid inclusions • skarn mineralization • two-fluid model • Sardinia • Italy

Mineralogical Magazine; June 1990 v. 54; no. 375; p. 279-287; DOI: 10.1180/minmag.1990.054.375.13
© 1990, The Mineralogical Society
Mineralogical Society (www.minersoc.org)