The Great Bear magmatic zone, Northwest Territories, hosts numerous giant quartz veins and stockwork zones. These zones can be up to 100m wide and up to 10km long, with two or more generations of quartz. A few of the giant quartz vein zones host base-metal uranium mineralization, and some are proximal to mineralization, although most are barren. Cathodoluminescence imaging shows the quartz veins have complex growth zones and a trace element study suggests that these zones are the result of Al and Li substitution in the quartz lattice. Oxygen isotope (18Oqtz) values of quartz generally fall between +8 to +14.6 (VSMOW). Fluid inclusion homogenization temperatures range from 100 to 375C, and the fluids have variable salinities. The fluids that created the giant quartz veins are epithermal in nature with a meteoric water brine signature, and formed as a result of multiple fluid pulses and re-fracturing events.

This thesis attempts to develop our understanding of volcanic magma plumbing systems and the magmatic processes that operate within them, such as fractional crystallisation, crustal partial melting, assimilation, and magma mixing. I utilise petrology, rock and mineral geochemistry, and isotope systematics to seek to improve our ability to forecast the eruptive frequency and style of active volcanoes, an aspect often lacking in current volcano monitoring efforts. In particular, magma reservoir dynamics are investigated from a mineral scale at Katla volcano in Iceland, to a sub-mineral scale at Merapi, Kelud, and Toba volcanoes in Indonesia. The magma plumbing architecture of Katla volcano on Iceland is explored in the first part of this thesis. Crystalline components within tephra and volcanic rock preserve a record of the physical and chemical evolution of a magma, and are analysed through oxygen isotopic and thermobarometric techniques to temporally constrain changes in reservoir depth and decode the petrogenesis of the lavas. We find both prolonged upper crustal magma storage and shallow level assimilation to be occurring at Katla. The results generated from combining these analytical strands reveal the potential for unpredictable explosive volcanism at this lively Icelandic volcano. The second part of this thesis examines the magma plumbing systems of Merapi, Kelud and Toba volcanoes of the Sunda arc in Indonesia at higher temporal and petrological resolution than possible for Katla (e.g., due to the crystal poor character of the rocks). For this part of the thesis, minerals were analysed in-situ to take advantage of sub-crystal scale isotopic variations in order to investigate processes of shallow-level assimilation in the build-up to particular eruptions. We find that intra-crystal analyses reveal an otherwise hidden differentiation history at these volcanoes, and establish a better understanding as to how they may have rapidly achieved a critical explosive state. The outcomes of this thesis therefore deepen our knowledge of evolutionary trends in magma plumbing system dynamics, and highlight the importance of understanding the geochemical processes that can prime a volcano for eruption. Lastly, I emphasise the vital contribution petrology can make in current volcano monitoring efforts.

