Basaltic lavas from Harrat Uwayrid, Saudi Arabia, record the evolving magmatic and tectonic context of the Arabian Peninsula from at least the mid‐Miocene to the present day. New ⁴⁰Ar/³⁹Ar ages spanning from the mid to late Miocene reveal that mid‐Miocene mafic volcanism formed a large, subalkaline volcanic plateau parallel to Red Sea rifts. Subsequent volumetrically subordinate late Miocene‐Quaternary alkaline volcanism erupted monogenetic cinder cones roughly orthogonal to the earlier volcanic field. The source region for all samples was affected by both fluid and silicate metasomatism; inferred mantle mineral assemblages include amphibole for mid‐Miocene lavas and phlogopite for late Miocene‐Quaternary samples. Calculated melting depths become shallower with time across the Miocene volcanic episode (∼20–15 Ma) but become deeper in the late Miocene to Quaternary (∼10–0 Ma), indicating melting pressures and temperatures significantly higher than those recorded in Miocene lavas despite progressive lithospheric thinning. We offer a two‐stage model for the formation of Harrat Uwayrid: (a) Early‐ and mid‐Miocene rifting associated with the Red Sea opening facilitated adiabatic melting of uppermost mantle lithosphere to form the early volcanic plateau and (b) Plate motion changes in the mid‐ and late‐Miocene initiated the Dead Sea Fault and destabilized a dense pyroxenitic lower lithosphere leading to foundering or lithospheric drip beneath Harrat Uwayrid that allowed deep lithospheric melting and formed the young volatile‐rich eruptives.

This study aims at exploiting multi-spectral data, acquired from ASTER, satellite to explore areas of hydrothermal alteration and Gossan including massive Sulphide deposits. Auger sulphide is a good source of raw materials such as economic copper, silver, gold and zinc. Major steps involved in the analysis of ASTER satellite data have been discussed using ERDAS Imagine Software. The extent of interdependence among spectral regions, hydrothermal alteration and Gossan has been studied through digital image analysis and classification. The visual interpretation techniques have been employed to identify and earmark hydrothermal alteration and Gossan zones on the satellite image for carrying out subsequent supervised image classification. Imagery Analysis was supported by the color composite, developed by exposing bands 4, 6 & 9 with Red, Green and Blue radiations respectively, to make iron-rich cap or Gossan and hydrothermal alteration zones prominent. The Gossan-laden regions appeared in Red color while the hydrothermal alteration zones took color range from reddish green to light green. Image enhancement has also been achieved through the application of image ratioing techniques and an improved color composite was developed by exposing results of band ratios of band 5 & band 7, band 5 & band 4, and band 2 & band 1 with Red, Green and Blue radiations respectively. Resultantly, the combination of visual interpretation, previous knowledge of the landcover and digital image processing techniques applied on the ASTER Satellite imagery in multi-spectral mode, has proved beneficial in studying hydrothermal alteration zones and Gossan in the Nuqrah area.