The geochemical and Sr-Nd isotopic characteristics of the Palaeozoic S-types granites of far north Queensland: implications for S-type granite petrogenesis  

Authors / CoAuthors

Champion, D.C. | Bultitude, R.J.

Abstract

Palaeozoic S- and I-type granites crop out extensively (~3400 km2) in the eastern and central parts of the Ordovician?Devonian Hodgkinson Province of far north Queensland. S-types dominate and form two NW to NNW trending belts, sub-parallel to major structural elements in the province. The S-types granites have been subdivided into two major (Cooktown, Whypalla) and five minor (Mount Alto, Wangetti, Tinaroo, Mount Formartine, Emerald Creek) supersuites (Bultitude & Champion, 1992; Champion & Bultitude, 1994). Most are Permian (~280 to 255 Ma); only the Emerald Creek and Mount Formartine Supersuites are older. Possible petrogenetic models for the generation of S-type granites, in general, range from crustal melting to multi-component mixing. The most obvious potential source for the north Queensland S-types is the voluminous quartzofeldspathic flysch of the Hodgkinson Province. However, most of these rocks are too mature, with chemical and isotopic signatures (?Nd values of -11 to -15 at 280 Ma), reflecting their derivation from felsic rocks similar to those exposed in the Proterozoic inliers to the west. Volcanolithic arenites, with the appropriate ?Nd value (-4.7 at 280 Ma), although not common, have been found in the far east of the province. Consequently, Champion & Bultitude (1994) proposed a source protolith consisting of both supracrustal and infracrustal arc-derived rocks, of late Proterozoic and/or early-middle Palaeozoic age. These rocks either form part of, or underlie the Hodgkinson Province assemblage. The presence of Devonian and Ordovician granites in the region, with similar chemistry and isotopic signatures to the Permian S-type granites, strongly indicates the existence of older protoliths capable of producing S-type granites. Multi-component models are more difficult to evaluate. The scarcity of 'microdioritic' enclaves and other possible indicators of mixing/mingling in the Permian S-type granites, combined with the overlapping Nd isotopic signatures for the Permian S- and I-type granites, imply magma mixing was not a significant factor. This does not rule out multiple-source components as implied by the range in ?Nd values shown by the S-types. One possibility is a multi-component protolith comprising either a heterogeneous source (such as a mixture of supracrustal and infracrustal rocks) or, alternatively, a mixed source produced during a pre-Permian magmatic event that involved significant crustal (sedimentary) contamination. Both scenarios are compatible with the preferred model protolith described above.

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nonGeographicDataset

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36676

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Keywords

• External PublicationScientific Journal Paper

( Theme )

• geochemistry

( Theme )

• geology

( Theme )

• petrology

• AU-QLD

Australian and New Zealand Standard Research Classification (ANZSRC)

• Earth Sciences

• Published_Internal

Publication Date

2001-05-04T00:00:00

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geoscientificInformation

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[-18.0, -15.0, 144.0, 146.0]

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