This study examines rock art sites containing scratched petroglyphs in the Bennett Hills, Idaho. Despite their research potential, scratched petroglyphs have received little attention in rock art research or literature. This study contributes valuable data to scratched rock art research and the corpus of rock art research in general. Two samples of ten scratched petroglyph sites were examined and recorded for a total of twenty petroglyph sites. Using formal and contextual research methods, multiple attributes of scratched petroglyphs are identified and analyzed. The formal qualities of scratched petroglyphs are examined to define the extent and to characterize the motif assemblage. Formal qualities were also studied to test hypotheses concerning the relationship between scratched and pecked petroglyph styles and associations between scratched petroglyphs and other archaeological phenomena. The contexts of scratched petroglyphs are studied on site and landscape scales to identify correlations with other archaeological phenomena and environments. The formal analyses revealed that there are more scratched petroglyphs in the Bennett Hills than records and literature currently indicate. Few site records document the presence of scratched petroglyphs, although as a result of this analysis it appears to be ubiquitous in the Bennett Hills. It is possible that scratched petroglyphs are under recorded in other locales as well, and that further investigations may identify a greater frequency of scratched petroglyphs throughout the Great Basin. Proper identification of scratched petroglyphs may alter how these properties are evaluated and in turn how they are managed. The Bennett Hills encompass a limited and unique assemblage of scratched petroglyph motifs that are dissimilar to petroglyphs manufactured using other techniques. This is significant in that it helps support the idea that scratched petroglyphs are distinct. Rather than just an alternative method to pecking, scratched petroglyphs serve a unique function that is different from and independent of pecked petroglyphs. Contextual analyses indicated that scratched petroglyphs are located in patterned and significant associations with artifacts, features, environments, and landscapes. The contextual analysis suggested that scratched rock art was produced in a public context in close proximity to subsistence related activities, perhaps in association with resource gathering events. There are various hypotheses that deal with the interaction between scratched and pecked petroglyph styles. Scratched petroglyphs occur both independent of and in association with other pecked petroglyph styles, although scratched petroglyphs do not commonly occur with any one pecked motif. When scratched and pecked petroglyph styles overlap scratched petroglyphs are always later than and superimposed over earlier pecked petroglyphs. Data was collected to test three hypotheses concerning the intention of association between scratched and pecked petroglyphs. It does not appear that scratched petroglyphs serve to obliterate earlier pecked petroglyphs or function as a sketch that would be pecked later. There is evidence that some scratched petroglyphs enhance earlier pecked petroglyphs however, this hypothesis cannot sufficiently describe the range of patterns and associations found in the Bennett Hills scratched petroglyph assemblage. Hypotheses suggesting associations between scratched rock art and other archaeological phenomena were also examined. The association between scratched petroglyphs and scratched stones is deserving of further research. It may also be too soon to dismiss the association between scratched petroglyphs and quartz. The examination of scratched petroglyphs in the Bennett Hills provides a unique insight into the minds of the makers of these petroglyphs, contributing valuable data our knowledge of the prehistoric peoples of the Bennett Hills and surrounding areas.

This thesis compares hypotheses about Fremont agricultural investment to evaluate the relationship between dry or rainfall farming and irrigation farming. Recent identification of a Fremont irrigation feature at Pleasant Creek provides an opportunity to study farming commitment through labor investment. A comparison of relative efficiencies of irrigated and dry-farmed maize using experimental digging exercises and cross-cultural comparisons generate data about the range of investment, carrying capacity, and the contexts of selection operating under circumstances like those at Pleasant Creek. The analysis shows that irrigated maize efficiency remains equivalent to or lower than dry-farmed maize. Irrigation labor costs influence maize return rates more with fewer years of canal operation and suggest that technological investment in irrigation at the project site would be “worth it” only with anticipated long-term commitment. For instance, labor costs of irrigation amortized over time show that initial construction costs no longer affect energetic return rates of maize after four to six years of canal use. Beyond this span of time, field labor and processing time condition overall return rates more than distinctive labor costs of irrigation. The application of carrying capacity scenarios indicates the canal likely supported between 30 and 100 individuals. Analysis of infrastructural complexity and labor group size suggests that Pleasant Creek was home to a group operating within complexity beyond egalitarian forager organization. The level of investment and productivity suggests a community, likely bound by kinship ties with a corporate management style, engaged in subsistence-level agriculture that served to expand the farmable area and reduce the risk of food shortage in an agriculturally marginal area.

