Generation of the Mt Kinabalu Granite by Crustal Contamination of Intraplate Magma Modelled by Equilibrated Major Element Assimilation with Fractional Crystallization (EME-AFC)

Burton-Johnson, A; Macpherson, CG; Ottley, CJ; Nowell, GM; Boyce, AJ

Abstract

New geochemical data are presented for the composite units of the Mount Kinabalu granitoid intrusion of Borneo and utilised to explore the discrimination between crustal- and mantle-derived granitic magmas. The geochemical data demonstrate that the units making up this composite intrusion became more potassic through time. This was accompanied by an evolution of isotope ratios from a continental-affinity towards a slightly more mantle-affinity (87Sr/86Sri ∼0·7078; 143Nd/144Ndi ∼0·51245; 206Pb/204Pbi ∼18·756 for the oldest unit compared to 87Sr/86Sri ∼0·7065, 143Nd/144Ndi ∼0·51250 and 206Pb/204Pbi ∼18·721 for the younger units). Oxygen isotope ratios (calculated whole-rock δ18O of +6·5–9·3‰) do not show a clear trend with time. The isotopic data indicate that the magma cannot result only from fractional crystallization of a mantle-derived magma. Alkali metal compositions show that crustal anatexis is also an unsuitable process for genesis of the intrusion. The data indicate that the high-K units were generated by fractional crystallization of a primary, mafic magma, followed by assimilation of the partially melted sedimentary overburden. We present a new, Equilibrated Major Element -Assimilation with Fractional Crystallization (EME-AFC) approach for simultaneously modelling the major element, trace element, and radiogenic and oxygen isotope compositions during such magmatic differentiation; addressing the lack of current AFC modelling approaches for felsic, amphibole- or biotite-bearing systems. We propose that Mt Kinabalu was generated through low degree melting of upwelling fertile metasomatized mantle driven by regional crustal extension in the Late Miocene.

Citation

Burton-Johnson, A., Macpherson, C., Ottley, C., Nowell, G., & Boyce, A. (2019). Generation of the Mt Kinabalu Granite by Crustal Contamination of Intraplate Magma Modelled by Equilibrated Major Element Assimilation with Fractional Crystallization (EME-AFC). Journal of Petrology, 60(7), 1461-1487. https://doi.org/10.1093/petrology/egz036

• Journal Article Type: Article
• Acceptance Date: Jul 11, 2019
• Online Publication Date: Jul 16, 2019
• Publication Date: Jul 16, 2019
• Deposit Date: Sep 2, 2019
• Publicly Available Date: Jul 16, 2020
• Journal: Journal of Petrology
• Print ISSN: 0022-3530
• Electronic ISSN: 1460-2415
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 60
• Issue: 7
• Pages: 1461-1487
• DOI: https://doi.org/10.1093/petrology/egz036
• Public URL: https://durham-repository.worktribe.com/output/1323740