Conditions of formation and origin of fluids of quartz-tourmaline veins in the La Châtaigneraie tungstiferous district (Massif Central, France) : fluid inclusions and stable isotopes

Abstract : A combined stable-isotope and microthermometric study was applied to wolframite-bearing and arsenopyrite-bearing quartz-tourmaline veins, quartz-tourmaline veins associated with leucogranite, schist and the two types of granite - massive monzogranite and leucogranite stocks - of the tungsten Châtaigneraie district, in order to estimate pressure-temperature formation conditions of quartz-tourmaline veins and determine the origin of mineralizing fluids. Pressure-temperature conditions of barren-quartz-tourmaline-veins are estimated at 1.4 +/- 0.4kbars (around 5 km depth under lithostatic regime) and 487 +/- 34°C. Oxygen and hydrogen isotopic compositions of mineralizing fluids indicate a dominant component of leucogranite-derived fluids in wolframite-bearing veins whereas arsenopyrite-bearing veins are strongly equilibrated with host schist.