Letteratura scientifica selezionata sul tema "Earth lower mantle"

Determining the composition of Earth's lower mantle, which constitutes almost half of its total volume, has been a central goal in the Earth sciences for more than a century given the constraints it places on Earth's origin and evolution. However, whether the major element chemistry of the lower mantle, in the form of, e.g., Mg/Si ratio, is similar to or different from the upper mantle remains debated. Here we use a multidisciplinary approach to address the question of the composition of Earth's lower mantle and, in turn, that of bulk silicate Earth (crust and mantle) by considering the evidence provided by geochemistry, geophysics, mineral physics, and geodynamics. Geochemical and geodynamical evidence largely agrees, indicating a lower-mantle molar Mg/Si of ≥1.12 (≥1.15 for bulk silicate Earth), consistent with the rock record and accumulating evidence for whole-mantle stirring. However, mineral physics–informed profiles of seismic properties, based on a lower mantle made of bridgmanite and ferropericlase, point to Mg/Si ∼ 0.9–1.0 when compared with radial seismic reference models. This highlights the importance of considering the presence of additional minerals (e.g., calcium-perovskite and stishovite) and possibly suggests a lower mantle varying compositionally with depth. In closing, we discuss how we can improve our understanding of lower-mantle and bulk silicate Earth composition, including its impact on the light element budget of the core. ▪The chemical composition of Earth's lower mantle is indispensable for understanding its origin and evolution.▪Earth's lower-mantle composition is reviewed from an integrated mineral physics, geophysical, geochemical, and geodynamical perspective.▪A lower-mantle molar Mg/Si of ≥1.12 is favored but not unique.▪New experiments investigating compositional effects of bridgmanite and ferropericlase elasticity are needed to further our insight.

For investigating the pressure dependence of thermal expansivity of materials, we have developed a formulation using the Stacey relationship between the reciprocal of pressure derivative of bulk modulus and the ratio of pressure and bulk modulus. The formulation presented here satisfies the boundary conditions both at zero pressure and also in the limit of infinite pressure at extreme compression. A physically acceptable relationship has been obtained between the volume derivative of thermal expansivity and the pressure derivatives of bulk modulus under adiabatic condition. The seismological data for the Earth lower mantle have been used to demonstrate the validity of the relationship between thermoelastic properties derived in the present study.

Recent progress in theoretical mineral physics based on the ab initio quantum mechanical computation method has been dramatic in conjunction with the rapid advancement of computer technologies. It is now possible to predict stability, elasticity, and transport properties of complex minerals quantitatively with uncertainties that are comparable to or even smaller than those attached in experimental data. These calculations under in situ high-pressure ( P) and high-temperature conditions are of particular interest because they allow us to construct a priori mineralogical models of the deep Earth. In this article, we briefly review recent progress in studying high- P phase relations, elasticity, thermal conductivity, and rheological properties of lower mantle minerals including silicates, oxides, and some hydrous phases. Our analyses indicate that the pyrolitic composition can describe Earth's properties quite well in terms of density and P- and S-wave velocity. Computations also suggest some new hydrous compounds that could persist up to the deepest mantle and that the postperovskite phase boundary is the boundary of not only the mineralogy but also the thermal conductivity. ▪ The ab initio method is a strong tool to investigate physical properties of minerals under high pressure and high temperature. ▪ Calculated thermoelasticity indicates that the pyrolytic composition is representative to the chemistry of Earth's lower mantle. ▪ Simulations predict new dense hydrous phases stable in the whole lower mantle pressure and temperature condition. ▪ Calculated lattice thermal conductivity suggests a heat flow across the core mantle boundary no greater than 10 TW.

In this review, we address the current status of numerical modeling of the mantle transition zone and uppermost lower mantle, focusing on the hydration mechanism in these areas. The main points are as follows: ( a) Slab stagnation and penetration may play significant roles in transporting the water in the whole mantle, and ( b) a huge amount of water could be absorbed into the deep mantle to preserve the surface seawater over the geologic timescale. However, for further understanding of water circulation in the deep planetary interior, more mineral physics investigations are required to reveal the mechanism of water absorption in the lower mantle and thermochemical interaction across the core–mantle boundary region, which can provide information on material properties to the geodynamics community. Moreover, future investigations should focus on determining the amount of water in the early planetary interior, as suggested by the planetary formation theory of rocky planets. Moreover, the supplying mechanism of water during planetary formation and its evolution caused by plate tectonics are still essential issues because, in geodynamics modeling, a huge amount of water seems to be required to preserve the surface seawater in the present day and to not be dependent on an initial amount of water in Earth's system. ▪ Slab stagnation and penetration of the hydrous lithosphere are essential for understanding the global-scale material circulation. ▪ Thermal feedback caused by water-dependent viscosity is a main driving mechanism of water absorption in the mantle transition zone and uppermost lower mantle. ▪ The hydrous state in the early rocky planets remains to be determined from cosmo- and geochemistry and planetary formation theory. ▪ Volatile cycles in the deep planetary interior may affect the evolution of the surface environment.

