A geração de resíduos orgânicos juntamente com a erosão, são dois grandes problemas ambientais mundiais. São responsáveis pela redução da produtividade agrícola e pelos altos impactos ambientais. O presente projeto teve como objetivo a utilização de resíduos orgânicos gerados na agropecuária, na forma de composto orgânico, para a recuperação de áreas degradadas pela erosão hídrica. Foram avaliados os efeitos de quatro doses de composto (0, 20, 40 e 100 Mg.ha-1) na recuperação dos solos degradados por erosão. Somado a isto foi também avaliado o efeito da dose de composto sobre o processo de encrostamento superficial do solo. O projeto foi composto por dois experimentos, um com a ausência da erosão e o outro com presença de erosão (remoção de uma camada de 50 cm de solo), sendo realizados concomitantemente na mesma área. O delineamento experimental usado para cada experimento foi o inteiramente casualizado com 4 tratamentos (0, 20, 40 e 100 Mg.ha-1) e 4 repetições. Para o monitoramento da recuperação do solo e do processo de encrostamento em função das diferentes doses de composto, amostras deformadas e indeformadas de solo foram coletadas para análises físicas e químicas de rotina, para medidas da densidade do solo, para confecção de curvas características de retenção de água, e para análises micromorfológicas e de imagens. No campo foram realizados o monitoramento da chuva, da condutividade hidráulica e da infiltração de água no solo. Ficou claro que com o aumento da dose de composto orgânico aplicado no solo, melhor era a condição química do mesmo. Os valores dos elementos aumentavam conforme a dose de composto era também aumentada. A ação da matéria orgânica no solo colaborou com um aumento na retenção de água no solo a partir das doses de 40 e 100 Mg.ha-1. Esta melhor retenção de água favoreceu juntamente com a química, o crescimento das culturas no período seco garantindo assim uma maior produção de matéria seca das culturas implantadas, principalmente na dose de 100 Mg.ha-1. Com o aumento da porosidade do solo ao longo do tempo estudado em todas as doses de composto aplicado, a densidade do solo diminuiu onde o composto estava presente, se tornando mais constante em altas doses seus valores. A condutividade hidráulica do solo foi reduzida ao longo dos dois experimentos para todas as doses de composto aplicado. Essa redução pode ser explicada pelo aumento do encrostamento superficial do solo ao longo do tempo principalmente nas doses de 0 e 20 Mg.ha-1, dificultando a infiltração de água no solo. Portanto, a aplicação de altas doses de composto orgânico aceleram a recuperação dos atributos químicos e físicos do solo, assim como colaboram na redução da formação de vesículas nas crostas superficiais e diminuem os efeitos do impacto das gotas de chuvas na formação do encrostamento. / The generation of organic waste along with soil erosion are two major environmental problems worldwide. They are responsible for the reduction of agricultural productivity and high environmental impacts. The objective of this dissertation is the use of organic waste generated in agriculture, in the form of organic compost, for the recovery of degraded areas by water erosion. The effects of four doses of compost (0, 20, 40 and 100 Mg.ha-1) in the recovery of degraded soils by erosion, was tested. Added to this, the effect of the dose of compost on the process of soil surface crusting surface was also tested. The project was composed of two experiments, one with no erosion and the other with erosion (removal of a layer of 50 cm of soil), conducted concurrently in the same area. The experimental design for each experiment was completely randomized with 4 treatments (0, 20, 40 and 100 Mg.ha-1) and 4 replications. For the monitoring of the recovery of soil and the process of crusting according to the different doses of compost, deformed and undeformed soil samples were collected for routine physical and chemical analyses soil density evaluation, determination of the characteristic water retention curve, and for micromorphological and image analysis. In the field, rain, hydraulic conductivity and soil water infiltration were monitored. It was clear that with the increasing doses of organic compost used in the soil, the chemical condition meliorated. The content of the nutrients increased as the dose of compost was also increased. The action of organic matter in the soil collaborated with an increase in its water retention mainly for doses of 40 and 100 Mg.ha-1. This better water retention helped, together with the chemical recuperation, in the growth of the crops in the dry season thereby ensuring a higher dry matter yield, mainly in the dose of 100 Mg.ha-1. The increasing soil porosity over time observed in all doses of compost applied, led to a decrease in the soil density. The hydraulic conductivity of the soil was reduced in both experiments for all the applied compost doses. This reduction can be explained by the increase of the soil crusting process over time, especially in the doses of 0 and 20 Mg.ha-1, hampering the water infiltration in the soil. Therefore, the application of high doses of organic compost accelerates the recuperation of the chemical and physical attributes of the soil. It also collaborates in reducing the formation of vesicles in the superficial crust and decreases the effects of the impact of the raindrops on the crust formation.

