Готові списки джерел за темами / Arc Crust

Добірка наукової літератури з теми "Arc Crust"

Автор: Grafiati
Опубліковано: 10 грудня 2022
Оновлено: 28 січня 2023

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Статті в журналах з теми "Arc Crust"

1

LEAT, P. T., R. D. LARTER, and I. L. MILLAR. "Silicic magmas of Protector Shoal, South Sandwich arc: indicators of generation of primitive continental crust in an island arc." Geological Magazine 144, no. 1 (October 27, 2006): 179–90. http://dx.doi.org/10.1017/s0016756806002925.

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Protector Shoal, the northernmost and most silicic volcano of the South Sandwich arc, erupted dacite–rhyolite pumice in 1962. We report geochemical data for a new suite of samples dredged from the volcano. Geochemically, the dredge and 1962 samples form four distinct magma groups that cannot have been related to each other, and are unlikely to have been related to a single basaltic parent, by fractional crystallization. Instead, the silicic rocks are more likely to have been generated by partial melting of basaltic lower crust within the arc. Trace element and Sr–Nd isotope data indicate that the silicic volcanics have compositions that are more similar to the volcanic arc than the oceanic basement formed at a back-arc spreading centre, and volcanic arc basalts are considered to be the likely source for the silicic magmas. The South Sandwich Islands are one of several intra-oceanic arcs (Tonga–Kermadec, Izu–Bonin) that have: (1) significant amounts of compositionally bimodal mafic–silicic volcanic products and (2) 6.0–6.5 km s−1P-wave velocity layers in their mid-crusts that have been imaged by wide-angle seismic surveys and interpreted as intermediate-silicic plutons. Geochemical and volume considerations indicate that both the silicic volcanics and plutonic layers were generated by partial melting of basaltic arc crust, representing an early stage in the fractionation of oceanic basalt to form continental crust.
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Davidson, Jon, Simon Turner, Heather Handley, Colin Macpherson, and Anthony Dosseto. "Amphibole “sponge” in arc crust?" Geology 35, no. 9 (2007): 787. http://dx.doi.org/10.1130/g23637a.1.

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3

Tomlinson, K. Y., R. P. Hall, D. J. Hughes, and P. C. Thurston. "Geochemistry and assemblage accretion of metavolcanic rocks in the Beardmore–Geraldton greenstone belt, Superior Province." Canadian Journal of Earth Sciences 33, no. 11 (November 1, 1996): 1520–33. http://dx.doi.org/10.1139/e96-115.

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The Beardmore–Geraldton greenstone belt lies between the Wabigoon volcanic arc (Onaman–Tashota terrane) and the Quetico metasedimentary subprovince and thus has an important bearing on the accretionary model that has been proposed for the amalgamation of these terranes. This paper presents geochemical evidence for the petrogenetic affinities of the volcanic units of the western half of the Beardmore–Geraldton greenstone belt. These data suggest that the metavolcanic rocks of the greenstone belt form a series of distinct packages. Trace element data are used to demonstrate the similarities and differences of each unit of lavas and to characterize their source region and likely tectono-magmatic setting. The data indicate that three separate fragments of volcanic crust representing oceanic crust, arc crust, and back-arc crust formed in a small arc system and were juxtaposed prior to collision with the Wabigoon arc. These fragments of crust were then accreted to the Wabigoon arc where sedimentation was followed by thrusting and folding resulting in shortening of the belt. Delamination of the volcanic units is thought to have been responsible for the preservation of just the pillow lava sequence of oceanic crust. Lower crustal or crust–mantle delamination of the Wawa arc and underplating of the Quetico are thought to have been responsible for the late and long-lived, high-grade metamorphic event in the Quetico and such "flake tectonics" are thought to have been an important process in the interaction between the Wabigoon, Quetico, and Wawa subprovinces.
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4

Lee, Cin-Ty A., Peter Luffi, Emily J. Chin, Romain Bouchet, Rajdeep Dasgupta, Douglas M. Morton, Veronique Le Roux, Qing-zhu Yin, and Daphne Jin. "Copper Systematics in Arc Magmas and Implications for Crust-Mantle Differentiation." Science 336, no. 6077 (April 5, 2012): 64–68. http://dx.doi.org/10.1126/science.1217313.

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Arc magmas are important building blocks of the continental crust. Because many arc lavas are oxidized, continent formation is thought to be associated with oxidizing conditions. On the basis of copper’s (Cu’s) affinity for reduced sulfur phases, we tracked the redox state of arc magmas from mantle source to emplacement in the crust. Primary arc and mid-ocean ridge basalts have identical Cu contents, indicating that the redox states of primitive arc magmas are indistinguishable from that of mid-ocean ridge basalts. During magmatic differentiation, the Cu content of most arc magmas decreases markedly because of sulfide segregation. Because a similar depletion in Cu characterizes global continental crust, the formation of sulfide-bearing cumulates under reducing conditions may be a critical step in continent formation.
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5

Lee, Cin-Ty, and Boda Liu. "Thick crust, hydrous magmas, and the paradox of voluminous cold magmatism." Volcanica 4, no. 2 (October 25, 2021): 227–38. http://dx.doi.org/10.30909/vol.04.02.227238.

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Andesites are refined and “cold” magmas compared to their basaltic parents, yet large volumes of andesites are generated at continental arcs. We show that large andesitic plutons are favored when arc crust attains a thickness of ~60 km while mafic plutons are small and favored when arc crust is thin. Using simple thermal models, we show that large, long-lived and relatively cold partially molten zones, sustained by recharge of hydrous basaltic magmas, are favored at depth when arc crust is thick due to the reduced efficiency of heat loss with increasing crustal thickness. Thin crust and drier magmas favor hotter and thinner partially molten zones. Our study provides an explanation for the apparent paradox that the most voluminous magmas in continental arc settings are cold. The origin of andesites may be linked to the interplay between magmatic differentiation, the availability of water, and the processes that control crustal thickness.
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Jagoutz, Oliver, Pierre Bouilhol, Urs Schaltegger, and Othmar Müntener. "The isotopic evolution of the Kohistan Ladakh arc from subduction initiation to continent arc collision." Geological Society, London, Special Publications 483, no. 1 (September 19, 2018): 165–82. http://dx.doi.org/10.1144/sp483.7.

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AbstractMagmatic arcs associated with subduction zones are the dominant active locus of continental crust formation, and evolve in space and time towards magmatic compositions comparable to that of continental crust. Accordingly, the secular evolution of magmatic arcs is crucial to the understanding of crust formation processes. In this paper we present the first comprehensive U–Pb, Hf, Nd and Sr isotopic dataset documenting c. 120 myr of magmatic evolution in the Kohistan-Ladakh paleo-island arc. We found a long-term magmatic evolution that is controlled by the overall geodynamic of the Neo-Tethys realm. Apart from the post-collisionnal melts, the intra-oceanic history of the arc shows two main episodes (150–80 Ma and 80–50 Ma) of distinct geochemical signatures involving the slab and the sub-arc mantle components that are intimately linked to the slab dynamics.
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Kent, Adam J. R. "Quaternary Volcanism in the Cascade Arc." Elements 18, no. 4 (August 1, 2022): 232–38. http://dx.doi.org/10.2138/gselements.18.4.232.

