Determinación de los blancos de exploración en base a la respuesta espectral de los minerales de alteración hidrotermal en los alrededores del Establecimiento Ganadero Don Raúl, Macizo Nordpatagónico, Patagonia Argentina.

Abstract

The northeastern sector of the North Patagonian Massif hosts mineralization formed during the Gondwanic and Mesozoic metallogenic epochs. Three metalotects are relevant during these epochs: i- Permian granites, ii- Triassic ignimbrites, and iii- Jurassic lavas and ignimbrites. This study aims to contribute to the metallogenetic exploration of the region through the investigation of hydrothermal alteration zones surrounding the Establecimiento Don Raúl, located between Valcheta and Aguada Cecilio, Río Negro province. With this purpose, alteration targets that could potentially lead to the discovery of commercially viable mineral deposits were identifield. The first step in research was to compile bibliographic and cartographic resources from the study area. Subsequently, ASTER satellite images were employed to identify potential hydrothermal alteration areas. These images were processed using ENVI 4.7 software, applying radiance corrections to the VNIR, SWIR, and TIR bands. To asses the presence and distribution of alteration minerals, different indices (OHIa, ALI, CI swir, Cao), RGB composites (468, 654) as well as RGB ratio composites were generated. Through a comprehensive analysis of the information obtained from the ASTER satellite images and the cartography, produced by photointerpretation and field mapping, hydrothermal alteration targets were defined and located in outcrops of the Jurassic lava and ignimbrite metalotect belonging to the Marifil Volcanic Complex. Petrographic studies suggest that the targets exhibit an alteration paragenesis consisting of quartz + white micas, kaolinite, + iron oxides and hidroxides. This paragenesis of alteration minerals is consistent with phyllic and argillic type alterations. Finally, using all the available information, detailed geological and alteration mapping of the study area was produced. Since no further magmatic activity was registered in the area, and considering the close spatial relation of the alteration with the Marifil Volcanic Complex rocks, a Jurassic age is proposed for phyllic and argillic alteration founded. The value of multi-spectral satellite imagery lies in its ability to identify various hydrothermal alteration zones and establish their connection to its host rocks (metallotect). In this study, a genetic association is suggested between the examined hydrothermal alterations and the Jurassic lavas and ignimbrites in the region. Based on the findings of this study, and taking into account previous research in the region, the methodology applied here could prove valuable in other areas of the North Patagonian Massif where Jurassic lavas and ignimbrites with metallotects potential are found Likewise, this approach could be extended to other regions with similar metallotects characteristics, enabling the identification and expansion of explorations targets.