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https://hdl.handle.net/2440/126941
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Type: | Journal article |
Title: | Experimental alteration of monazite in granitic melt: Variable U–Th–Pb and REE mobility during melt-mediated coupled dissolution-precipitation |
Author: | Varga, J. Raimondo, T. Daczko, N.R. Adam, J. |
Citation: | Chemical Geology, 2020; 544:1-16 |
Publisher: | Elsevier |
Issue Date: | 2020 |
ISSN: | 0009-2541 1872-6836 |
Statement of Responsibility: | Jan Varga, Tom Raimondo, Nathan R.Daczko, John Adam |
Abstract: | Monazite U–Th–Pb geochronology of high-temperature and melt-bearing metamorphic rocks sometimes produces a continuum of concordant ages (‘smear’) without well-defined age populations. In combination with textural and geochemical criteria, these datasets are typically interpreted to infer either variable Pb-loss between two discrete events or protracted metamorphism lasting >50 Myr. We experimentally react monazite with granitic melt (0.7 GPa and 750 °C) to produce a range of complex monazite textures and age patterns similar to those found in natural high-temperature rock samples. Our observations show that within a short duration (≤24 h experiment time), variable REE, Y, Th, U and Pb mobility is achieved via coupled dissolution-precipitation in a melt-bearing system. An ultra-local interface melt is saturated in dissolved components, including the U–Th–Pb isotopic character of the original monazite, such that newly precipitated monazite may copy or partly inherit the age of a precursor grain. This implies that monazite grown via coupled dissolution-precipitation may not faithfully record the age or duration of metamorphism in melt-bearing rocks typical of a variety of geodynamic settings. |
Keywords: | Monazite; experimental petrology; U–Th–Pb; coupled dissolution-precipitation; metamorphism |
Rights: | © 2020 Elsevier B.V. All rights reserved. |
DOI: | 10.1016/j.chemgeo.2020.119602 |
Grant ID: | http://purl.org/au-research/grants/arc/DP160103449 |
Published version: | http://dx.doi.org/10.1016/j.chemgeo.2020.119602 |
Appears in Collections: | Aurora harvest 4 Geology & Geophysics publications |
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