Geochemistry of a silicified, felsic volcaniclastic suite from the early Archaean Panorama Formation, Pilbara Block, Western Australia: an evaluation of depositional and post-depositional processes with special emphasis on the rare-earth elements

doi:10.1016/0301-9268(93)90046-5

Precambrian Research

Volume 60, Issues 1–4, January 1993, Pages 99-116

https://doi.org/10.1016/0301-9268(93)90046-5 Get rights and content

Abstract

Many elements in a suite of pervasively silicified, dacitic volcaniclastic and volcanic rocks from the early Archaean Panorama Formation, Warrawoona Group, Western Australia, were strongly depleted or enriched relative to those in equivalent unaltered units during widespread, post-depositional metasomatism. The present compositions of the altered rocks are dominated by Al₂O₃, K₂O, and SiO₂ and lie on or close to a quartz-sericite mixing line. The Al contents were probably inherited from the original dacitic rocks while Si, some K and possibly Rb may have been introduced during metasomatism. The elements Mg, Ca, Na and, to a lesser extent, Fe, Mn, and Sr, have been depleted relative to Al during alteration whereas silica has been greatly enriched. The high and variable Ba concentrations suggest that Ba, like Si, was introduced during silicification. The REE and Th were relatively immobile during alteration, and were diluted during silicification in the same proportion as Al.

Most of the rocks represent detrital sand- and silt-sized felsic tephra, debris eroded from felsic volcanic rocks or ash-fall deposits that underwent a short interval of transport and deposition dominated by physical rather than chemical processes. A few siltstones contain clay minerals that probably formed by the chemical weathering of Warrawoona Group basalts. The siltstones have lower Th and La concentrations, lower $La Lu$ ratios, and higher Sc and Cr concentrations than felsic rocks in the suite.

Regional alteration pervasively silicified the original sediments shortly after deposition. The replacement mineral assemblage indicates a maximum temperature for hydrothermal alteration of about 350°C. Because of the lack of chemical weathering and the low temperature of post-depositional alteration, REE abundances in volcaniclastic rocks of the Panorama Formation reflect their felsic volcanic provenance and are interpreted to have preserved a relict magmatic signature. The lack of a negative Eu anomaly and high $La Lu$ ratio (chondrite-normalized ratio is 7 to 39) suggest that magmas of the Panorama Formation formed by direct melting of an eclogite residue without subsequent crystallization of feldspar during the commencement of cratonization of the Pilbara Block. This origin differs from the origin of some other silicic volcanic rocks of the Duffer Formation, representing earlier felsic volcanic activity of the Warrawoona Group, that were produced by fractional crystallization from basaltic parents. This suggests a polygenetic origin for felsic magmas of the Warrawoona Group.

References (57)

M.E. Barley et al.
Sedimentary evidence for an Archean shallow-water volcanic-sedimentary facies, eastern Pilbara Block, Western Australia
Earth Planet. Sci. Lett.
(1979)
M.E. Barley et al.
Archean calc-alkaline volcanism in the Pilbara Block, Western Australia
Precambrian Res.
(1984)
M.R. Bhatia
Rare earth element geochemistry of Australian Paleozoic graywackes and mudrocks: provenance and tectonic control
Sediment. Geol.
(1985)
D.E. Buckley et al.
Atomic absorption analysis of eighteen elements from a single decomposition of aluminosilicates
Chem. Geol.
(1971)
R.L. Cullers
Mineralogical and chemical changes of soil and stream sediment formed by intense weathering of the Danburg granite, Georgia, U.S.A.
Lithos
(1988)
R.L. Cullers et al.
Rare earth elements in igneous rocks of the continental crust: intermediate and silicic rocks-ore petrogenesis
R.L. Cullers et al.
The rare earth element distributions in clay minerals and in the clay-sized fractions of the Lower Permian Havensville and Eskridge shales of Kansas and Oklahoma
Geochim. Cosmochim. Acta
(1975)
R.L. Cullers et al.
Rare-earths in size fractions and sedimentary rocks from Pennsylvanian-Permian age from the mid-continent of the U.S.A.
Geochim. Cosmochim. Acta
(1979)
R.L. Cullers et al.
Geochemistry and petrogenesis of lamproites, Late Cretaceous age, Woodson County, Kansas, U.S.A.
Geochim. Cosmochim. Acta
(1985)
R.L. Cullers et al.
Rare earth element and mineralogic changes in Holocene soil and stream sediment: a case study in the Wet Mountains, Colorado, U.S.A
Chem. Geol.
(1987)

R.L. Cullers et al.