This article reviews some of the recent advances made within the field of mineral physics. In order to link the observed seismic and density structures of the lower mantle with a particular mineral composition, knowledge of the thermodynamic properties of the candidate materials is required. Determining which compositional model best matches the observed data is difficult because of the wide variety of possible mineral structures and compositions. State-of-the-art experimental and analytical techniques have pushed forward our knowledge of mineral physics, yet certain properties, such as the elastic properties of lower mantle minerals at high pressures and temperatures, are difficult to determine experimentally and remain elusive. Fortunately, computational techniques are now sufficiently advanced to enable the prediction of these properties in a self-consistent manner, but more results are required. A fundamental question is whether or not the upper and lower mantles are mixing. Traditional models that involve chemically separate upper and lower mantles cannot yet be ruled out despite recent conflicting seismological evidence showing that subducting slabs penetrate deep into the lower mantle and that chemically distinct layers are, therefore, unlikely. Recent seismic tomography studies giving three-dimensional models of the seismic wave velocities in the Earth also base their interpretations on the thermodynamic properties of minerals. These studies reveal heterogeneous velocity and density anomalies in the lower mantle, which are difficult to reconcile with mineral physics data.

A new combined rhenium-osmium– and platinum-group element data set for basalts from the Moon establishes that the basalts have uniformly low abundances of highly siderophile elements. The data set indicates a lunar mantle with long-term, chondritic, highly siderophile element ratios, but with absolute abundances that are over 20 times lower than those in Earth's mantle. The results are consistent with silicate-metal equilibrium during a giant impact and core formation in both bodies, followed by post–core-formation late accretion that replenished their mantles with highly siderophile elements. The lunar mantle experienced late accretion that was similar in composition to that of Earth but volumetrically less than (∼0.02% lunar mass) and terminated earlier than for Earth.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2011.
Cataloged from PDF version of thesis. Vita.
Includes bibliographical references (p. 151-165).
I have investigated the effect of composition, especially ferric iron and aluminum, on the equations of state and phase stability of perovskite and post-perovskite. The presence of trivalent cations decreases the bulk modulus of perovskite at pressures corresponding to the upper lower mantle. Ferric iron in perovskite undergoes a spin-pairing transition from the high spin state to low spin in the octahedral site. Ferric iron in the dodecahedral site remains high spin. In the absence of aluminum, the spin transition is gradual between 0 and 55 GPa, and bulk modulus increases at the completion of the spin transition. In the presence of aluminum, there is an abrupt increase in the amount of low spin ferric iron near 70 GPa, likely the result of site mixing. The high compressibility of the structure below 70 GPa results in the volume nearing that of magnesium endmember, MgSiO₃ , perovskite. Concurrent with the spin transition in aluminum-bearing perovskite, the structure stiffens. The increase in density and bulk modulus at -70 GPa results in an increase in bulk sound speed that may be related to heterogeneities in bulk sound speed observed seismically at 1200-2000 km depth in the Earth. The effect of composition on the perovskite to postperovskite phase transition was also investigated. No change in the spin state of ferric iron was found at the perovskite to post-perovskite phase transition: ferric iron is low spin in the octahedral site and high spin in the dodecahedral site. At the phase transition, ferric iron only slightly broadens the perovskite plus post-perovskite mixed phase region while ferrous iron and aluminum were each found to significantly broaden the mixed phase region to hundreds of kilometers thick. The effect of background mineral phases was assessed for a basaltic system, rich in aluminum. The coexisting minerals were found to significantly reduce the effect of the aluminum, producing a boundary that is potentially sharp enough for seismic detection in silicon-rich systems, such as basalt.
by Krystle Carina Catalli.
Ph.D.

Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1999.
Includes bibliographical references.
This study is a geochemical investigation of the evolution of the Kerguelen plume, on the basis of upper mantle and lower crustal xenoliths. Ultramafic xenoliths include harzburgites predominant, a lherzolite, dunites and pyroxenites, whereas lower crustal xenoliths are cumulate gabbros recrystallized under granulite facies conditions. On the basis of the whole rock major element characteristics and trace element abundance patterns in clinopyroxenes, the harzburgites were found to be residues of extensive melting at high pressures within the Kerguelen plume. These were then recrystallized at low pressures and metasomatized by plume generated melts. Details of the metasomatic process were determined from trace element variations in clinopyroxene in connection to texture. This demonstrated that meltrock reaction and the precipitation of new clinopyroxenes occurred by metasomatic carbonatitic melts. It was also found that some of the harzburgites had distinctly unradiogenic Os isotopic compositions and were identified as originating from the sub-Gondwanaland lithosphere. On the basis of major and trace element compositions, the granulite xenoliths were found to be originally gabbroic cumulates formed from plume-derived basaltic melts emplaced at the base of the crust by underplating and subsequently recrystallized isobarically under granulite conditions. The Sr, Nd and Os isotopic compositions of the peridotite and granulite xenoliths demonstrate that the Kerguelen plume is isotopically heterogeneous and displays a temporal progression toward more enriched Sr and Nd isotopic compositions from the Ninetyeast Ridge to granulite xenoliths to Kerguelen basalts and Heard Island basalts.
by Deborah Renee Hassler.
Ph.D.

