Fractionation modelling of segregations in the Toomba Basalt, north Queensland

Stephenson, P.J., Zhang, M., and Spry, M. (2000) Fractionation modelling of segregations in the Toomba Basalt, north Queensland. Australian Journal of Earth Sciences, 47 (2). pp. 291-300.

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Abstract

Segregations that are darker than their host basalt are locally common in the Late Pleistocene Toomba Basalt flow northwest of Charters Towers. At Basalt Corner this flow has been inflated to a thickness of 17 m and segregations are displayed in pipes, sheets, veins and vesicles. Their chemical compositions are distinct from the host hawaiite and least-square mixing solutions provide close models involving crystallisation of olivine, plagioclase, augite and magnetite in the cooling host basalt and gas-pressure extraction of residual melt to form the segregations. Trace-element concentrations are consistent with this mechanism and can, in general, be modelled using mineral partition coefficients from the literature. Segregations may concentrate near the edges of the inflation structures

Item ID: 12775
Item Type: Article (Refereed Research - C1)
Keywords: basalt; lava flows; magmatic segregation; petrology; Queensland
ISSN: 1440-0952
Date Deposited: 16 Jul 2012 04:20
FoR Codes: 04 EARTH SCIENCES > 0403 Geology > 040304 Igneous and Metamorphic Petrology @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
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