The United States Department of Homeland Security launched Secure Communities in 2009, expanding Immigration and Customs Enforcement’s (ICE) jurisdiction and establishing partnerships between federal immigration officers and municipal law enforcement agencies (LEAs) across the country. The effects of Secure Communities have been numerous. While rates of deportations had been rising annually for decades, the program granted ICE with even more power to detain and deport undocumented immigrants and dramatically increased federal collaboration with LEAs. Secure Communities was terminated by then Secretary of Homeland Security Jeh Johnson in 2014; replaced by the comparable, but lesser known, Priority Enforcement Program (PEP); and reinstated in January of 2017 immediately following the inauguration of Donald Trump. This thesis focuses on the greater implications Secure Communities has on immigrant sense of safety and more generally on public health. As anti-immigrant rhetoric and fear of deportations are on the rise, there have been noticeable disengagements of immigrant populations from public services. I investigate the impacts of Trump’s anti-immigrant platform in 2016 and reinstatement of Secure Communities in 2017 on how immigrant communities in South Central Los Angeles make use of health clinics.

<p> The movement of diamond drills by tracked vehicles and drill trailers in south Central Keewatin was studied during the summer of 1980. Tests of the physical ground strength showed that the ability of the terrain to resist disturbance from tracked vehicle operations depended on two main physical factors: the type of surficial material and the presence of water. Moisture contents varied throughout the summer so that the response of till and peat to compression and shear was not constant. As the summer proqressed, the increasing depth of thaw and gradual surface drying caused strengthening of both major types of surficial material. As a result, vehicle trafficability gradually increased throughout the summer. While surface rutting increased the depth of thaw compared to an undisturbed site, especially in peat, after the first few weeks of the thaw this had little apparent effect on vehicle trafficability. In many cases the vehicle disturbance was largely aesthetic giving the impression that the terrain disturbance was much more serious than it actually was.</p> <p> Although the load distribution of the vehicle tracks concentrated much of the longitudinal stress directly beneath the bogie wheels, in most cases the performance of the tracked vehicle itself was adequate. However, problems caused by the drill trailer wheels resulted in unnecessary mechanical strain on the vehicles and created marked increases in terrain disturbance.</p> / Thesis / Bachelor of Arts (BA)

Historically, Devonian Corniferous hydrocarbon production in south-central Kentucky has been a major contributor to the total hydrocarbon resources within Butler, Edmonson, and Warren counties. The Corniferous adds to the already large hydrocarbon totals produced from the Illinois Basin; however, this hydrocarbon contribution does not come without major pitfalls and inconsistencies. The south-central Kentucky Devonian Corniferous rocks comprise a diverse and complex hydrocarbon system made up of multiple migration pathways, trapping mechanisms, and seals. The multiple Corniferous units all derive production from the same source rock: the New Albany Shale. A Geographic Information System (GIS) containing data on surface elevations, structure contours and faults, geophysical well logs, well-scale oil and gas production, and lease to regional-scale oil and gas production has been compiled to produce a threedimensional (3-D) model using kriging with barriers to explain spatially the complexities of the Devonian Corniferous in south-central Kentucky. This model identifies the potential source rocks, the hydrocarbon charging and migration pathways, reservoirs, and reservoir seals. This model also utilizes kernel density estimation for developing an understanding of the spatial relationship of stratigraphic units being targeted within the Devonian relative to the spatially modeled Devonian Corniferous structures. This model also indicates locations and depths of key producing zones within south-central Kentucky. This project also explains the potential reasoning leading to the development of the Devonian Corniferous as a major hydrocarbon resource by placing it in the context of the underlying Silurian Corniferous and the multiple Siluro-Devonian unconformities positioned throughout the entire Siluro-Devonian section. This project bridges the gap between: 1) potential buried Silurian-age reef systems located south of the Pennyrile Fault zone, 2) the pervasive high porosity sections found in the lower Clear Creek Limestone unit, and 3) the development of expansive secondary partial dolomitization related to unconformable surfaces in the Middle and Upper Devonian Corniferous.