La dynamique du réseau et les propriétés vibratoires des matériaux sont généralement bien décrites par un modèle harmonique à des températures basses et modérées, où les phonons sont supposés se comporter de manière indépendante. Toutefois, à des températures élevées, cette hypothèse ne tient plus car les interactions entre les phonons deviennent significatives. La compréhension de ces interactions anharmoniques entre les modes du réseau est cruciale tant pour la recherche fondamentale que pour les applications pratiques, car elles influencent considérablement les propriétés physiques telles que le transport thermique, les propriétés élastiques, la conductivité électrique et la supraconductivité.La conductivité thermique des minéraux constituant les intérieurs planétaires joue un rôle clé dans le contrôle du transfert de chaleur à l'intérieur des planètes, influençant ainsi la dynamique planétaire et l'histoire thermochimique (Samuel et al., 2021). Le flux de chaleur du noyau vers le manteau a un impact direct sur le degré de chauffage basal du manteau, le taux de refroidissement du noyau et la croissance du noyau interne, qui à leur tour affectent la dynamique du noyau externe et la génération et l'évolution du champ magnétique. Ainsi, la compréhension des interactions entre phonons permet de mieux comprendre l'histoire et l'évolution de la Terre..L'objectif de cette thèse est d'étudier le comportement des termes anharmoniques dans les conditions extrêmes de température et de pression du manteau inférieur de la Terre, en se concentrant sur l'oxyde de magnésium (MgO) qui est un membre terminal du ferropericlase (Mg,Fe)O qui constitue 20 % du volume du manteau. Cette étude utilise des méthodes basées sur la théorie de la fonctionnelle de la densité (DFT), en particulier la théorie de la fonctionnelle de la densité perturbative (DFPT) et l'approximation harmonique stochastique auto consistante (SSCHA). Ces méthodologies permettent d'accéder à l'anharmonicité jusqu'au quatrième ordre (interactions à quatre phonons). Les résultats seront comparés aux mesures de diffusion inélastique des rayons X (IXS) et de spectroscopie infrarouge (IR) effectuées dans notre groupe à différentes températures.Ensuite, nous discuterons de la conductivité thermique (CT) obtenue par l'équation de transport de Boltzmann en fonction de la température, en soulignant l'importance de la prise en compte des défauts dans l'analyse de la CT. Nous explorons ensuite les conditions extrêmes du manteau inférieur de la Terre, avec des températures de milliers de kelvins et des pressions à l'échelle du Mbar, pour identifier le comportement de l'anharmonicité dans le MgO dans toute cette région. Notre traitement théorique élucide l'origine microscopique de la chute observée de la conductivité thermique au fond du manteau inférieur, attribuée à l'interaction entre les interactions à trois et quatre phonons, et souligne l'importance de la présence de défauts sur la conductivité thermique du réseau, même dans des conditions extrêmes de température et de pression
The lattice dynamics and vibrational properties of materials are typically well described by a harmonic model at low and moderate temperatures, where phonons are assumed to behave independently. However, at high temperatures, this assumption fails as phonon interactions become significant. Understanding these anharmonic interactions between lattice modes is crucial for both fundamental research and practical applications, as they significantly influence physical properties such as thermal transport and elastic properties.Thermal conductivity of the minerals constituting planetary interiors plays a key role in controlling heat transfer within planets, thereby influencing planetary dynamics and thermo-chemical history (Samuel et al., 2021). The heat flux from the core to the mantle directly impacts the degree of basal heating of the mantle, the rate of core cooling, and inner core growth, which in turn affect outer core dynamics and magnetic field generation and evolution. Thus, understanding phonon interactions provides insights into Earth's history and evolution.The aim of this thesis is to investigate the behavior of anharmonic terms at the extreme temperature and pressure conditions of Earth's lower mantle, focusing on Magnesium Oxide (MgO) which is an end-member for ferropericlase (Mg,Fe)O that constitutes 20% of the mantle's volume. This study employs Density Functional Theory (DFT) based methods, specifically Density Functional Perturbation Theory (DFPT) and the Stochastic Self-Consistent Harmonic Approximation (SSCHA). These methodologies allow access to anharmonicity up to the fourth-order (four-phonon interactions). The results will be benchmarked against Inelastic X-ray Scattering (IXS) and Infra-Red spectroscopy (IR) measurements conducted in our group at varying temperatures.Subsequently, we will discuss the thermal conductivity (TC) obtained through the Boltzmann transport equation as a function of temperature, emphasizing the importance of considering defects in the analysis of TC. We then explore the extreme conditions of Earth's lower mantle, with temperatures of thousands of Kelvin and pressures at the Mbar scale, to identify the behavior of anharmonicity in MgO throughout this region. Our theoretical treatment elucidates the microscopic origin of the observed drop in TC at the bottom of the lower mantle, attributed to the interplay between three- and four-phonon interactions and emphasizes on the importance of presence of defects on lattice thermal conductivity even at extreme T and P conditions