xix, 189 p. : ill. (some col.), maps (some col.) / Caldera-forming eruptions are dramatic and destructive natural phenomena, causing severe and sustained consequences to society. This dissertation presents new geochemical and geochronologic data for caldera-forming tuffs and pre- and post-caldera rhyolites of the two youngest caldera complexes in the Snake River Plain (SRP) in the western USA: Heise (6.6-4.5 Ma) and Yellowstone (2.1-0.6 Ma). Caldera complex evolution at Heise and Yellowstone can be described by formation of 3-4 spatially overlapping "nested" calderas, successive collapse of intracaldera fill, and development of a large hydrothermal system. Comparison between Heise and Yellowstone reveals that late-stage rhyolite eruptions have drastic depletions in 18 O that require remelting of large volumes (1,000's of km 3 ) of hydrothermally altered rock. Archean xenoliths and Phanerozoic rocks of the crustal basement beneath the SRP province are not depleted in 18 O and therefore cannot be a source of these rhyolites. Isotopic mixing models indicate that early large-volume rhyolites are produced by melting and hybridization of the crust by mantle-derived basalt, and late-stage rhyolites tap hydrothermally altered portions of intracaldera rocks from previous eruptions. Caldera-forming eruptions at Heise culminated 4.45 Ma with eruption of the 1,800 km 3 Kilgore Tuff, the most voluminous 18 O-depleted rhyolite in the SRP and worldwide. O, Sr, and Nd isotope geochemistry, zircon ages, mineral and whole-rock geochemistry, and liquidus temperatures for Kilgore Tuff samples erupted >100 km apart are similar and/or overlapping within error, indicating derivation from a remarkably homogeneous low-δ 18 O magma reservoir (δ 18 O=3.4[per thousand]). Caldera-wide batch assembly and homogenization of variably 18 O-depleted melt pockets with diverse zircon populations can explain the Kilgore Tuff's genesis. Central Plateau Member (CPM) rhyolites at Yellowstone have the same timing (∼2 million years after the initiation of volcanism), magnitude of δ 18 O depletion (∼3[per thousand] depleted relative to normal rhyolites), and cumulative eruptive volume (∼4,000-4,500 km 3 ) as the Kilgore Tuff of the Heise volcanic field. Isotopic, age, and geochemical data for CPM rhyolites show that they become progressively more homogeneous and evolved from 260 ka to 75 ka. Whereas the Kilgore Tuff erupted climactically as an explosive caldera-forming tuff, CPM rhyolite eruptions record sequential, predominantly effusive, "snapshots" of magma assembly, homogenization, and differentiation. This dissertation includes co-authored materials both previously published and submitted for publication. / Committee in charge: Ilya Bindeman, Chairperson; Gregory Retallack, Member; Mark Reed, Member; W. Andrew Marcus, Outside Member

abstract: This project investigates social mobility in premodern states through a contextualized program of isotopic research at the archaeological site of Teotihuacan, Mexico. Due to the lack of a concrete methodology that can be used to recover information concerning rates of social mobility from archaeological remains, many traditional archaeological models either ignore social mobility or assume that boundaries between socioeconomic strata within archaic states were largely impermeable. In this research, I develop a new methodological approach to the identification of socially mobile individuals in the archaeological record based on changes in the diet across the lifecourse that can be detected through isotopic paleodietary indicators. Drawing upon cross-cultural research surrounding the relationship between diet and socioeconomic status and established methodologies in the biogeochemical analysis of human remains, this methodological approach provides a basis for broader comparative studies evaluating the nature of social mobility within archaic states. I then test the practical application of this methodology by applying it to a mortuary sample including individuals from distinctive socioeconomic groups from the pre-Hispanic city of Teotihuacan, Mexico. The study recovers and uses the dietary isotope ratios within bone and tooth samples from 81 individuals buried throughout the city 1) to define the dietary correlates of wealth and status at Teotihuacan and 2) to identify individuals displaying lifetime dietary changes consistent with changes in socioeconomic status. In addition to supplementing our current understanding of Teotihuacan foodways and processes of geographic migration into the city, I identify an adult male individual from the La Ventilla B apartment compound who displays dietary changes throughout his life that are consistent with downward socioeconomic mobility from a high status socioeconomic group in early adolescence to an intermediate status group later in adulthood. I conclude by identifying ways to move forward with the comparative archaeology of socioeconomic mobility in premodern contexts and highlight the applicability of archaeological information to our understanding of present-day processes of social mobility. / Dissertation/Thesis / Doctoral Dissertation Anthropology 2017

In this article, we document a detailed analytical characterisation of zircon M127, a homogeneous 12.7 carat gemstone from Ratnapura, Sri Lanka. Zircon M127 has TIMS-determined mean U-Pb radiogenic isotopic ratios of 0.084743 +/- 0.000027 for Pb-206/U-238 and 0.67676 +/- 0.00023 for Pb-207/U-235 (weighted means, 2s uncertainties). Its Pb-206/U-238 age of 524.36 +/- 0.16 Ma (95% confidence uncertainty) is concordant within the uncertainties of decay constants. The delta O-18 value (determined by laser fluorination) is 8.26 +/- 0.06 parts per thousand VSMOW (2s), and the mean Hf-176/Hf-177 ratio (determined by solution ICP-MS) is 0.282396 +/- 0.000004 (2s). The SIMS-determined delta Li-7 value is -0.6 +/- 0.9 parts per thousand (2s), with a mean mass fraction of 1.0 +/- 0.1 mu g g(-1) Li (2s). Zircon M127 contains similar to 923 mu g g(-1) U. The moderate degree of radiation damage corresponds well with the time-integrated self-irradiation dose of 1.82 x 10(18) alpha events per gram. This observation, and the (U-Th)/He age of 426 +/- 7 Ma (2s), which is typical of unheated Sri Lankan zircon, enable us to exclude any thermal treatment. Zircon M127 is proposed as a reference material for the determination of zircon U-Pb ages by means of SIMS in combination with hafnium and stable isotope (oxygen and potentially also lithium) determination.