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The Cascade arc has produced a remarkable diversity of volcanic rocks over the Quaternary period. The major stratovolcanoes that define the arc front are dominated by eruptions of andesitic and dacitic intermediate magmas, produced largely by fractionation, melting, assimilation, and mixing within the crust. In addition, relative to many other subduction zones, the arc has produced significant mafic volcanism. These more primitive magmas reveal complexity in mantle wedge dynamics, sources, and magma production processes, and suggest that there are significant differences along the arc in the amount of magma that enters the lower Cascade crust from the underlying mantle.
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Liu, Xue Long, Na Zhang, and Jian Kang. "The Lead Isotope Characteristics and Tracing Significance of Ore Metallogenic Material in the Geza Arc,Yunnan." Advanced Materials Research 1073-1076 (December 2014): 2054–57. http://dx.doi.org/10.4028/www.scientific.net/amr.1073-1076.2054.

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Geza arc is the important parts of Yidun island arc in southwest of Sanjiang tectonic magmatic belts, it located in the southern tip of the Yidun island arc, which is a newly discovered copper polymetallic ore concentration area in the recently years in China. Based on the development stage of island arc orogenic, the distribution of intrusive rocks, composition, geochemical characteristics, Geza island arc granits belt can be divided into three belts. Geza island arc several typical porphyry deposits Pb isotopic data show that Pb206/Pb204 17.680~19.165, Pb207/Pb204 15.453~15.773,change in scope, Pb208/Pb204 37.730~39.654. Most of samples are normal lead, Pb isotopes focused on the side of orogenic evolution line and the lower crust range,with the characteristics of crust-mantle mixed source.
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CHEN, BIN, and BOR-MING JAHN. "Geochemical and isotopic studies of the sedimentary and granitic rocks of the Altai orogen of northwest China and their tectonic implications." Geological Magazine 139, no. 1 (January 2002): 1–13. http://dx.doi.org/10.1017/s0016756801006100.

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The Altai orogen (northwest China) represents the southwestern margin of the Central Asian Orogenic Belt. Geochemical and Nd–Sr isotope analyses were carried out on the Palaeozoic sedimentary and granitic rocks in order to trace their sources and to evaluate the pattern of continental growth of the orogen. Nd isotopic data for both the granites and sediments suggest a significant proportion of middle Proterozoic crust beneath the Altai orogen. However, addition of juvenile material (arc/back-arc oceanic crust) during Palaeozoic times is also significant. Trace elements and isotopic data of sediments suggest their sources were immature. They represent mixtures between a Palaeozoic juvenile component and an evolved continental crust. The early Palaeozoic sediments show εNd(T) = −3.4 to −5.0, TDM = 1.5–1.8 Ga, and ISr = 0.710–0.712. They represent a passive margin setting, with a predominance of evolved crustal material in the source. The Devonian sequences, however, might have been deposited in a back-arc basin setting, produced by subduction of the Junggar oceanic crust along the Irtysh fault. A significant addition of arc material into the sedimentary basin is responsible for the highly variable εNd values (−6 to 0) and ISr (0.711–0.706). The Carboniferous rocks were also deposited in a back-arc basin setting but with predominantly arc material in the source as suggested by an abrupt increase in εNd(T) (+6 to +3) and decrease in ISr (0.7045–0.7051). Voluminous syn-orogenic granitoids have εNd(T) = +2.1 to −4.3, ISr = 0.705–0.714 and TDM = 0.7–1.6 Ga. They were not derived by melting of local metasedimentary rocks as suggested by previous workers, but by melting of a more juvenile source at depth. Post-orogenic granites have higher εNd(T) (∼ +4.4) than the syn-orogenic granitoids, indicating their derivation from a deeper crustal level where juvenile crust may predominate.
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Kepezhinskas, Pavel, Nikita Kepezhinskas, and Nikolai Berdnikov. "Gold, platinum and palladium enrichments in arcs: role of mantle wedge, arc crust and halogen-rich slab fluids." E3S Web of Conferences 98 (2019): 08010. http://dx.doi.org/10.1051/e3sconf/20199808010.

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Arc-related magmas are frequently enriched in Au, Pt and Pd in respect to MORB and OIB igneous suites. Magmatic arcs commonly host large-scale hydrothermal Au and Au-Cu and PGE mineralization related to young volcanic systems and zoned ultramafic complexes respectively. Island-arc mantle xenoliths show Au, Pt, Pd enrichments related to mantle wedge metasomatism by slab-derived fluids. Long-lived plumbing systems in arc crust (arc magma chambers) show further enhancement of Au, Pt and Pd enrichments through subduction-related metamorphic and metasomatic processes in the presence of halogen-rich, aqueous fluids. We propose that Au-Pt-Pd enrichments in arcs are caused by mantle wedge-slab interactions followed by differentiation and metamorphism of magmatic conduits in arc crust.
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Більше джерел

Дисертації з теми "Arc Crust"

1

Edwards, Caroline Marion Hawkey. "A comparison of arc evolution on continental and oceanic crust, Sunda Arc, Indonesia." Thesis, Royal Holloway, University of London, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361452.

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2

Mercer, Celestine Nicole. "Mineralogical indicators of magmatic and hydrothermal processes in continental arc crust /." Connect to title online (Scholars' Bank) Connect to title online (ProQuest), 2009. http://hdl.handle.net/1794/10250.

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3

Mercer, Celestine Nicole 1979. "Mineralogical indicators of magmatic and hydrothermal processes in continental arc crust." Thesis, University of Oregon, 2009. http://hdl.handle.net/1794/10250.

