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Over the years, global growth in population and changing climate has contributed to shifts in vegetation species composition, and lower production of grass biomass. Several studies have been conducted globally to quantify grassland biomass utilizing satellite data, but rarely in African Savannah, particularly in Jibiro grazing land, Nigeria. In this study, the grass above-ground biomass (GAB) was estimated from Sentinel-2A/2B data using (i) in-situ samplings on GAB and (ii) upscaling the measured GAB to corresponding satellite data. Spectral indices show that the vegetation index number (VIN) is the best suited vegetation index for modelling GAB (R2 > 0.86, p < 0.001) and is verified (RMSE ±15.99/100 g) with an equally independent assessment set. The result indicated that the grazing reserve has maximum GAB production of 0.76 ton/ha as of September and least GAB of 0.001 ton/ha in January 2018. This study contributes to planning rotational grazing in study area and similar ecosystem. [ABSTRACT FROM AUTHOR]

• Alteration minerals and thermal anomally are detected using remote sensing imagery for an aseismic geologic setting. • The approach developed here is applicable for prospecting geothermal systems around the world. • Geothermal prospect map of Yankari Park, Nigeria is produced to show high potential zones for geothermal exploration. The aim of this investigation is to evaluate the applicability of multispectral satellite imagery for hydrothermal alteration mineral mapping and thermal anomaly detection as a proxy for the characterization of subtle geothermal systems in an aseismic geologic setting. The Yankari Park, an area in northeastern Nigeria characterized by several surface manifestations of hotsprings and hydrothermally altered rock deposits was selected for this study. The study evaluates the effectiveness of the Independent Component Analysis and Mixture Tuned Matched Filtering (MTMF) algorithm for target detection of hydrothermal alteration zones and the Single Channel Algorithm for thermal anomaly detection associated with subtle geothermal systems using spectral bands of Landsat-8, ASTER and Landsat-7, respectively. The results indicated that the use of verified image endmember spectra gives more accurate results compared to that from library spectra by implementing MTMF. Results of mapping thermally anomalous pixels did not conform to known locations of the thermal springs, however, examining the spatial correlation of the anomaly areas with the major fault-fracture systems from the geological map of the study area indicates a close affinity between them and with previously reported thermal gradients within heat conserving sedimentary formations. This investigation has significant implications as it signifies the need for the integrative use of alteration mineral mapping and thermal anomaly detection for cost-effective prefeasibility stage mapping of geothermal systems in an aseismic geologic setting located in African plate and other regions around the world. [ABSTRACT FROM AUTHOR]

Concealed and fossilized geothermal systems are not characterized by obvious surface manifestations like hotsprings and fumaroles, therefore, could not be easily identifiable using conventional techniques. In this investigation, the applicability of Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Hyperion data-sets were evaluated in discriminating hydrothermal alteration minerals associated with geothermal systems as a proxy in identifying subtle Geothermal systems at Yankari Park, Nigeria. Feature-oriented principal component selection, spectral angle mapper, linear spectral unmixing were applied to ASTER data based on spectral characteristics of hydrothermal alteration key minerals for a systematic selective extraction of the information of interest. Analytical imaging and geophysics-developed processing methods were applied to Hyperion data for mapping iron oxide/hydroxide minerals and clay mineral assemblages in hydrothermal alteration zones. The results indicate that ASTER and Hyperion could be complemented for reconnaissance stage of targeting subtle alteration mineral assemblages associated with geothermal systems. [ABSTRACT FROM AUTHOR]