The Antarctic continent has traditionally been a successful searching ground for meteoritic material due to its cold and dry climate. Meteorites, and their microscopic analogues micrometeorites, were originally sampled from Antarctic ice and snow. Recently, however, a large collection of micrometeorites was discovered in sedimentary traps and moraine deposits from the Transantarctic Mountains, where extraterrestrial dust particles have accumulated for a prolonged time span (ca. 3–4 Ma). Micrometeorites (or ‘cosmic dust’) show unique chemical and isotopic signatures, which originate from a large and diverse amount of asteroidal and cometary bodies within the Solar System. In addition, they document major events such as the origin and evolution of the Solar System, and provide insight into the source region of their precursor bodies. These sedimentary deposits consequently represent a valuable archive that documents the flux of extraterrestrial material to Earth and ancient meteoritic events over Antarctica.Yet, much of this information is lost during the atmospheric entry stage, where cosmic dust is subjected to frictional heating and is partially or completely molten down. This may significantly alter the original physicochemical and isotopic properties of extraterrestrial dust particles. A thorough understanding of these physicochemical processes is thus required to reconstruct the atmospheric entry of cosmic dust (but also larger objects) and interpret their chemical and isotopic data. During the course of this PhD research, multiple sedimentary deposits from the Sør Rondane Mountains (Dronning Maud Land, East Antarctica) were petrographically examined and chemically-isotopically characterized using state-of-the-art instruments. Furthermore, various experiments and numerical models were constructed to replicate the atmospheric entry stage of both small- and large-sized meteoritic material. This study has demonstrated that the Sør Rondane Mountains sedimentary deposits contain a rich and pristine variety of extraterrestrial- and impact-related materials, including micrometeorites, microtektites and meteoritic condensation spherules. Statistical analysis suggests that the Sør Rondane Mountains micrometeorite collection is representative of the contemporary flux of cosmic dust to Earth. Extraterrestrial material is subjected to a complex interplay of redox and volatilization processes during atmospheric entry heating, which allow to explain the chemical trends observed in cosmic dust. Isotopic studies also suggest that at least a minor fraction of the micrometeorite population has sampled new, unknown types of asteroidal and/or cometary bodies. Microtektites and meteoritic condensation spherules have been linked to major meteoritic events on Earth ca. 790 ka and ca. 430 ka ago, respectively, and underline the importance of the Earth’s atmosphere during their formation. The results of this PhD research emphasize the scientific value of Antarctic sedimentary deposits and provide more insight into the processes taking place during the atmospheric entry of extraterrestrial material. / Le continent antarctique a traditionnellement été un terrain de recherche fructueux pour le matériel extraterrestre en raison de son climat froid et sec. Les météorites et leurs analogues microscopiques, les micrométéorites, ont été à l'origine échantillonnés dans la glace et la neige de l'Antarctique. Plus récemment, une grande collection de micrométéorites a été découverte dans des pièges sédimentaires et des dépôts de moraine des montagnes transantarctiques, où des particules de poussière extraterrestres se sont accumulées pendant une période prolongée (environ 3-4 Ma). Les micrométéorites (ou « poussière cosmique ») présentent des signatures chimiques et isotopiques uniques, qui proviennent d'une quantité importante et diversifiée de corps astéroïdes et cométaires au sein du système solaire. En outre, elles documentent des événements majeurs tels que l'origine et l'évolution du système solaire et donnent un aperçu de la région source de leurs corps parents. Ces dépôts sédimentaires