Geochemistry and U-Pb Geochronology of Miocene and Cambrian-Precambrian Units at Mpala Research Center in Laikipia County, Kenya

Abstract

This paper initiates a petrochronological study of Mpala Research Center in Laikipia County, Kenya. Previous work has conducted low resolution geologic mapping of the region, but robust U-Pb age data is lacking and the area remains understudied. This study seeks to constrain the composition and ages for the Nglesha Phonolites, the Ndura Complex, the Don Dol Gneisses, and G2 intrusive granites. Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), we find ages for 8 of 13 samples in this study. Ages were determined for the Ndura Complex, the Don Dol Gneisses, and the G2 intrusive granites. Of the 8 ages, 3 contained concordant data and provide ages we can state with confidence. An age of 590 ± 14 Ma was determined from sample AP22-4 of the Ndura Complex, an ages of 582.6 ± 8.1 Ma and 811 ±13 Ma were determined for samples AP22-9 and AP22-10 of the Don Dol Gneisses (all 2σ uncertainties). The remainder of the samples from which ages were calculated provide ages which contain discordant data, and cannot be stated with certainty.