The Hlagothi Complex: The identification of fragments from a Mesoarchaean large igneous province on the Kaapvaal Craton

A. P. Gumsley, M. O. De Kock, H. M. Rajesh, M. W. Knoper, U. Söderlund, R. E. Ernst

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Abstract

In this paper, we present geochronological, geochemical and palaeomagnetic results from the Hlagothi Complex and a NW-trending dolerite dyke swarm on the southeastern region of the Kaapvaal Craton in northern KwaZulu-Natal, South Africa. The Hlagothi Complex consists of layered sills of meta-peridotite, pyroxenite and gabbro intruding into the Pongola Supergroup. U-Pb baddeleyite ages on the Hlagothi Complex and a NW-trending dyke of 2866. ±. 2. Ma and 2874. ±. 2. Ma, respectively, reveal a ca. 2.87. Ga magmatic event on the southeastern Kaapvaal Craton. The geochemical signature of the Hlagothi Complex recognises two discrete groupings, with a magmatic source that is chemically distinct from those of the older rift-related Nsuze and Dominion groups. Additional units on the Kaapvaal Craton can be linked with this new 'Hlagothi' event based on spatial and temporal association, and geochemistry: 1) the Thole Complex, 2) parts of the Usushwana Complex, and 3) flood basalts within the Mozaan Group and Central Rand Group. The association between all these units suggests a previously unrecognised large igneous province in the southeastern Kaapvaal Craton. Our palaeomagnetic data identifies a possible primary magnetisation within the least-altered lithologies of the Hlagothi Complex (with a virtual geographic pole at 23.4°N, 53.4°E, dp. =. 8.2° and dm. =. 11.8°). The bulk of samples however, displayed two episodes of remagnetisation. These are likely to be associated with 2.85 to 2.75. Ga aged granitoids across the southeastern Kaapvaal Craton, and tectonic activity in the nearby Meso- to Neoproterozoic Namaqua-Natal mobile belt. A short-lived (≤. 8. Ma) mantle plume is proposed to have caused the ca. 2.87. Ga magmatism, and also may well have controlled sedimentation within the Pongola-Witwatersrand basin. Volcanism during uplift would have been fed through a series of feeder dykes and sills, of which the Hlagothi Complex and NW-trending dykes are part of.

Original languageEnglish
Pages (from-to)333-348
Number of pages16
JournalLithos
Volume174
DOIs
Publication statusPublished - Aug 1 2013

Fingerprint

large igneous province
craton
Association reactions
Geochemistry
Lithology
Tectonics
Sedimentation
Poles
Magnetization
sill
baddeleyite
remagnetization
mobile belt
dike swarm
pyroxenite
flood basalt
mantle plume
diabase
gabbro
magnetization

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology

Cite this

Gumsley, A. P. ; De Kock, M. O. ; Rajesh, H. M. ; Knoper, M. W. ; Söderlund, U. ; Ernst, R. E. / The Hlagothi Complex : The identification of fragments from a Mesoarchaean large igneous province on the Kaapvaal Craton. In: Lithos. 2013 ; Vol. 174. pp. 333-348.
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The Hlagothi Complex : The identification of fragments from a Mesoarchaean large igneous province on the Kaapvaal Craton. / Gumsley, A. P.; De Kock, M. O.; Rajesh, H. M.; Knoper, M. W.; Söderlund, U.; Ernst, R. E.

In: Lithos, Vol. 174, 01.08.2013, p. 333-348.

Research output: Contribution to journalArticle

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T1 - The Hlagothi Complex

T2 - The identification of fragments from a Mesoarchaean large igneous province on the Kaapvaal Craton

AU - Gumsley, A. P.

AU - De Kock, M. O.

AU - Rajesh, H. M.

AU - Knoper, M. W.

AU - Söderlund, U.

AU - Ernst, R. E.

