Lithology, geochemistry and geochronology of the Aillik Group and foliated granitic intrusions: implications on the formaton and early evolution of the Aillik domain, Makkovik province, Labrador

• Main Author: LaFlamme, Crystal
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2011
• Subjects: Makkovik; Middle Head
• Online Access: https://research.library.mun.ca/9594/; https://research.library.mun.ca/9594/1/LaFlamme_Crystal.pdf

The Makkovik Province of eastern Labrador is part of an accretionary orogenic belt that formed during the Paleoproterozoic Makkovikian orogeny. The Aillik domain represents one of three domains that make up the Makkovik Province and is composed of the Aillik Group, a package of Paleoproterozoic bi-modal volcano-sedimentary rocks, and abundant variably deformed Paleoproterozoic intrusive suites. The Aillik Group has experienced several phases of deformation and has been metamorphosed to lower amphibolite facies during the Makkovikian orogeny. Two areas, Middle Head and Pomaidluk Point, are the focus of this project and are used as case studies to assess and examine the Aillik Group with respect to the objectives as outlined below. Middle Head is dominated by arkosic sandstone, felsic tuff, rhyolite and basalt; whereas, Pomiadluk Point is composed primarily of felsic tuff and polymictic conglomerate with lesser preserved rhyolite and basalt. This study consists of detailed bedrock mapping in conjunction with: insitu SHRIMP U-Pb zircon geochronology, insitu LA-MC-ICPMS Hf isotopic geochemistry, major and trace element geochemistry, and whole rock Nd isotope geochemistry. These methods are used to: 1) constrain the timing of volcanism within the Aillik Group, 2) determine the source of magmatism, 3) resolve the overall tectonic setting in which the Aillik Group was deposited, and 4) briefly investigate the subsequent evolution of the Aillik domain. -- U-Pb SHRIMP zircon geochronology on felsic tuff samples yields magmatic ages that range from ca. 1852 at Middle Head to ca. 1854 - 1862 Ma at Pomiadluk Point. These U-Pb ages indicate that sections of the Aillik Group occurring 27 km from one another were deposited contemporaneously, and that felsic volcanism continued to as late as ca. 1852 Ma. A foliated Paleoproterozoic granite from Middle Head yields an age of 1805 ±4 Ma, which further constrains the timing of deformation within the Aillik Group as continuing past its emplacement. One population of inherited ...