Papers by Jeanine Schmidt
Deposit geology Lens-like bodies of stratiform sulfide minerals (lead, zinc, ± iron) as much as a... more Deposit geology Lens-like bodies of stratiform sulfide minerals (lead, zinc, ± iron) as much as a few tens of meters in thickness are interbedded with fine-grained dark clastic and chemical sedimentary rocks. These deposits may have large lateral extent (hundreds of meters to kilometers). Mineralized rock varies from a single layer to numerous bodies that may be vertically stacked or lateral equivalents. The most common associated sulfate mineral is barite which may be peripheral to or stratigraphically above the deposit (Rammelsberg and Meggen, Germany; Tom, Yukon Territory; Lady Loretta, Australia; and Red Dog, Alaska), or it may form crudely segregated mixtures with sulfide minerals (Cirque, British Columbia). Many deposits have no associated barite (HYC, Australia; Sullivan, British Columbia; and Howard's Pass, Yukon Territory). Stockwork, disseminated, or vein-type ore, interpreted as feeder zones to stratiform mineralized rock, are sometimes found underlying or adjacent t...
This compilation of mineral occurrences and indicators is a product of the Alaskan Mineral Resour... more This compilation of mineral occurrences and indicators is a product of the Alaskan Mineral Resource Assessment Program (AMRAP) Level III mapping project within the Baird Mountains l e by 3" quadrangle during the 1983-86 field seasons. This report consists of a sample-locality map and table that summarizes previously known mineral occurrences and describes new occurrences and mineralization indicators located during the AMRAP field program. Sample locations on the map are numbered in two groups (1-194 and 195-290), both increasing from upper left to lower right, by l:63,360-scale quadrangle (D-6, D-5, D-4 ... D-l, C-6, C-5 ... C-l...). Map numbers 1-194 show locations of sulfide and oxide minerals, barite, fluorite, and copper carbonate and copper oxide minerals. The numbers also include locations of rock samples described in the field as gossans bleached, altered-appearing, or heavily ironstained rocks that have high geochemical values in one or more elements (greater than one ...
Analytical results and sample locality maps of mineralized and unmineralized rock samples from th... more Analytical results and sample locality maps of mineralized and unmineralized rock samples from the Baird Mountains quadrangle, Alaska: U.S. Geological Survey Open-File Report OF 88-256-B, 26 p., (3) 5 1/4-inch diskettes, 2 plates.
US Geol Surv Bull, 1993
DEEP-WATER LITHOFACIES AND CONODONT FAUNAS OF THE LISBURNE GROUP, WEST-CENTRAL BROOKS RANGE, ALAS... more DEEP-WATER LITHOFACIES AND CONODONT FAUNAS OF THE LISBURNE GROUP, WEST-CENTRAL BROOKS RANGE, ALASKA By Julie A. Dumoulin, Anita G. Harris, and Jeanine M. Schmidt ... 13 & oo 3 ra o a. u o 1* iz £ Q. " tT3-Q. ? 2 w 8 < BO| o| e/" j > ID 00» Jafl m ...
The Baird Mountains quadrangle lies north of the Arctic Circle between 67'and 68'latitu... more The Baird Mountains quadrangle lies north of the Arctic Circle between 67'and 68'latitude and between 159'and 162'longitude. The quadrangle covers 2 14,015 km and is situated in the southwestern Brooks Range between the Noatak and Kobuk Rivers. The earliest ...
Economic Geology, 1988
The Arctic volcanogenic massive sulfide prospect, located in the Ambler mineral district of north... more The Arctic volcanogenic massive sulfide prospect, located in the Ambler mineral district of northwestern Alaska, includes three types of hydrothermally altered rocks overlying, underlying, and interlayered with semimassive sulfide mineralization. Hydrothermal alteration of wall rocks and deposition of sulfide and gangue minerals were contemporaneous with Late Devonian or Early Mississippian basalt-rhyolite volcanism. Whole-rock analyses of altered rocks surrounding the prospect indicate that strong chemical gradients exist in major and minor oxides and volatiles. These were not homogenized or overprinted by Late Jurassic (?) to Middle Cretaceous greenschist to glaucophane-schist facies metamorphism. Very low alkali contents and moderate to very high contents of Ba, F, and Mg are the major chemical characteristics of the pervasively altered rocks. The strong Mg metasomatism, high Ba contents, and limited extent of altered rocks suggest a rapid influx of relatively cold seawater into a hot hydrothermal vent system. Alteration developed asymmetrically around a linear fissure, suggesting fracture control of ore fluids rather than a point source. Micro-probe analyses of phyllosilicates from the Arctic area indicate two discrete mineral populations. Magnesian chlorite, barian white mica, and barian fiuorphlogopite in hydrothermally altered rocks have compositions distinct from similar minerals (chlorite, phengite, biotite) developed during high-pressure metamorphism in metapelitic and metavolcanic lithologies. These differences in mineral chemistry are the result of differences in protolith composition caused by hydrothermal alteration-metasomatism. Without mineral composition data, the contacts between some alteration assemblages and relatively unaltered metavolcanic and metasedimentary rocks with similar mineralogy cannot be determined.