Au cours de la dernière phase d'accrétion, les planètes terrestres ont connu des impacts géants violents et très énergétiques. A la suite du chauffage causé par les impacts, la Terre primitive était partiellement ou totalement fondue, et un océan magmatique a été formé dans la couche externe de la Terre. Le refroidissement successif de l'océan magmatique a causé la cristallisation fractionnée du manteau primitif. Cependant, il reste beaucoup d'incertitudes à propos de l'accrétion de la Terre primitive, comme la profondeur et la durée de vie d'un (ou plusieurs) océan(s) magmatique(s), l'effet de la recristallisation du manteau sur la ségrégation chimique entre les différents réservoirs de la Terre et ainsi de suite. La connaissance des propriétés de fusion du manteau profond est important aussi pour examiner la possibilité d'une fusion partielle actuellement. L'objectif était d'aborder quelques problèmes concernant le manteau inférieur terrestre : Quelle est la séquence de fusion entre les phases dominantes dans le manteau inférieur ? Est-ce qu'on peut expliquer la zone à ultra-basse vélocité (ULVZ) avec la fusion partielle d'un manteau pyrolytique (ou chondritique) ? Quel est le partage du fer entre les phases silicatées liquides et solides dans le manteau profond ? Est-ce qu'on peut donner des informations nouvelles sur les propriétés d'un océan magmatique profond à partir des courbes de fusion du manteau primitif ? Dans cette étude les courbes de fusion et les relations de fusion ont été analysées en utilisant la cellule à enclume de diamant chauffé au laser (LH-DAC) pour des pressions entre 25 et 135 GPa et des températures jusqu'à plus que 4000 K, i.e. pour des conditions de P-T qui correspondent au manteau inférieur terrestre entier. Les compositions utilisées ont été le raccord entre MgO et MgSiO3 et une composition de type chondritique pour le manteau terrestre. J'ai utilisé deux techniques in-situ de radiation-synchrotron pour déduire les propriétés de fusion à hautes pressions ; la diffractométrie au rayons-X et la fluorescence au rayons-X. Les nouveaux résultats obtenus dans cette étude sont : (...)

