Petrogenesis of a TTG intrusive suite: the La Dauversière pluton, Abitibi greenstone belt, Canada

Abstract

Insights into the source and partial-melting conditions of tonalite-trondhjemite-granodiorite (TTG) intrusive suites provide essential constraints on the tectonic regimes prevailing before 2.5 Ga. As case studies on individual suites increase, the TTG group becomes more heterogeneous, offering detailed insights into the evolution of the Archean crust. This study focuses on the La Dauversière pluton, a TTG suite in the Chibougamau area, Abitibi greenstone belt, Canada, to unravel complex differentiation processes in a pluton with a relatively limited volume. According to whole rock and zircon chemistry, the La Dauversière pluton is a TTG suite that contains less Na and LREE than other TTG suites of the Abitibi greenstone belt. Whole rock chemistry and melt inclusions in zircon also point to an atypical fractional crystallization process that favors K enrichment, contrasting with the Na enrichment trends observed in most TTG suites globally. Magma hybridization, with late magma pulses interacting with early phases partially crystallized at depth, likely explains the chemistry of the La Dauversière pluton. The source of these magmas differs from the basaltic source that gave rise to most TTG suites of the Abitibi greenstone belt, possibly because older basement occurs in the Chibougamau area and is lacking in the rest of the greenstone belt. The La Dauversière pluton underscores the importance of interpreting the petrogenesis of individual TTG suites before inferring global source processes and geodynamic settings.