The paleoproterozoic metaplutonic suite of Voisey's Bay, Labrador: a geochemical, tectonic and metallogenic investigation

• Main Author: Rawlings, Alana Maxine
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2001
• Subjects: Nain
• Online Access: https://research.library.mun.ca/6551/; https://research.library.mun.ca/6551/1/AlanaMaxineRawlings.pdf; https://research.library.mun.ca/6551/3/AlanaMaxineRawlings.pdf

The Paleoproterozoic Torngat Orogen of northern Labrador welds the Nain and Rae Archean cratons. A suite of calc-alkaline metaplutonic rocks has been identified in the Voisey’s Bay area and these rocks are believed to represent a southern extension of similar metaplutonic rocks identified along the some 500 km length of the orogeny. In addition the ore-bearing troctolites of the recently discovered Voisey’s Bay Ni-Co-Cu deposit are located within the metaplutonic suite. -- This study involves detailed geology, geochemistry, isotopic composition and geochronology of the Paleoproterozoic metaplutonic suite in the Voisey’s Bay area. To determine: (1) the petrogenesis of the metaplutonic rocks and constrain the Paleoproterozoic tectonic setting of the region; and (2) the role of the metaplutonic rocks in crustal contamination of the Voisey’s Bay troctolitic intrusion and the genesis of the Ni-Cu-Co deposit. -- The Paleoproterozoic metaplutonic rocks are a relatively undifferentiated, mafic to intermediate calc-alkaline batholith. The rocks have been metamorphosed to upper amphibolite of granulite facies and interleaved with newly discovered sulfide-rich paragneisses, amphibolite and meta-anorthosite. Recent mapping of this thesis shows that the metaplutonic suite covers a sizeable geographic area encompassing most parts of the Voisey’s Bay Ni-Cu-Co ore system. Two samples give ages of 1893 +/-1 Ma and 1890 +/-2 Ma by U-Pb zircon TIMS geochronology. Based on LAM-ICP-MS, one of these samples contained inherited zircon cores, some 50-100 Ma older than the igneous population, but no Archean cores were found in this sample of the two others. Metatonalite rocks of this suite probably form during a slightly younger magmatic event dated 18 1883 +/-5 Ma. All the compositions are enriched in relative amounts of Ba, Sr, Rb, Ar and Hf; and have negative Nb-Ta anomalies. This trace element chemistry of the rocks is distinctive and markedly similar to the Voisey’s Bay deposit, specifically in possessing Th-U and Nb-Ta depletions ...