Thesis (MSc (Earth Sciences))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The NE-trending South Central Zone of the Pan-African (ca. 550-500) Damara orogen in central Namibia exposes deeply eroded mid-crustal rocks, thought to represent the magmatic arc of the Damara orogen. Above average exposure of outcrop left unmodified by subsequent post-orogenic processes made it possible to study the internal architecture of a ca. 50km traverse, stretching from the continental suture-zone (between the Congo craton in the NW and the underplating Kalahari craton in the SE) at the Okahandja Lineament Zone, well into the leading edge of the Congo craton and into the magmatic-arc, the South Central Zone. This study considers and characterises the change in structural styles and strain intensities in rocks of the Damara Supergroup and intrusions, across the traverse between the towns of Otjimbingwe in the SE and Karibib in the NW. In the SE of the traverse in the Okahandja Lineament Zone, steep, upright, tightly folded D2 fabrics in meta-turbidites of the Tinkas and Kuiseb Formations record bulk NW-SE shortening and steep SW extrusion of rocks. Penetrative non-coaxial fabrics imply a high-angle collsion between the Congo and Kalahari cratons. This is in contrast to oblique collision described by a number of previous authors (e.g. Blaine (1977), Stanistreet et al. (1991), Tack & Bowden, 1999). A marked decrease in D2 strain, and the presence of the silisiclastic basal Nosib group suggests the presence of the underlying basement rocks and thus the leading edge of the Congo craton only a few km NW of the Okahandja lineament. 8km NW of the Okahandja lineament is a km-scale NW verging F1 nappe, cored by basement gneisses and refolded into a series of bi-vergent, doubly-plunging F2 folds, the Audawib fold complex. The nappe is interpreted to have formed along a retroshear during early continental collision (syn-D1, early-D2). Tectonically overprinted basement rocks are indicative of thermal weakening, that resulted in the development of thick-skinned tectonics. Intruded mainly to the NW of and around the aforementioned nappe are the areally extensive syn-D2 Salem-type granites. Salem-type granites are shallowly intruded below the nappe and have likely detached the F1 nappe from its root. NW of the Salem-type granites lies a basement window of ca. 15km2 surrounded by the lower formations of the Damara Supergroup. Sheared marbles and D1 (early D2) diorites along the basement contact indicate a shallow sheared detachment occurring just above the basement. Basement rocks (1) unaffected by Damaran (D1-D2) tectonism and (2) unconformably overlain by the Damara Supergroup are indicative of thin skin tectonics in this part of the South Central Zone, some 30km NW of the Okahandja Lineament zone. Intrusive rocks across the South Central Zone suggest that deformation in the NW ceased by 540 Ma, while deformation along the Okahandja Lineament continued until at least 520 Ma. iii Along the Okahandja lineament, high angle continental collision resulted in tight, co-axial folding and lateral extrusion of rocks along the continental backstop. The introduction of numerous late-D2 granites around the Okahandja Lineament Zone (such as the massive Donkerhuk granite) resulted in thermal weakening of the crust, helping to accommodate lateral extrusion. Thermal weakening of the basement allowed the development of thick-skinned tectonics and the formation of the Audwib nappe. In the NW, cooler, more rigid crust deformed very differently to those in the SE, through shallow shearing, thin skinned tectonics. Diachronous timing of the deformation in rocks in the NW and SE of the traverse is due in part to the rheologic difference between cooler rocks in the NW that had locked up to deformation, much earlier than thermally weakened ones in the SE at the plate collision margin, where tectonic stresses where greater. / AFRIKAANSE OPSOMMING: Die NE-strekkende Suid Sentral Sone van die Pan-Afikaanse (ca. 550-500) Damara gordel in sentraal Namibië stel diep gëerodeerde gesteentes van die middelkors blood wat die magmaties boog van die Damara orogeen verteenwoordig. Goeie dagsome, ongemodifiseer deur subsekwente naorogenises prosesse het dit moontlik gemaak om ‘n studie aan te pak van die interne argitektuur van ‘n omenby 50km opname wat strek van die kontinentale skeidings sone (tussen die Congo kraton in die NW en die onderplatende Kalahari kraton in die SE) by die Okahandja Lineament Sone, tot ver oor die die voorste punt van die Congo kraton in die magmatiese-boog, die Suid Sentral Sone. Hierdie studie neem in ag en karakteriseer die verandering in struktuur styl en drukvervormings (strain) intensiteit in klippe van die Damara Supergroep, tussen die dorpies Otjimbingwe in die SE en Karibib in die NW. In die SE van die traverse in die Okahandja lineament zone vind ’n mens styl, regop, styf gevoude D2 maaksels in die Tinkas en Kuiseb Formasies, wat bulk NW-SE verkortende en styl SW ekstrusie van rotse