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Precise U-Pb baddeleyite age dating of the Usushwana Complex, southern Africa - Implications for the Mesoarchaean magmatic and sedimentological evolution of the Pongola Supergroup, Kaapvaal Craton

Gumsley, Ashley LU ; Olsson, Johan LU ; Söderlund, Ulf LU ; de Kock, Michiel; Hofmann, Axel and Klausen, Martin (2015) In Precambrian Research 267. p.174-185
Abstract
The Usushwana Complex of the south-eastern Kaapvaal Craton (South Africa and Swaziland), intrudes the ca. 3.6-3.1 Ga basement of the craton, as well as the Mesoarchaean volcanic and sedimentary cover succession of the Pongola Supergroup. New high-precision U-Pb dating of gabbros belonging to the Piet Retief Suite of the Usushwana Complex yield ages of 2989 +/- 1 Ma, 2990 +/- 2 Ma and 2978 +/- 2 Ma. The Piet Retief Suite represents part of an intricate magmatic feeder to a major volcanic event which gave rise to the oldest known continental flood basalts on Earth, the Nsuze volcanic rocks. Broadly coeval SE-trending dolerite dykes of the Barberton-Badplaas Dyke Swarm in the larger region of the south-eastern Kaapvaal Craton formed along the... (More)
The Usushwana Complex of the south-eastern Kaapvaal Craton (South Africa and Swaziland), intrudes the ca. 3.6-3.1 Ga basement of the craton, as well as the Mesoarchaean volcanic and sedimentary cover succession of the Pongola Supergroup. New high-precision U-Pb dating of gabbros belonging to the Piet Retief Suite of the Usushwana Complex yield ages of 2989 +/- 1 Ma, 2990 +/- 2 Ma and 2978 +/- 2 Ma. The Piet Retief Suite represents part of an intricate magmatic feeder to a major volcanic event which gave rise to the oldest known continental flood basalts on Earth, the Nsuze volcanic rocks. Broadly coeval SE-trending dolerite dykes of the Barberton-Badplaas Dyke Swarm in the larger region of the south-eastern Kaapvaal Craton formed along the same structural trend as the Usushwana Complex. One such dyke is dated herein to 2980 +/- 1 Ma. Using the high-precision U-Pb geochronological data, the Nsuze volcanic rocks can now be resolved into at least two magmatic episodes which can be correlated with parts of the Pongola Supergroup. The first episode at ca. 2.99-2.98 Ga is broadly coeval with the Pypklipberg (Nhlebela) volcanic rocks, whereas the second at ca. 2.97-2.96 Ga was near synchronous to the Agatha volcanic rocks. A dolerite sill intruding into the Mozaan Group of the Pongola Supergroup, thought to be part of the Usushwana Complex, was dated to 2869 +/- 5 Ma, and is instead coeval with the Hlagothi Complex further to the south, and provides a new minimum age for deposition of the Mozaan Group. (C) 2015 Elsevier B.V. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Usushwana Complex, Pongola Supergroup, Dolerite dykes, Dolerite sills, U-Pb baddeleyite, ID-TIMS
in
Precambrian Research
volume
267
pages
174 - 185
publisher
Elsevier
external identifiers
  • wos:000359874800010
  • scopus:84937002169
ISSN
0301-9268
DOI
10.1016/j.precamres.2015.06.010
language
English
LU publication?
yes
id
c27a6f6b-c4f7-44cc-ae3f-17846c0f44f8 (old id 7972206)
date added to LUP
2015-09-23 08:58:26
date last changed
2017-05-21 03:00:30
@article{c27a6f6b-c4f7-44cc-ae3f-17846c0f44f8,
  abstract     = {The Usushwana Complex of the south-eastern Kaapvaal Craton (South Africa and Swaziland), intrudes the ca. 3.6-3.1 Ga basement of the craton, as well as the Mesoarchaean volcanic and sedimentary cover succession of the Pongola Supergroup. New high-precision U-Pb dating of gabbros belonging to the Piet Retief Suite of the Usushwana Complex yield ages of 2989 +/- 1 Ma, 2990 +/- 2 Ma and 2978 +/- 2 Ma. The Piet Retief Suite represents part of an intricate magmatic feeder to a major volcanic event which gave rise to the oldest known continental flood basalts on Earth, the Nsuze volcanic rocks. Broadly coeval SE-trending dolerite dykes of the Barberton-Badplaas Dyke Swarm in the larger region of the south-eastern Kaapvaal Craton formed along the same structural trend as the Usushwana Complex. One such dyke is dated herein to 2980 +/- 1 Ma. Using the high-precision U-Pb geochronological data, the Nsuze volcanic rocks can now be resolved into at least two magmatic episodes which can be correlated with parts of the Pongola Supergroup. The first episode at ca. 2.99-2.98 Ga is broadly coeval with the Pypklipberg (Nhlebela) volcanic rocks, whereas the second at ca. 2.97-2.96 Ga was near synchronous to the Agatha volcanic rocks. A dolerite sill intruding into the Mozaan Group of the Pongola Supergroup, thought to be part of the Usushwana Complex, was dated to 2869 +/- 5 Ma, and is instead coeval with the Hlagothi Complex further to the south, and provides a new minimum age for deposition of the Mozaan Group. (C) 2015 Elsevier B.V. All rights reserved.},
  author       = {Gumsley, Ashley and Olsson, Johan and Söderlund, Ulf and de Kock, Michiel and Hofmann, Axel and Klausen, Martin},
  issn         = {0301-9268},
  keyword      = {Usushwana Complex,Pongola Supergroup,Dolerite dykes,Dolerite sills,U-Pb baddeleyite,ID-TIMS},
  language     = {eng},
  pages        = {174--185},
  publisher    = {Elsevier},
  series       = {Precambrian Research},
  title        = {Precise U-Pb baddeleyite age dating of the Usushwana Complex, southern Africa - Implications for the Mesoarchaean magmatic and sedimentological evolution of the Pongola Supergroup, Kaapvaal Craton},
  url          = {http://dx.doi.org/10.1016/j.precamres.2015.06.010},
  volume       = {267},
  year         = {2015},
}