Geochemistry and petrogenesis of the kilimanjaro volcanic rocks of the Amboseli area,Kenya |
| |
| Authors: | L A J Williams |
| |
| Institution: | 1. Department of Geology, University College, Nairobi
|
| |
| Abstract: | The paper summarizes the geochemical and petrogenetic aspects of an investigation of late Tertiary to Recent volcanic rocks in the Amboseli area of southern Kenya. A study of chemical variations in the Amboseli and Kilimanjaro lavas distinguishes a mildly alkaline series (alkali olivine basalts, trachybasalts/trachyandesites, trachytes, rhomb porphyries and phonolites) from a strongly alkaline series embracing subordinate nephelinitic, phonolitic and tephritic lavas. The two series probably evolved independently from a source in the mantle. A comparison of Kilimanjaro with other East African volcanoes shows that the focus of strongly alkaline volcanicity moved from eastern Uganda and western Kenya to northern Tanzania at the end of Miocene times. The Pliocene to Recent centres near the Kenya-Tanzania border show evidence of decreasing alkalinity from a western zone of nephelinite-phonolite volcanoes to an eastern region in which central volcanoes are characterized by the association of strongly and mildly alkaline suites. |
| |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ |
|