The Bay Resource Management Plan (RMP) area in southwestern Alaska, north and northeast of Bristo... more The Bay Resource Management Plan (RMP) area in southwestern Alaska, north and northeast of Bristol Bay contains significant potential for undiscovered locatable mineral resources of base and precious metals, in addition to metallic mineral deposits that are already known. A quantitative probabilistic assessment has identified 24 tracts of land that are permissive for 17 mineral deposit model types likely to be explored for within the next 15 years in this region. Commodities we discuss in this report that have potential to occur in the Bay RMP area are Ag, Au, Cr, Cu, Fe, Hg, Mo, Pb, Sn, W, Zn, and platinum-group elements. Geoscience data for the region are sufficient to make quantitative estimates of the number of undiscovered deposits only for porphyry copper, epithermal vein, copper skarn, iron skarn, hot-spring mercury, placer gold, and placer platinum-deposit models. A description of a group of shallow-to intermediate-level intrusion-related gold deposits is combined with grade and tonnage data from 13 deposits of this type to provide a quantitative estimate of undiscovered deposits of this new type. We estimate that significant resources of Ag, Au, Cu, Fe, Hg, Mo, Pb, and Pt occur in the Bay Resource Management Plan area in these deposit types. At the 10 th percentile probability level, the Bay RMP area is estimated to contain 10,067 metric tons silver, 1,485 metric tons gold, 12.66 million metric tons copper, 560 million metric tons iron, 8,100 metric tons mercury, 500,000 metric tons molybdenum, 150 metric tons lead, and 17 metric tons of platinum in undiscovered deposits of the eight quantified deposit types. At the 90 th percentile probability level, the Bay RMP area is estimated to contain 89 metric tons silver, 14 metric tons gold, 911,215 metric tons copper, 330,000 metric tons iron, 1 metric ton mercury, 8,600 metric tons molybdenum and 1 metric ton platinum in undiscovered deposits of the eight deposit types. Other commodities, which may occur in the Bay RMP area, include Cr, Sn, W, Zn, and other platinum-group elements such as Ir, Os, and Pd. We define 13 permissive tracts for 9 additional deposit model types. These are: Besshiand Cyprus, and Kuroko-volcanogenic massive sulfides, hot spring gold, low sulfide gold veins, Mississippi-Valley Pb-Zn, tin greisen, zinc skarn and Alaskan-type zoned ultramafic platinum-group element deposits. Resources in undiscovered deposits of these nine types have not been quantified, and would be in addition to those in known deposits and the undiscovered resources listed above. Additional mineral resources also may occur in the Bay RMP area in deposit types, which were not considered here.
Clark Bar is a strongly altered and oxidized zone of Paleocene granitic rocks intruded by aplitic... more Clark Bar is a strongly altered and oxidized zone of Paleocene granitic rocks intruded by aplitic to aphanitic felsic dikes along Clark Creek in the northern Talkeetna Mountains, southern Alaska. Major-, minor-, and trace-element geochemistry of fresh plutonic host rocks, altered rocks, and stream sediment suggest that the prospect has a potential to host granitoid SnMo-Ag mineralization. Regional mapping and lithogeochemistry suggest that many of the Tertiary plutonic rocks exposed in the northern Talkeetna Mountains belong to the “specialized” granite or granophile suite. Much of the area of the northern Talkeetna Mountains where these granites are exposed is prospective for various Sn-, Mo-, and Ag-enriched granophile deposits.