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N2 - In this paper, we present geochronological, geochemical and palaeomagnetic results from the Hlagothi Complex and a NW-trending dolerite dyke swarm on the southeastern region of the Kaapvaal Craton in northern KwaZulu-Natal, South Africa. The Hlagothi Complex consists of layered sills of meta-peridotite, pyroxenite and gabbro intruding into the Pongola Supergroup. U-Pb baddeleyite ages on the Hlagothi Complex and a NW-trending dyke of 2866. ±. 2. Ma and 2874. ±. 2. Ma, respectively, reveal a ca. 2.87. Ga magmatic event on the southeastern Kaapvaal Craton. The geochemical signature of the Hlagothi Complex recognises two discrete groupings, with a magmatic source that is chemically distinct from those of the older rift-related Nsuze and Dominion groups. Additional units on the Kaapvaal Craton can be linked with this new 'Hlagothi' event based on spatial and temporal association, and geochemistry: 1) the Thole Complex, 2) parts of the Usushwana Complex, and 3) flood basalts within the Mozaan Group and Central Rand Group. The association between all these units suggests a previously unrecognised large igneous province in the southeastern Kaapvaal Craton. Our palaeomagnetic data identifies a possible primary magnetisation within the least-altered lithologies of the Hlagothi Complex (with a virtual geographic pole at 23.4°N, 53.4°E, dp. =. 8.2° and dm. =. 11.8°). The bulk of samples however, displayed two episodes of remagnetisation. These are likely to be associated with 2.85 to 2.75. Ga aged granitoids across the southeastern Kaapvaal Craton, and tectonic activity in the nearby Meso- to Neoproterozoic Namaqua-Natal mobile belt. A short-lived (≤. 8. Ma) mantle plume is proposed to have caused the ca. 2.87. Ga magmatism, and also may well have controlled sedimentation within the Pongola-Witwatersrand basin. Volcanism during uplift would have been fed through a series of feeder dykes and sills, of which the Hlagothi Complex and NW-trending dykes are part of.

AB - In this paper, we present geochronological, geochemical and palaeomagnetic results from the Hlagothi Complex and a NW-trending dolerite dyke swarm on the southeastern region of the Kaapvaal Craton in northern KwaZulu-Natal, South Africa. The Hlagothi Complex consists of layered sills of meta-peridotite, pyroxenite and gabbro intruding into the Pongola Supergroup. U-Pb baddeleyite ages on the Hlagothi Complex and a NW-trending dyke of 2866. ±. 2. Ma and 2874. ±. 2. Ma, respectively, reveal a ca. 2.87. Ga magmatic event on the southeastern Kaapvaal Craton. The geochemical signature of the Hlagothi Complex recognises two discrete groupings, with a magmatic source that is chemically distinct from those of the older rift-related Nsuze and Dominion groups. Additional units on the Kaapvaal Craton can be linked with this new 'Hlagothi' event based on spatial and temporal association, and geochemistry: 1) the Thole Complex, 2) parts of the Usushwana Complex, and 3) flood basalts within the Mozaan Group and Central Rand Group. The association between all these units suggests a previously unrecognised large igneous province in the southeastern Kaapvaal Craton. Our palaeomagnetic data identifies a possible primary magnetisation within the least-altered lithologies of the Hlagothi Complex (with a virtual geographic pole at 23.4°N, 53.4°E, dp. =. 8.2° and dm. =. 11.8°). The bulk of samples however, displayed two episodes of remagnetisation. These are likely to be associated with 2.85 to 2.75. Ga aged granitoids across the southeastern Kaapvaal Craton, and tectonic activity in the nearby Meso- to Neoproterozoic Namaqua-Natal mobile belt. A short-lived (≤. 8. Ma) mantle plume is proposed to have caused the ca. 2.87. Ga magmatism, and also may well have controlled sedimentation within the Pongola-Witwatersrand basin. Volcanism during uplift would have been fed through a series of feeder dykes and sills, of which the Hlagothi Complex and NW-trending dykes are part of.

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