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7_MankinsNeal_GGDay2017.pptx
No full textVein Orientation and Structural Geology of the Boulder Batholith, Mount Thompson Quadrangle, southwestern Montana
By N. Mankins
Abstract
The Mount Thompson 7.5 Minute Quadrangle is located in the central Boulder Batholith, between the cities of Butte and Helena. The Boulder batholith is host to numerous metalliferous vein deposits, including those in the Butte District. Recent USGS (EDMAP)-funded geologic mapping at 1:24,000 scale in the Mount Thompson Quadrangle during the summer of 2016 focused on new measurements of vein and fault orientation and compilation of previous data. The orientations of vein systems observed in the Mount Thompson Quadrangle are similar to the orientations reported elsewhere in the Boulder Batholith.
Most of the veins in the quadrangle shortly post-date the 76 Ma Butte Granite unit of the Boulder Batholith, and cut this unit and older rocks in the quadrangle. Two distinct vein orientations have been identified on stereonet plots: 1) massive milky-grey East-West (azimuth 98˚) quartz veins that have dips that range from 73˚ North to 72˚ South, and 2) NE-SW (azimuth 157˚) striking quartz-chalcedony veins with dip range 65˚NW-76˚SE. Vein mineralogy includes three subsets: 1) massive grey quartz 70-80% of which locally contain quartz vugs with abundant sulfides (Pyrite > Galena), 2) quartz-sulfide-poor veins 65% with chalcedony, 3) cm-scale milky quartz veins 70% with tourmaline. At the Montana Tunnels Mine a younger set of sulfide-rich (Pyrite > Sphalerite > Galena) veins, Eocene in age, cut the ~50 Ma diatreme breccia and a Lowland Creek Volcanics pyroclastic vent. The Boulder batholith veins are systematically zoned on the km scale around heat centers from high to low temperature from central tourmaline- to quartz-sulfide- to quartz-chalcedony in the periphery.Keywords: Thesis, Map, Research, UndergraduateKeywords: Thesis, Map, Research, Undergraduat
Paragenetic Evolution of the Robertson Deposit: Eocene Intrusion Related Gold Deposit in the Northern Shoshone Range, Nevada
No full textThe Robertson deposit, formerly known as Tenabo, is an Eocene intrusion-related gold deposit 5 km north of Pipeline, which is a 20 Moz+ Carlin-type gold deposit in the northern Shoshone Range, Nevada. Carlin-type gold deposits have been the focus of many studies as they represent the second largest accumulation of gold in the world, and a growing body of scientific literature indicates that the source for this gold may be related to Eocene magmatism. The presence of an Eocene intrusion-related gold deposit within 5 km of a Carlin-type deposit begs the question of whether the two deposits are genetically related, however detailed characterized of Robertson deposit is needed before this link can be examined. Most of the previously defined gold mineralization at Robertson occurred near the contacts of intrusions and hosted by hornfels in the overlying lithologies. Ongoing exploration has discovered significant free visible gold both within the stock and in distal settings within metasedimentary host rocks. Here, gold mineralization is spatially and temporally related to an intrusive complex referred to as the Tenabo stock, and based on petrographic and geochemical analysis, is composed of successive intrusive phases including an early ilmenite-bearing diorite, andesite dikes, hypabyssal dacitic porphyry dikes, composite ilmenite-bearing granodiorite, granitic porphyry dikes (formerly called feldspar porphyry dikes), pebble dikes, and subvolcanic rhyolitic dikes. The purpose of this study is to characterize gold mineralization as it relates to intrusive phases, alteration styles, and structural controls by combining fieldwork, petrography, geochemistry and geochronology. This study is the first in depth examination of Robertson focusing on gold mineralization within intrusive phases and in distal settings, presenting six new U/Pb LA-ICP-MS ages of intrusive phases, one molybdenite Re/Os age, and one hydrothermal orthoclase 40Ar/39Ar age, conservatively constraining gold mineralization to 39.65-35.77 Ma. Emplacement of the Tenabo stock resulted in contact metamorphism of the host siliciclastic lithologies yielding quartz, biotite, and calc-silicate hornfels, which formed an aureole up to 1 km from the stock. Subsequent hydrothermal alteration followed, including endo/exoskarn, potassic alteration, sericitic alteration, and chloritic alteration. Petrographic observations of veins at Robertson indicate