Produzione di una carta geologica dell'area del Manaslu, attraverso il telerilevamento, l'analisi petrografica e spettrofotometrica

Remote sensing in the Himalayan belt is an increasingly powerful tools for glacial and geo-morphological mapping purposes (Quinceya et al.,2007). Rock composition analysis is also possible by studying the signal emitted from the surface and captured by the remote sensors. The remote sensing allow to obtain a global cognition of structures and of the main litologies are present in the selected areas. However, during this type of analyses many difficulties could be met: cloudy cover, snow, glaciers, vegetation and steep topography are among the major problems to be solved when processing data. The examined area is located in the Gandaki region between the Budhi Gandaki and the Marshyangdi valleys which delimit the Manaslu massif (Pecher & Guillot, 2011) in Central Nepal (Central Himalaya). This work aims to apply the remote sensing tecniques in order to investigate the possible structural and lithological correlations among the valleys cited above and other nearby structural transects within the Greater Himalayan Sequence, the metamorphic core of the Himalaya, where the occurrences of hightemperature shear zones have been previously reported (Montomoli et al., 2013, 2015). The final goal will be an updated geological map of Manaslu area as much detailed as possible, considering the difficulties due to altitude and limited accessibility. Moreover, as rock type discrimination, we use also lichens as proxy for different kinds of lithology (Bertoldi et al., 2011). The multispectral analysis has been applied on a ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) image which include 9 bands in the VNIR (Visible and Near Infrared) and SWIR (Shortwave Infrared) fields. Vegetation, snow and ice were masked to isolate and filter rocky pixels and to focus the image only on its potential geological aspects. The interpretation of false color composed on Principal Components on masked images were particularly useful as a guidance during detailed field work. Indeed, field work confirms the successful in discrimating the various lithologies of the study-area. A further improvement of the geological map will be provided by bands ratios and from supervised classification based on spectra obtained from ROI (Region Of Interest) and from collected samples. We show, how according this procedure, an accurate geological map could be obtained, with the aim to investigate lateral continuity of geological units and of tectonic discontinuities along the between the Budhi Gandaki and the Marshyangdi valleys and to investigate relationship between plutons and low-angle-normal-fauls