Mapping the Igwisi Hills kimberlite volcanoes, Tanzania: understanding how deep-sourced mantle magmas behave at the Earth`s surface

Richard J. Brown, R S. Sparks
2010
This is a Full Scientific Report resulting from NERC Geophysical Equipment Facility Loan 894, principal investigator Prof Stephen Sparks

Abstract

The Igwisi Hills volcanoes, Tanzania, are the youngest and best-preserved kimberlite volcanoes on Earth. Uniquely they preserve the surface deposits and constructs, which are absent at all other kimberlite volcanoes. They provide an unparalleled opportunity to investigate the eruptive dynamics of ultrabasic kimberlite magmas. The volcanoes are situated in a remote part of western Tanzania and detailed topographic maps and high resolution aerial photography do not exist. As part of a detailed field study of the volcanoes, a Leica 1200 differential GPS, loaned from GEF, was used to undertake a high resolution topographic survey of the Igwisi Hills volcanoes. RTK continuous GPS surveying of the volcanoes and their surrounds captured the morphology of the volcanoes and provided the base for the first detailed geological map of these unique edifices. The field study revealed important new insights into kimberlite volcanism, including the presence of viscous kimberlite lava flows (e.g., a lava coulee) and kimberlite cinder cones. The detailed GPS survey captured primary morphological features pertinent to understanding the nature of the eruptions and will help to constrain the volume of the volcanic constructs and the erupted products.


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