the succession of three main stages referred as 1) pre-gold, 2) syn-gold, and 3) post-gold. The pre-gold stage includes barren quartz veins, potassic alteration veins comprised of biotite veinlets and quartz-K-feldspar, quartz �" arsenopyrite, quartz �" chalcopyrite, and quartz �" molybdenite veins. The syn-gold stage is composed of quartz �" gold ± Bi-Te-Se-Pb-Ag-S sulfosalt veins, consisting of native gold seen as single grains in quartz gangue and/or on the surface of pyrrhotite, arsenopyrite, chalcopyrite, and loellingite grains. The post-gold veins encompass pyrite ± quartz, quartz �" calcite �" polymetallic sulfide veins with Pb-Zn-Sb-Ag-Sn base metal sulfides, bull quartz veins, and calcite veins. Cross-cutting relationships along with geochronological data indicate that gold mineralization resulted from the emplacement of upper Eocene (40.99-37.38 Ma) reduced ilmenite-bearing intrusive phases that intruded into Ordovician-Devonian siliciclastic sedimentary lithologies, forming a high-tonnage, low-grade gold deposit characterized by a Au-As-Bi-Te-Cu metal association, similar to reduced intrusion related gold deposits and gold skarns described globally. Based on petrographic and geochemical evidence, it is concluded that mineralizing conditions for gold precipitation were under relatively low sulfur fugacity and oxidation state, leading to preferential formation of minerals such as native Bi, arsenopyrite, pyrrhotite, and loellingite, typical of low-sulfidation assemblages. Under such conditions it is possible to transport gold to lower temperatures <300°C, where native gold is commonly associated with Bi-bearing minerals or to even lower temperatures (~150-200°C) where it remains within the lattice of sulfides as invisible gold, typifying Carlin-type deposits
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MankinsNealE2017.pdf
No full textVein Orientation and Structural Geology of the Boulder Batholith, Mount Thompson Quadrangle, southwestern Montana
By N. Mankins
Abstract
The Mount Thompson 7.5 Minute Quadrangle is located in the central Boulder Batholith, between the cities of Butte and Helena. The Boulder batholith is host to numerous metalliferous vein deposits, including those in the Butte District. Recent USGS (EDMAP)-funded geologic mapping at 1:24,000 scale in the Mount Thompson Quadrangle during the summer of 2016 focused on new measurements of vein and fault orientation and compilation of previous data. The orientations of vein systems observed in the Mount Thompson Quadrangle are similar to the orientations reported elsewhere in the Boulder Batholith.
Most of the veins in the quadrangle shortly post-date the 76 Ma Butte Granite unit of the Boulder Batholith, and cut this unit and older rocks in the quadrangle. Two distinct vein orientations have been identified on stereonet plots: 1) massive milky-grey East-West (azimuth 98˚) quartz veins that have dips that range from 73˚ North to 72˚ South, and 2) NE-SW (azimuth 157˚) striking quartz-chalcedony veins with dip range 65˚NW-76˚SE. Vein mineralogy includes three subsets: 1) massive grey quartz 70-80% of which locally contain quartz vugs with abundant sulfides (Pyrite > Galena), 2) quartz-sulfide-poor veins 65% with chalcedony, 3) cm-scale milky quartz veins 70% with tourmaline. At the Montana Tunnels Mine a younger set of sulfide-rich (Pyrite > Sphalerite > Galena) veins, Eocene in age, cut the ~50 Ma diatreme breccia and a Lowland Creek Volcanics pyroclastic vent. The Boulder batholith veins are systematically zoned on the km scale around heat centers from high to low temperature from central tourmaline- to quartz-sulfide- to quartz-chalcedony in the periphery.Keywords: Undergraduate, Thesis, Research, Ma
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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Vein Orientation and Structural Geology of the Boulder Batholith, Mount Thompson Quadrangle, southwestern Montana
Get PDFThe Mount Thompson 7.5 Minute Quadrangle is located in the central Boulder Batholith, between the cities of Butte and Helena. The Boulder batholith is host to numerous metalliferous vein deposits, including those in the Butte District. Recent USGS (EDMAP)-funded geologic mapping at 1:24,000 scale in the Mount Thompson Quadrangle during the summer of 2016 focused on new measurements of vein and fault orientation and compilation of previous data. The orientations of vein systems observed in the Mount Thompson Quadrangle are similar to the orientations reported elsewhere in the Boulder Batholith.
