Growth fault control of Early Archaean cherts, barite mounds and chert-barite veins, North Pole Dome, Eastern Pilbara, Western Australia

https://doi.org/10.1016/S0301-9268(97)00062-4Get rights and content

Abstract

This paper describes the results of detailed mapping and combined structural and sedimentologic investigation of the ∼ 3.5 Ga old North Pole Chert along the eastern and southern flanks of the North Pole granitoid dome of the Pilbara craton. The following relationships have been found. (1) Stepwise and repeated thickening over north block-down listric normal growth faults, now tilted to 120 E. Apart from the thickness distribution, the growth fault character has been inferred from progressive upward decrease of throw towards gentle flexuring, and the presence of roll-over anticlines, in a restored pre-tilt cross-section. The faults are unrelated to the actual geometry of the dome, and overprinted by pre-doming compressive deformation. (2) A reconsideration of the sedimentary model of the chert-barite unit with emphasis on vertical grainsize distribution and facies architecture shows direct synsedimentary fault control. (3) Black chert veins, clustered in the hangingwall blocks of the growth faults follow a conjugate fracture pattern in and immediately beneath the North Pole Chert, symmetrical with respect to the synsedimentary fault geometry. Upwards, the veins terminate in the lowermost chert-barite unit of the North Pole Chert; downwards, the majority of the veins converge towards centres at the growth faults in the underlying basalt. (5) Barite occurs: in veins, in association with black chert; as large synsedimentary mounds (15 m high, 50 m wide), formed on the original shallow subaqueous basin floor; as commonly silicified sinters and sedimentary or early diagenetic evaporite associated with littoral and/or stromatoloidal facies. The barite mounds are directly connected with chert-barite veins, and are uplapped by banded sedimentary chert and diamictite with barite clasts. Field relationships suggest precipitation of barite, particularly in the mounds, may have been primary and synsedimentary. Vein barite at or near the original depositional surface of the chert is associated with base metal sulphide at depth. The tectono-sedimentary relationships between normal faults, sedimentation patterns and thickness distribution, primary and secondary chert, synsedimentary barite mounds, stratiform barite and chert-barite veins, support a tensional fault-controlled, hydrothermal model with Ba, Si and sulphide emanation in ca 50 m depth of water. Such a model envisages boiling and/or degassing above vents to locally mix a normally stratified water body, causing instantaneous oxidization into sulphate. The sedimentary model of the North Pole Chert indicates repeated uplift and subsidence, with development of faults and fractures, the intensity of which diminished from the lowermost chert-barite unit of the North Pole Chert to the uppermost, fifth unit.

References (55)

  • W.P. Lanier et al.

    Sedimentology of the Middle Marker (3.4 Ga), Onverwacht Group, Transvaal, South Africa

    Precam. Res.

    (1982)
  • D.R. Lowe

    Restricted shallow-water sedimentation of early Archean stromatolithic and evaporitic strata of the Strelley Pool Chert, Pilbara Block, W.A.

    Precam. Res.

    (1983)
  • N.J. McNaughton et al.

    Constraints on the age of the Warrawoona Group, eastern Pilbara Block, Western Australia

  • K. Sugitani

    Geochemical characteristics of Archean cherts and other sedimentary rocks in the Pilbara Block, Western Australia: evidence for Archean seawater enriched in hydrothermally-derived iron and silica

    Precam. Res.

    (1992)
  • R.I. Thorpe et al.

    U Pb zircon geochronology of Archaean felsic units in the Marble Bar region, Pilbara Craton, Western Australia

    Precam. Res.

    (1992)
  • W.M. Van Haaften et al.

    Evidence for multiphase deformation in the Archean basal Warrawoona Group in the Marble Bar area, East Pilbara, Western Australia

    Precam. Res.

    (1998)
  • S.M. Awramik

    New fossil finds in old rock

    Nature

    (1986)
  • M.E. Barley

    Volcanism and hydrothermal alteration, Warrawoona Group, East Pilbara

  • M.E. Barley

    A review of Archean volcanic-hosted massive sulphide and sulphate mineralization in Western Australia

    Econ. Geol.

    (1992)
  • K.K. Bertine et al.

    Submarine barite-opal rocks of hydrothermal origin

    Science

    (1975)
  • R. Buick

    Life and conditions in the early Archaean: evidence from 3500 m.y. old shallow-water sediments in the Warrawoona Group, North Pole, Western Australia

  • R. Buick

    Microfossil recognition in Archean rocks: an appraisal of spheroids and filaments from a 3500 m.y. old chert-barite unit at North Pole, Western Australia

    Palaios

    (1990)
  • R. Buick et al.

    Cherts in the Warrawoona Group: Early Archaean silicified sediments deposited in shallow-water environments

  • R. Buick et al.

    Evaporitic sediments of early Archean age from the Warrawoona Group, North Pole, W.A.

    Sedimentology

    (1990)
  • R. Buick et al.

    Stromatolite recognition in ancient rocks: an appraisal of irregular laminated structures in an early Archaean chert-barite unit from North Pole, Western Australia

    Alcheringa

    (1981)
  • R. Buick et al.

    Record of emergent continental crust ∼ 3.5 billion years ago in the Pilbara craton of Australia

    Nature

    (1995)
  • R.A.F. Cas

    Submarine volcanism: eruption styles, products, and relevance to understanding the host-rock successions to volcanic-hosted massive sulphide deposits

    Econ. Geol.

    (1992)
  • Cited by (109)

    • Early Archean biogeochemical iron cycling and nutrient availability: New insights from a 3.5 Ga land-sea transition

      2022, Earth-Science Reviews
      Citation Excerpt :

      Given our focus on jaspilites, no samples from A2 were taken. The syn-depositional nature of many of the chert-barite veins support the volcanic caldera model put forth for the Dresser Formation lower chert-barite sequence (Nijman et al., 1998; Van Kranendonk et al., 2008, 2019a; Tadbiri and Van Kranendonk, 2020), and provide important constraints on hydrothermal fluid compositions. It is expected that Fe in the A1 jaspilites should reflect local sources, either from the deep, local vein system, or from surface water runoff, given the inferred lacustrine or restricted depositional conditions indicated by their restricted lateral occurrence.

    View all citing articles on Scopus
    1

    Present address: Netherlands Research School of Sedimentary Geology, Free University, Amsterdam. The Netherlands.

    2

    Present address: Shell U.K., Exploration and Production, Aberdeen. Scotland.

    View full text