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Анотація:
xviii, 177 p. : ill., maps. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
This dissertation explores several important consequences of H 2 O-rich fluids in magmatic and ore-forming systems within continental arc crust. North Sister, a stratovolcano in the Oregon High Cascades, provides a window into magma generation processes in the deep crust. Eruption of a remarkably limited basaltic andesite composition over the lifespan of this volcano may reflect last equilibration of mantle derived magma within a deep crustal hot zone. High pressure, water-undersaturated phase equilibrium experiments show that an anhydrous, augite-rich gabbro at ∼12 kbar (40 km depth) and ∼ 1175°C is the most probable lithology with which North Sister basaltic andesite with ∼3.5 wt% H 2 O last equilibrated within the deep crust before erupting. While magma often erupts at the planets surface as at North Sister, a greater volume never reaches the surface and solidifies within the upper crust. Exsolution of magmatic fluids is an inevitable consequence of crystallization of hydrous crustal magmas. The fate of these fluids is the focus of the remainder of this dissertation. Modeling of CO 2 and H 2 O variations during crystallization of granitic magma reveals that exsolution of a large mass of fluid occurs only after CO 2 is largely degassed, creating ideal conditions for hydrofracturing and formation of porphyry copper deposits. CO 2 and H 2 O solubility relations suggest that H 2 O-rich magma was required to produce the porphyry-Cu-Mo deposit at Butte, Montana, which may explain its distinctively deep generation. Electron microprobe analyses of Ti in quartz and Zr in rutile in samples from Butte yield porphyry magma temperatures (630-770°C) that overlap substantially with hydrothermal vein temperatures (<430-750°C). Veins display large temperature ranges (50-250°C) that signify variable degrees of cooling of hot magmatic fluids upon contact with cooler wall rock during vein growth. Modeling of Ti diffusion in quartz suggests that individual dikes and veins likely cooled over short timescales (10s-1000s years), indicating that porphyry systems may evolve by episodic magmatic fluid injections with discrete thermal spikes. Modeling of Ti diffusion in quartz combined with electron backscatter diffraction maps show that small hydrothermal quartz veins likely formed by epitaxial growth. This dissertation includes co-authored material both previously published and in preparation for submission.
Committee in charge: A. Dana Johnston, Chairperson, Geological Sciences; Mark Reed, Member, Geological Sciences; Paul Wallace, Member, Geological Sciences; Richard P. Taylor, Outside Member, Physics
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4

Freymuth, Heye. "The role of the oceanic crust in the genesis of volcanic arc magmas." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.684749.

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Volcanic arc magmas are usually thought to receive components from three different sources: the subarc mantle, fluids derived from the subducted oceanic crust and lithospheric mantle, and melts derived from subducted sediments. This thesis re-evaluates this model based on isotopic data for magmas from the Izu, New Britain and Mariana arcs. High (230Th/232Th) ratios of up to 2.5 and U excess over Th in samples from the Izu and New Britain arcs are shown to be inconsistent with a derivation from subducted sediments or the sub-arc mantle and are instead argued to reflect a contribution of a melt of the mafic oceanic crust. In addition to Th, the magmas require a number of incompatible elements to be added to the sub-arc mantle. Many of these elements have traditionally been interpreted to be derived from a melt of subducted sediments. Yet, radiogenic Nd and Hf isotopes in these samples do not indicate the presence of a sediment melt. In order to explain this discrepancy, a model is presented in which the component previously identified as sediment melt is a mixture of a sediment melt and a melt of the mafic oceanic crust. Mo isotopes are suggested as a novel tracer for subduction components in volcanic arc magmas and a potential tracer for deep recycling of material transported into the mantle beyond subduction zones. Mo isotope ratios are presented for samples from oceanic sediments, the altered top part of the mafic oceanic crust, and volcanic arc magmas from the Mariana arc, thus defining input and output parameters for a subduction zone. Mo is shown to be preferentially transported in an isotopically distinct fluid derived from the subducted slab. Fluid addition leads to values of 0'98Mo in the Mariana arc lavas ~0.1-0.3 %0 higher than in MORB.
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Alvarado, Patricia Monica. "Crustal Seismicity in the Back-Arc Region of the Southern Central Andes from Historic to Modern Times." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195537.

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The western margin of South America between 30ºS and 36ºS is seismically active. While the largest magnitude earthquakes are the interplate subduction zone events, the historically most devastating earthquakes have been the moderate-to-large magnitude earthquakes with depths < 35 km in the Andean back-arc. This region is characterized by accreted terranes later reactivated during Mesozoic extensional processes. Crustal seismicity in the back-arc is related to the thin-skinned Precordillera (PC) fold-thrust belt and the thick-skinned Sierras Pampeanas (SP) basement-cored uplifts overlying the flat slab segment. South of 33ºS, the active volcanic arc above the normally dipping subducted plate is also seismically active at crustal depths. In this study we combined historical and regional broadband seismic data to characterize moderate-to-large earthquakes and the crustal structure in this region. We have digitized and modeled teleseismic records of the 1944 and 1952 San Juan, Argentina PC earthquakes. Both events have shallow source depths, short duration of the source time functions with a thrusting focal solution for the 1944 (Mw 7.0) earthquake and a major strike-slip component in the 1952 (Mw 6.8) earthquake solution. By modeling regional broadband waveforms collected during the CHile-ARgentina Geophysical Experiment (CHARGE) during 2000 and 2002 we constrained the seismic moment tensor and improved focal depths for 27 crustal (3.5 < Mw < 5.1) earthquakes. We found predominantly thrust-fault focal mechanisms and focal depths of 10-26 km for earthquakes over the flat slab region; the eastern SP and active arc have earthquakes with strike-slip focal mechanisms and shallower depths. We used these same earthquakes to determine the crustal structure using raypaths that sample different geologic terranes. Our results indicate high Vp, low Vs for the northern Cordillera, PC and western SP thicker crust; low Vp, low Vs and a thinner crust beneath the arc (south of 33°S) consistent with a mafic composition and partial melt. The eastern SP basement shows low Vp, low Vs and thinner crust consistent with a more quartz-rich composition. These differences have an important control on the present day Andean earthquake deformation and the high seismic hazard posed in this region.
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Jolis, Ester M. "Magma-Crust Interaction at Subduction Zone Volcanoes." Doctoral thesis, Uppsala universitet, Berggrundsgeologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-198085.

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The focus of this work is magma-crust interaction processes and associated crustal volatile release in subduction zone volcanoes, drawing on rock, mineral, and gas geochemistry as well as experimental petrology. Understanding the multitude of differentiation processes that modify an original magma during ascent to the surface is vital to unravel the contributions of the various sources that contribute to the final magmas erupted at volcanoes. In particular, magma-crust interaction (MCI) processes have been investigated at a variety of scales, from a local scale in the Vesuvius, Merapi, and Kelut studies, to a regional scale, in the Java to Bali segment of the Sunda Arc.  The role of crustal influences is still not well constrained in subduction systems, particulary in terms of the compositional impact of direct magma crust interplay. To address this shortcoming, we studied marble and calc-silicate (skarn) xenoliths, and used high resolution short timescale experimental petrology at Vesuvius volcano. The marbles and calc-silicates help to identify different mechanisms of magma-carbonate and magma-xenolith interaction, and the subsequent effects of volatile release on potential eruptive behaviour, while sequential short-duration experiments simulate the actual processes of carbonate assimilation employing natural materials and controlled magmatic conditions. The experiments highlight the efficiency of carbonate assimilation and associated carbonate-derived CO2 liberated over short timescales. The findings at Merapi and Kelut demonstrate a complex magmatic plumbing system underneath these volcanoes with magma residing at different depths, spanning from the mantle-crust boundary to the upper crust. The erupted products and volcanic gas emissions enable us to shed light on MCI-processes and associated volatile release in these systems. The knowledge gained from studying individual volcanoes (e.g., Merapi and Kelut) is then tested on a regional scale and applied to the entire Java and Bali arc segment. An attempt is presented to distinguish the extent of source versus crustal influences and establish a quantitative model of late stage crustal influence in this arc segment. This thesis therefore hopes to contribute to our knowledge of magma genesis and magma-crust interaction (MCI) processes that likely operate in subduction zone systems worldwide.
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7

Klein, Benjamin Zachary. "Processes and rates of arc crust growth and differentiation in the Southern Sierra Nevada crustal section." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/121759.

