Ar-40/Ar-39 dating of exceptional concentration of metals by weathering of Precambrian rocks at the Precambrian-Cambrian boundary

John Parnell*, Darren F Mark, Robert Frei, Anthony E Fallick, Rob M Ellam

*Corresponding author for this work

Research output: Contribution to journalArticle

5 Citations (Scopus)
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Abstract

The sub-Cambrian surface, including diverse metalliferous deposits, shows evidence of intense weathering of Precambrian rocks to form supergene-enriched ores and metalliferous placers, followed by widespread peneplanation. Much of the metal would have been flushed to the Cambrian ocean during peneplanation. An Ar-40/Ar-39 age of 542.62 +/- 0.38 Ma (1 sigma, full external precision, Renne et al., 2011) for metalliferous alteration clays in Scotland shows that this event occurred immediately prior to the Precambrian-Cambrian boundary. A negative delta Cr-53 isotopic signature for the clay is consistent with mobilization on land of redox sensitive metals by oxidative terrestrial weathering. This unprecedented flushing of metals from the weathered Precambrian surface would have contributed to the chemistry of the earliest Cambrian ocean at a time of marked faunal evolution. (C) 2014 Elsevier B.V. All rights reserved.

Original languageEnglish
Pages (from-to)54-63
Number of pages10
JournalPrecambrian Research
Volume246
DOIs
Publication statusPublished - Jun 2014

Keywords

  • Precambrian
  • Precambrian-Cambrian boundary
  • great unconformity
  • ore deposits
  • weathering
  • Metazoan
  • Fish Canyon sanidine
  • K-40 decay constants
  • isotopic composition
  • joint determination
  • chromium isotopes
  • improved accuracy
  • geochronology
  • constraints
  • supergorup
  • transition

Cite this

Ar-40/Ar-39 dating of exceptional concentration of metals by weathering of Precambrian rocks at the Precambrian-Cambrian boundary. / Parnell, John; Mark, Darren F; Frei, Robert; Fallick, Anthony E; Ellam, Rob M.

In: Precambrian Research, Vol. 246, 06.2014, p. 54-63.

Research output: Contribution to journalArticle

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title = "Ar-40/Ar-39 dating of exceptional concentration of metals by weathering of Precambrian rocks at the Precambrian-Cambrian boundary",
abstract = "The sub-Cambrian surface, including diverse metalliferous deposits, shows evidence of intense weathering of Precambrian rocks to form supergene-enriched ores and metalliferous placers, followed by widespread peneplanation. Much of the metal would have been flushed to the Cambrian ocean during peneplanation. An Ar-40/Ar-39 age of 542.62 +/- 0.38 Ma (1 sigma, full external precision, Renne et al., 2011) for metalliferous alteration clays in Scotland shows that this event occurred immediately prior to the Precambrian-Cambrian boundary. A negative delta Cr-53 isotopic signature for the clay is consistent with mobilization on land of redox sensitive metals by oxidative terrestrial weathering. This unprecedented flushing of metals from the weathered Precambrian surface would have contributed to the chemistry of the earliest Cambrian ocean at a time of marked faunal evolution. (C) 2014 Elsevier B.V. All rights reserved.",
keywords = "Precambrian, Precambrian-Cambrian boundary, great unconformity, ore deposits, weathering, Metazoan, Fish Canyon sanidine, K-40 decay constants, isotopic composition, joint determination, chromium isotopes, improved accuracy, geochronology, constraints, supergorup, transition",
author = "John Parnell and Mark, {Darren F} and Robert Frei and Fallick, {Anthony E} and Ellam, {Rob M}",
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AB - The sub-Cambrian surface, including diverse metalliferous deposits, shows evidence of intense weathering of Precambrian rocks to form supergene-enriched ores and metalliferous placers, followed by widespread peneplanation. Much of the metal would have been flushed to the Cambrian ocean during peneplanation. An Ar-40/Ar-39 age of 542.62 +/- 0.38 Ma (1 sigma, full external precision, Renne et al., 2011) for metalliferous alteration clays in Scotland shows that this event occurred immediately prior to the Precambrian-Cambrian boundary. A negative delta Cr-53 isotopic signature for the clay is consistent with mobilization on land of redox sensitive metals by oxidative terrestrial weathering. This unprecedented flushing of metals from the weathered Precambrian surface would have contributed to the chemistry of the earliest Cambrian ocean at a time of marked faunal evolution. (C) 2014 Elsevier B.V. All rights reserved.

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KW - Metazoan

KW - Fish Canyon sanidine

KW - K-40 decay constants

KW - isotopic composition

KW - joint determination

KW - chromium isotopes

KW - improved accuracy

KW - geochronology

KW - constraints

KW - supergorup

KW - transition

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