représentent par conséquent une archive précieuse qui documente le flux de matière extraterrestre vers la Terre et les événements météoritiques anciens au-dessus de l'Antarctique.Pourtant, une grande partie de cette information est perdue au cours de l'étape d'entrée dans l'atmosphère, où la poussière cosmique est soumise à un chauffage par friction et est partiellement ou complètement fondue. Cela peut altérer considérablement les propriétés physico-chimiques et isotopiques d'origine des particules de poussière extraterrestres. Une compréhension approfondie de ces processus physico-chimiques est donc nécessaire pour reconstituer l'entrée atmosphérique des poussières cosmiques (mais aussi des objets plus gros) et interpréter leurs données chimiques et isotopiques. Au cours de cette recherche de doctorat, plusieurs dépôts sédimentaires des montagnes Sør Rondane (Dronning Maud Land, Antarctique de l'Est) ont été examinés pétrographiquement et caractérisés chimiquement et isotopiquement. En outre, diverses expériences et modèles numériques ont été construits pour reproduire l'étape d'entrée dans l'atmosphère de matériaux météoritiques de petite et de grande taille.Cette étude a démontré que les dépôts sédimentaires des montagnes Sør Rondane contiennent une variété riche et peu altérée de matériaux extraterrestres et de cratères d’impacts, notamment des micrométéorites, des microtektites et des sphérules de condensation météoritique. L'analyse statistique suggère que la collection de micrométéorites des montagnes Sør Rondane est représentative du flux contemporain de poussière cosmique vers la Terre. La matière extraterrestre est soumise à une interaction complexe de processus d'oxydo-réduction et de volatilisation lors de l'entrée dans l'atmosphère, ce qui permet d'expliquer les tendances chimiques observées dans la poussière cosmique. Des études isotopiques suggèrent également qu'au moins une fraction mineure de la population de micrométéorites a échantillonné de nouveaux types inconnus d’astéroïdes et/ou de comètes. Les microtektites et les sphérules de condensation météoritiques ont été liées à des événements météoritiques majeurs sur Terre il y a ~790 ka et ~430 ka, respectivement, et soulignent l'importance de l'atmosphère terrestre lors de leur formation. Les résultats de cette recherche doctorale soulignent la valeur scientifique des dépôts sédimentaires de l'Antarctique et donnent un meilleur aperçu des processus qui se déroulent lors de l'entrée dans l'atmosphère de matière extraterrestre / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Coral-based climate studies commonly use elemental ratios and stable isotopes of coral skeletons to address seawater temperature and hydrologic balance issues in the tropical surface oceans. Replication, or cross-checking, a standard technique used to assess the fidelity of proxy records in paleoclimatology has not been widely applied in coral-based climate studies, primarily because of the time and cost associated with generating multiple records from a single reef site. Modern and paleoclimate reconstructions based on a single proxy-coral record from a site may contain errors if individual corals from the same reef record different geochemical signals. In this study we perform a replication test using elemental ratios and stable isotopes in three Porites corals from New Caledonia. The reef complex offshore Amédée Island, New Caledonia is an ideal site to perform a coral replication test because instrumental sea surface temperatures (SST) and sea surface salinity measurements (SSS) have been made there for over 25 years. In this study, we compare sub-monthly resolved, geochemical variations (Sr/Ca, δ18O and δ13C) in three Porites lutea coral heads, located ~500 m apart, with the instrumental SST and SSS records over the interval 1992-1967. The monthly coral Sr/Ca and δ18O time series are well correlated to each other (r=0.86, p<.0001) and to the monthly instrumental SST record (r= -0.86, p<.0001, coral Sr/Ca to SST; r= -0.77, p<.0001, coral δ18O to SST). The three, sub-monthly resolved, 30-year coral Sr/Ca-SST