Most of the veins in the quadrangle shortly post-date the 76 Ma Butte Granite unit of the Boulder Batholith, and cut this unit and older rocks in the quadrangle. Two distinct vein orientations have been identified on stereonet plots: 1) massive milky-grey East-West (azimuth 98˚) quartz veins that have dips that range from 73˚ North to 72˚ South, and 2) NE-SW (azimuth 157˚) striking quartz-chalcedony veins with dip range 65˚NW-76˚SE. Vein mineralogy includes three subsets: 1) massive grey quartz 70-80% of which locally contain quartz vugs with abundant sulfides (Pyrite > Galena), 2) quartz-sulfide-poor veins 65% with chalcedony, 3) cm-scale milky quartz veins 70% with tourmaline. At the Montana Tunnels Mine a younger set of sulfide-rich (Pyrite > Sphalerite > Galena) veins, Eocene in age, cut the ~50 Ma diatreme breccia and a Lowland Creek Volcanics pyroclastic vent. The Boulder batholith veins are systematically zoned on the km scale around heat centers from high to low temperature from central tourmaline- to quartz-sulfide- to quartz-chalcedony in the periphery
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Senior_Thesis_Poster.ppt
No full textVein Orientation and Structural Geology of the Boulder Batholith, Mount Thompson Quadrangle, southwestern Montana
By N. Mankins
Abstract
The Mount Thompson 7.5 Minute Quadrangle is located in the central Boulder Batholith, between the cities of Butte and Helena. The Boulder batholith is host to numerous metalliferous vein deposits, including those in the Butte District. Recent USGS (EDMAP)-funded geologic mapping at 1:24,000 scale in the Mount Thompson Quadrangle during the summer of 2016 focused on new measurements of vein and fault orientation and compilation of previous data. The orientations of vein systems observed in the Mount Thompson Quadrangle are similar to the orientations reported elsewhere in the Boulder Batholith.
Most of the veins in the quadrangle shortly post-date the 76 Ma Butte Granite unit of the Boulder Batholith, and cut this unit and older rocks in the quadrangle. Two distinct vein orientations have been identified on stereonet plots: 1) massive milky-grey East-West (azimuth 98˚) quartz veins that have dips that range from 73˚ North to 72˚ South, and 2) NE-SW (azimuth 157˚) striking quartz-chalcedony veins with dip range 65˚NW-76˚SE. Vein mineralogy includes three subsets: 1) massive grey quartz 70-80% of which locally contain quartz vugs with abundant sulfides (Pyrite > Galena), 2) quartz-sulfide-poor veins 65% with chalcedony, 3) cm-scale milky quartz veins 70% with tourmaline. At the Montana Tunnels Mine a younger set of sulfide-rich (Pyrite > Sphalerite > Galena) veins, Eocene in age, cut the ~50 Ma diatreme breccia and a Lowland Creek Volcanics pyroclastic vent. The Boulder batholith veins are systematically zoned on the km scale around heat centers from high to low temperature from central tourmaline- to quartz-sulfide- to quartz-chalcedony in the periphery.Keywords: Map, Undergraduate, Thesis, Researc
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MT Thompson Prelim Map.pdf
No full textVein Orientation and Structural Geology of the Boulder Batholith, Mount Thompson Quadrangle, southwestern Montana
By N. Mankins
Abstract
The Mount Thompson 7.5 Minute Quadrangle is located in the central Boulder Batholith, between the cities of Butte and Helena. The Boulder batholith is host to numerous metalliferous vein deposits, including those in the Butte District. Recent USGS (EDMAP)-funded geologic mapping at 1:24,000 scale in the Mount Thompson Quadrangle during the summer of 2016 focused on new measurements of vein and fault orientation and compilation of previous data. The orientations of vein systems observed in the Mount Thompson Quadrangle are similar to the orientations reported elsewhere in the Boulder Batholith.
Most of the veins in the quadrangle shortly post-date the 76 Ma Butte Granite unit of the Boulder Batholith, and cut this unit and older rocks in the quadrangle. Two distinct vein orientations have been identified on stereonet plots: 1) massive milky-grey East-West (azimuth 98˚) quartz veins that have dips that range from 73˚ North to 72˚ South, and 2) NE-SW (azimuth 157˚) striking quartz-chalcedony veins with dip range 65˚NW-76˚SE. Vein mineralogy includes three subsets: 1) massive grey quartz 70-80% of which locally contain quartz vugs with abundant sulfides (Pyrite > Galena), 2) quartz-sulfide-poor veins 65% with chalcedony, 3) cm-scale milky quartz veins 70% with tourmaline. At the Montana Tunnels Mine a younger set of sulfide-rich (Pyrite > Sphalerite > Galena) veins, Eocene in age, cut the ~50 Ma diatreme breccia and a Lowland Creek Volcanics pyroclastic vent. The Boulder batholith veins are systematically zoned on the km scale around heat centers from high to low temperature from central tourmaline- to quartz-sulfide- to quartz-chalcedony in the periphery.Keywords: Map, Undergraduate, Research, Thesi
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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