Many aspects of Proterozoic massif-type anorthosite petrogenesis have been, and remain, controversial. Mafic lower crust and depleted mantle have both been proposed as mutually exclusive sources of these near-monomineralic, temporally restricted batholiths. The debate surrounding the magma source has also led to uncertainty regarding the tectonic setting of these massifs, with a range of possibilities including convergent, divergent and anorogenic settings. The dramatic geochemical effects of crustal contamination in these massifs are well known and strong crustal signatures are evident in most, if not all, Proterozoic anorthosite massifs. The source debate, in the simplest sense, reduces to whether the ubiquitous crustal signature is derived principally from melting of a lower crust or is an effect of crustal assimilation. The origin of this crustal signature, and whether it obscures the original isotopic composition of the magmas or not, has fuelled the debate surrounding the source of the anorthosites. Using major element, trace element and isotopic compositions, as well as energyconstrained assimilation-fractional-crystallisation (EC-AFC) modelling from samples representing various stages of the polybaric crystallisation history of the magmas, including high-pressure megacrysts, anorthosites and their internal mineral phases, I remove the obfuscating effects of possible crustal contamination and probe the source of the magmas. In order to assess the effects of crustal contamination, if any, anorthosites from three massifs – the Mealy Mountains Intrusive Suite, Nain Plutonic Suite (both in eastern Canada) and Rogaland Anorthosite Province (Norway), have been analysed – all of which intrude into crust of significantly different age and chemical character. Sm-Nd geochronology of high-Al, high-pressure orthopyroxene megacrysts, as well as the comagmatic, host anorthosites, indicate that the magmatic system is long-lived, with an age difference between the megacrysts and hosts of ~110-130 million years. Isotopic compositions of primitive megacrysts qualitatively show that the magmas were derived from melting of the depleted mantle. Strong links between the isotopic offset from depleted mantle evolution and the age and composition of the surrounding crust confirm that the geochemical nature of the crustal contaminant plays a significant role in the petrogenesis of the anorthositic rocks. The geochronological indications of a long-lived magmatic system point to Proterozoic anorthosite formation in a continental magmatic arc – one of the only environments capable of supplying geographically-localised magma and heat to the base of the crust for over 100 million years. Proposed divergent or ‘anorogenic’ settings could not plausibly supply magma to the base of the crust for over 100 m.y. without initiating ocean formation or continental break-up. Anorthosite emplacement at mid-crustal levels may coincide with late- to post-orogenic events in several terranes, but evidence presented for a long-lived magmatic system is incongruent with this proposed setting. In this thesis, I propose that the petrogenesis of these intrusives must span both orogenic and post-orogenic periods. An overlap in megacryst crystallisation age with the onset of calc-alkaline orogenic magmatism in the Sveconorwegian Orogen, both occuring ~100 m.y. before anorthosite emplacement, confirms that initial magma and megacryst formation coincides with the main phase of magmatic and orogenic activity in a convergent magmatic arc. These geochronological constraints have implications for regional geodynamics in the Sveconorwegian Orogen (and the Labrador region) with the evidence providing corroboratory support for a long-lived accretionary orogen, as opposed to the widely-held view that the Sveconorwegian orogeny was predominantly collisional. Compositions of high-pressure megacrysts, anorthosites and analysis of internal isotopic disequilibrium indicates that lower crustal contamination has a significant influence on the isotopic composition of the rocks, with relatively minor contributions from the mid- to upper crust. Energy-constrained AFC modelling confirms that significant lower crustal contamination occurs during ponding of magmas at the Moho and is able to reproduce the observed isochronous isotopic compositions of the megacrysts as well as the compositions of the host anorthosites. Evidence of varying degrees of internal isotopic disequilibrium reinforces the significant role that assimilation of crust of different age and chemical nature have on the compositions of Proterozoic anorthosites. Unexpected patterns of isotopic disequilibrium show that anorthosite petrogenesis is not a “simple” case of progressive crustal contamination during polybaric ascent of viscous, partially-molten 4 magma mushes, but is more likely to involve significant differentiation and solidification at lower crust depths, followed by ascent of high-crystallinity bodies (> 50 % crystallinity) to upper crustal levels. Although the composition of the bulk continental crust is different to plagioclase-rich Proterozoic anorthosites, both are missing a mafic component. It is unclear how this missing mafic component was generated in the continental crust, because most of the evidence for these crustal differentiation processes is sequestered below or near the Moho. However, Proterozoic anorthosites, formed by viscous, plagioclase-rich mushes, entrain rare cumulate megacrysts from these depths and consequently preserve evidence of magmatic differentiation processes at the Moho. The evidence for the formation and sequestration of dense ultramafic cumulates in ponding magmas at the Moho can not only explain the missing mafic component in Proterozoic anorthosites, but also suggests that cumulate formation in crust-forming, arc environments is a significant process and should be taken into account in models dealing with evolution and differentiation of the continental crust. Sampling and petrographic and geochemical analysis of five pegmatitic segregations, or “pods”, from anorthosites of the Mealy Mountains Intrusive Suite reveal a diverse range of compositions from mafic, Fe-rich and Si-poor, to Fe-poor and Sirich felsic compositions and from monzogranite through quartz-monzodiorite and monzodiorite to Fe-P-rich gabbronorite. Each pod shows a range of noteworthy graphic, myrmekitic and symplectic textures on a variety of scales, along with distinctive mineralogical assemblages and highly-enriched trace element compositions. Derivitive minerals (e.g. apatite and zircon), high concentrations of Fe, Ti, P (and in some cases SiO2) and 10-1000 times chondrite enrichment suggest that many of the pods are highly fractionated. U-Pb zircon geochronology reveals that all the pods are the same age as the anorthositic hosts and confirms that the Mealy Mountains Intrusive Suite was emplaced between 1654 and 1628 Ma. Using the aforementioned evidence, I show that the pods represent the fluid-bearing, late-stage crystallisation products of a residual liquid in the massif anorthosite system and provide a window into the final stages of crystallisation in the anorthosite system. A range of rock types (monzonites, monzonorites, ferrodiorites and jotunites) observed in similar pod-like structures, as well as dykes and plutons, have also been documented in other Proterozoic anorthosite massifs. These have, at one time or another, controversially been interpreted as the residual liquids of anorthosite crystallisation. The observation of in-situ pods with similar compositions to all of the aforementioned rock types and displaying textures indicative of late-stage crystallisation support the notion that these associated lithologic units are comagmatic with, but residual to, the anorthosites and are not residual liquids of other crustally-derived rocks, immiscible liquids, parental magmas or cumulates. Isotopic compositions of these highly-fractionated, late-stage pods also overlap with those of anorthosites, lending further evidence to the case that upper crustal contamination plays only a minor role in developing the chemical signature of the anorthosites. With these results I propose that the nature/composition of the residual liquids of Proterozoic anorthosite magmas can vary dramatically, depending on geochemical differences in the original magma pulses and by mixing of mobilised, independently-evolved segregations of residual liquids. This process could explain why so many varied rock types associated with Proterozoic anorthosites have been suggested as residual liquids: these rocks all represent residual liquids resulting from varying degrees of differentiation, subsequent mobilisation, mixing and final solidification as plutons or dykes. Proterozoic anorthosite petrogenesis is an inherently polybaric process and so by its very nature produces a range of complicated and contradictory features which have clouded interpretation of numerous aspects of the rocks formation. In analysing crystallisation products from numerous stages of the anorthosites polybaric history, I have been able to probe the magmatic processes operating at different stages of Proterozoic anorthosite petrogenesis. In doing so I show that the magmas are derived from melting of the depleted mantle in continental-arc-like settings – two controversial aspects of Proterozoic anorthosite petrogenesis. These constraints on the source and tectonic setting will allow renewed investigation into the ultimate question surrounding Proterozoic anorthosites: why are these rock types restricted to the Proterozoic and what clues does this temporal restriction offer about Earth’s geodynamic evolution during this period? The assertion in this thesis that 5 Proterozoic anorthosites formed in arc environments dictates that subduction processes or geodynamic conditions during the Proterozoic favoured the production of voluminous masses of plagioclase, because modern-day magmatic arc terranes show no evidence of anorthosites with similar compositions. However, calcic anorthositic inclusions and xenoliths are observed in modern-day volcanic and continental arcs suggesting that anorthosites may be forming in these environments, but that conditions such as water content or style of subduction are different to the Proterozoic, producing less and compositionally different plagioclase and anorthosite. The results of this thesis shed new light on and refine the petrogenesis of Proterozoic anorthosites, but the focus of research must now shift to explaining the temporal restriction of these intrusions and the implications of this restriction for the geodynamic evolution on Earth during the Proterozoic.

