Mercury deposits in metamorphic settings: the example of Levigliani and Ripa mines, Apuane Alps (Tuscany, Italy)

In addition to the world-class epithermal deposits in the Monte Amiata area (Southern Tuscany), mercury production in Tuscany is recorded from the Lev igliani and Ripa deposits in Apuane Alps. Both deposits are hosted by sedim entary and subordinate volcanic rock sequences. belonging to the Apuane Met amorphic Complex (AMC), metamorphosed in the greenschist facies during the Apenninic orogeny (ca. 27-8 Ma). At Ripa, mineralization is very simple, consisting of cinnabar with minor p yrite in quartz gangue. Its emplacement is obviously controlled by shear st ructures produced during the second Apenninic deformation event (D-2) At Levigliani, both the setting and the mineral assemblage are more complex . Mineralization is confined to a lithologic horizon comprised of carbonati c chloritic phyllites and calc-alkaline metabasites. The mineralizing proce ss spanned the entire tectono-metamorphic Apenninic event. A first mineral assemblage (cinnabar I + zincian metacinnabar + pyrite) was formed under co nditions presumably not far from the metamorphic thermal peak, whereas a se cond assemblage (cinnabar II + mercurian sphalerite + pyrite native mercury chalcopyrite galena pyrrhotite grumiplucite) was formed in a retrograde st age. In both deposits, the overall P-T-X features of fluid inclusions in quartz are similar to those previously established for syn-metamorphic hydrotherma l circulation in AMC. At Ripa, the syn-D-2 shear structures provided a hydr ologic trap for mercury mobilized from an unknown source. At Levigliani, th e strict lithological control, the protracted nature of the mineralizing pr ocess, and the similarities to the setting of Palaeozoic peri-Mediterranean mercury deposits, suggest a small scale remobilization from a pre-existing anomaly. (C) 2001 Elsevier Science B.V. All rights reserved.