Geochemical signature of provenance in sand-size material in soil and stream sediments near the Tobacco Root Batholith, Montana, U.S.A.

Chem. Geol.

(1988)

M.J. DiMarco et al.

Stratigraphy and sedimentology of an early Archean felsic volcanic sequence, Eastern Pilbara Block, Western Australia, with special reference to the Duffer Formation and implications for crustal evolution

Precambrian Res.

(1989)

M.J. DiMarco et al.

Shallow-water volcaniclastic deposition in the Early Archean Panorama Formation, Warrawoona Group, eastern Pilbara Block, Western Australia

Sediment. Geol.

(1989)

K.C. Duchac et al.

Origin and timing of the metasomatic silicification of an early Archean komatiite sequence, Barberton Mountain Land, South Africa

Precambrian Res.

(1987)

R.A. Exley

Microprobe studies of REE-rich accessory minerals: implications for Skye granite petrogenesis and REE mobility in hydrothermal systems

Earth Planet. Sci. Lett.

(1980)

L.P. Gromet et al.

The North American shale composite: its compilation, major and trace element characteristics

Geochim. Cosmochim. Acta

(1984)

G.E. Gordon et al.

Instrumental activation analysis of standard rocks with high resolution X-ray detectors

Geochim. Cosmochim. Acta

(1968)

B. Jahn et al.

REE geochemistry and isotopic data of Archean silicic volcanics and granitoids from the Pilbara Block, Western Australia: implications for the early crustal evolution

Geochim. Cosmochim. Acta

(1981)

J. Ludden et al.

An evaluation of the behavior of rare earth elements during the weathering of sea-floor basalts

Earth Planet. Sci. Lett.

(1979)

S.M. McLennan et al.

Rare earth elements in Huronian (Lower Proterozoic) sedimentary rocks: composition and evolution of the pre-Kenoran continental crust

Geochim. Cosmochim. Acta

(1979)

S.M. McLennan et al.

Rare earth element-thorium correlations in sedimentary rocks and the composition of the continental crust

Geochim. Cosmochim. Acta

(1980)

S.M. McLennan et al.

Geochemistry of Archean shales of the Pilbara Supergroup, Western Australia

Geochim. Cosmochim. Acta

(1983)

A. Michard et al.

The REE content of some hydrothermal fluids

Chem. Geol.

(1986)

W.B. Nance et al.

Rare earth element patterns and crustal evolution 1. Australian post-Archean sedimentary rocks

Geochim. Cosmochim. Acta

(1976)

W.B. Nance et al.

Rare earth element patterns and crustal evolution II. Archean sedimentary rocks from Kalgoorlie, Australia

Geochim. Cosmochim. Acta

(1977)

R.T. Pidgeon

3450 Ma old volcanics in the Archean layered greenstone succession of the Pilbara Block, Western Australia

Earth Planet. Sci. Lett.

(1978)

S.R. Taylor et al.

The rare earth evidence in Precambrian sedimentary rocks: implication for crustal evolution

T.R. Wildeman et al.

Rare earths in Archean graywackes from Wyoming and from the Fig Tree Group, South Africa

Geochim. Cosmochim. Acta

(1973)

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¹: Present address: Shell Western E. and P., Inc., P.O. Box 4252, Houston, TX 77210-4252, USA.

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Geochemistry of a silicified, felsic volcaniclastic suite from the early Archaean Panorama Formation, Pilbara Block, Western Australia: an evaluation of depositional and post-depositional processes with special emphasis on the rare-earth elements

Abstract

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