aandui. Deurdringende nie-coaksiale maaksels impliseer n hoë-hoek botsing tussen die Congo en Kalahari kratons. Dit is in teenstryding met skeefhoekige botsing wat voorgestel is deur verskeie vorige outeurs (e.g. Blaine (1977), Stanistreet et al. (1991), Tack & Bowden, 1999). ‘n Vermindering in D2 drukvervorming (strain) en die teenwoordigheid van van die silisiklastiese basale Nosib groep, stel die verteenwoordigehid van die onderliggende vloergesteentes voor en sodoende, dat die voorste punt van die onderliggende Congo kraton net ‘n paar kilomeer NW van die Okahandja Lineament onwikkel is. 8km NW van die Okahandja Lineamnet is daar ‘n km-skaalse NW neigende F1 dekbladvou gekern deur gneis van die vloer gesteentes en hervou is tot ‘n klomp, bi-neigende, iv dubbel duikende F2 plooie in wat vernoem word die Audawib vou kompleks. Die dekbladvou word geinterpriteer om te gevorm het vooraan a retro-verkuiwing, gedurende vreeë kontinentale botsing (syn-D1, vroeë-D2). Oorverskuifde en herververvormde vloer gesteentes is ‘n aanduideing van termale verswakking in die aarkors, wat gelei het tot “thick-skinned” tektoniek. Intrusiewe gesteenste om, en na die NW van die Audawib dekblad vou is die’ weidverspreide Salem-tipe graniet. Syn-D2 Salem-tipe graniete is vlak intrusief to onder die dekblad vou en het waarskynlik die F1 vou van sy wortel sone ontkoppel. NW van die Salem tipe graniete lê ‘n 15km2 groote venster in die vloer gesteentes in omring deur die onderste formasies van die Damara Supergroep. Verskuifde marmer sowel en D1 (vroee-D2) dioriet lae op die vloer gesteente se boonste kontak dui daarop dat hierdie boonste kontak verskeurings losmaakpunt is, ‘n tektoniese kontak. Vloergesteentes (1) ongeaffekteerde deur Damara (D1-D2) tektoniek en (2) onkonformeerbare kontak met oorliggende klippe van die Damara Supergroep is ‘n aanduding van “thin-skinned” tektoniek in die gedeelte van die Suid Sentral Sone 30km NW van die Okahandja Lineament Sone. Intrusiewe gesteentes gee aanduidings dat deformasie in die NW reeds ge-eeindig teen 540 Ma, terwyl vervorming in die Okahandja Lineament Sone nog aktief was tot minstens 520 Ma. Oor die Okahandja Lineament het die hoe-hoekige kontinentale botsing gelei tot stywe ko-aksiale plooing en laterale ekstrusie van gesteentes langs die kontinentale “backstop”. Die intrusie van verskeie laat-D2 grantiete (soos die masiewe Donkerhuk graniet) in die Okahandja lineament sone het gelei tot termale verswaking van die kors wat gehelp het om laterale ekstrusie van klippe te akkomodeer. Termale verswakking van vloer gesteentes het gelei tot die onwikkeling van “thickskinned” tektoniek en die vorming van die Audawib dekblad vou. In die NW, het koeler, stewiger gesteentes anders vervorm as daardies verder suid, deur vlak skeur-verkuiwings, “thin-skinned” tectonics. Nie-samelopende vervorming in gesteentes in die NW en SE van die opname is die gevolg van die rheologiese verskil tuseen die koeler gesteentes in die NW wat vroeer bestand geraak het teen vervorm as warmer gesteentes in die SE teenaan die botsings sone, waar tektoniese druk boonop groter was.

Student Number : 9707731W - PhD thesis - School of Geography, Archaeology and Environmental Studies - Faculty of Science / Southern Mozambique has experienced changes in land-use and land-cover over the last 45 years. South Central Chibuto is a dynamic environmental change ‘hotspot’ of this region, and because of the socio-economic development that is taking place it is unveiling a number of land-use changes in Mozambique. In this research, environmental changes in the region are shown to be a function of various socioeconomic and biophysical drivers of change. A variety of research methods including interpretation of aerial photographs and satellite images, analysis of archival material, Participatory Rural Appraisal (PRA) and structured interviews, have been used to derive some of the drivers of environmental change. These drivers of change include socio-economic factors, the colonial dual economy and the increase in cash crop production that led to negative impacts on some lands in the steep slopes of the ancient dunes, the post-independence policy of nucleation of settlements that has induced extensive conversions of land use together with the war and the recent shifts into a market economy that have led to further intensification of land use. The biophysical drivers include, among others but not limited to, fluctuations in rainfall, with periods of alternating dry and wet spells shaping land-use change, as well as single shock events, such as extreme droughts and floods. New factors, including the HIV/AIDS pandemic and globalization have been identified as having an impact on the livelihoods in the study area. A valuable, local-scale case or place-based case study approach is shown to enable a detailed and rich analysis of the complex trajectory of environmental change. Finally, lessons drawn from this study are shown to have the potential to inform policies for sustainable livelihoods in Mozambique.

