Browsing by Subject "Electron microprobe analysis"

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    The Bronze-Age obsidian industry at Tell Mozan (Ancient Urkesh), Syria: redeveloping electron microprobe analysis for 21st-Century sourcing research and the implications for obsidian use and exchange in Northern Mesopotamia after the neolithic.
    (2010-10) Frahm, Ellery Edward
    Obsidian tools continued to be utilized in Northern Mesopotamia well beyond the introduction of metal but have received little archaeological attention. It is widely held that obsidian sourcing can offer little new information during a period in which there is a variety of artifacts and texts available to study. Obsidian, though, is unparalleled in its widespread use and ability to be sourced, so it provides unique information about contact, exchange, and migration. Its sourcing can complement other types of information and be used to test existing hypotheses. Before the recent excavations at Tell Mozan (ancient Urkesh) in northeastern Syria, most of the information about its inhabitants, the Hurrians, was inferred from linguistic or textual evidence. Identifying the sources of their obsidian artifacts can be useful for testing some of the highly debated inferences. The research at hand involved three primary goals. I sought, first, to demonstrate a sophisticated approach to obsidian studies in the Near East and, second, to redevelop an analytical technique -- electron microprobe analysis -- for sourcing obsidian. Therefore, I assembled and analyzed a reference collection of over 900 geological obsidian specimens from dozens of sources in Turkey as well as Armenia, Georgia, Azerbaijan, and Russia. I sourced a large number of artifacts (n = 97) so that I could explore spatial and temporal patterns on a site level. In addition, this analytical technique, if applied critically, can (i) control for obsidian as a mixture, (ii) measure artifacts non-destructively, and (iii) discern two chemically similar obsidian sources: Nemrut Dag and Bingöl A. Thus, based on my results, I not only differentiate these obsidians but also pinpoint the collection loci, down to a kilometer, of the Nemrut Dag obsidians found at Tell Mozan. My third goal involved identifying the sources of obsidian represented among the Bronze-Age artifacts at Tell Mozan. These results were, in turn, used to explore temporal and spatial patterns of the obsidian sources used at the site, consider broader implications for obsidian use in Bronze-Age Mesopotamia, and examine two issues regarding Urkesh and its Hurrian inhabitants. The overall similarities for two site areas suggest that people living in various parts of Urkesh had similar access to the same obsidian sources. On the other hand, all the sourced obsidian from the temple came from one flow at Nemrut Dag and a service courtyard of the palace contains the only Cappadocian obsidian. In fact, the greatest variety of sources is found in units containing palace courtyards. Regarding the broader implications, there is evidence at Tell Mozan of production of prismatic obsidian blades and bladelets (e.g, flakes with cortex, cores, and early-series blades), suggesting they were not imported from a production center. In addition, there is a prevailing assumption that, if Bingöl B obsidian is found at a site, one can presume that all of the peralkaline obsidian artifacts came from Bingöl A, not Nemrut Dag. My results reveal that this assumption, based on maximal efficiency, is specious. The hypothesis of a Hurrian "homeland" as far northeast as Armenia (or beyond) is considered -- but not supported -- in light of my obsidian data. There are no obsidians from northeastern Turkey, Armenia, Azerbaijan, Georgia, or Russia that would point to a link to those regions. The atypical variety of obsidian sources at the site suggests that the city may have had a mountainous hinterland to the north. When compared to the existing data for other Khabur Triangle sites, my results support a possible exchange link between Tell Mozan and Tell Brak, perhaps as part of an early Hurrian kingdom. The research at hand involved three primary goals. I sought, first, to demonstrate a sophisticated approach to obsidian studies in the Near East and, second, to redevelop an analytical technique -- electron microprobe analysis -- for sourcing obsidian. Therefore, I assembled and analyzed a reference collection of over 900 geological obsidian specimens from dozens of sources in Turkey as well as Armenia, Georgia, Azerbaijan, and Russia. I sourced a large number of artifacts (n = 97) so that I could explore spatial and temporal patterns on a site level. In addition, this analytical technique, if applied critically, can (i) control for obsidian as a