Esta pesquisa investigou a cobertura pedológica para compreender os processos pedogenéticos que atuam na formação e evolução das depressões fechadas existentes no Compartimento Três Cantos. A área de estudo está situada no sudoeste do município de Maracaí-SP, no interflúvio entre o ribeirão das Anhumas e o rio Capivara, afluentes do rio Paranapanema. A área apresenta depressões fechadas na parte cimeira, com solos vermelho-amarelos e vermelhos, de textura média, e couraças. Para atingirmos o nosso objetivo avaliamos duas topossequências na depressão da lagoa Mandacaru, e os fatores regionais e locais que poderiam contribuir para a formação e evolução das depressões. O estudo da cobertura pedológica seguiu os procedimentos da Análise Estrutural da Cobertura Pedológica propostos por Boulet et al. (1982). Os resultados mostraram que os processos pedológicos que predominam na área são latossolização, a hidromorfia e a iluviação. A latossolização transforma a couraça em Latossolos. A hidromorfia ataca a couraça e os horizontes Bw, transformando-os em uma estrutura em blocos quando seca, e maciça quando úmida, é combinada com o processo de iluviação que transforma o horizonte A e Bt em E, resultando em Argissolos. A latossolização foi o primeiro processo à transformar as couraças, e com a instalação de condições mais úmidas, a hidromorfia transformou as couraças e os latossolos, deformando o platô em que estavam instalados. A hidromorfia, portanto, seria a responsável pelo início da formação da depressão, e o processo de iluviação seria subsequente e contribuiria para o aprofundamento e alargamento das depressões. A formação das depressões está relacionada à estrutura geológica, e as depressões são o estágio inicial da rede de drenagem, como pode ser observado nas áreas em que as depressões foram abertas e que os solos ainda não estão ajustados à nova forma das vertentes. / This research investigates the pedological cover to understand genetic processes at work in the formation and evolution of closed depressions in the Três Cantos compartment. The study area is located in the municipality Maracaí-SP (Brazil), at the interfluve between Anhumas and Capivara rivers, both tributaries of the Paranapanema River. The area has closed depressions in the top of local surface, with red-yellow and red soils and iron crust. To achieve our goal we evaluated two toposequences in the Mandacaru depression, as well as regional and local factors that could contribute to the formation and evolution of depressions. The procedures adopted for this research were based on the Structural Analysis of the Pedologic Coverage, proposed by Boulet et al. (1982). The results showed that the pedological processes that dominate are latosolization, hydromorphy and illuviation. The latosolization transforms the iron crust into Latosol in the Brazilian System of Soil Classification (Ferrasols -FAO, 2006). The hydromorphy that attacks the iron crust and Bw horizons resulting in a block structure when dry, and massive when wet combined with the illuviation process that transforms the horizons A and Bt into E result in Argisol in the Brazilian System of Soil Classification (Lixisols FAO, 2006). The latosolization process was the first to transform the iron crust, followed by wet conditions, transforming the iron crust and latosols due to hydromorphy action; consequently, the plateau was deformed. Hydromorphy, therefore, was responsible for initiating depression formation and subsequently the illuviation process contributed to it. Currently these two processes act deepening and widening the depressions. The formation of depressions is related to the geological structure, and these depressions are the initial stage of the areas drainage system, as may be observed in areas where the depressions have been opened, and where the soils are not yet adjusted to the new form of the slope.

