Download or read book Geochemical Study of Volcanism Associated with the Early Stages of Continental Rifting in Northern Tanzania written by Cassi Renée Paslick and published by . This book was released on 1995 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book American Doctoral Dissertations written by and published by . This book was released on 1995 with total page 896 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Integrating Volatile and Trace Element Geochemistry to Evaluate Sources of Volcanism in Oceanic and Continental Rift Environments written by Erica Lynn Maletic and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A close relationship between lithospheric extension and mantle plumes is commonly assumed as the driving force for evolving divergent plate boundaries that manifest as a rift in either oceanic or continental settings. While lithospheric extension is robustly supported by geophysical and geochemical evidence, the role of mantle plumes is often less clear. In fact, in many cases, ongoing integrated geochemical and geophysical work suggest that heterogenous asthenospheric and sub-continental lithospheric mantle components or complex interactions between those two reservoirs (i.e., variable asthenospheric erosion or delamination of lithospheric mantle, especially the SCLM associated with continental rifts) may more robustly account for geological, geochemical, and geophysical observations at many of the prominent rifts, including each of the three rifts explored as part of this thesis. Herein, we integrate trace element and gas geochemistry from three prominent rift zones, including: 1) the Equatorial Mid-Atlantic Ridge (MAR) (5°N to 7°S), 2) the West Antarctic Rift System (WARS), and 3) the East African Rift System (EARS), to evaluate magmatic sources and processes that influence their evolution. Basalts from the Equatorial MAR provide an ideal setting to study the compositional variations in the upper mantle related to mixing and investigate interactions between mantle plumes and ridges without the risks of crustal contamination associated with working in continental settings. MORBs from the northern Equatorial MAR (5°N to 3°S) display trace element, radiogenic isotope, and helium isotopic characteristics indicative of mixing between the depleted mantle (DM) and a HIMU plume while the southern Equatorial MAR (3°S to 7°S) exhibit extremely depleted MORB compositions. The DM basalts have significantly lower (factor of 2) volatile (H2O and Cl)/Pb ratios in samples with the extremely non-radiogenic Pb isotope ratios, but vary by less than ~50% when volatile concentrations are normalized to 204Pb to control for partial melting/fractional crystallization, suggesting the volatile contents fluctuate with the degree of partial melting and source variation. In contrast to the MAR, the WARS and EARS are both continental rifts with ample opportunity for influence by crustal contamination. WARS volcanics in Victoria Land exhibit OIB-like trace element compositions with dominantly MORB-like gas signatures (e.g., La/Lu up to 155; 3He/4He ~7RA). Elevated CO2/3He cannot be accounted for strictly by the influences of magmatic degassing, indicating an addition of CO2 from the more alkaline source in the magmatic mixture. Based on the positive correlations between CO2 and several trace element ratios (e.g., Zr/Hf, Rb/Sr, Th/U), we suggest that subduction-related alteration of the mantle induced metasomatism of the SCLM across the region and eventually led to the formation of alkaline-rich volcanics, contrary to previous suggestions of a prolonged HIMU (high 238U/204Pb) plume in the region. Mantle upwelling in this region entrained magma bodies with noble gases derived from the uprising asthenosphere, which can be characterized by higher 3He/4He than typical subduction, SCLM, or HIMU sources. Volcanics in the Virunga Volcanic Province in the EARS (specifically at Mount Nyiragongo and Mount Nyamuragira) exhibit highly alkaline, silica-undersaturated lavas with even more extreme enrichments of incompatible elements (e.g., high field strength elements) than the WARS. Although VVP volcanics consistently display these atypical, but starkly similar compositions, we note significant and corresponding changes in both helium isotopes and trace elements even over the course of a few years in the region. To a first order, volcanics from the VVP region are consistent with WARS volcanism, and we envision a similar conceptual model for the evolution of the SCLM and associated volcanics in this region. We suggest that subduction-related alteration of the mantle during the Proterozoic accretion of the Tanzania Craton induced metasomatic enrichment of incompatible elements into the SCLM across the region and formed the basis for the formation of alkaline-rich volcanics. Next, we hypothesize that following the cessation of subduction during the Proterozoic, asthenospheric upwelling, and lithospheric delamination led to partial melting of highly devolatilized and incompatible-rich SCLM to generate the volcanic products we observe today. With this conceptual model in mind, we envision that the helium isotopic values observed in the current study area result from the influence of dominantly asthenospheric mantle interacting with and generating variable degrees of partial melts of the SCLM instead of a HIMU (high 238U/204Pb) plume in the region.
