I. Geochemistry and source characteristics of alkalic igneous rocks of Central Montana. II. The release factor for nonradiogenic volatiles on Mars. III. Detection of kimberlitic diatremes using Landsat

Alkalic igneous rocks of the Central Montana Alkalic Province (CMAP) are divisible into two petrologic groups: a kimberlite-alnoite suite; and a shonkinite-minette-phonolite suite. Both appear to be mantle-derived. Geochemistry and isotopic values of the kimberlitic suite span the range between Group I kimberlites and lamproites such as Prairie Creek, Arkansas. Major element variations in this suite are primarily due to crystal fractionation, but a subset of the alnoites have trace element and isotopic compositions that suggest kimberlitic magma interacted with ancient LREE-enriched and HFSE-depleted trace-element-rich material. This material may be continental lithosphere enriched by fluids or small-melt-fraction silicate melts derived from subducted oceanic crust or sediments. Shonkinitic suite major element variations are also derived by crystal fractionation, but from a phonolitic parent. Trace element features of the least-evolved members mimic modern arc magmas, but incompatible element and isotopic values that suggest a long residence time in a high Rb/Sr, low Sm/Nd, and low U/Pb source. The shonkinitic suite may be derived from ancient arc magma bodies within the continental lithosphere, or from aesthenospheric mantle contaminated with ancient continental crust subducted during the Eocene. In some cases, these melts interacted with trace-element-rich areas in the lithosphere similar to those inferred for the kimberlitic suite.;The release factor for non-radiogenic volatiles (e.g., water) on Mars is estimated to be 0.017 to 0.112, based on the volcanic history of the planet and the ;The feasibility of using Landsat TM and MSS for kimberlite exploration is examined, using the Missouri Breaks Diatremes as a training area. Reflectance spectra of soils from the diatremes and surrounding sediments provide guidelines for image processing. Ratios of TM5/TM7 and TM6/PC1 were the most effective. These were most successful in areas where diatreme soils were well-exposed. MSS was not effective. Detection of kimberlites would be more certain with imaging systems having several bands within the range of TM7.