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Анотація:
Thesis: Ph. D. in Geology, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references.
This thesis presents a multidisciplinary investigation of the processes and timescales for the construction of arc crust, with a focus on the exposed crustal section in the southernmost Sierra Nevada Batholith, California. This section exposes plutons that were emplaced at pressures ranging from 3-10 kbars, as well as metamorphic wall rocks. Chapters 1 and 2 represent focused studies of the Bear Valley Intrusive Suite (BVIS), the dominant igneous component of the crustal section. Chapter 1 presents new magmatic structural data and whole rock geochemical data that highlight a discontinuity in the BVIS between a lower crust dominated by originally shallowly lying mafic cumulates and an upper crust dominated by steeply oriented felsic intrusives. These observations are used to constrain the thermal state of the arc during the emplacement of the BVIS. Chapter 2 is a high-precision CA-ID-TIMS U/Pb zircon geochronology study of the BVIS.
This study shows that the entire BVIS was emplaced within 1.1 million years, and thus represents the highest documented (intrusive) subduction zone magmatic flux. Chapter 3 focuses on the contribution of the metamorphic wall-rocks to the observed crustal section. Using detrital zircon geochronology, I argue that these wall-rocks preserve an inverted stratigraphy that is most easily explained if these sediments were first subducted and subsequently returned as relaminated material, which would make these materials the first in situ example of relaminated sediments. Chapters 4 and 5 present broader studies of subduction zone processes in space and time. In Chapter 4, I present a study based on a global compilation of modern arc lavas.
This study develops new proxies that use distinctive major element trends produced by fractionating magmas to qualitatively constrain the hydration state and initial fractionation pressure of differentiating magmas, and finds that magmas in continental arcs typically evolve at wetter and higher-pressure conditions compared to island arcs. Finally, Chapter 5 investigates the dynamics of subducted slabs through Earth's history and finds that, based on anticipated higher mantle temperatures and concomitant thicker, more mafic oceanic crust, subducted slabs in the Archean are unlikely to have stagnated within or immediately below the mantle transition zone.
by Benjamin Zachary Klein.
Ph. D. in Geology
Ph.D.inGeology Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences
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Jones, Rosemary Ellen. "Subduction zone processes and continental crust formation in the southern Central Andes : insights from geochemistry and geochronology." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9672.

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Subduction zones, such as the Andean convergent margin, are the sites at which new continental crust is generated, and where subducting material is either recycled to the crust via arc magmatism or transferred to the deep mantle. The composition of arc magmas and associated new continental crust reflects variable contributions from mantle, crustal and subducted reservoirs. Insights into crustal growth and recycling processes in the southern Central Andes, specifically in the Pampean flat-slab segment, have been gained by utilising a range of petrological, geochronological and geochemical techniques. These techniques have been applied to a suite of Late Cretaceous (~73 Ma) to Late Miocene (~6 Ma) intrusive (granitoids) and extrusive (basalts to rhyolites) arc rocks collected from an east - west transect across the Andean Cordillera. The oxygen and hafnium isotopic composition of the accessory mineral zircon allows mantle-derived melts contaminated with older, upper continental crustal to be identified. Boron isotopic compositions of melt inclusions, combined with concentrations of certain incompatible trace elements, can be used to assess the source and influence of fluids derived from subducting material on the melt source region. The southern Central Andes provides a particularly interesting area to study these processes as the thickness of the continental crust has increased significantly over the course of the Cenozoic (from ~35 km to >50 km) and the angle of the subducting Nazca plate has shallowed since ~18 Ma, causing the position of the volcanic arc to migrate to the east. In order to unravel the complexities involved with constraining the contributions to arc magmas at an active continental margin, a range of geochronological, geochemical, and geothermobarometric techniques, including high resolution, micro-analysis of mineral phases and melt inclusions, have been applied. High resolution, U-Pb dating of magmatic zircon has improved regional stratigraphy in the Pampean flat-slab segment (between ~29 and 32 °S) and provided an accurate temporal constraint for geochemical and geothermobarometric data. The results of in-situ O and Lu-Hf isotope analysis of zircon show both distinct temporal and spatial variations across the Andean arc. The observed isotopic variability is attributed to variable contamination of mantle-derived melts with distinct Andean basement terranes, which vary east – west in composition and age. ‘Mantle-like’ δ18O(zircon) values, juvenile initial ƐHf(zircon) values and a lack of inherited, xenocrystic zircon cores, suggests the Late Cretaceous (~73 Ma) to Eocene (~39 Ma) plutons located in the Principal Cordillera of Chile, experienced very little interaction with the upper continental crust. Amphibole – plagioclase geothermobarometry indicates these calc-alkaline granitoids, which form extensive north – south trending belts, were emplaced at shallow depths in the crust (~4 – 5 km). Therefore the Late Cretaceous to Late Eocene is interpreted as a period of significant upper crustal growth. The isotopic variability in the Late Oligocene (~26 Ma) to Late Miocene (~6 Ma) arc magmatic rocks demonstrates that during thickening of the continental crust and migration of the Andean arc to the east, arc magmas assimilated Late Paleozoic to Early Mesozoic basement. In addition, arc magmas erupted/emplaced in the Argentinean Precordillera (i.e. farthest east from the trench) assimilated a Grenville-aged (~ 1330 – 1030 Ma) basement. The youngest arc magmas (~6 Ma) erupted in the Frontal Cordillera also show evidence for the assimilation of this ancient basement terrane, potentially signalling under-thrusting beneath the Frontal Cordillera. Overall, the later part of the Cenozoic represents a period of crustal reworking. Boron concentrations and isotope ratios measured in pyroxene hosted melt inclusions and for the first time in zircon hosted melt inclusions, are higher than the values expected for the mantle wedge and show significant variations with time. The source of the Paleocene (~61 Ma) arc magmas were influenced by fluids primarily derived from altered oceanic crust. Lower δ11B values and boron concentrations obtained for Oligocene (25 – 23 Ma) arc magmatic rocks reflects a diminished influence of slab-derived fluids reflecting a greater depth to the top of the slab. Fluids derived from serpentinite influenced the source of the arc magmas after ~19.5 Ma. This has been linked with the intersection of the Juan Fernández Ridge, a volcanic seamount chain associated with hydrated and serpentinised oceanic lithosphere.
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9

Pfänder, Jörg A. "Oceanic crust and island arc formation in Central Asia during late Neoproterozoic times evidence from petrological and geochemical studies /." [S.l.] : [s.n.], 2001. http://ArchiMeD.uni-mainz.de/pub/2002/0051/diss.pdf.