Na região dos Andes Patagônicos entre os 41 a 44° S estão expostos amplos e contínuos afloramentos de rochas graníticas do segmento norte do Batólito Norte-Patagônico (BNP). Durante sua evolução a maior parte das rochas graníticas foram colocadas em rochas metamórficas, e outras partes foram colocadas em rochas vulcânicas do Jurássico-Berriasano, sedimentares e vulcânicas do Cretáceo Inferior, vulcânicas do Cretáceo Superior e sedimentares do Mioceno. Parte desta atividade magmática está associada à gênese de depósitos de minério. As rochas plutônicas expostas apresentam uma gradação desde dioritos até granitos e leucogranitos, apesar de que a área é largamente dominada por variedades intermediárias a ácidas. Determinações K-Ar permitiram identificar extensos e volumosos eventos plutônicos que descrevem duas faixas de orientação N-S durante o Cretáceo Inferior (ca. 120-100 Ma) e Mioceno (ca. 20-7 Ma), discretos durante o Jurássico Superior (ca. 155 Ma) e o Cretáceo Superior (ca. 95-70 Ma), restritos durante o Plioceno (ca. 5-3 Ma), e um provável evento plutônico no Eoceno (ca. 54-34 Ma), ao passo que experimentos Ar/Ar confirmam os eventos magmáticos do Cretáceo Inferior (ca. 126-100 Ma) e Mioceno (ca. 19-9 Ma). Determinações U-Pb convencionais indicam a provável perda e herança de Pb, apesar de confirmar os eventos magmáticos do Cretáceo Inferior (ca.129-114 Ma) e Mioceno (ca. 22-13 Ma). Além disso, as determinações U-Pb convencionais em zircões revelam a presença de rochas magmáticas pré-Andinas do Devoniano Inferior (ca. 400 Ma) provavelmente relacionadas com rochas do Maciço Norte-Patagônico. Determinações U-Pb SHRIMP em zircões indicam 110,0±9,6 Ma para um monzogranito e de 126,3±6,7 Ma para um piroxênio dioritio, 8,4±0,3 Ma para um tonalito e 13,26±0,19 Ma para um andesito porfirítico, e de 385,9±7,4 Ma para um corpo de microdiorito tectonizado. Estes dados indicam que o início da atividade plutônica é representada em ambos das faixas por pequenos corpos de colocação superficial, e a idade U-Pb SHRIMP do Devoniano confirma o evento magmático inferido das idades U-Pb convencionais. A distribuição de idades mostra um padrão complexo, mas, permite definir eventos magmáticos do Cretáceo, preferencialmente localizados, a E da Zona de Falha Liquiñe-Ofqui (ZFLO), do Mioceno no interior e a O desta estrutura, e do Plioceno no traço principal da ZFLO. A atividade plutônica do Mioceno, em direção a trincheira é diferente que o padrão definido para a região centro-norte dos Andes chilenos, onde é verificada a migração do arco magmático para a E com a conseqüente diminuição de idades neste sentido. Composições isotópicas de Sr e Nd mostram baixos e positivos teores de Nd com Sr entre -4 e +7 sugerindo que o BNP no segmento estudado, foi composto a partir de mistura de matérias do manto com fusão de crosta inferior, como é demonstrado pelos trabalhos anteriores, em áreas vizinhas. As composições isotópicas de Pb em feldspato, das mesmas amostras datadas por U-Pb convencional, variou com a idade, plútons com 206Pb/204Pb >18,62 são do Mioceno, enquanto que aqueles plútons com 206Pb/204Pb <18,57 são do Cretáceo, com uma relação inversa entre os plútons do Mioceno, o que é atribuído à variável interação com o embasamento metamórfico. Mineralizações de metais base com Au e Ag estão hospedadas em rochas vulcânicas do Cretáceo e limitadas à faixa magmática do Cretáceo Inferior e mineralizações de Au-As estão hospedadas no Microdiorito do Devoniano e em rochas metamórficas do Paleozóico e limitadas à faixa magmática do Mioceno. Além disso, em ambos as faixas, ocorrências de Cu-Mo são relatadas associadas com monzogranitos e tonalitios. Mineralizações de metais preciosos e de base no prospecto Las Juntas estão relacionados com alteração silíca-adularia e quartzo-sericita e deposição de pirita, esfalerita, galena com conteúdos de Ag e Bi, e calcopirita, e menor hematita, tetraedrite, arsenopirita, bornita e calcocita, em veios, vênulas, brechas e escassa disseminação. Os teores são variáveis, mas em veios mineralizados em Cu os teores podem atingir até 15% Cu, e em brechas mineralizadas em Cu-Pb-Zn os teores podem atingir até 32% Pb, 23% Zn e 0,28% Cu, com 1,4 para 1.300 ppm de Ag e 0,02 para 3,9 ppm de Au. Dados de inclusões fluidas indicam temperaturas de homogeneização variando entre 140 a 230º C, salinidades entre 3 a 6% em peso de NaCl equiv., e de deposição de metais base durante ebulição e mistura. Mineralizações de Au-As no prospecto Pichicolo estão relacionadas com alteração silíca e quartzo-sericita e deposição de arsenopirita e pirita, e menor pirrotita, calcopirita e bornita, em vênulas, stockwork e disseminação. Os teores variam entre 0,02 a 2,0 ppm de Au. Dados de inclusões fluidas indicam temperaturas de homogeneização entre 180 a 270º C, salinidades entre de 3 a 5% em peso de NaCl equiv., e deposição metálica durante ebulição e mistura. A mineralização, alteração e as características químicas e físicas de fluidos