A geração de resíduos orgânicos juntamente com a erosão, são dois grandes problemas ambientais mundiais. São responsáveis pela redução da produtividade agrícola e pelos altos impactos ambientais. O presente projeto teve como objetivo a utilização de resíduos orgânicos gerados na agropecuária, na forma de composto orgânico, para a recuperação de áreas degradadas pela erosão hídrica. Foram avaliados os efeitos de quatro doses de composto (0, 20, 40 e 100 Mg.ha-1) na recuperação dos solos degradados por erosão. Somado a isto foi também avaliado o efeito da dose de composto sobre o processo de encrostamento superficial do solo. O projeto foi composto por dois experimentos, um com a ausência da erosão e o outro com presença de erosão (remoção de uma camada de 50 cm de solo), sendo realizados concomitantemente na mesma área. O delineamento experimental usado para cada experimento foi o inteiramente casualizado com 4 tratamentos (0, 20, 40 e 100 Mg.ha-1) e 4 repetições. Para o monitoramento da recuperação do solo e do processo de encrostamento em função das diferentes doses de composto, amostras deformadas e indeformadas de solo foram coletadas para análises físicas e químicas de rotina, para medidas da densidade do solo, para confecção de curvas características de retenção de água, e para análises micromorfológicas e de imagens. No campo foram realizados o monitoramento da chuva, da condutividade hidráulica e da infiltração de água no solo. Ficou claro que com o aumento da dose de composto orgânico aplicado no solo, melhor era a condição química do mesmo. Os valores dos elementos aumentavam conforme a dose de composto era também aumentada. A ação da matéria orgânica no solo colaborou com um aumento na retenção de água no solo a partir das doses de 40 e 100 Mg.ha-1. Esta melhor retenção de água favoreceu juntamente com a química, o crescimento das culturas no período seco garantindo assim uma maior produção de matéria seca das culturas implantadas, principalmente na dose de 100 Mg.ha-1. Com o aumento da porosidade do solo ao longo do tempo estudado em todas as doses de composto aplicado, a densidade do solo diminuiu onde o composto estava presente, se tornando mais constante em altas doses seus valores. A condutividade hidráulica do solo foi reduzida ao longo dos dois experimentos para todas as doses de composto aplicado. Essa redução pode ser explicada pelo aumento do encrostamento superficial do solo ao longo do tempo principalmente nas doses de 0 e 20 Mg.ha-1, dificultando a infiltração de água no solo. Portanto, a aplicação de altas doses de composto orgânico aceleram a recuperação dos atributos químicos e físicos do solo, assim como colaboram na redução da formação de vesículas nas crostas superficiais e diminuem os efeitos do impacto das gotas de chuvas na formação do encrostamento. / The generation of organic waste along with soil erosion are two major environmental problems worldwide. They are responsible for the reduction of agricultural productivity and high environmental impacts. The objective of this dissertation is the use of organic waste generated in agriculture, in the form of organic compost, for the recovery of degraded areas by water erosion. The effects of four doses of compost (0, 20, 40 and 100 Mg.ha-1) in the recovery of degraded soils by erosion, was tested. Added to this, the effect of the dose of compost on the process of soil surface crusting surface was also tested. The project was composed of two experiments, one with no erosion and the other with erosion (removal of a layer of 50 cm of soil), conducted concurrently in the same area. The experimental design for each experiment was completely randomized with 4 treatments (0, 20, 40 and 100 Mg.ha-1) and 4 replications. For the monitoring of the recovery of soil and the process of crusting according to the different doses of compost, deformed and undeformed soil samples were collected for routine physical and chemical analyses soil density evaluation, determination of the characteristic water retention curve, and for micromorphological and image analysis. In the field, rain, hydraulic conductivity and soil water infiltration were monitored. It was clear that with the increasing doses of organic compost used in the soil, the chemical condition meliorated. The content of the nutrients increased as the dose of compost was also increased. The action of organic matter in the soil collaborated with an increase in its water retention mainly for doses of 40 and 100 Mg.ha-1. This better water retention helped, together with the chemical recuperation, in the growth of the crops in the dry season thereby ensuring a higher dry matter yield, mainly in the dose of 100 Mg.ha-1. The increasing soil porosity over time observed in all doses of compost applied, led to a decrease in the soil density. The hydraulic conductivity of the soil was reduced in both experiments for all the applied compost doses. This reduction can be explained by the increase of the soil crusting process over time, especially in the doses of 0 and 20 Mg.ha-1, hampering the water infiltration in the soil. Therefore, the application of high doses of organic compost accelerates the recuperation of the chemical and physical attributes of the soil. It also collaborates in reducing the formation of vesicles in the superficial crust and decreases the effects of the impact of the raindrops on the crust formation.