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10

Moyer, Griffin Amoss. "Strain Accommodation, Metamorphic Evolution, And 3d Kinematics Of Transpressional Flow Within The Lower Crust Of A Cretaceous Magmatic Arc In Fiordland, New Zealand." ScholarWorks @ UVM, 2019. https://scholarworks.uvm.edu/graddis/1110.

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The George Sound Shear Zone (GSSZ) exposed in Bligh Sound within Fiordland, New Zealand allowed us to reconstruct the kinematics of transpressive flow in >100 km2 of exhumed Cretaceous lower crust. We compare the three-dimensional characteristics of the deformation to theoretical models of transpression that assume steady-state flow in a homogeneous medium. This assumption is rarely the case for shear zones that experience metamorphism during deformation. We determined the three-dimensional kinematics of the GSSZ and evaluated the effects of metamorphism on strain accommodation and structural fabric evolution in the GSSZ to determine if metamorphism is an important parameter that transpressional models should account for. We found that metamorphism aided strain localization within the GSSZ and resulted in a style of structural fabric development that deviates from predictions made by theoretical models. We used foliation and lineation orientation data and field observations to determine GSSZ kinematics. Asymmetric pyroxene σ-porphyroclasts and hornblende fish show top-down-to-the-SW apparent normal shear sense with a sinistral component. The Z-axes of oblate SPO ellipsoids define the vorticity normal section and the moderately WNW-plunging vorticity vector. Foliation deflections relative to the shear zone boundaries yielded a vorticity magnitude (Wk) of ≥0.8. Our kinematic results suggest that the GSSZ records inclined, triclinic transpression with sinistral, top-down-to-the-SW simple shear-dominated flow. We used finite strain analysis and petrographic analysis to determine that metamorphism influences strain accommodation. Finite strain analyses were performed in 3D on 16 samples using the Rf/ɸ, Fry, and Intercept methods to determine the SPO fabric ellipsoids at different stages of deformation. Petrographic analysis was performed to identify metamorphic reactions using syn-kinematic minerals and constrain deformational temperatures using deformation mechanisms of plagioclase. Early deformation formed a ~13 km wide prolate fabric at granulite facies. Deformation later localized into a ~2-4.6 km wide oblate, mylonitic fabric at upper amphibolite facies. This fabric cross-cuts the prolate fabric and is characterized by metamorphic hornblende and biotite produced from retrogressive hydration reactions. Samples with syn-kinematic biotite contain more shear bands and display more grain size reduction of plagioclase than samples without this phase, suggesting these samples may have accommodated more strain. Changes in syn-kinematic metamorphic minerals were accompanied by steepening of stretching lineations and by changes in foliation orientation. Our analyses show that retrogressive hydration metamorphism aided strain localization within a cross-cutting oblate fabric, and the uneven distribution of biotite within this domain potentially influenced along strike variation in strain magnitude and fabric ellipsoid symmetry. Our results highlight the influence of fluid-induced metamorphism on shear zone evolution and call for new transpressional models to incorporate changes in rheology due to syn-kinematic metamorphism.
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Книги з теми "Arc Crust"

1

Yanagi, Takeru. Arc Volcano of Japan: Generation of Continental Crust from the Mantle. Tokyo: Springer-Verlag Berlin Heidelberg, 2011.

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Ėvoli͡u︡t͡s︡ii͡a︡ drevneĭ sialicheskoĭ kory v ostrovoduzhnykh sistemakh Vostochnoĭ Azii. Vladivostok: DVNT͡S︡ AN SSSR, 1985.

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3

Colour me girl crush. London: Portico, 2014.

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4

Ministral, Josep. Crist de l'olivera: El mural de Llers. Figueres [Spain]: Brau Edicions, 2014.

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Massana, Ramon Puig. El rostre de Jesús, el Crist: Passeig fenomenològic per dos mil anys d'iconografia cristològica. Barcelona: La Formiga d'Or, 1998.

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6

Curso de Verano sobre el Franciscanismo en Andalucía. El franciscanismo en Andalucía: El arte franciscano en las catedrales andaluzas : conferencias del VI Cruso de Verano (Priego de Córdoba, del 31 de julio al 5 de agosto de 2001). Córdoba: CajaSur, Obra Social y Cultural, 2005.

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7

Yanagi, Takeru. Arc Volcano of Japan: Generation of Continental Crust from the Mantle. Springer, 2011.

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8

Yanagi, Takeru. Arc Volcano of Japan: Generation of Continental Crust from the Mantle. Springer, 2016.

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9

Woodsworth, Glenn J., Margaret E. Rusmore, Harold H. Stowell, and Lincoln S. Hollister. Architecture and Evolution of the Crust during Continental Arc Magmatism: A Transect through the Coast Mountains Batholith, British Columbia. Geological Society of America, 2020. http://dx.doi.org/10.1130/fld058.

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Originally prepared for the GSA Thompson Field Forum that ran from Terrace to Prince Rupert, British Columbia, this guide describes the geology along the Skeena River transect of the Coast Mountains batholith, the largest Cordilleran batholith of western North America and one of the largest continental-margin batholiths in the world. The last guide to this area was published in 1983 and this new volume is the only modern overview of the last decades of work. The authors use the transect as a basis to examine the growth of the Coast Mountains batholith as a whole, emphasizing commonalities and variations with the batholith and how these traits may reflect magmatic processes that create convergent-margin batholiths.
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10

Schaefer, Lola M. Musty-Crust Animals ABC (Musty-Crusty Animals). Tandem Library, 2002.

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Частини книг з теми "Arc Crust"

1

Yanagi, Takeru. "Continental Crust and Granitic Plutons." In Arc Volcano of Japan, 1–7. Tokyo: Springer Tokyo, 2011. http://dx.doi.org/10.1007/978-4-431-53996-4_1.

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Calvert, A. J. "The Seismic Structure of Island Arc Crust." In Frontiers in Earth Sciences, 87–119. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-540-88558-0_4.

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3

Folinsbee, R. E., H. Baadsgaard, G. L. Cumming, and D. C. Green. "A Very Ancient Island Arc." In The Crust and Upper Mantle of the Pacific Area, 441–48. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm012p0441.

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4

Yanagi, Takeru. "Island Arc Volcanic Rocks and the Upper Continental Crust." In Arc Volcano of Japan, 77–102. Tokyo: Springer Tokyo, 2011. http://dx.doi.org/10.1007/978-4-431-53996-4_7.

