Browsing by Author "Miller, James D., Jr."
Now showing 1 - 20 of 32
- Results Per Page
- Sort Options
Item Bedrock Geology of the Babbitt Northeast Quadrangle, St. Louis and Lake Counties, Minnesota(University of Minnesota, 2002) Miller, James D., Jr.; Severson, M.J.; Foose, M.P.Item Digitization of geologic data from 1985-1993 COGEOMAP program area, Minnesota(Minnesota Geological Survey, 1994) Miller, James D., Jr.; Wahl, T.E.; Bauer, E.J.Item Duluth mapping project(Minnesota Geological Survey, 1993) Miller, James D., Jr.; Green, J.C.; Chandler, V.W.Item Geology, geochemistry, and PGE potential of mafic-ultramafic intrusions in Minnesota, excluding the Duluth Complex(Minnesota Geological Survey, 2006) Jirsa, M.A.; Miller, James D., Jr.; Severson, M.J.This open-file contains data from both the first and the second phase of a 3-year study to evaluate platinum group element potential in mafic-ultramafic intrusions throughout Minnesota, excluding the Duluth Complex. Specifically, it reports the results of geochemical analyses conducted on 20 intrusions selected from more than 150 that were inventoried during the first phase of the study released in 2003. Some overlap may occur between the geochemical data listings from Phase 1 and Phase 2.Item Guidebook 20. Field Trip Guidebook for the Geology and Ore Deposits of the Midcontinent Rift in the Lake Superior Region(Minnesota Geological Survey, 1995) Miller, James D., Jr.This guidebook has been prepared for the field conference and symposium on "The Petrology and Metallogeny of Volcanic and Intrusive Rocks of the Midcontinent Rift System" that will be held in Duluth, Minnesota in August of 1995 as part of International Geological Correlation Program (IGCP) Project 336 ("Petrology and Metallogeny of Mafic and Ultramafic Magmatism"). The four-year-Iong IGCP project was begun in 1992 to investigate the petrology and metallogeny of various intracontinental mafic igneous provinces with an overall goal of establishing geological criteria for targeting mineral deposits in such environments. The principal goal of the 1995 meeting is to showcase to the international scientific and exploration communities the significant advances in our understanding of the structure, mineralization, and magmatic history of the Midcontinent rift. Toward this end, three field trips have been organized around the three-day symposium to be held August 25-27, 1995 in Duluth. The field trips are designed to provide a broad overview of the geologic framework of the Midcontinent rift, where it is best exposed in the western Lake Superior region. Field trip I (August 19 -24) looks at the physical volcanology of the flood basalts exposed on Isle Royale. Field trip II (August 22-24) highlights the stratigraphy, structure and mineralization of the volcanic and sedimentary rocks forming the southern limb of the Midcontinent rift in Wisconsin and Upper Michigan. The post-symposium field trip ill (August 28-September 1) focusses on the geology and ore deposits associated with the intrusive rocks of the Midcontinent rift exposed along the north shore of Lake Superior in Minnesota and Ontario.Item Information Circular 37. Scientific Core Drilling in Parts of Itasca, St. Louis, and Lake Counties, Northeastern Minnesota, 1989-1991(Minnesota Geological Survey, 1993) Meints, Joyce P.; Jirsa, Mark A.; Chandler, V.W.; Miller, James D., Jr.This information circular is the fifth since 1980 to report on the basic results of test drilling (Fig. 1) by the Minnesota Geological Survey (MGS). As with the previous projects, this test drilling was conducted primarily to provide a better understanding of the Precambrian geology in areas of Minnesota where bedrock is covered by variable thicknesses of glaciogenic sediment, and thus could not be thoroughly mapped by standard outcrop mapping and sampling procedures. The drilling summarized here was conducted during 1989-1991 in areas where the bedrock is locally well exposed, but where exposures are separated by covered terrane. Thus, the selection of drill targets was constrained largely by the interpretation of geophysical surveys (Chandler, 1983a, b). Our procedure is to formulate a regional geologic interpretation based on geophysical maps, new and existing outcrop data and the archived records of previous drilling, and then to constrain and test the interpretation by selective drilling. The results have been incorporated into new geologic maps of the region including Jirsa and others (1991) and Southwick (in prep.). An important secondary objective of this project is to describe the Quaternary deposits that overlie bedrock, though no systematic regional interpretation of those deposits has been undertaken to date. This report summarizes