Subduction zones are regions of intense earthquake activity up to great depth. Sources are located inside the subducting lithosphere and, as a consequence, seismic radiation from subduction zone earthquakes is strongly affected by the interior slab structure. The wave field of these intraslab events observed in the forearc region is profoundly influenced by a seismically slow layer atop the slab surface. This several kilometer thick low-velocity channel (wave guide) causes the entrapment of seismic energy producing strong guided wave phases that appear in P onsets in certain regions of the forearc. Observations at the Chile-Peru subduction zone presented here, as well as observations at several other circum-pacific subduction zones show such signals. Guided wave analysis contributes details of immense value regarding the processes near the slab surface, such as layering of subducted lithosphere, source locations of intraslab seismicity and most of all, range and manner of mineralogical phase transitions. <br><br> Seismological data stem from intermediate depth events (depth range 70 km - 300 km) recorded in northern Chile near 21 Grad S during the collaborative research initiative " Deformation Processes in the Andes" (SFB 267). A subset of stations - all located within a slab-parallel transect close to 69 Grad W - show low-frequency first arrivals (2 Hz), sometimes followed by a second high-frequency phase. <br><br> We employ 2-dimensional finite-difference simulations of complete P-SV wave propagation to explore the parameter space of subduction zone wave guides and explain the observations. Key processes underlying the guided wave propagation are studied: Two distinct mechanisms of decoupling of trapped energy from the wave guide are analyzed - a prerequisite to observe the phases at stations located at large distances from the wave guide (up to 100 km). Variations of guided wave effects perpendicular to the strike of the subduction zone are investigated, such as the influence of phases traveling in the fast slab. Further, the merits and limits of guided wave analysis are assessed. Frequency spectra of the guided wave onsets prove to be a robust quantity that captures guided wave characteristics at subduction zones including higher mode excitation. They facilitate the inference of wave guide structure and source positioning: The peak frequency of the guided wave fundamental mode is associated with a certain combination of layer width and velocity contrast. The excitation strength of the guided wave fundamental mode and higher modes is associated with source position and orientation relative to the low-velocity layer. <br><br> The guided wave signals at the Chile-Peru subduction zone are caused by energy that leaks from the subduction zone wave guide. On the one hand, the bend shape of the slab allows for leakage at a depth of 100 km. On the other, equalization of velocities between the wave guide and the host rocks causes further energy leakage at the contact zone between continental and oceanic crust (70 km depth). Guided waves bearing information on deep slab structure can therefore be recorded at specific regions in the forearc. These regions are determined based on slab geometry, and their locations coincide with the observations. <br><br> A number of strong constraints on the structure of the Chile-Peru slab are inferred: The deep wave guide for intraslab events is formed by a layer of 2 km average width that remains seismically slow (7 percent velocity reduction compared to surrounding mantle). This low-velocity layer at the top of the Chile-Peru slab is imaged from a depth of 100 km down to at least 160 km. Intermediate depth events causing the observed phases are located inside the layer or directly beneath it in the slab mantle. The layer is interpreted as partially eclogized lower oceanic crust persisting to depth beyond the volcanic arc. / Subduktionszonen sind bis in große Tiefen von intensiver Erdbebentätigkeit geprägt. Die Erdbebenquellen befinden sich in der subduzierten Lithosphäre (Slab), ihr Wellenfeld wird deshalb stark von der internen Slab-Struktur beeinflusst. Eine Schicht mit reduzierter seismischer Geschwindigkeit im