The results of the study of granites of the north-east of the Verkhoyansk-Kolyma orogen bearing rare-earth mineralization are summarized in the article. Ore-bearing granites are classified as A-type of postorogenic and rift-related geodynamic conditions. Three groups are identified in them, differing in the origin and scale of the associated rareearth mineralization. The most ore-bearing granites are spatially and genetically related to alkaline�ultrabasic � alkaline-basic formations and formed within a long-lived hotspot from granite melt, generated from a fenitized crustal substrate under the influence of a flow of transmagmatic fluids. Granite massifs are limited ore-bearing, crystallized from melts generated in the Paleoproterozoic substrates of the lower crust under the influence of heat and fluids, related to the mantle magmas and bearing clear signs of mixing of basic and acidic melts during crystallization. These massifs are localized within the Indigirka crustal extension belt, where the presence of buried centers of the basic melts is assumed, which activation caused the re-melting of crustal substrates. Granites that do not bear signs of mantle-crustal interaction usually have only dispersed accessory rare-earth mineralization.

ABSTRACT: Eastern China, which lies to the east of the Hu Huanyong Line that connects the Heihe and Tengchong areas, has a high population density, a developed economy, and a huge demand for energy. To determine the geothermal resources in eastern China, this study analyzed the typical geothermal systems in this region based on disciplines of structural geology, and petrology. As a result, this study determined the distribution patterns of medium and deep geothermal resources in this region. Eastern China is a superimposed region of three major global tectonic domains, namely Paleo-Asia, Circum-Pacific, and Tethyan. Its crust-mantle structure presents a special flyover pattern, while its shallow surface has alternating basins and mountains and well-spaced uplifts and depressions. Studies have shown that medium-high-temperature geothermal resources in China are mainly distributed in the Mesozoic-Cenozoic basins in eastern China. However, they are dominated by medium-temperature geothermal resources with low abundance. The geothermal reservoir types mainly include porous sandstone reservoirs, karstified fractured-vuggy carbonate reservoirs, and fissured granite reservoirs. 1. INTRODUCTION Eastern China, which lies to the east of the Hu Huanyong Line that connects the Heihe and Tengchong areas, consists of Northeast China, North China, the middle and lower reaches of the Yangtze River, Southwest China, and South China from north to south, has a high population density, hosting 96% of the total population of China, as well as a developed economy and a huge demand for energy (Fig. 1). As an earth-derived energy source, geothermal resources are clean, renewable, and highly competitive and can be used for indoor heating, industrial and agricultural utilization, and power generation. The successive launch of national projects in China, such as the Deep Resource Exploration and Exploitation Program, began the exploration of the deep earth in China, and important achievements have been increasingly achieved in basic geology and geothermal geology. Moreover, research on deep-crust temperature and crust-mantle dynamic mechanisms has been gradually intensified (Shi 1990; Xu et al., 1995; He et al., 2001; An et al., 2007; Wang et al., 2012; Qiu et al., 2015). Remarkable progress has been made in research on terrestrial heat flow (Jiang et al., 2016, 2019), geothermal system types (Chen et al., 1996; Zhang et al., 2017), the division of geotectonic units and geothermal units (Pan et al., 2009; He et al., 2017), the selection and evaluation of optimal exploration areas (He et al., 2020; Zhang et al., 2020; Ke et al., 2022), hot dry rock development experiments (Wang et al., 2022), and geothermal applications (Wang et al., 2014), laying a solid foundation for the study of deep geothermal resources.

Abstract The field under study is witnessing an increasing trend in NPT events while drilling vertical wells through high stressed shale formations and the underlying depleted sandstone reservoir in the same section. The field has multiple sets of faults with lateral variations in stress azimuth and completion quality with the regional strike-slip regime. High angled wells are being planned to increase reservoir coverage and perform hydro fracturing. This paper provides details of capturing stress regime variation along with the effects of depletion in offset wells and identify suitable azimuth of planned well with drilling risks through a 3D geomechanical study. Comprehensive 1D mechanical earth models are constructed using open hole logs, core data and available hydro-fracturing results for wells in the field. Rock mechanical properties have been calibrated at well scale as per core data. Poro-elastic horizontal strain method at well scale indicates a strike-slip to reverse fault variation with significant horizontal stress anisotropy as evident from the closure pressure range of 9,500 psi to 12,500 psi. 3D numerical geomechanical model has been constructed considering structural discontinuities, rock mechanical properties and formation pressure to estimate the principal stresses. Stress direction data from dipole sonic measurements and breakout azimuth from borehole image logs are used for calibration in 3D model incorporating faults. Stress path for depletion has been estimated. Results from the study suggested change in casing policy specifically to have a liner isolating the overburden formations where more than 800 m should be drilled prior to entering the depleted reservoir formation. 3D geomechanical analysis reckons that the mud weight should be in the range of 12.7 kPa/m to 13.1 kPa/m during building up the well profile at 80 deg inclination in overlying shale while 1D study suggesting a range of 13.2 kPa/m to 13.7 kPa/m. Along well path at 80deg to 90deg deviation within reservoir layer toward minimum horizontal stress azimuth, mud weight requirement was found to be much lower at 11.5 kPa/m to 12.1 kPa/m. Apart from mud weight, BHA and chemicals were optimized to avoid differential sticking and better hole cleaning for respective sections. Actual mud weight used was in the range of 12.8 kPa/m to 13.1 kPa/m for building up with no torque and drag issue while running liner and BHA trips. Mud weight was maintained in the range of 11.5 kPa/m to 11.8 kPa/m in the horizontal section with minimum breakouts and smoother hole condition. Cuttings shape and size analysis were performed regularly to check well behavior and manage downhole pressure higher than shear failure limit. Using 3D Geomechanical study and continuous monitoring of drilling parameters in near real-time, the buildup and reservoir sections have been drilled within schedule with no major NPT event and saved at least one week of rig days.