sugerem para ambos os prospectos características de epitermais de baixa sulfetação. O método Re-Os foi utilizado em molibdenitas hospedadas em plútons de monzogranito e tonalito para determinar a idade da mineralização de Cu-Mo. As idades obtidas (ca. 119 e 9,1 a 8,2 Ma) sugerem que a mineralização ocorreu em sistemas hidrotermais intimamente associada com os eventos magmáticos de Cretáceo Inferior e Mioceno, o que confirma a interpretação acerca da existência das faixas metalogéneticas polimetálicas do Cretáceo Inferior e aurífera do Mioceno propostas para a Cordilheira Norte-Patagônica. Biotita do monzogranito hospedeiro de mineralizaçao de Cu-Mo na aldeia Palena foi datada por Ar/Ar em 114,7 Ma, e outra datação, próxima da ocorrência, em 114,2 Ma. Biotita do tonalito hospedeiro da mineralização de Cu-Mo no estuário Reloncaví foi datada por Ar/Ar em 8,53 Ma, e outra datação, próxima da ocorrência, em 8,64 Ma. A proximidade e a superposição, dentro do erro analítico, entre as idades Ar/Ar em biotita, em ambas as áreas, sugerem que a alteração hidrotemal não foi estendida. Uma idade isocrônica Rb-Sr de 126±8 Ma obtida de rochas hidrotermalmente alteradas com mineralização polimetálica é interpretada como a idade do evento hidrotermal. Experimentos Ar/Ar em sericita hidrotemal de granulação muito fina com mineralização de Au-As mostra redistribuição de Ar por \'recoil\' e a idade integrada de 142±2 Ma sugere que a associação mineralização- magmatismo félsico do Jurássico não deve ser descartada. Composições isotópicas de Sr e Nd de rochas hospedeiras e ígneas associadas indicam que os magmas são principalmente derivados do manto com contaminação de crosta continental variável. Composições isotópicas de Pb em minerais de minério, rochas hospedeiras e ígneas associadas, em ambos os prospectos, se agrupam próximos da curva do orógeno no modelo da \'plumbotectonica\'. Em um diagrama 206Pb/204Pb-207Pb/204Pb, os minerais de minério e as rochas ígneas associados do prospecto Las Juntas são menos radiogênicos (206Pb/204Pb <18.6) que o prospecto Pichicolo (206Pb/204Pb >18.6). Este modelo é compatível com a idade absoluta cretácea da mineralização para Las Juntas e com a idade miocena assumida para Pichicolo. As tendências alongadas da composição de Pb nos minerais de minério indicam, principalmente, um modelo orogênico, sugerindo mistura variável de chumbo a partir de diferentes fontes, sobretudo de crosta superior. / In the Patagonian Andes region between 41 and 44° S extensive and continuous plutonic rocks of the North-Patagonian Batholith north segment are exposed. During their evolution most of the granitic rocks were emplaced in metamorphic rocks and other parts were emplaced in Late Jurassic-Berriasan volcanic rocks, Early Cretaceous sedimentary and volcanic rocks, Late Cretaceous volcanic rocks and Miocene sedimentary rocks. Part of this magmatic activity is associated with ore deposit genesis. The exposed plutonic rocks range mainly from diorites to granites and leucogranites, although the area is extensively dominated by intermediate to acid varieties. K-Ar determinations have allowed identification of extensive and voluminous plutonic events which describe two N-S oriented belts during the late Lower Cretaceous (ca. 120-100 Ma) and Miocene (ca. 20-7 Ma), discreet during the Upper Jurassic (ca. 155 Ma) and the Upper Cretaceous (ca. 95-70 Ma), restricted during the early Pliocene (ca. 5-3 Ma) and a probable plutonism in Eocene times (ca. 54-34 Ma), while Ar/Ar experiments confirm the late Lower Cretaceous (ca. 126-100 Ma) and Miocene (ca. 19-9 Ma) magmatic events. Conventional U-Pb determinations indicate the probable inheritance and loss of Pb, although they confirm the late Lower Cretaceous (ca. 129-114 Ma) and Miocene (ca. 22-13 Ma) magmatic events. In addition, the zircons conventional U-Pb determinations show the presence of pre-Andean Lower Devonian magmatic rocks (ca. 400 Ma) probably linked with rocks of the North- Patagonian Massif. Zircon U-Pb SHRIMP determinations indicate 110.0±9.6 Ma for a monzogranitic pluton and 126.3±6.7 Ma for a pyroxene dioritic stock, 8.4±0.3 Ma for a tonalitic pluton and 13.26±0.19 Ma for hornblende andesitic porphyry, and 385.9±7.4 Ma for a tectonized microdioritic body. These data indicate that the early plutonic activity is represented, in Mesozoic and Cenozoic belts, by basic to intermediate small bodies of shallow emplacement, and the SHRIMP U-Pb Devonian age confirms a magmatic event previously inferred by conventional U-Pb ages. The age distribution shows a complex pattern, which nevertheless allows, magmatic Cretaceous events to be located, preferably, to the E of the Liquiñe-Ofqui Fault Zone, magmatic Miocene events located in and to the W of this structure, and magmatic Pliocene events located in the main branch of the Liquiñe-Ofqui Fault Zone to be defined. The Miocene plutonic activity towards the trench is different to the defined pattern for the north-central