oberen Bereich der Platte kann als Wellenleiter für diese Signale fungieren. In der nur wenige Kilometer dicken Schicht entstehen sogenannte geführte Wellen, die in Teilen des Forearc beobachtet werden. Diese Phasen bergen wertvolle Informationen über die Struktur nahe der Slab-Oberfläche, wie zum Beispiel Dicke der Schichtung, Herdlokationen und vor allem Tiefe und Art mineralogischer Umsetzungen. <br><br> Die Beobachtungen stammen von mitteltiefen Beben (70 km - 300 km) im Untersuchungsgebiet in Nord-Chile und wurden im Rahmen des Sonderforschungsbereich 267 " Deformationsprozesse in den Anden" aufgezeichnet. Stationen in einem Streifen um 69 Grad W, der sich parallel zum Streichen der Subduktionszone erstreckt, zeigen niederfrequente Ersteinsätze, denen teilweise höherfrequente Phasen folgen. <br><br> Mit Hilfe eines 2-dimensionalen Finite-Differenzen-Algorithmus werden die P-SV Wellenausbreitung simuliert, und die Beobachtungen erklärt. Zentrale Fragestellungen zu Wellenleitern in Subduktionszonen werden untersucht: Es werden zwei Mechanismen, die das Auskoppeln seismischer Energie aus dem Wellenleiter ermöglichen beschrieben - eine Grundvoraussetzung für das Auftreten von geführten Wellen in großen Entfernungen vom Wellenleiter (bis zu 100 km). Des weiteren werden Stärken und Grenzen der Analyse von geführten Wellen erörtert. <br><br> Die Spektren der geführten Wellenzüge erweisen sich als robuste Messgröße, um die Charakteristika des Wellenleiters zu bestimmt. Struktur des Wellenleiters und Quellpositionen können so für festgelegte Quell-Empfänger-Geometrien abgeleitet werden. Die Peak-Frequenz der Grundmode wird durch eine Kombination aus Dicke der Schicht und Geschwindigkeitskontrast bestimmt. Die Stärke der Anregung der Grundmode und höherer Moden lässt auf die Lage und Orientierung der Erdbebenquelle relativ zur Schicht schließen. Geschwindigkeitskontrast, Schichtdicke und Quellposition sind von herausragender Bedeutung, um mineralogische Interpretationen des Wellenleiters zu überprüfen. <br><br> Aufbauend auf die Simulationen werden die Beobachtungen interpretiert und Auskunft über die Struktur der Chile-Peru Subduktionszone erhalten: Eine dünne Schicht an der Slab-Oberfläche (durchschnittlich 2 km dick) trägt geringere seismische Geschwindigkeiten als der umgebende Mantel und fungiert als Wellenleiter für intra-platten Ereignisse in Tiefen von 100 bis mindestens 160 km. Ereignisse, die geführte Wellen hervorrufen, liegen in dieser Schicht oder direkt darunter im subduzierten Mantel. Um zu den Stationen in der Forearc-Region zu gelangen, entkoppelt ein Teil der geführten Wellen in einer Tiefe von circa 100 km aus der Niedergeschwindigkeitsschicht. Die Krümmung des Slab erlaubt das Austreten der Wellen und nimmt auch Einfluss auf die Pulsformen. <br><br> Der Wellenleiter in der Chile-Peru Subduktionszone ergibt sich als unregelmäßige Schicht mit reduzierter seismischer Geschwindigkeit, in der geführte Wellen entstehen, in unterschiedlichen Tiefen wieder austreten, und an die freie Oberfläche gelangen. Die Beobachtungsgebiete befinden sich im Forearc und werden durch die Geometrie und Struktur der subduzierten Platte festgelegt. <br><br> Die nur wenige Kilometer dicke, seismisch langsame Schicht an der Oberfläche des Chile-Peru Slab legt nahe, dass die Unterkruste der subduzierten Platte bis in große Tiefen besteht und nicht vollständig eklogitisiert ist. Abgeleitete Schichtdicke, Geschwindigkeitskontrast

The investigation was designed to explore the structure, composition and activity of a biological soil crust on an acidic, sandy soil from a temperate climate. The crust covers several hundreds of square meters on the hilltop of a large terminal moraine. The conjugate alga <i>Zygogonium ericetorum</i> forms the essential matrix for the crust, a dense web of algal filaments with interspersed lichens and mosses. The crust is composed of three layers, with an uppermost layer consisting nearly entirely of a dense algal mat. In lower layers, a parasitic fungus, penetrating the algal cells, is another important component of the crust community. In this soil crust, photosynthetic and respiratory activity is stabilized at low water activities.