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Yanagi, Takeru. "Search for the Formation Mechanism of Continental Crust." In Arc Volcano of Japan, 27–43. Tokyo: Springer Tokyo, 2011. http://dx.doi.org/10.1007/978-4-431-53996-4_4.

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6

Yanagi, Takeru. "Chemical Composition of Continental Crust and the Primitive Mantle." In Arc Volcano of Japan, 9–17. Tokyo: Springer Tokyo, 2011. http://dx.doi.org/10.1007/978-4-431-53996-4_2.

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Kay, R. W., and S. Mahlburg Kay. "Recycled Continental Crustal Components in Aleutian arc Magmas: Implications for Crustal Growth and Mantle Heterogeneity." In Crust/Mantle Recycling at Convergence Zones, 145–61. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0895-6_15.

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8

Uyeda, Seiya, and Victor Vacquier. "Geothermal and Geomagnetic Data in and Around the Island Arc of Japan." In The Crust and Upper Mantle of the Pacific Area, 349–66. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm012p0349.

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Kriens, Bryan, and Brian Wernicke. "Characteristics of a Continental Margin Magmatic Arc as a Function of Depth: The Skagit-Methow Crustal Section." In Exposed Cross-Sections of the Continental Crust, 159–73. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-0675-4_7.

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10

Miyamura, Setumi. "Seismicity of Island Arcs and Other Arc Tectonic Regions of the Circum-Pacific Zone." In The Crust and Upper Mantle of the Pacific Area, 60–69. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gm012p0060.

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Тези доповідей конференцій з теми "Arc Crust"

1

Johnston, Scott M., Alan D. Chapman, Emily C. Dektar, and Andrew R. C. Kylander-Clark. "IGNEOUS AND METAMORPHIC CHRONOLOGY OF SALINIAN ARC LOWER ARC CRUST, CENTRAL CALIFORNIA COAST." In 115th Annual GSA Cordilleran Section Meeting - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019cd-329508.

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2

Duan, Haochen, Abigail K. Barker, Heejin Jeon, Martin J. Whitehouse, and Chao Zhang. "Crustal Anatexis Forms Continental Crust in the Izu Rear-Arc." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.617.

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3

Johns, Wes, Sean R. Mulcahy, Sarah M. Roeske, William C. McClelland, Emily Houlihan, Andrew Tholt, Patricia Webber, Matthew A. Coble, and Jeffrey D. Vervoort. "TIMING AND KINEMATICS OF INTRA-ARC DEFORMATION IN THE MIDDLE CRUST OF THE FAMATINA ARC." In 115th Annual GSA Cordilleran Section Meeting - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019cd-329629.

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4

Mocha, Nick, Shelby Littleton, Scott M. Johnston, Alan D. Chapman, and Andrew R. C. Kylander-Clark. "ZIRCON PETROCHRONOLOGY OF SALINIAN ARC MIDDLE CRUST, EASTERN SANTA LUCIA MOUNTAIN, CALIFORNIA." In 116th Annual GSA Cordilleran Section Meeting - 2020. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020cd-347435.

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5

Pitsillides, Iason, Alan Chapman, Scott Johnston, Andrew Kylander-Clark, Shelby Littleton, and Nick Mocha. "ZIRCON PETROCHRONOLOGY OF SALINIAN ARC MIDDLE CRUST, EASTERN SANTA LUCIA MOUNTAIN, CALIFORNIA." In Cordilleran Section-117th Annual Meeting-2021. Geological Society of America, 2021. http://dx.doi.org/10.1130/abs/2021cd-363165.

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6

Waldman, Ryan, Gene Yogodzinski, Folkmar Hauff, Michael Bizimis, Brian R. Jicha, Maxim Portnyagin, Reinhard Werner, and Kaj Hoernle. "NATURE OF NORTHWEST PACIFIC ALTERED OCEANIC CRUST AND IMPLICATIONS FOR ARC MAGMATISM." In GSA Connects 2022 meeting in Denver, Colorado. Geological Society of America, 2022. http://dx.doi.org/10.1130/abs/2022am-379500.

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Ratschbacher, Barbara, Tarryn K. Cawood, Scott R. Paterson, Mariano A. Larrovere, Alexander D. Lusk, Pablo H. Alasino, Christopher Benton Rick, and Vali Memeti. "DO INTRUSIVE BODIES WEAKEN OR STRENGTHEN THE ARC CRUST – OR BOTH? AN EXAMPLE FROM THE FAMATINIAN ARC, ARGENTINA." In 116th Annual GSA Cordilleran Section Meeting - 2020. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020cd-347580.

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8

Rezeau, Hervé, Benjamin Klein, and Oliver Jagoutz. "Mixing damp and wet basalts in the deep arc crust: a new recipe to form uniform differentiated arc melts?" In Goldschmidt2021. France: European Association of Geochemistry, 2021. http://dx.doi.org/10.7185/gold2021.8120.

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9

Wang, Rui, Jeremy Richards, and Jingbo Zhang. "Sulfide Saturation in Thick Arc Crust Plays no Role for Porphyry Cu Deposit Formation." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2753.

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10

Isava, Virginia, Marty Grove, and J. Brian Mahoney. "PB ISOTOPIC VARIATION OF CRETACEOUS ARC CRUST IN THE PACIFIC NORTHWEST, U.S.A. AND CANADA." In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-351191.

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Звіти організацій з теми "Arc Crust"

1

Ames, D. E., O. Van Breemen, and J. S. Scoates. Evidence for recycled Mesoarchean crust in the Ruttan arc succession, Rusty Lake belt, Trans-Hudson Orogen, Manitoba: U-Pb isotopic data; Radiogenic Age and Isotopic Studies: Report 15. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2002. http://dx.doi.org/10.4095/213601.

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2

Harris, L. B., P. Adiban, and E. Gloaguen. The role of enigmatic deep crustal and upper mantle structures on Au and magmatic Ni-Cu-PGE-Cr mineralization in the Superior Province. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328984.

