HALLAZGO DE ZINCSILITA ACOMPAÑADA DE WILLEMITA Y HEMIMORFITA EN LA VETA LASTENIA DEL DISTRITO Pb-Zn CAMPANA MAHUIDA, NEUQUÉN

GALLEGOS, E.; BERBEGLIA, Y.; MARTÍNEZ DOPICO, C.I.; LAGORIO, S.; VATTUONE, M.E.; LATORRE, C.O.

Río Cuarto, Pcia. de Córdoba

Congreso; MINMET- VII Congreso de Mineralogía y Metalogenia; 2004

Asociación Mineralógica Argentina; Universidad Nacional de Río Cuarto

FINDING OF ZINCSILITE ASSOCIATED WITH WILLEMITE AND HEMIMORPHITE IN THE LASTENIA VEIN OF THE CAMPANA MAHUIDA PB-ZN DISTRICT, NEUQUÉNThe mineralogy of the second worldwide discovery of zincsilite (Zn3 Si4.O10 (OH)2.4H2O) was studied by petrographic microscope, XRD, HREM and EDS. Other zinc silicates as hemimorphite and willemite crystallize together. All of them are found in the oxidation zone, from epithermal Lastenia veins of the Pb-Zn district, Campana Mahuida, Patagonian Andes, Neuquén. Zincsilite is a rare montmorillonite group mineral without Al. Crystals show some milimeters in lenght, they are monoclinic, with laminar pseudohexagonal {001} habit forming parallel groups. It is traslucent, with white colour and pearly luster and has perfect cleavage {001}. The optical character shows: 2Vα = 50° and strong dispersion r>v. Chemical analyses by EDS show a similar composition of the zincsilite type locality. Zinc silicates originate from sphalerite in the silica rich oxidation zone in relatively acidic environment, that preclude carbonate crystallization.