We develop a two dimensional model that simulates the response of the crust to prolonged mantle-derived intrusions in arc environments. The domain includes the entire crustal section and upper mantle and focuses on the evolving thermal structure due to intrusions and external tectonic forcing. We monitor the thermal response, melt fraction and volume for different environments after a definite time by considering geologically relevant melt flux and extensional tectonic rates. The amount of crustal melt versus fractionated primary mantle melts present in the crustal column helps determine crustal structure and growth through time. We observe that with a geophysically estimated flux and tectonic rate, the mantle-derived magma bodies can melt the surrounding volume of crust. We express the amount of crustal melting in terms of an efficiency; therefore we define the melting efficiency as the ratio of the melted volume of crustal material to the volume of melt expected from a strict enthalpy balance as explained by Dufek and Bergantz (2005). Melting efficiencies are less than 1.0 in real systems because heat diffuses to sections of the crust that never melt. The maximum calculated efficiency is 0.05 in our model while most of our simulations show zero efficiency. Additionally, maximum total melt amount is observed in relatively greater extensional environments (0.02 m/yr) and high intrusion rates (10⁻² m³/m²/yr) and in long time periods (2 x 10⁶ years). However, maximum crustal melting in the same environment is reached in 1.2 x 10⁶ years. The relative amounts of mantle-derived and crustal melts in the total volume of magma suggest that the majority of magma composition in crustal column is derived from the mantle material.

In arid and semi-arid deserts, soils are commonly covered with biological soil crusts. The study of arid biocrusts and their ecological function has become increasingly common in the literature over the last several decades. Interestingly, no mention is made of biological soil crusts in forested ecosystems, raising the question as to whether they exist in these areas and if they do, why they have yet to be recognized as such? Through the use a parallel logic, this study finds that biocrusts do indeed exist in forests, a novel relationship in forest ecology and seeks to determine if there exist ecophysical explanations for the abundance and distribution throughout the forest landscape. This study examined the effects of climate variables and substrate types on the abundance, distribution and overall cover of forest soil biocrust at fifty-two sites in southern Oregon, U.S.A. Sites were randomly selected within established buffer zones in the Siuslaw, Rogue-Sisikyou, Umpqua, and Fremont-Winema National Forests. The methods of Belnap et al 2001 were tested and then modified for application in forested ecosystems. Data were collected on the relative abundance and distribution of biocrust morphological groups across available substrates, community biocrust morphology, aspect, elevation and soil texture, pH and organic matter content. Site-specific data on average annual precipitation and minimum/maximum temperatures was collected using the PRISM Climate Model. This study found substrate colonization by specific morphological groups mixed across the study; though dominant communities were observed for each substrate present, substrate availability appears to be confounded by a number of variables (climate, stand age and structure and litter layer) not controlled for in this study. Biocrust community morphologies varied across sites, primarily influenced by the surface texture of the substrate and morphology of the individual. Relatively smooth surfaces (rock, bare soil) often resulted in smooth biocrust morphologies, whereas rough surfaces (dead wood, bare soil) tended to result in a rolling morphology. Litter layer directly influenced the relative proportion of substrates colonized, notably affecting dead wood and mineral soil biocrusts. Total biocrust cover increased as precipitation increased as did biocrust preference for dead wood substrates while mineral soil remained unchanged and rock surfaces were negatively represented. Aspect generally followed the anticipated distribution of total biocrust cover with the highest cover on N and NW aspects and lowest on the W aspect. Increases in elevation were negatively related to overall biocrust cover. Soil texture was not found to be directly related to overall biocrust cover, attributed in part to the highly adaptive nature of the biocrust community. Soil organic matter (SOM) influenced total biocrust cover with positive correlations between total cover and increasing SOM content. Soil pH increased as expected across the precipitation range (17 to 159 in/yr) of the transect. Total biocrust cover was found to trend with soil pH, but is believed to be attributed to the parallel relationship between precipitation and pH, rather than pH alone given the relative moderate pH range (4.39 to 6.54) of the study. The distribution and abundance of forest soil biocrusts is strongly influenced by precipitation. The confounding influence of precipitation to litter layer depth and organic matter content (through gradients of vegetative productivity) and soil pH further are concluded to influence substrate preference by morphological groups. Across the variables examined, similarities between the two communities (arid and forest) in response to climate and soil chemistry show parallel relations, justifying the formal establishment of biological soil crust community in forested regions. The differences between communities related to the presence of trees validate the establishment of forest soil biocrusts as distinct community in both form and ecological function with the forests. / Graduation date: 2013

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.

