Lehman, George Albert2021-05-252021-05-251980-01https://hdl.handle.net/11299/220196A Thesis submitted to the faculty of the Graduate School of the University of Minnesota by George Albert Lehman in partial fulfillment of the requirements for the degree of Master of Science, January 1980. Plates 1 and 2 referenced in the thesis are also attached to this record, along with the Plate 1 Key.The area studied consists of sections 20 - 29 and 32 - 36 of T60N, R6W of the Cramer, Minnesota 15' quadrangle. Units exposed include the anorthositic "series," troctolitic "series," and felsic "series" of the Duluth Complex, volcanic rocks of the North Shore Volcanic Group, melagabbroic-gabbroic intrusive rocks, diabasic rocks, and a hypabysal intrusive. Bedrock units are locally covered by a variety of glacial deposits related to the Rainy Glacial Lobe of the Wisconsin Ice Age. Troctolites and gabbros of the troctolitic series of the Duluth Complex display cummulate textures and regular cryptic (chemical) variation in the anorthite content of plagioclase (An78 to An58), the forsterite content of olivine (Fo70 to Fo50), and in the FeO/FeO+MgO ratio in augite (22 - 40). Orientations of igneous laminations as well as the areal distribution of rock types and cryptic variations strongly suggest the troctolitic series is a sill-like intrusion which differentiated in place as the result of crystal settling.en-USUniversity of Minnesota DuluthPlan As (thesis-based master's degrees)Department of Earth and Environmental SciencesMaster of ScienceMaster of Science in GeologyThesis or Dissertation