02444caa a22003134a 4500 42063 AR-SsjUBGM 20251222143702.0 251215nuuuuuuuuag 000 0 spa d AR-SsjUBGM AR-SsjUBGM ag Colombo, Fernando 58827 Mineralogical characterization of topaz from miarolitic pegmatites and w-bearing greisen in the a-type El Portezuelo granite, Papachacra (Catamarca Province). Relevamiento: 2009. 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. por ciento F, most crystals being slightly zoned) and has very low MgO and TiO2 (= 0.02 wt. por ciento), low FeO (=; 0.03 wt. por ciento), and up to 0.10 wt. por ciento 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. Artículo en pdf (RAGA 64_2_194.pdf) Granito tipo a Pegmatita Topacio Catamarca 6203 El Portezuelo 58830 Artículo 24605 Lira, Raúl 58831 Pannunzio Miner, Elisa V. 58832 Asociación Geológica Argentina editor 20581 Revista Asociación Geológica Argentina vol.64, no.2, p.194-200 0004-4822 AR cdu idgym 2009-09-30 42063 42063 0 0 cdu 0 0 GM GM 2025-12-22 0 C-5 2025-12-22 00:00:00 2025-12-22 AR