A 3500 Ma plutonic and volcanic calc-alkaline province in the Archaean East Pilbara Block

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Authors:Bickle, M. J.; Bettenay, L. F.; Barley, M. E.; Chapman, H. J.; Groves, D. I.; Campbell, I. H.; de Laeter, J. R.
Author Affiliations:Primary:
Univ. West. Aust., Dep. Geol., Nedlands, West. Aust. 6009, Australia
Other:
Univ. Toronto, Earth and Planet. Sci. Erindale Campus, Canada
West. Aust. Inst. Technol., Dep. Phys. and Geosci., Australia
Volume Title:Contributions to Mineralogy and Petrology
Source:Contributions to Mineralogy and Petrology, 84(1), p.25-35. Publisher: Springer International, Heidelberg-New York, International. ISSN: 0010-7999
Publication Date:1983
Note:In English. 59 refs.; illus. incl. 21 anal., 5 tables, geol. sketch maps
Summary:Variably foliated, predominantly granodioritic plutonic rocks from the northern part of the Shaw batholith, E Pilbara Archaean craton, NW Western Australia, are dated at 3499 + or - 22 m.y. by a whole-rock Pb/Pb isochron. These rocks intrude the surrounding greenstone sequence, from which their age is indistinguishable. High-strain grey gneisses which occupy much of the western and southern Shaw batholith are chemically and isotopically similar to the North Shaw suite and are inferred to have derived from this suite by tectonic processes. Felsic volcanic rocks within the greenstones, together with a major portion of the granitic batholiths, apparently formed in a calc-alkaline volcanic and plutonic province approx 3500 m.y. ago. This suite is similar to modern calc-alkaline suites on the basis of major-element, REE and most other trace-element contents. The Archaean suite contrasts with modern equivalents only in having lower concentrations of HREE and higher Ni and Cr. The North Shaw suite is similar to that of Archaean gneiss belts for most elements and fits the hypothesis that the Shaw batholith is transitional to the upper crustal level of a high-grade gneiss belt. Enrichment of the gneissic crust in alkali and heat-producing elements is inferred to have taken place by igneous and hydrothermal processes over a protracted time interval. Late- and post-tectonic adamellite and granite melts intrude the gneissic rocks, and there is isotopic evidence suggesting that the gneisses were enriched in Rb by pegmatite injection approx 3000 m.y. ago. Major- and trace-element data for 17 Shaw batholith granitoids are presented, with Pb- and Sr-isotopic data. [P.Br.]
Subjects:Absolute age; Archean; Batholiths; Calc-alkalic composition; Chemical composition; Dates; Geochemistry; Gneisses; Granites; Granodiorites; Igneous rocks; Intrusions; Magmas; Magmatic associations; Metals; Metamorphic rocks; Pb/Pb; Petrology; Plutonic rocks; Precambrian; Properties; Rare earths; Stratigraphy; Trace elements; Volcanic rocks; Australasia; Australia; Western Australia; Shaw Batholith
Abstract Numbers:84M/2035
Record ID:1987059145
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique
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