FLUID INCLUSION STUDY OF STIBNITE USING INFRARED MICROSCOPY: AN EXAMPLE FROM THE BROUZILS ANTIMONY DEPOSIT (VENDEE, ARMORICAN MASSIF, FRANCE)

摘要

A microthermometric study using infraredmicroscopy was performed on fluid inclusions hosted in stibnitecrystals of the Brouzils antimony deposit, in order tocharacterize the fluids responsible for the deposition of theantimony at the cud of the Variscan metallogenic sequence.Primary fluid inclusions in stibnite were moderately saline (3.5-4.75 wt percent NaCl equiv) with homogenization temperaturesvarying between 140 deg and 160 deg C. Two generations oflater fluids are also contained in the stibnite samples. The firstgeneration of secondary fluid inclusions is found exclusively instibnite and is characterized by low salinities (1.35-2.2 wtpercent NaCl equiv), homogenization temperatures ofapproximately 215 deg C, and the presence of one or more solidmineral phases. The second generation of fluid inclusions isyounger and is found in stibnite along secondary planes as wellas in quartz gangue; it corresponds to H_2O-CO_2 fluid withhomogenization temperatures of about 180 deg C. This infraredmicroscopy study thus shows that the quartz and stibnite of theBrouzils veins are not cogenetic and reveals the polyphasecharacter of the vein infill in which three successive episodes ofhydrothermal circulation are identified.