time series have mean SST values that agree within 0.2o C with the instrumental mean SST value. A similar comparison for the coral δ18O-SST records indicate a maximum difference between predicted and observed mean SST of 0.5˚C. Analysis of the monthly climatological means also indicates that Sr/Ca-SST records closely match the instrumental SST record ±0.4˚C; a similar comparison using the δ18O-SST record yields an average offset of ±0.6˚C between observed and predicted monthly SST. Stacking the three records to form composite Sr/Ca-SST and δ18O-SST records does not appreciably improve the goodness of fit between the proxy and instrumental SST records; hence a coral-based proxy climate record from a single coral accurately reflects the observed record of climate variability at this locality. These results support the concept that high fidelity climate records can be generated using a single coral core.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016. / Ph. D. Joint Program in Oceanography (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2012 / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 179-192). / Since the Last Glacial Maximum (LGM, ~ 20,000 years ago) air temperatures warmed, sea level rose roughly 130 meters, and atmospheric concentrations of carbon dioxide increased. This thesis combines global models and paleoceanographic observations to constrain the ocean's role in storing and transporting heat, salt, and other tracers during this time, with implications for understanding how the modem ocean works and how it might change in the future. -- By combining a kinematic ocean model with "upstream" and "downstream" deglacial oxygen isotope time series from benthic and planktonic foraminifera, I show that the data are in agreement with the modem circulation, quantify their power to infer circulation changes, and propose new data locations. -- An ocean general circulation model (the MITgcm) constrained to fit LGM sea surface temperature proxy observations reveals colder ocean temperatures, greater sea ice extent, and changes in ocean mixed layer depth, and suggests that some features in the data are not robust. -- A sensitivity analysis in the MITgcm demonstrates that changes in winds or in ocean turbulent transport can explain the hypothesis that the boundary between deep Atlantic waters originating from Northern and Southern Hemispheres was shallower at the LGM than it is today. / by Daniel Edward Amrhein. / Ph. D.

No description available.

In 2001, 3269 unidentified individuals were found in a mass grave on the Northern part of Vilnius, Lithuania. Artifactual context indicates that these individuals were likely soldiers that were a part of Napoleon’s Grand Army. Stable oxygen isotope analysis was performed on bone apatite from 9 femoral bone samples to determine whether or not these individuals were Lithuanian locals and to test ratio variation. If individuals were foreigners, then geographical origins were approximated utilizing percentages of C4 plants from Holder (2013) and δ18O values that were extracted from bone apatite. The carbonate oxygen isotope compositions (δ18Ocarbonate) of bone apatite from the femoral samples (-4.4‰ to -6.2‰) indicate that these individuals were from central and western Europe (-4.0‰ to -6.9‰). It is significant that none of the individuals have values consistent with the area around Lithuania (-10.0‰ to -11.9‰), because it means that they all were non-local. It is also indicative that the Lithuanians were not burying their citizens in the grave and therefore strongly support that these individuals were Napoleonic soldiers. Additionally, although C4 percentages in the diet ranged from 17.8% to 31.7%, which overlaps with eastern European consumption patterns (approximately 15% to 25% of C4 plants) (Reitsema et al., 2010), the slight shift towards a higher C4 percentage is more representative of a central and western European diet. These results are significant because they provide stable isotopic evidence that these individuals were Napoleon’s soldiers whom participated in the Russian campaign of 1812.