Remote spectral–compositional analysis of basalt mineralogy at Hansteen-Billy, Moon

Abstract

The Hansteen-Billy region of the Moon lying toward the southwest edge of Oceanus Procellarum is characterized by emplacement of three different aged basaltic units viz. INm, Im, and Em. The present study primarily utilizes high-resolution Chandrayaan-I, Moon Mineralogy Mapper (M3) data clipped at ~2.5 μm for mineral analysis of these units. The spectra of all the three regions show two prominent absorption bands. Spectral analysis characterizes the earliest INm basalts as low-Ca pyroxenes with large band area ratios (BAR) and nearly similar B-I and B-II strength. The Em and Im basalts are Ca and high-Ca pyroxenes, respectively, with relatively less BAR values and more B-II/B-I strength. The relative content of their spectra after olivine correction appears to be dominated by pyroxene. The obtained results have been used for estimation of the compositional characteristics of pyroxenes from laboratory-based calibration equations. The pyroxene composition for INm basalts indicates their pigeonitic affinity, whereas the Im and Em basalts is close to augite. The estimated temperature of crystallization suggests that basalts in this region evolved at higher temperature and are preserved in a metastable condition due to quick cooling. Furthermore, the area is characterized by increase in concentration of both the Fe and Ti with age as assessed from Clementine mineral map. The obtained results have been discussed in relation with source of the magma.