Chilean Andes, where the magmatic arc migration to the E and the consequent age diminution in this same direction is verified. Nd and Sr isotopic compositions show low and positive Nd values together with Sr between -4 and +7 suggesting that the North-Patagonian Batholith in the studied segment, has been composed from mixing of mantle derived or mafic lithospheric material with melting of lower continental crust, as is shown by previous work in neighboring areas. The Pb isotopic compositions in feldspar, of the same dating samples by U-Pb conventional method, varied with the age, plutons with 206Pb/204Pb greater than 18.62 are Miocene, whereas those plutons with 206Pb/204Pb less than 18.57 are Cretaceous, with an inverse relation between Miocene plutons, which is attributed to varying interaction grade with the metamorphic basement. Metal base-mineralization with Au and Ag contains are hosted in Cretaceous volcanic rocks and restricted to the Lower Cretaceous magmatic belt and Au-As mineralization are hosted in Devonian microdiorite and Paleozoic metamorphic rocks and restricted to the Miocene magmatic belt. Also, in both belts Cu-Mo occurrences are reported in associated with monzogranites and tonalities, respectively. Metal base and precious mineralizations in the Las Juntas Prospect are related to silicicadularia and quartz-sericite alteration and deposition of pyrite, sphalerite, Ag-bearing and Bi-bearing galena, and chalcopyrite, and minor hematite, tetrahedrite, arsenopyrite, bornite and chalcocite, in vein, veinlets and minor breccia bodies, and scarce dissemination. Ore grades are variable, but in mineralized Cu-veins the values reach up 15% Cu, and in Pb-Zn-Cu breccias the values reach up 32% Pb, 23% Zn and 0.28% Cu, 1.4 to 1,300 ppm Ag and 0.02 to 3.9 ppm Au. Fluid inclusion data indicate homogenization temperatures varying between 140 to 230 ºC, salinities ranging from 3 to 6 weight % NaCl equivalent, and metal base deposition during boiling and mixing events. Asmineralizations with gold contain in the Pichicolo Prospect are related to silicic and quartz-sericite alterations and deposition of arsenopyrite and pyrite, and minor pyrrotite, chalcopyrite and bornite, in veinlets, stockwork and dissemination. Grades vary between 0.02 to 2.0 ppm Au. Fluid inclusion data indicate homogenization temperatures varying between 180 to 270 ºC, salinities ranging from 3 to 5 weight % NaCl equivalent, and metallic deposition during boiling and mixing events. The mineralization, alteration and the chemical and physical fluid characteristics suggest for both studied prospects epithermal low-sulphidation features. Re-Os method in molybdenites hosted in monzogranitic and tonalitic plutons have been used to determine timing of Cu-Mo mineralizations. The obtained ages (ca. 119 and 9.1 to 8.2 Ma) suggest that the mineralization occurred in hydrothermal systems closely associated with late Lower Cretaceous and Miocene plutonic events, which confirm the interpretation about the existence of Lower Cretaceous and Miocene metallogenic belts proposed for the North-Patagonian Cordillera. Biotite of the monzogranitic host rock directly related with the Palena village molybdenite mineralization was dated by Ar/Ar in 114.7 Ma, and near of the occurrence in 114.2 Ma. Biotite of the tonalite host rock directly related with the Reloncaví estuary molybdenite mineralization was dated by Ar/Ar in 8.53 Ma and near of the occurrence in 8.64 Ma. The proximity, and superposition within the analytical error, between the Ar/Ar biotite ages, in both areas, suggests non extended hydrothermal alteration. Rb-Sr isochron age of 126±8 Ma obtained from hydrothermally alterated rocks in a polymetallic prospect is interpreted as the age of the hydrothermal event. Ar/Ar step-heating experiments in hydrothermal very fine grain sericite from Au-As mineralization shown Ar-redistribution by recoil effect and the integrated age of 142±2 Ma suggest that the association mineralization-Jurassic volcanic felsic magmatism should not be discarded. Sr and Nd isotopic compositions of the host and igneous-related mineralization rocks indicate that magmas are mainly mantle derived with variable little crustal contamination. Pb isotopic compositions of the ore minerals, host and igneous-related mineralization rocks in both prospect clusters near of the orogene curve within a plumbotectonic model. On 206Pb/204 versus 207Pb/204Pb plot, the ore minerals and the associated igneous units of the Las Juntas prospect are less radiogenic (206Pb/204Pb <18.6) that the Pichicolo prospect (206Pb/204Pb >18.6). This model is compatible with the absolute Cretaceous mineralization-age determined for the Las Juntas prospect and with the constraint Miocene mineralization-age for the Pichicolo prospect. The elongate trends of the ore minerals in the general clusters indicate mainly an orogenic model fit, suggesting variable mixing of lead from different sources, mainly from upper crust.