Abstract Sand management has been a longstanding challenge in the Oil and Gas industry, exacerbating the complexities further in Mature and Marginal Clastic oil and gas fields. These fields typically exhibit significantly low productivities and thereby low recovery volumes of remaining oil and/or gas in place, thereby expensive sand control measures prove economically unviable. This underscores the imperative need for the industry to embrace digitalization and data analytics in Sand Management as a means of bolstering Net Present Value (NPV) and the field economics and reserves monetization. The unmitigated production of sand in many of these fields necessitates a shift from existing and failed downhole sand control to effective and holistic sand management to circumvent and manage facility capacity constraints. In this paper, we will introduce an innovative approach combining sub-surface reservoir sanding behaviour analysis with advanced surface sand management techniques, driven by cutting-edge digital analytic tools, which is one of its kind in the Oil and Gas Industry. Our intensive research findings and consequent recommendations include: Pioneering Digital Holistic Sand Management.Demonstrating enhancement in production rates, managing risks on the surface facilities, lower deferment of production and reduced Workover operations and costs.Decreasing Capital & Operating Expenditure: Strategies to optimize resource allocation.Reducing Carbon Footprint through sand management.Case Studies: Detailed exploration of unique algorithms and logics tailored for specific fields. Our strategy, executed in collaboration with seasoned Sand Management professionals and advanced tools, delves into rock mechanics at a granular level and enables the assessment of well-specific sand production severity and the establishment of an Effective Sand Production Index (ESPI), which is an innovative technique for relative sand production estimation. This empowers field operators to prioritize high-risk wells, optimizing resource allocation. Furthermore, our approach involves simulated development of the Mechanical Earth Model (MEM) and Critical Drawdown Pressure (CDP) profile which enables a comprehensive understanding of the sand production behaviour of different reservoirs. On the surface, the methodology includes a unified module for simulation, analysis, and prediction of all risks associated with sand production. Notably: Particle-Specific Sand Mapping: Using detailed particle size distribution (PSD) analysis.Comprehensive Total Metal Loss Assessments: Incorporating both erosion and corrosion.Time-Based Metal Loss and Depositional Analysis: Facilitating dynamic visualization of depositional risks.Performance Coefficient Charts: Supporting Choke Health Analysis and failure prediction.Specialized algorithm for Intermittent Gas Lift wells: simulating Sand Deposition and transport behaviour during Gas Lift and Shut-in cycles. This paper will also showcase how the tools & the strategies have been rigorously validated through successful case studies in clastic oil and gas fields around the world, affirming its capability in comprehensively and effectively addressing the multifaceted sand production risks. In summary, our approach represents a pioneering application of digitalization in holistic sand management, providing operators with a broader perspective beyond traditional downhole control measures. By adopting this strategy, industry can unlock restricted potential and, on an average, provide an 3-5% incremental production in mature and marginal fields.