Download or read book The Afar Volcanic Province Within the East African Rift System written by G. Yirgu and published by Geological Society of London. This book was released on 2006 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: The seismically and volcanically active East African Rift System is an ideal laboratory for continental break-up processes: it encompasses all stages of rift development. Its northernmost sectors within the Afar volcanic province include failed rifts, nascent sea-floor spreading, and youthful passive continental margins associated with one or more mantle plumes. A number of models have been proposed to explain the success and failure of continental rift zones, but there remains no consensus on how strain localizes to achieve rupture of initially 125-250 km-thick plates, or on the interaction between the plates and asthenospheric processes. This collection of papers provides new structural, stratigraphic, geochemical and geophysical data and numerical models needed to resolve fundamental questions concerning continental break-up and mantle plume processes. The focus is on how mantle melt intrudes and is distributed through the plate, and how this magma intrusion process controls along-axis segmentation and facilitates break-up.
Download or read book Petrology and Geochemistry of Continental Rifts written by E.R. Neumann and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the NATO Advanced Study Institute, Oslo, Norway, July 27-August 5, 1977
Download or read book Extreme Natural Hazards Disaster Risks and Societal Implications written by Alik Ismail-Zadeh and published by Cambridge University Press. This book was released on 2014-04-17 with total page 431 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a unique, interdisciplinary approach to disaster risk research, combining cutting-edge natural science and social science methodologies. Bringing together leading scientists, policy makers and practitioners from around the world, it presents the risks of global hazards such as volcanoes, seismic events, landslides, hurricanes, precipitation floods and space weather, and provides real-world hazard case studies from Latin America, the Caribbean, Africa, the Middle East, Asia and the Pacific region. Avoiding complex mathematics, the authors provide insight into topics such as the vulnerability of society, disaster risk reduction policy, relations between disaster policy and climate change, adaptation to hazards, and (re)insurance approaches to extreme events. This is a key resource for academic researchers and graduate students in a wide range of disciplines linked to hazard and risk studies, including geophysics, volcanology, hydrology, atmospheric science, geomorphology, oceanography and remote sensing, and for professionals and policy makers working in disaster prevention and mitigation.
Download or read book Composition Deep Structure and Evolution of Continents written by R.D. van der Hilst and published by Elsevier. This book was released on 1999-10-22 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ensemble of manuscripts presented in this special volume captures the stimulating cross-disciplinary dialogue from the International Symposium on Deep Structure, Composition, and Evolution of Continents, Harvard University, Cambridge, Massachusetts, 15-17 October 1997. It will provide an update on recent research developments and serve as a starting point for research of the many outstanding issues. After its formation at mid-oceanic spreading centers, oceanic lithosphere cools, thickens, and subsides, until it subducts into the deep mantle beneath convergent margins. As a result of this continuous recycling process oceanic lithosphere is typically less than 200 million years old (the global average is about 80 Myr). A comprehensive, multi-disciplinary study of continents involves a wide range of length scales: tiny rock samples and diamond inclusions may yield isotope and trace element signatures diagnostic for the formation age and evolution of (parts of) cratons, while geophysical techniques (e.g., seismic and electromagnetic imaging) constrain variations of elastic and conductive properties over length scales ranging from several to many thousand kilometers. Integrating and reconciling this information is far from trivial and, as several papers in this volume document, the relationships between, for instance, formation age and tectonic behavior on the one hand and the seismic signature, heat flow, and petrology on the other may not be uniform but may vary both within as well as between cratons. These observations complicate attempts to determine the variations of one particular observable (e.g., heat flow, lithosphere thickness) as a function of another (e.g., crustal age) on the basis of global data compilations and tectonic regionalizations. Important conclusions of the work presented here are that (1) continental deformation, for instance shortening, is not restricted to the crust but also involves the lithospheric mantle; (2) the high wavespeed part of continental lithospheric mantle is probably thinner than inferred previously from vertically travelling body waves or form global surface-wave models; and (3) the seismic signature of ancient continents is more complex than expected from a uniform relationship with crustal age.
