Stable and radioactive isotopic study of chilled margins and dikes in the Nain complex, Labrador

• Main Author: Mayer, David L.
• Other Authors: Kalamarides, Ruth I., Department of Geology
• Format: Thesis
• Language: English
• Published: Northern Illinois University 1994
• Subjects: Dikes (Geology) > Newfoundland > Labrador; Geology > Newfoundland > Labrador; Continental margins > Newfoundland > Labrador; Radioactive tracers > Newfoundland > Labrador; Stable isotope tracers; Newfoundland; Nain
• Online Access: http://commons.lib.niu.edu/handle/10843/15212

Includes bibliographical references (pages [75]-77). The Nain complex is a 19,000 km2 anorthosite massif. It is part of the Elsonian magmatic province of central and northern Labrador which intruded into the boundary between the Early Proterozoic Churchill Province and the Archean Nain Province. This massif contains the typical anorthosite - norite - troctolite series of rocks that characterizes these massifs, along with many gabbros, granites, metasediments and exposed Archean basement rocks. Based on the analyses of chilled margins of leuconoritic and leucotroctolitic intrusions, and contemporaneous dikes, two broad magma suites have been identified by Berg. One is a suite containing high Si02 (49-51 wt%) and low Ti02, and the other is identified by low Si02 (47-48 wt%) and high Ti02 contents. These two suites were emplaced approximately 1.3 Ga; and it is thought that they crystallized from heterogeneous sources that produced magmas that appear to have undergone a varying degree of assimilation of crustal residues. The contaminate is thought to be a plagioclase pyroxene granulite situated at the base of the crust or in the upper mantle. The 6lsO , Rb/Sr, Sm/Nd and U/Pb isotopic data support this view. In addition, the data indicate that only small amounts of in situ alteration and contamination affected the samples, indicating that the data observed reflect the source processes of assimilation and fractional crystallization. M.S. (Master of Science)