the results of studies in two areas of vastly different geology: 1) Archean and Early Proterozoic rocks of the Cook area in west-central St. Louis and eastern Itasca Counties, and 2) Middle Proterozoic rocks of the central Duluth Complex in parts of St. Louis and Lake Counties. The geology of each area is summarized in the "results" section of this report.Item Information Circular 44. Geochemical Evaluation of Platinum Group Element (PGE) Mineralization in the Sonju Lake Intrusion, Finland, Minnesota(Minnesota Geological Survey, 1999) Miller, James D., Jr.This study was undertaken to evaluate the potential for stratiform platinum group element (PGE) mineralization in the Sonju Lake intrusion (SLI). The SLI is a well differentiated, tholeiitic, mafic layered intrusion that is part of the multiple intrusive Beaver Bay Complex, and is exposed near Finland, Minnesota. Geochemical analyses of outcrop and drill-core samples that span the 1200-m-thick SLI were interpreted in the context of (1) data from PGE reefs in other tholeiitic layered intrusions (most notably the Skaergaard intrusion of East Greenland), and (2) models of PGE and sulfide mineralization in tholeiitic intrusions. The geochemical data show that a PGE-mineralized horizon is present approximately two-thirds of the way up from the base of the moderately south-dipping, sheet-like SLI. PGE mineralization was apparently related to initial sulfide saturation and subsequent exsolution of sulfide melt from the SLI magma. The data also indicate that as it settled, the sulfide melt efficiently scavenged PGEs from the SLI magma, and concentrated them into a relatively narrow interval of gabbroic cumulates. The geochemical signature of the SLI is remarkably similar to that of the PGE-bearing Platinova reef in the Skaergaard intrusion. The highest Pd, Pt and Au concentrations in SLI outcrop samples are far from economic grade (360, 66, and 85 ppb respectively); but a more precise evaluation of peak grade, thickness, and lateral continuity requires drilling and analysis of the entire interval. When the results of the study reported here are combined with evidence for similar mineralization in the Layered Series at Duluth, they indicate that tholeiitic layered intrusions of the Duluth and Beaver Bay complexes are favorable exploration targets for reef-type PGE mineralization.Item Lake Superior-Born of Fire and Ice(Minnesota Geological Survey, 2000) Miller, James D., Jr.; Jirsa, Mark A.; Leversedge, PhillipSet of panels designed as an explanation of the geology along Shovel Point Trail in Tettegouche State Park.Item M-065 Geologic map of the Silver Bay and Split Rock Point NE quadrangles, Lake County, Minnesota(Minnesota Geological Survey, 1988) Miller, James D., Jr.Item M-066 Geologic map of the Illgen City quadrangle, Lake County, Minnesota(Minnesota Geological Survey, 1989) Miller, James D., Jr.; Green, J.C.; Boerboom, T.J.Item M-072 Geologic Map of the Doyle Lake and Finland quadrangles, Lake County, Minnesota(Minnesota Geological Survey, 1993) Miller, James D., Jr.; Green, J.C.; Boerboom, T.J.; Chandler, V.W.Item M-081 Bedrock geologic map of the Silver Island Lake, Wilson Lake, and western Toohey Lake quadrangles, Lake and Cook Counties, Minnesota(Minnesota Geological Survey, 1994) Boerboom, T.J.; Miller, James D., Jr.Item M-082 Bedrock geologic map of the Cabin Lake and Cramer quadrangles, Lake and Cook Counties, Minnesota(Minnesota Geological Survey, 1994) Miller, James D., Jr.; Boerboom, T.J.; Jerde, E.A.Item M-091 Bedrock geologic map of Allen quadrangle, St. Louis County, Minnesota(Minnesota Geological Survey, 1999) Severson, M.J.; Miller, James D., Jr.Item M-101 Bedrock geologic map of the central Duluth Complex and western part of the Beaver Bay Complex, Lake and St. Louis Counties, Minnesota(Minnesota Geological Survey, 1999) Miller, James D., Jr.; Chandler, V.W.Item M-119 Geologic map of the Duluth Complex and related rocks, northeastern Minnesota(Minnesota Geological Survey, 2001) Miller, James D., Jr.; Green, J.C.; Severson, M.J.; Chandler, V.W.; Peterson, D.M.Item M-139 Bedrock geology of the Two Harbors quadrangle, Lake County, Minnesota(Minnesota Geological Survey, 2003) Boerboom, T.J.; Green, J.C.; Miller, James D., Jr.Item M-140 Bedrock geology of the Castle Danger quadrangle, Lake County, Minnesota(Minnesota Geological Survey, 2003) Boerboom, T.J.; Green, J.C.; Miller, James D., Jr.Item M-148 Bedrock geology of the Ely and Basswood Lake 30' X 60' quadrangles, northeast Minnesota(Minnesota Geological Survey, 2004) Jirsa, M.A.; Miller, James D., Jr.Item M-159 Bedrock geology of the Babbitt quadrangle, St. Louis and Lake Counties, Minnesota(Minnesota Geological Survey, 2005) Miller, James D., Jr.; Severson, M.J.