Open-File Report
The U.S. Geological Survey has created a geochemical database of geologic material samples collec... more The U.S. Geological Survey has created a geochemical database of geologic material samples collected in Alaska. This database is readily accessible to anyone with access to the Internet. Designed as a tool for mineral or environmental assessment, land management, or mineral exploration, the initial version of the Alaska Geochemical Database-U.S. Geological Survey Data Series 637-contains geochemical, geologic, and geospatial data for 264,158 samples collected from 1962-2009: 108,909 rock samples; 92,701 sediment samples; 48,209 heavy-mineral-concentrate samples; 6,869 soil samples; and 7,470 mineral samples. In addition, the Alaska Geochemical Database contains mineralogic data for 18,138 nonmagnetic-fraction heavy mineral concentrates, making it the first U.S. Geological Survey database of this scope that contains both geochemical and mineralogic data. Examples from the Alaska Range will illustrate potential uses of the Alaska Geochemical Database in mineral exploration. Data from the Alaska Geochemical Database have been extensively checked for accuracy of sample media description, sample site location, and analytical method using U.
Scientific Investigations Report
Horizontal coordinate information is referenced to the insert datum name (and abbreviation) here ... more Horizontal coordinate information is referenced to the insert datum name (and abbreviation) here for instance, "North American Datum of 1983 (NAD 83
Geologic map of the Cook Inlet region, Alaska, including parts of the Talkeetna, Talkeetna Mountains, Tyonek, Anchorage, Lake Clark, Kenai, Seward, Iliamna, Seldovia, Mount Katmai, and Afognak 1:250,000-scale quadrangles Scientific Investigations Map
A compilation on this scale could only be done with the assistance of many geologists, far more k... more A compilation on this scale could only be done with the assistance of many geologists, far more knowledgeable about the geology of various regions of Alaska than we are. We thank Chris Nye, Emily Finzel, and Dwight Bradley for discussions and information that assisted our compilation effort. The Alaska Department of Natural Resources, Division of Oil and Gas provided strong encouragement and financial support to assist with the preparation of this map; its assistance was invaluable. Technical review of the manuscript by Les Magoon, Michael Fisher, and Richard Stanley and editorial review by Theresa Iki was greatly appreciated and helped to improve the text and map.
Open-File Report
Talkeetna Mountains quadrangle Descriptions of the mineral occurrences shown on the accompanying ... more Talkeetna Mountains quadrangle Descriptions of the mineral occurrences shown on the accompanying figure follow. See U.S. Geological Survey (1996) for a description of the information content of each field in the records. The data presented here are maintained as part of a statewide database on mines, prospects and mineral occurrences throughout Alaska.
Open-File Report
The scope of each of these new mission areas is broader than the science directions outlined in t... more The scope of each of these new mission areas is broader than the science directions outlined in the USGS Science Strategy and together cover the scope of USGS science activities. In 2010, I also commissioned seven Strategic Science Planning Teams (SSPTs) to draft science strategies for each USGS mission area. Although the existing Bureau Science Strategy could be a starting point for this exercise, the SSPTs had to go well beyond the scope of the existing document. What is of value and enduring from the work of the programs that existed under the former science disciplines needed to be reframed and reinterpreted under the new organization of the science mission areas. In addition, new opportunities for research directions have emerged in the five years since the Bureau Science Strategy was drafted, and exciting possibilities for cooperating and collaborating in new ways are enabled by the new mission focus of the organization. Scientists from across the Bureau were selected for these SSPTs for their experience in strategic planning, broad range of experience and expertise, and knowledge of stakeholder needs and relationships. Each SSPT was charged with developing a long-term (10-year) science strategy that encompasses the portfolio of USGS science in the respective mission area. Each science strategy will reinforce others because scientific knowledge inherently has significance to multiple issues. Leadership of the USGS and the Department of the Interior will use the science vision and priorities developed in these strategies for program guidance, implementation planning, accountability reporting, and resource allocation. These strategies will guide science and technology investment and workforce and human capital strategies. They will inform our partners regarding opportunities for communication, collaboration, and coordination. The USGS has taken a significant step toward demonstrating that we are ready to collaborate on the most pressing natural science issues of our day and the future. I believe a leadership aligned to support these issue-based science directions and equipped with the guidance provided in these new science strategies in the capable hands of our scientists will create a new era for USGS of which we can all be proud.
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Papers by Jeanine Schmidt