mixture, (ii) measure artifacts non-destructively, and (iii) discern two chemically similar obsidian sources: Nemrut Dag and Bingöl A. Thus, based on my results, I not only differentiate these obsidians but also pinpoint the collection loci, down to a kilometer, of the Nemrut Dag obsidians found at Tell Mozan. My third goal involved identifying the sources of obsidian represented among the Bronze-Age artifacts at Tell Mozan. These results were, in turn, used to explore temporal and spatial patterns of the obsidian sources used at the site, consider broader implications for obsidian use in Bronze-Age Mesopotamia, and examine two issues regarding Urkesh and its Hurrian inhabitants. The overall similarities for two site areas suggest that people living in various parts of Urkesh had similar access to the same obsidian sources. On the other hand, all the sourced obsidian from the temple came from one flow at Nemrut Dag and a service courtyard of the palace contains the only Cappadocian obsidian. In fact, the greatest variety of sources is found in units containing palace courtyards. Regarding the broader implications, there is evidence at Tell Mozan of production of prismatic obsidian blades and bladelets (e.g, flakes with cortex, cores, and early-series blades), suggesting they were not imported from a production center. In addition, there is a prevailing assumption that, if Bingöl B obsidian is found at a site, one can presume that all of the peralkaline obsidian artifacts came from Bingöl A, not Nemrut Dag. My results reveal that this assumption, based on maximal efficiency, is specious. The hypothesis of a Hurrian "homeland" as far northeast as Armenia (or beyond) is considered -- but not supported -- in light of my obsidian data. There are no obsidians from northeastern Turkey, Armenia, Azerbaijan, Georgia, or Russia that would point to a link to those regions. The atypical variety of obsidian sources at the site suggests that the city may have had a mountainous hinterland to the north. When compared to the existing data for other Khabur Triangle sites, my results support a possible exchange link between Tell Mozan and Tell Brak, perhaps as part of an early Hurrian kingdom.
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    Electron Microprobe Analysis of Alteration Mineralogy at the Archean Five Mile Lake Volcanic Associated Massive Sulfide Mineral Prospect in the Vermilion District of Northeastern Minnesota
    (University of Minnesota Duluth, 2003-05) Hocker, Stephanie M; Hudak, George J; Heine, John J
    Alteration mineral assemblage mapping at the Five Mile Lake Prospect in the Vermilion District of northeastern Minnesota has identified two distinct types of alteration zones within 2.7 billion year-old volcanic and volcaniclastic rocks associated with volcanic-hosted massive sulfide (VHMS) mineralization (Hudak et al., in press; Odette et al., 2001a, 2001b; Peterson, 2001). Regional semi-conformable alteration zones are composed of various proportions of quartz + epidote ± amphibole ± chlorite ± plagioclase feldspar. These regional, semiconformable alteration zones are locally crosscut by several relatively narrow, northeast trending disconformable alteration zones composed of fine-grained chlorite and/or sericite that are closely associated with synvolcanic fault zones. Electron microprobe analyses of the various alteration mineral phases (epidote group minerals, chlorite, amphibole, white mica, and feldspar) have been conducted in an effort to better understand the hydrothermal processes associated with the development of the semiconformable and disconformable alteration zones at the Five Mile Lake Prospect. These analyses indicate that: a) epidote group minerals range in composition from oisite/clinozoisite to pistacite; b) chlorite is dominantly ripidolite; c) amphibole is primarily actinolite and ferroactinolite, with magnesio-hornblende and ferro-hornblende also present; d) sericite is finegrained muscovite; and e) feldspar is albite. This mineral chemistry suggests the presence of a complex, long-lived hydrothermal system that evolved from seafloor-proximal (hundreds of meters) to deeper subseafloor environments (~1-3 km) as the volcanic rocks were buried by rapid, dominantly effusive mafic to intermediate volcanism and associated sedimentation. Alteration mineral chemistry at the Five Mile Lake Prospect is remarkably similar to that from the Noranda VHMS mining camp of Canada as well as other VHMS orebodies. This mineral chemistry, combined with favorable volcanology and numerous untested geophysical targets, suggest that the Five Mile Lake Prospect, as well as the uppermost several hundred meters of the Lower Member of the Ely Greenstone, have excellent exploration potential for VHMS mineral deposits.