Topics: (1) Current Missions, (2) Small Satellites and Cubesat AOCS/GNC (Hardware & Subsystems), (3) Space Mission AOCS/GNC Validation & Verification. Abstract: In the last decade, the space business is maturing from being strongly customized for each specific mission to being more industrial, following what other more mature industrial areas have done in the past, for example automotive. On one side there is the need to reduce costs to access space, so lean philosophies are seen as a good approach; on the other side, those approaches need large numbers to be effective. Moreover, the need to have standard products with an increasing number of missions is strong also to manage them in a proper way, becoming unfeasible and inconvenient to customize each single platform or subsystem when producing a certain number of them. When numbers are sufficiently high, a more industrialized approach becomes feasible, convenient, and welcome. This has been the case in D-Orbit in recent years, with an increasing number of ION missions to carry CubeSats in space and deliver them in the appropriate orbits, and several other programs to develop in parallel for Earth Observation and, later on, In-Orbit Servicing. The growing number of programs the AOCS & GNC team was involved in led to the necessity to coordinate better the parallel AOCS developments. The problem could have been that, if left without a common guidance, the different AOCS projects, in the different programs, would have diverged, making it very difficult to manage them and further develop the AOCS SW in the future. From this need, the project of a unique AOCS Platform (AOCP) is born, with the main objective to have only one AOCS SW for all the programs, making it sufficiently flexible and modular to easily adapt to mission-specific needs. Furthermore, the configuration for each different project shall be quick and easy, with the addition of a certain degree of automation for several V&V processes, to well fit with the growing number of ION-SCV missions and other programs incoming without requiring much effort every time a new mission starts, and ultimately speed up the process while maintaining the quality and confidence of the final product. With these objectives in mind, a new repository structure as well as a new SW management strategy have been developed. The AOCP comprises the development of the AOCS SW that is integrated in ION missions as well as the AOCS SW that is to be used in other D-Orbit missions. The development of the AOCP derives from each of the projects of D-Orbit as well as from the required improvements gathered from in-flight performance. The ability to base every project, with different requirements, on the same SW is done through versioning. Each SW version carries new modifications, bug-fixes, and improvements with respect to the previous one, but also allows flexibility in the avionics that can be used and adapted for each version. The R&D projects carried out at D-Orbit derive added requirements, which are implemented parallelly in the AOCP and posteriorly used in the industrialization process. Each SW version can be further developed and maintained in parallel and bugfixes need only to be improved in the source. The chain of features or bugfixes that are implemented creating a new SW version can be posteriorly uploaded in a flying ION mission allowing to demonstrate capabilities in a very fast way and validate in flight. This grants the possibility of minimizing the time between any change of the SW that is requested and the corresponding in-flight heritage. Different ION versions carry different SW versions, creating a range of configurable products that adapt to each client’s mission, in the same approach as done in the automotive industry. Each product created is a configuration of the AOCP functionalities and, in terms of avionics used: number of actuating devices, sensors, number of Star Trackers, presence of gyros, etc. This provides the possibility of having more economical products that achieve different performances tailored to each client and adapted to each mission demand: with higher/lower pointing accuracies, associated to higher/lower costs, duration, or payload type, among others. The Industrialization of the AOCP has been successfully achieved with an automatization that allows the modification of mission-specific parameters without any AOCS team involvement in the process, making each ION launch very productive in a time-demanding environment. This is achievable and scalable to every D-Orbit project due to the transversality of the AOCS SW along the different R&D missions. In this way, the effort in modifying the SW and adapting it to each mission is highly reduced from an AOCS point of view, as it is performed in an automatic way, decreasing like so, the implication in the industrialization process. With the same philosophy in mind, tasks like the calibration of the sensors, before each ION launch, can be done in an automatic way just using as input the raw measurements. The ability to sustain just one AOCS SW for all of D-Orbit’s missions is very advantageous from the point of view of maintainability and improvement. This requires a large flexibility from the SW’s point of view, that allows adapting it to the different R&D missions as well as the different launches of ION. Being able to sustain modifications and bug-fixes that can be rapidly tested in-flight, along with improvements, is increasing the performances to all the products range and provide new capabilities which are in high demand in the New Space industry. The SW’s flexibility makes it a highly demanded product that can adapt to the requested necessities of every mission. Additionally, the capability to Industrialize and optimize the mission preparation through automatizations is very advantageous and time-saving, and will for sure be the future of the New Space Companies.

A complete suite of bulk major- and trace-elements measurements combined with macroscopic/microscopic observations and mineralogy guided by scanning electron microscope-energy dispersive spectrometry (SEM-EDS) analyses were applied on Nekuashu (2.55 Ga) and Pelland (2.32 Ga) intrusions in northern Canada, near the Strange Lake rare earth elements (REE) deposit, to evaluate their magmatic evolution and possible relations to the Mesoproterozoic Strange Lake Peralkaline Complex (SLPC). These Neoarchean to earliest-Paleoproterozoic intrusions, part of the Core Zone in southeastern Churchill Province, comprise mainly hypersolvus suites, including hornblendite, gabbro, monzogabbro/monzodiorite, monzonite, syenite/augite-syenite, granodiorite, and mafic diabase/dyke. However, the linkage of the suites and their petrogenesis are poorly understood. Geochemical evidence suggests a combination of 'intra-crustal multi-stage differentiation', mainly controlled by fractional crystallization (to generate mafic to felsic suites), and 'accumulation' (to form hornblendite suite) was involved in the evolution history of this system. Our model proposes that hornblendite and mafic to felsic intrusive rocks of both intrusions share a similar basaltic parent magma, generated from melting of a hydrous metasomatized mantle source that triggered an initial REE and incompatible element enrichment that prepared the ground for the subsequent enrichment in the SLPC. Geochemical signature of the hornblendite suite is consistent with a cumulate origin and its formation during the early stages of the magma evolution, however, the remaining suites were mainly controlled by 'continued fractional crystallization' processes, producing more evolved suites: gabbronorite/hornblende-gabbro ? monzogabbro/monzodiorite ? monzonite ? syenite/augite-syenite. In this proposed model, the hydrous mantle-derived basaltic magma was partly solidified to form the mafic suites (gabbronorite/hornblende-gabbro) by early-stage plagioclase-pyroxene-amphibole fractionation in the deep crust while settling of the early crystallized hornblende (+pyroxene) led to the formation of the hornblendite cumulates. The subsequent fractionation of plagioclase, pyroxene, and amphibole from the residual melt produced the more intermediate suites of monzogabbro/monzodiorite. The evolved magma ascended upward into the shallow crust to form monzonite by K-feldspar fractionation. The residual melt then intruded at shallower depth to form syenite/augite-syenite with abundant microcline crystals. The granodiorite suite was probably generated from lower crustal melts associated with the mafic end members. Later mafic diabase/dykes were likely generated by further partial melting of the same source at depth that were injected into the other suites.