Paka volcano in the northern Kenya Rift : Volcanic evolution, petrology and insights into its geothermal system

Abstract

This paper describes a PhD research proposal to be undertaken at Paka volcano in the northern Kenya Rift. The Kenya Rift spreads from Lake Turkana to northern Tanzania. A marked variation in the structural orientation style has led to the division of the Rift into three main segments i.e. the northern, central and the southern sector. Volcanism is prominent in the northern and central sectors and to lesser extend in the south sector. This is ascribed to the numerous volcanoes in both sectors of the rift with a clear distinction in volcanism culminating in the bimodal character of rocks in the north rift. This research focuses on Paka Volcano, a low lying multivent volcano located in the northern sector of the Kenyan Rift. The geological history of Paka as earlier outlined was largely hampered by scarce radiometric data, comprehensive sequence of volcanic events therefore has inherent inconsistencies. This leads to uncertainty in the assessment and understanding of its volcanic evolution. On the other hand, geochemical studies lack isotope data and complete trace element analysis and therefore some aspects of a petro genetic model cannot be fully explained. The genetic relationship of the multiple vents in the area is yet another important aspect that is unexplored. Additionally, the knowledge of the subsurface is mainly through indirect data leading to generated conceptual models that may have fundamental inaccuracies. In this study the first ever available direct data from of drill cuttings will be presented.

This project seeks to fill in the aforementioned data and knowledge gaps by carrying out detailed study through surface mapping in a new stratigraphic framework to generate and present a series of time-reconstructed eruptive maps of Paka caldera so as to develop a volcanological model outlining pre-caldera, syn-caldera and post-caldera events and also provide baseline data for geohazard assessment. Additionally, trace element and isotope geochemistry will be applied to model petrogenesis and magma processes in Paka and in the assessment of whether the multivents in the area are cogenetic or otherwise. Finally, direct data in terms of drill cuttings will be analysed petrographically and through chemical analytical techniques to understand the underlying rocks of Paka, relationship of surface and subsurface rocks, determine the base of the volcano, establish an alteration mineral structure of Paka and develop a model to constrain the available geophysical data. Through this study, therefore, best approaches for development, utilization and monitoring of the geothermal resource can be generated. This will enhance the pace of geothermal development, hence socio-economic improvement of the surrounding communities in Kenya. It will also contribute to the knowledge of the geothermal and geoscience community. The project is supported by a United Nation University fellowship and the Geothermal Development Company.