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Aeromagnetic and ground gravity data for the Canadian Superior Province, filtered to extract long wavelength components and converted to pseudo-gravity, highlight deep, N-S trending regional-scale, rectilinear faults and margins to discrete, competent mafic or felsic granulite blocks (i.e. at high angles to most regional mapped structures and sub-province boundaries) with little to no surface expression that are spatially associated with lode ('orogenic') Au and Ni-Cu-PGE-Cr occurrences. Statistical and machine learning analysis of the Red Lake-Stormy Lake region in the W Superior Province confirms visual inspection for a greater correlation between Au deposits and these deep N-S structures than with mapped surface to upper crustal, generally E-W trending, faults and shear zones. Porphyry Au, Ni, Mo and U-Th showings are also located above these deep transverse faults. Several well defined concentric circular to elliptical structures identified in the Oxford Stull and Island Lake domains along the S boundary of the N Superior proto-craton, intersected by N- to NNW striking extensional fractures and/or faults that transect the W Superior Province, again with little to no direct surface or upper crustal expression, are spatially associated with magmatic Ni-Cu-PGE-Cr and related mineralization and Au occurrences. The McFaulds Lake greenstone belt, aka. 'Ring of Fire', constitutes only a small, crescent-shaped belt within one of these concentric features above which 2736-2733 Ma mafic-ultramafic intrusions bodies were intruded. The Big Trout Lake igneous complex that hosts Cr-Pt-Pd-Rh mineralization west of the Ring of Fire lies within a smaller concentrically ringed feature at depth and, near the Ontario-Manitoba border, the Lingman Lake Au deposit, numerous Au occurrences and minor Ni showings, are similarly located on concentric structures. Preliminary magnetotelluric (MT) interpretations suggest that these concentric structures appear to also have an expression in the subcontinental lithospheric mantle (SCLM) and that lithospheric mantle resistivity features trend N-S as well as E-W. With diameters between ca. 90 km to 185 km, elliptical structures are similar in size and internal geometry to coronae on Venus which geomorphological, radar, and gravity interpretations suggest formed above mantle upwellings. Emplacement of mafic-ultramafic bodies hosting Ni-Cr-PGE mineralization along these ringlike structures at their intersection with coeval deep transverse, ca. N-S faults (viz. phi structures), along with their location along the margin to the N Superior proto-craton, are consistent with secondary mantle upwellings portrayed in numerical models of a mantle plume beneath a craton with a deep lithospheric keel within a regional N-S compressional regime. Early, regional ca. N-S faults in the W Superior were reactivated as dilatational antithetic (secondary Riedel/R') sinistral shears during dextral transpression and as extensional fractures and/or normal faults during N-S shortening. The Kapuskasing structural zone or uplift likely represents Proterozoic reactivation of a similar deep transverse structure. Preservation of discrete faults in the deep crust beneath zones of distributed Neoarchean dextral transcurrent to transpressional shear zones in the present-day upper crust suggests a 'millefeuille' lithospheric strength profile, with competent SCLM, mid- to deep, and upper crustal layers. Mechanically strong deep crustal felsic and mafic granulite layers are attributed to dehydration and melt extraction. Intra-crustal decoupling along a ductile décollement in the W Superior led to the preservation of early-formed deep structures that acted as conduits for magma transport into the overlying crust and focussed hydrothermal fluid flow during regional deformation. Increase in the thickness of semi-brittle layers in the lower crust during regional metamorphism would result in an increase in fracturing and faulting in the lower crust, facilitating hydrothermal and carbonic fluid flow in pathways linking SCLM to the upper crust, a factor explaining the late timing for most orogenic Au. Results provide an important new dataset for regional prospectively mapping, especially with machine learning, and exploration targeting for Au and Ni-Cr-Cu-PGE mineralization. Results also furnish evidence for parautochthonous development of the S Superior Province during plume-related rifting and cannot be explained by conventional subduction and arc-accretion models.
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Manor, M. J., and S. J. Piercey. Whole-rock lithogeochemistry, Nd-Hf isotopes, and in situ zircon geochemistry of VMS-related felsic rocks, Finlayson Lake VMS district, Yukon. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328992.

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The Finlayson Lake district in southeastern Yukon is composed of a Late Paleozoic arc-backarc system that consists of metamorphosed volcanic, plutonic, and sedimentary rocks of the Yukon-Tanana and Slide Mountain terranes. These rocks host &amp;gt;40 Mt of polymetallic resources in numerous occurrences and styles of volcanogenic massive sulphide (VMS) mineralization. Geochemical and isotopic data from these rocks support previous interpretations that volcanism and plutonism occurred in arc-marginal arc (e.g., Fire Lake formation) and continental back-arc basin environments (e.g., Kudz Ze Kayah formation, Wind Lake formation, and Wolverine Lake group) where felsic magmatism formed from varying mixtures of crust- and mantle-derived material. The rocks have elevated high field strength element (HFSE) and rare earth element (REE) concentrations, and evolved to chondritic isotopic signatures, in VMS-proximal stratigraphy relative to VMS-barren assemblages. These geochemical features reflect the petrogenetic conditions that generated felsic rocks and likely played a role in the localization of VMS mineralization in the district. Preliminary in situ zircon chemistry supports these arguments with Th/U and Hf isotopic fingerprinting, where it is interpreted that the VMS-bearing lithofacies formed via crustal melting and mixing with increased juvenile, mafic magmatism; rocks that were less prospective have predominantly crustal signatures. These observations are consistent with the formation of VMS-related felsic rocks by basaltic underplating, crustal melting, and basalt-crustal melt mixing within an extensional setting. This work offers a unique perspective on magmatic petrogenesis that underscores the importance of integrating whole-rock with mineral-scale geochemistry in the characterization of VMS-related stratigraphy.
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4

Rupke, Andrew, and Tyler Boden. Great Salt Lake North Arm Salt Crust Monitoring, Spring 2017 Update. Utah Geological Survey, January 2020. http://dx.doi.org/10.34191/ofr-714.

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5

Jagniecki, Elliot, Andrew Rupke, Stefan Kirby, and Paul I. nkenbrandt. Salt Crust, Brine, and Marginal Groundwater of Great Salt Lake's North Arm (2019 To 2021). Utah Geological Survey, November 2021. http://dx.doi.org/10.34191/ri-283.

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Following the construction of the railroad causeway in 1959, a perennial halite (NaCl) bottom crust has been known to exist in the north arm (Gunnison Bay) of Great Salt Lake, Utah, but the lake conditions controlling accumulation or dissolution of the crust are not well defined, including how depth-controlled chemodynamic and hydrodynamic factors influence the degree of the halite saturation. Immediately prior to the opening of a new bridge in the causeway in early December 2016 when north arm lake elevation was at a historical low (just above 4189 feet), the north arm lake brine was at halite saturation. After the opening, inflow of less saline south arm water mixed with north arm water, raised lake elevation, and diluted the north arm lake brine to undersaturation with respect to halite. The following five years have resulted in annual and seasonal fluctuations of halite saturation states. Beginning in mid-2019, the Utah Geological Survey began a study of the north arm to better understand and document the transitions of halite saturation state following the bridge opening using newly collected data as well as reviewing available past data.
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6

Regis, D., and M. Sanborn-Barrie. Delimiting the extent of 'Boothia terrane' crust, Nunavut: new U-Pb geochronological results. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330703.

