In:
Journal of Petrology, Oxford University Press (OUP), Vol. 60, No. 7 ( 2019-07-01), p. 1461-1487
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.
Type of Medium:
Online Resource
ISSN:
0022-3530
,
1460-2415
DOI:
10.1093/petrology/egz036
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
2019
detail.hit.zdb_id:
1466724-1
SSG:
13