This work focuses on crustal interaction in magmatic systems, drawing on experimental petrology and elemental and isotope geochemistry. Various magma-chamber processes such as magma-mixing, fractional crystallisation and magma-crust interaction are explored throughout the papers comprising the thesis. Emphasis is placed on gaining insights into the extent of crustal contamination in ocean island magmas from the Canary Islands and the processes of magma-crust interaction observed both in nature and in experiments. This research underscores that the compositions of ocean island magmas, even primitive types which are classically used as probes of the mantle, are susceptible to modification by crustal contamination. The principal mechanisms of contamination identified from work on both Tenerife and Gran Canaria (Canary Islands) are assimilation and partial melting of the pre-existing island edifice and intercalated sediments by newly arriving magma (i.e. “island recycling”). The information that we can gain from studying solidified magma and entrained crustal xenoliths concerning the rates and mechanisms of crustal assimilation is, however, limited. To address this shortcoming, a series of time-variable crustal carbonate assimilation experiments were carried out at magmatic pressure and temperature using natural materials from Merapi volcano, Indonesia. A temporally constrained reaction series of carbonate assimilation in magma has hence been constructed. The experiments were analysed using in-situ techniques to observe the progressive textural, elemental, and isotopic evolution of magma-carbonate interaction. Crucially, carbonate assimilation was found to liberate voluminous crustally-derived CO2 on a timescale of only seconds to minutes in the experiments. This points to the role of rapid crustal degassing in volcanic volatile budgets, and, pertinently, in magnifying hazardous volcanic behaviour. This thesis, therefore, delivers detailed insights into the processes of magma-crust interaction from experiments and geochemistry. The outcomes confirm that crustal processes are significant factors in both, i) ocean island magma genesis, and ii) magma differentiation towards compositions with greater explosive potential which can, in turn, manifest as hazardous volcanism. / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 707

The oldest dated rocks from the Acasta gneisses of the western Slave Province, Canada present an igneous age of ~4030 Ma. Following this the detrital zircons from the Jack Hills, Narryer Gneiss Terrane, Yilgarn Craton, Western Australia are identified as 4404 ±8 Ma. These discoveries suggest that crustal formation started as early as the Priscian Eon. Hitherto the Earth has gone through a series of interactions involving the atmosphere, hydrosphere, crust, mantle and core. However, only limited remnants of these early processes remain on the accessible crust due to extensive crustal reworking. The Southern Granulite Terrane (SGT) in the southern part of India represents the most extensive exposure of lower crustal granulite terranes in the world. This study mainly focuses on the characteristics of Archean (~2500 Ma) tectonics and nature of subsequent crustal growth, which led to the formation of Archean Nilgiri Block. Detailed fieldwork in this terrane and subsequent petrographic analysis revealed charnockites, hornblende-biotite gneiss, metagabbro/mafic granulite, websterite, amphibolite, Grt-Ky metasediment, metatuff and banded iron formation as the main rock types in this terrane. Field and petrographic results show a regional trend with garnet-orthopyroxene-biotite-quartz-plagioclase-K- feldspar bearing charnockites in the southern part which gets subsequently enriched in clinopyroxene that forms garnet-absent two pyroxene granulites consisting of orthopyroxene-clinopyroxene-quartz-plagioclase-K-feldspar towards the central part. Further north, metagabbro/mafic granulite is enriched in garnet-clinopyroxene-plagioclase assemblage. Websterite, amphibolite, metasediment, metatuff and banded iron formation are stacked and closely associated within this mafic belt in the north. The metagabbro represents peak P-T conditions of ~850°C and ~14kbar compared to the charnockites, which recorded a peak P-T of ~850°C and 9-10kbar. Petrographic results of oxide minerals show that the southern charnockitic part is abundant in rutile-ilmenite association represent reduced conditions compared to the oxidized magnetite-hematite-ilmenite associations in the mafic rocks. This oxidation trend is followed by pyrrhotite-chalcopyrite enriched southern charnockitic region that transforms to pyrite rich northern mafic belt. Ilmenite¬titanite association with no sulphides characterizes the hornblende-biotite gneiss in the entire Nilgiri Block. The geochemical variations of major, trace and rare earth elements show that the granulite-amphibolite grade felsic rocks evolved in an arc magmatic process leaving behind mafic magma, which later intruded into these rocks, in a subduction related arc magmatic process. The U-Pb LA-ICPMS and SHRIMP dating of charnockite, hornblende-biotite gneiss and met gabbros shows ca. 2550 Ma formation age and ca. 2450 Ma metamorphism in this terrane.