%0 Journal Article
%T Mineralogical Characterization Of Topaz From Miarolitic Pegmatites And W-Bearing Greisen In The A-Type El Portezuelo Granite, Papachacra (Catamarca Province) Caracterizaci車n mineral車gica de topacio de pegmatitas miarol赤ticas y un greisen portador de W en el plut車n de tipo A El Portezuelo (Granito Papachacra), provincia de Catamarca
%A Fernando Colombo
%A Ra迆l Lira
%A Elisa V. Pannunzio Miner
%J Revista de la Asociaci車n Geol車gica Argentina
%D 2009
%I Asociaci車n Geol車gica Argentina
%X The El Portezuelo Granite (Catamarca Province, NW Argentina), probably of Late Devonian or Early Carboniferous age, was emplaced at ≒ 2 kbar and displays the chemical characteristics of an A-type granite. It hosts small miarolitic pegmatites and dikes that belong to the NYF petrogenetic family, miarolitic class, miarolitic-REE subclass, with features more similar to those reported for the gadolinite-fergusonite type. Topaz is widespread both in pegmatites and in a W-bearing greisen genetically related to the granite. In pegmatites it occurs as crystals up to over 15 cm long, showing the forms {120} and {041} (dominant), and also {100}, {010}, {001}, {110}, {130}, {230}, {410}, {150}, {340}, {201}, {203}, {011}, {021}, {031}, {111}, {112}, {221}, {223}, and {445}. Crystals are colorless to pale yellow, more rarely brownish or bluish. Electron-microprobe analyses of gemmy crystals from pegmatites and greisen show that topaz is F-rich (between 19.01 and 20.12 wt. % F, most crystals being slightly zoned) and has very low MgO and TiO2 (≒ 0.02 wt.%), low FeO (≒; 0.03 wt.%), and up to 0.10 wt.% CaO. Refractive indices and unit-cell dimensions reflect the F-rich nature of the studied topaz. This occurrence produces the finest crystals yet known from western South America but probably has no economic potencial as gemstock producer. El Granito El Portezuelo (Provincia de Catamarca, Argentina noroccidental), de probable edad dev車nica superior a carbon赤fera inferior, se emplaz車 a ≒ 2 kbar y posee las caracter赤sticas de un granito de tipo A. Aloja pegmatitas miarol赤ticas y diques de reducidas dimensiones que pertenecen a la familia petrogen谷tica NYF, clase miarol赤tica, subclase miarol赤tica-elementos de tierras raras, con rasgos m芍s similares a los del tipo gadolinita-fergusonita. El topacio est芍 bastante difundido en las pegmatitas y en un greisen portador de W gen谷ticamente relacionado al granito. En pegmatitas se encuentra en cristales que superan los 15 cm, mostrando las formas {120} and {041} (dominantes), y tambi谷n {100}, {010}, {001}, {110}, {130}, {230}, {410}, {150}, {340}, {201}, {203}, {011}, {021}, {031}, {111}, {112}, {221}, {223} y {445}. Los cristales son incoloros a amarillo p芍lido, m芍s raramente pardos o celestes. An芍lisis con microsonda de electrones hechos en cristales de calidad de gema muestran que el topacio es rico en F (entre 19,01 y 20,12% F), y con muy bajo MgO y TiO2 (≒ 0,02 %), bajo FeO (≒ 0,03%), y hasta 0,10% de CaO. Los 赤ndices de refracci車n y las dimensiones de la celda unidad reflejan la naturaleza rica en F del topacio estudiado. Est
%K Topacio
%K Pegmatitas miarol赤ticas
%K Greisen
%K Granito de tipo A
%K El Portezuelo
%K Argentina
%K Topaz
%K Miarolitic pegmatites
%K Greisen
%K A-type granite
%K El Portezuelo
%K Argentina
%U http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0004-48222009000200002