Download or read book Encyclopedia of Geology written by and published by Academic Press. This book was released on 2020-12-16 with total page 5634 pages. Available in PDF, EPUB and Kindle. Book excerpt: Encyclopedia of Geology, Second Edition presents in six volumes state-of-the-art reviews on the various aspects of geologic research, all of which have moved on considerably since the writing of the first edition. New areas of discussion include extinctions, origins of life, plate tectonics and its influence on faunal provinces, new types of mineral and hydrocarbon deposits, new methods of dating rocks, and geological processes. Users will find this to be a fundamental resource for teachers and students of geology, as well as researchers and non-geology professionals seeking up-to-date reviews of geologic research. Provides a comprehensive and accessible one-stop shop for information on the subject of geology, explaining methodologies and technical jargon used in the field Highlights connections between geology and other physical and biological sciences, tackling research problems that span multiple fields Fills a critical gap of information in a field that has seen significant progress in past years Presents an ideal reference for a wide range of scientists in earth and environmental areas of study
Download or read book Seismicity in Volcanic Areas written by Derek Keir and published by Frontiers Media SA. This book was released on 2022-11-04 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Geotraveller written by Roger N. Scoon and published by Springer Nature. This book was released on 2021-03-25 with total page 439 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes famous geosites and historical localities in national parks and conservation areas from North America, East Africa, and Europe. The geosites include iconic landforms associated with active volcanoes, canyons, glaciated landscapes, natural rock monoliths, and rifts. The potential for geotourism in historical localities such as the famous Greco-Roman antiquities of Greece, Italy, and Turkey, is emphasised. Some of the geosites and historical localities provide evidence that previous civilizations coped with active geology and major climatic cycles, whilst others reveal evidence of famous geological events recognized in history and ancient mythology that helped shape our current civilization. The book assists tour guides and visitors (both geologists and non-specialists) interested in geotourism by providing an understanding of geological processes in the national parks and historical locations with the assistance of photographs and simplified geological maps.
Download or read book Continental Rift Formation and its Prehistory written by A.V. Razvalyaev and published by Routledge. This book was released on 2021-02-25 with total page 207 pages. Available in PDF, EPUB and Kindle. Book excerpt: Translation of the Russian edition of 1988 on peculiarities of the Arabian-Nubian Shield in the Precambrian, prerift magmatism in the Red Sea Rift zone, evolution of the crust in rift forming zones.
Download or read book Rheology and Deformation of the Lithosphere at Continental Margins written by Garry D. Karner and published by Columbia University Press. This book was released on 2004 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: Traditionally, investigations of the rheology and deformation of the lithosphere (the rigid or mechanically strong outer layer of the Earth, which contains the crust and the uppermost part of the mantle) have taken place at one scale in the laboratory and at an entirely different scale in the field. Laboratory experiments are generally restricted to centimeter-sized samples and day- or year-length times, while geological processes occur over tens to hundreds of kilometers and millions of years. The application of laboratory results to geological systems necessitates extensive extrapolation in both temporal and spatial scales, as well as a detailed understanding of the dominant physical mechanisms. The development of an understanding of large-scale processes requires an integrated approach. This book explores the current cutting-edge interdisciplinary research in lithospheric rheology and provides a broad summary of the rheology and deformation of the continental lithosphere in both extensional and compressional settings. Individual chapters explore contemporary research resulting from laboratory, observational, and theoretical experiments.
