Monazite as a monitor of melting, garnet growth and feldspar recrystallization in continental lower crust

• DOI: 10.1111/jmg.12150
• Publication Date: 2015-07-01T15:18:55Z
• Authors: G. Dumond; P. Goncalves; M. L. Williams; M. J. Jercinovic
• Keywords: Felsic; Grossular

Abstract Monazite is a common accessory phase in felsic granulite ribbon mylonites exposed the Upper Deck domain of Athabasca terrane, western Canadian Shield. Field relationships, bulk rock geochemistry and equilibria modelling Na 2 O–CaO–K O–FeO–MgO–Al O 3 –SiO –H O–TiO –Fe system are consistent with garnet‐rich rocks representing residual products ultrahigh temperature melting biotite‐bearing paragneisses driven by intraplating mafic magma continental lower crust. The c . 2.64–2.61 Ga Y‐rich resorbed monazite cores included garnet interpreted as relicts detrital grains deposited on Earth's surface after 2.61 Ga. Yttrium‐poor domains depleted Sm Gd linked to fluid‐absent biotite + plagioclase quartz ± sillimanite during prograde loading path from ≤ 0.8 ≥1.4 GP a. 2.61–2.55 Y‐depleted, Th‐rich crystallized presence ternary feldspar orthopyroxene peraluminous melt. 2.58–2.52 rims Th Ca enriched Eu localized melt extraction synchronous growth high‐pressure (HP) grossular‐rich at expense crustal thickening, culminating >950 °C. Re‐heating dextral transpressive reactivation 1.9 resulted syn‐kinematic (La Ce)‐enriched second generation garnet, concurrent recrystallization 1.0–1.2 600–700 this study marked positive Eu‐anomalies relative chondrite. A direct link implied between Y, Sm, two major phases crust: plagioclase. Positive associated modally abundant appear be directly related Eu‐enrichment depletions that consequences breakdown HP compositions.