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The Boothia Peninsula - Somerset Island region of north-central Nunavut is a frontier region (70-74°N, 94°W) long considered as part of Rae craton. Recent field mapping and acquisition of isotopic (U-Pb, Sm-Nd) data as part of the GEM-2 Boothia-Somerset project allowed this region's exposed Precambrian bedrock to be better characterized with respect to petrology and litho-geochemistry, and to be more extensively and more precisely time-calibrated. The discovery of unique, possibly exotic, basement characterized by a ca. 2.55-2.51 Ga TTG suite overlain by ca. 2.5 Ga metasedimentary rocks, cut by 2.49- 2.48 Ga plutons, are all atypical components of the Archean Rae crust. This new knowledge and the hint of similar 'Boothia terrane' crust south of Boothia Peninsula (Ryan et al., 2009), east of the Queen Maud block (Davis et al., 2014) in central Nunavut, and in northernmost Saskatchewan (Cloutier et al., 2021), raised the possibility this terrane may extend &amp;gt;1600 km across north-central Canada. During the foundational year of GEM-GeoNorth, the extent of Boothia terrane crust was explored through legacy samples collected during the 2012 GEM Frontiers' transect across mainland Nunavut. As part of this new study, field descriptions, photographic records and legacy samples were examined, and new U-Pb zircon geochronology was acquired. The new data and knowledge were used to: i) identify new components of Boothia terrane on the mainland southwest of Boothia Peninsula; ii) further distinguish this crust from that of Rae affinity; and iii) better constrain the depositional age of Sherman Group metasedimentary rocks.
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7

Scott, D. J. U-Pb ages of Archean crust in the southeast arm of the Rae Province, southeastern Ungava Bay, Quebec. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1998. http://dx.doi.org/10.4095/210054.

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8

Agassi, Menahem, Michael J. Singer, Eyal Ben-Dor, Naftaly Goldshleger, Donald Rundquist, Dan Blumberg, and Yoram Benyamini. Developing Remote Sensing Based-Techniques for the Evaluation of Soil Infiltration Rate and Surface Roughness. United States Department of Agriculture, November 2001. http://dx.doi.org/10.32747/2001.7586479.bard.

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The objective of this one-year project was to show whether a significant correlation can be established between the decreasing infiltration rate of the soil, during simulated rainstorm, and a following increase in the reflectance of the crusting soil. The project was supposed to be conducted under laboratory conditions, using at least three types of soils from each country. The general goal of this work was to develop a method for measuring the soil infiltration rate in-situ, solely from the reflectance readings, using a spectrometer. Loss of rain and irrigation water from cultivated fields is a matter of great concern, especially in arid, semi-arid regions, e.g. much of Israel and vast area in US, where water is a limiting factor for crop production. A major reason for runoff of rain and overhead irrigation water is the structural crust that is generated over a bare soils surface during rainfall or overhead irrigation events and reduces its infiltration rate (IR), considerably. IR data is essential for predicting the amount of percolating rainwater and runoff. Available information on in situ infiltration rate and crust strength is necessary for the farmers to consider: when it is necessary to cultivate for breaking the soil crust, crust strength and seedlings emergence, precision farming, etc. To date, soil IR is measured in the laboratory and in small-scale field plots, using rainfall simulators. This method is tedious and consumes considerable resources. Therefore, an available, non-destructive-in situ methods for soil IR and soil crusting levels evaluations, are essential for the verification of infiltration and runoff models and the evaluation of the amount of available water in the soil. In this research, soil samples from the US and Israel were subjected to simulated rainstorms of increasing levels of cumulative energies, during which IR (crusting levels) were measured. The soils from the US were studied simultaneously in the US and in Israel in order to compare the effect of the methodology on the results. The soil surface reflectance was remotely measured, using laboratory and portable spectrometers in the VIS-NIR and SWIR spectral region (0.4-2.5mm). A correlation coefficient spectra in which the wavelength, consisting of the higher correlation, was selected to hold the highest linear correlation between the spectroscopy and the infiltration rate. There does not appear to be a single wavelength that will be best for all soils. The results with the six soils in both countries indeed showed that there is a significant correlation between the infiltration rate of crusted soils and their reflectance values. Regarding the wavelength with the highest correlation for each soil, it is likely that either a combined analysis with more then one wavelength or several "best" wavelengths will be found that will provide useful data on soil surface condition and infiltration rate. The product of this work will serve as a model for predicting infiltration rate and crusting levels solely from the reflectance readings. Developing the aforementioned methodologies will allow increased utilization of rain and irrigation water, reduced runoff, floods and soil erosion hazards, reduced seedlings emergence problems and increased plants stand and yields.
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Zagorevski, A., C. R. van Staal, J. H. Bédard, A. Bogatu, D. Canil, M. Coleman, M. Golding, et al. Overview of Cordilleran oceanic terranes and their significance for the tectonic evolution of the northern Cordillera. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/326053.

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Ophiolite complexes are an important component of oceanic terranes in the northern Cordillera and constitute a significant amount of juvenile crust added to the Mesozoic Laurentian continental margin during Cordilleran orogenesis. Despite their tectonic importance, few systematic studies of these complexes have been conducted. Detailed studies of the pseudostratigraphy, age, geochemistry, and structural setting of ophiolitic rocks in the northern Cordillera indicate that ophiolites formed in Permian to Middle Triassic suprasubduction zone settings and were obducted onto passive margin sequences. Re-evaluation of ophiolite complexes highlights fundamental gaps in the understanding of the tectonic framework of the northern Cordillera. The previous inclusion of ophiolite complexes into generic 'oceanic' terranes resulted in significant challenges for stratigraphic nomenclature, led to incorrect terrane definitions, and resulted in flawed tectonic reconstructions.
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Allen, Luke, Joon Lim, Robert Haehnel, and Ian Dettwiller. Helicopter rotor blade multiple-section optimization with performance. Engineer Research and Development Center (U.S.), June 2021. http://dx.doi.org/10.21079/11681/41031.

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This paper presents advancements in a surrogate-based, rotor blade design optimization framework for improved helicopter performance. The framework builds on previous successes by allowing multiple airfoil sections to designed simultaneously to minimize required rotor power in multiple flight conditions. Rotor power in hover and forward flight, at advance ratio 𝜇 = 0.3, are used as objective functions in a multi-objective genetic algorithm. The framework is constructed using Galaxy Simulation Builder with optimization provided through integration with Dakota. Three independent airfoil sections are morphed using ParFoil and aerodynamic coefficients for the updated airfoil shapes (i.e., lift, drag, moment) are calculated using linear interpolation from a database generated using C81Gen/ARC2D. Final rotor performance is then calculated using RCAS. Several demonstrative optimization case studies were conducted using the UH-60A main rotor. The degrees of freedom for this case are limited to the airfoil camber, camber crest position, thickness, and thickness crest position for each of the sections. The results of the three-segment case study show improvements in rotor power of 4.3% and 0.8% in forward flight and hover, respectively. This configuration also yields greater reductions in rotor power for high advance ratios, e.g., 6.0% reduction at 𝜇 = 0.35, and 8.8% reduction at 𝜇 = 0.4.
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