Download or read book Geology of National Parks of Central Southern Kenya and Northern Tanzania written by Roger N. Scoon and published by Springer. This book was released on 2018-04-09 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book describes the interrelationship between the spectacular geology of an area of East Africa that includes a branch of the rift valley, as well as giant freestanding ice-capped mountains and extraordinarily toxic, alkaline lakes, and some of the greatest concentrations of wildlife on Earth. It suggests that geological processes that have shaped the iconic landforms, including active volcanoes, may also be responsible for the unusually diverse speciation which characterises the region. Moreover, it is not a coincidence that important palaeoanthropological discoveries have been unearthed in the region. National parks and conservation areas have tremendous potential for geotourism and the book assists both tour guides and visitors in this regard. In addition, the book may provide a better understanding to management of the importance of geology for sustaining wildlife.
Download or read book The Gregory Rift Valley and Neogene recent Volcanoes of Northern Tanzania written by John Barry Dawson and published by Geological Society of London. This book was released on 2008 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure and volcanic activity of the northern Tanzania sector of the Gregory Rift Valley have hitherto been less well described than those in Ethiopia and Kenya. This book focuses on northern Tanzania where, although the volcanic area is smaller than those to the north, there are major features such as Kilimanjaro, the highest mountain on the African continent; Ngorongoro, one of the largest calderas on Earth; and Oldoinyo Lengai, the world's only active carbonatite volcano. Following an account of the discovery and early exploration of the rift valley, there are descriptions of the individual volcanoes. These are set within the context of the regional geology and geophysics of the rift valley, and in relation to the structural evolution of the rift and its associated sedimentary basins which include Olduvai, an important site in the history of human evolution The volume concludes with a discussion of the volcanism as related to the plume-related African Superswell.
Download or read book The Encyclopedia of Igneous and Metamorphic Petrology written by Donald Bowes and published by Springer Science & Business Media. This book was released on 1990-02-28 with total page 635 pages. Available in PDF, EPUB and Kindle. Book excerpt: Featuring over 250 contributions from more than 100 earth scientists from 18 countries, The Encyclopedia of Igneous and Metamorphic Petrology deals with the nature and genesis of igneous rocks that have crystallized from molten magma, and of metamorphic rocks that are the products of re-crystallization associated with increases in temperature and pressure, mainly at considerable depths in the Earth's crust. Entries range from alkaline rocks to zeolite facies - providing information on the mineralogical, chemical and textural characters of rock types, the development of concepts and the present state of knowledge across the spectrum of igneous and metamorphic petrology, together with extensive lists of both commonly used and little used terms and bibliographies.
Download or read book Geology of Afar East Africa written by Jacques Varet and published by Springer. This book was released on 2017-11-14 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book summarizes the geological knowledge accumulated on Afar in the last 60 years, demonstrating that it is, and will remain, a real “hot spot” for geological and geophysical research. It provides insights into the Earth processes along diverging plate boundaries, the study of both the continental and oceanic lithosphere and underlying asthenosphere, and margins and transitions including magmatic, volcanic, tectonic, sedimentary, hydrothermal and geodynamic processes. The Afar triangle is a geological depression that developed where the Gulf of Aden, Red Sea and East African Rift Valley meet. It is considered to be one of the Earth system’s most important mantle plumes. In 1967, when the first expedition was organized, there was little information on the geology of the area, and even geographic base maps were lacking. However, the first satellite photographs from the Apollo and Gemini space missions offered a complete picture of the Red Sea-Gulf of Aden region, providing a new vision of the Afar triangle. The book describes the unique geological features that make Afar the only place in the world where an oceanic plate boundary with all its successive steps of development can be observed in the open air. It also presents the Afar triangle as one of the cradles of first, now extinct hominids. The Middle Awash area contains sites of several fossil discoveries, such as the well-known Lucy. The hydrothermal processes in Afar provide conditions suitable for the study of the most primitive forms of life (archaebacterial) and it is also one of the few places where significant quantities of telluric energy are available at the surface for geothermal development. Further, the area has economically interesting mineral deposits and illustrates a number of current climate change issues. In addition to providing geological information, the book shows that Afar is an area where an individual human population developed with its own language and culture, and which adapted to the rugged landscape and extremely dry and hot climate. It is a valuable resource for scientists and students, and also serves the needs of the Afar nation, currently split in three different countries as a result of recent historical events.