The Wrangellia composite terrane is one of the largest fragments of juvenile crust added to the North American continent since Mesozoic time, and refining its accretionary history has important implications for understanding how continents grow. New U-Pb geochronology and Hf isotopes of detrital zircons from Late Jurassic-Late Cretaceous strata from the forearc of the Wrangellia composite terrane allows more insight on the tectonic and paleogeographic history of the terrane. Our stratigraphically oldest samples from the Late Jurassic Naknek Formation have a detrital zircon U-Pb signature dominated by Early and Late Jurassic grains (195-190 Ma; 153-147 Ma). Hf isotopic compositions of these grains are juvenile to intermediate (εHf(t)=4.5-14.7). Disconformably above the Naknek Formation are two poorly understood units Ks and Kc. The Ks unit is dominated by Early to Late Jurassic grains (159-154 Ma) with a few Paleozoic grains (347-340 Ma). Hf isotopic compositions of Carboniferous-Jurassic grains are juvenile to intermediate (εHf(t)=6.0-18.8). The overlying Kc unit has Late to Early Jurassic zircons (198-161 Ma), and an increase in Paleozoic ages (374-323 Ma). Hf isotopic compositions of these grains are juvenile to intermediate (εHf(t)=4.5-14.7). Samples from the Matanuska Formation have major Late Cretaceous grains (90-71 Ma), and minor Early Cretaceous (137-106 Ma), Late to Early Jurassic (200-153 Ma), Paleozoic (367-277 Ma), and Precambrian grains (2597-1037 Ma). Hf compositions have a wider range from both the Late Cretaceous grains (εHf(t)=-1.5-14.9) and Paleozoic-Precambrian grains (εHf(t)=-23.7-16.3). Our results suggest an evolving provenance from Late Jurassic to Late Cretaceous time for the Wrangellia composite terrane forearc basin. The Late Jurassic Naknek Formation samples were dominantly derived from a juvenile to intermediate Jurassic igneous sediment source. During Early Cretaceous time, there is a slight increase in the number of Paleozoic grains in the Ks and Kc unit samples. The Early Cretaceous sediments have a mostly positive Hf isotopic compositions suggesting exhumation of Jurassic and Paleozoic juvenile igneous sediment sources. By Late Cretaceous time, our data illustrates another increase in Paleozoic grain abundances, in addition to the introduction of Precambrian grains, all with widely variable Hf isotopic compositions. We interpret this to reflect a larger sediment flux from the interior of Alaska where more evolved igneous rocks of that age are found.

Detrital zircon U-Pb geochronology is a useful tool for analyzing provenance in the sedimentary record. Differentiating recycled and first cycle populations in the detrital record, however, is not a straightforward process. A second potential problem in using detrital signatures to determine provenance of sediment lies in the assumption that detrital signatures of modern rivers reflect input from each exposed unit in the catchment boundaries. To investigate each of these problems, I present U-Pb analysis of detrital zircon (DZ) from modern river sand collected from 20 watersheds, 6 detrital apatite (DA) signatures from modern river sand, and 6 DA signatures from exposed strata, all within the Talkeetna Mountains (south-central Alaska). DA rarely survives past the first cycle of erosion and deposition due to its inability to survive chemical weathering, and thus dominantly represent igneous input in detrital signatures, whereas zircon can be of igneous origin or can survive multiple cycles of erosion and deposition. By comparing the DA signatures with the DZ signatures, I present a method to better differentiate first cycle, igneous sediment contributions from recycled populations within a detrital signature. The results of these comparisons show that DA signatures provide ages of igneous input into the detrital record; these ages are also reflected in the DZ signature, thus signaling these DZ populations as igneous in origin. This study also investigates the potential for DA recycling and DA input from recycled strata. To address the second problem, I present a method using GIS software and the most recent map of Alaska to create simulated signatures that records input on a scale proportionate to the exposed surface area of each bedrock unit. In ~35% of the watersheds tested, the simulated signatures predict trends similar to the DZ signatures from the modern river sands, in 55% of the watersheds tested the simulated signatures missed one or more populations present in the DZ signature, and in 10% of watersheds tested, the simulated signature predicted trends very different from the DZ signatures. In cases where the DZ and simulated signatures do not match, I believe this represents influences of climate and relief and zircon fertility.