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 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 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 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 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 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 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 Volcanism and Evolution of the African Lithosphere written by Luigi Beccaluva and published by Geological Society of America. This book was released on 2011-01-01 with total page 342 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 Magma Rock and Magma Mush Interactions as Fundamental Processes of Magmatic Differentiation written by Anastassia Borisova and published by Frontiers Media SA. This book was released on 2024-08-08 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: During transport, a percolating melt or magma may contact rock or a magmatic mush, resulting in inevitable interactions that may be described as magma/melt-rock or magma/melt-mush interactions. Examples of these types of interactions include mantle metasomatism, mineral-melt reaction in the mantle, mineral dissolution in magma, crustal wallrock partial melting, and thermal remobilization of preexisting mushy magma (rejuvenation of mush) by intruding high specific enthalpy magma. This spectrum of processes plays a major role in the composition, thickness, and age of the mantle lithosphere and its associated crust. These interactions also impact the asthenosphere because melts that form in the deepest parts of the mantle may ascend and interact with shallower mantle during transport.
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 244 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 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 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: A unique interdisciplinary approach to disaster risk research, including global hazards and case-studies, for researchers, graduate students and professionals.
Download or read book Magmatic Evolution of the North Tanzanian Divergence Zone East African Rift System written by Sara Mana and published by . This book was released on 2013 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: My study focuses on the magmatic evolution of the North Tanzanian Divergence zone (NTD). Using high precision 40Ar/39Ar geochronology I identify stages of magmatic activity and episodes of progressive magma migration. The newly developed temporal framework combined with elemental and isotopic geochemistry allows me to understand how the melting process has changed during the spatial and temporal evolution of the NTD. I use the abundances of key trace elements to identify the source mineralogy; including rare earth element (REE) modeling to constrain depths of melt separation. In addition, I employ radiogenic Sr-Nd-Pb isotope ratios to identify possible contributions from different mantle and crustal components. The NTD represents an example of an early stage continental rifting where lithospheric melts are generated during the interaction of a mantle plume and a heterogeneous metasomatized lithosphere. Melting occurs in the garnet stability zone. The first melt produced derives from fusible amphibole rich veins. Through the NTD rifting development, melting conditions change to generate alkali basalts with systematically different isotopic signatures. This episode of magmatism consists of an intense pulse, related to the inception of rifting, and characterized by melt separation occurring at shallower depths. The observed chemical signature can be explained either with the involvement of contributions from plume related fluids, or by melting of layered lithosphere. Subsequent volcanism has features consistent with mixing between the first two events. Through time we observe an eastwards migration of the magmatic activity consistent with the hypothesis of a fixed mantle plume and an overall westward migration of the African plate.
Download or read book The Core Mantle Boundary Region written by Michael Gurnis and published by American Geophysical Union. This book was released on 1998-02-04 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: The two giant heat engines responsible for plate tectonics and the geodynamo dynamically interact at the core-mantle boundary of the Earth's interior. A multidisciplinary approach is required to determine the composition, structure, and dynamics of the interface. This volume describes original and fundamental research in seismology, geodynamics, mineral physics, and geomagnetism.
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:
