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Direct dating of authigenic K-feldspar overgrowths from the Kilombero Rift of Tanzania

Hagen, E.; Kelley, S.P.; Dypvik, H.; Nilsen, O and Kjolhamar, B. (2001). Direct dating of authigenic K-feldspar overgrowths from the Kilombero Rift of Tanzania. Journal of the Geological Society, 158(5) pp. 801–807.

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Abstract

K-feldspars form important detrital and authigenic components in sediments but may be difficult to separate by conventional means for isotope analysis, particularly geochronology. UV lasers are being increasing applied to in situ analysis since they are strongly absorbed by clear minerals such as K-feldspar, and can achieve a spatial resolution of better than 20 mum for individual Ar/Ar analyses. Here we demonstrate separation of detrital K-feldspar with a mean age of 423 +/- 14 Ma and authigenic overgrowths with a mean age of 138 +/- 5 Ma in elastic sediments from the Msolwa Group of the Kilombero Rift of Tanzania. The young age obtained for authigenic K-feldspar overgrowth demonstrates that precipitation occurred more than 160 Ma after sedimentation, during the period of deepest burial and synchronous with the initial extensional phases of the intracontinental Anza and Sudan rifts, as well as the initial stages in the break-up and separation of South America and Africa.

Item Type: Journal Article
ISSN: 0016-7649
Keywords: Geochronology; Eastern Tanzania; South-Atlantic; laser-probe; Anza Rift; history; evolution; Kenya; sedimentation; province
Academic Unit/Department: Science > Environment, Earth and Ecosystems
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 4194
Depositing User: Simon Kelley
Date Deposited: 04 Jul 2006
Last Modified: 02 Dec 2010 19:51
URI: http://oro.open.ac.uk/id/eprint/4194
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