Abstract
Magmatic processes dominate Fe–Ti–V mineralization and revealing these processes is essential for providing a scientific foundation for exploration models. This study focuses on the metamorphosed Neoarchean (ca. 2728 Ma) tholeiitic layered Lac Doré Complex (LDC) that is currently being explored for V. Contamination may play an important role in the evolution of the Fe–Ti–V-enriched layered zone (magnetitite, anorthosite, and gabbro mostly, and ultramafic rocks locally) of the LDC. This hypothesis is tested by performing a detailed chemical and petrological investigation of serpentine-magnetite-dominated rocks located in the Mt. Sorcerer area. The studied rocks have evolved (apatite-bearing, Fe-rich, Cr-Ni-Ti-poor) and primitive (Mg-rich, Si-poor) characteristics. Pre-metamorphism rocks contained olivine Fo82–90 (now serpentine) and magnetite. These rocks formed from a Si-depleted magma under high fO2 conditions (+1.8 to +3.0 relative to the fayalite-magnetite-quartz buffer; FMQ). The V-content of the magnetite varies due to reversals related to multiple injections of an evolved basaltic magma in the upper part of the LDC. The magma interacted with Fe-Mg-rich and Si-Ca-poor carbonate-facies iron formation and crystallized in the presence of oxidizing CO2-bearing fluids. Compositional layering is poorly defined due to a fast cooling rate. Consequently, the distribution of V is relatively homogeneous in the Fe–Mg-rich units of the Mt. Sorcerer area.
Highlights
The Lac Doré Complex (LDC) is a metamorphosed Neoarchean layered intrusion located in the NE corner of the Abitibi Subprovince
The layered zone is the focus of most studies carried on the LDC [3,4,5] but many questions remain on its origin and magmatic evolution
The serpentine aggregates are rimmed by elongated grains of inclusion-free magnetite that correspond to Fe expelled from the structure of the olivine during metamorphism (Figure 5a,b)
Summary
The Lac Doré Complex (LDC) is a metamorphosed Neoarchean layered intrusion located in the NE corner of the Abitibi Subprovince. The exposed portion of the LDC comprises a thick anorthosite and gabbro dominated unit, a Fe-enriched layered zone, and a tonalitic unit designated sodagranophyre zone. As many similar Fe-enriched rocks observed in layered intrusions around the world, the layered zone of the LDC is potentially economic for V, Ti, and Fe. The layered zone is the focus of most studies carried on the LDC [3,4,5] but many questions remain on its origin and magmatic evolution. The layered zone is the focus of most studies carried on the LDC [3,4,5] but many questions remain on its origin and magmatic evolution Addressing these issues may have consequences for our general comprehension of Fe- and V-enriched magmas
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