Download or read book Trace Element Geochemistry of Oceanic Peridotites and Silicate Melt Inclusions written by Kevin Todd Michael Johnson and published by . This book was released on 1990 with total page 259 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mantle melting process is fundamental to basalt genesis and crustal accretion at mid-ocean ridges. It is believed that melts ascend more rapidly than the surrounding mantle, implying a process similar to fractional melting may be occurring, but geochemical evidence for this has been lacking. Furthermore, crustal accretion is thought to be episodic at slow spreading ridges, but sampling programs that can test this temporal variability are virtually nonexistent. This dissertation examines the trace element compositions of abyssal peridotites and discusses how they preserve details of the melting process that are not recognizable in mid-ocean ridge basalts. The results support fractional melting as the dominant melting process in the sub-ridge upper mantle. Evidence is also presented supporting non-steady state mantle melting at the Atlantis II Fracture Zone cutting the very slow spreading Southwest Indian Ridge. Trace element compositions of peridotite clinopyroxenes from fracture zones along the American-Antarctic and Southwest Indian Ridges vary as a function of proximity to hotspots. The results presented in Chapter 2 are consistent with higher degrees of melting and greater incompatible element depletion in the upper mantle near hotspots. All peridotites studied are consistent with being residues of fractional melting and inconsistent with batch melting. Some samples recovered near hotspots appear to have begun melting in the garnet stability field, deeper than samples recovered away from hotspots. Most samples show pronounced negative Zr and Ti anomalies, which increase with increasing incompatible element depletion (increased melting), on extended rare earth (spider) diagrams. The results of Chapter 2 indicated the importance of accurately knowing trace element partition coefficients between clinopyroxene and liquid. It was found that existing partitioning studies report either rare earth elements, Ti, or Zr, but not all elements together. Thus, there is ambiguity about relative partition coefficients for these elements. Accurate knowledge of partitioning is important in understanding the formation of negative Zr and Ti anomalies observed in peridotite clinopyroxenes as well as in constructing realistic melting models for peridotites. To that end, Chapter 3 reports the results of a clinopyroxene/basaltic liquid trace element partitioning study carried out on natural dredged basalts and experimental charges of mid-ocean ridge basalts. It was found that there are small negative anomalies in the partiton coefficients of Zr and Ti relative to adjacently plotted rare earth elements on spider diagrams. Fractional melting implies that small parcels of refractory (e.g., high Mg/[Mg+Fe]), incompatible element depleted melts must exist somewhere in the ascending body of melt. Since mixing, wall rock reaction, and fractional crystallization probably alter the compositions of silicate melts extensively on their way from source to surface, representatives of these refractory fractional melts will rarely be erupted as flows on the seafloor. However, some refractory silicate melt inclusions possess compositional characteristics akin to those expected in fractional melts, i.e. low incompatible element concentrations and fractionated trace element ratios. Chapter 4 is a study of refractory melt inclusions from a variety of tectonic settings. The inclusions were obtained from Dr. A.V. Sobolev of the Vernadsky Institute of Geochemistry, Soviet Academy of Sciences, Moscow. They are not ideally suited for studying mid-ocean ridge processes, as only a few of the inclusions are from this environment, but in general, the inclusions show more refractory, incompatible element depleted compositions than their host lavas. Furthermore, the suite of inclusions in different mineral phases contained in a single N-type mid-ocean ridge basalt show variable trace element characteristics indicating unrelated sources for some inclusions. The results of the study do not strongly endorse the fractional melting hypothesis, but some support is suggested by trace element depletions and fractionations warranting a more thorough study of a suite of inclusions. Finally, the along-ridge major and trace element variability in peridotites observed previously and in Chapter 2 is compared to the variability found in a single fracture zone. The high sampling density at the Atlantis IT Fracture Zone on the Southwest Indian Ridge, coupled with its great distance from a hotspot make it a good subject for a baseline study. It was found that the compositional variability observed in peridotites from the Atlantis II Fracture Zone covers nearly the whole range of compositions found along the AmericanAntarctic and Southwest Indian Ridges in Chapter 2. However, there are systematics to this wide range, suggesting different processes may control the depletions. On the eastern side of the transform, a compositional gradient is observed from the center of the eastern wall to the northern ridge-transform intersection. Peridotites on this side have become gradually more depleted in incompatible elements and modal clinopyroxene over at least the last 10-11 million years. Samples from the western side of the transform are, in general, more depleted than those from the eastern side and show some indication of a compositional gradient as well, although sampling is less dense. Basalts from the western side are clearly different in iron composition and degree of rare earth element fractionation. These differences are consistent with higher pressure, higher degrees of melting producing lavas on the western side. It is believed that the long wavelength chemical variations corresponding to hotspot proximity described in Chapter 2 result from regional thermal conditions in the upper mantle imposed, in large part, by the hotspots. On the other hand, the short wavelength variability on a fracture zone or spreading cell scale may result from episodic mantle upwelling and magma production due to non-steady state accretion at very slow spreading ridges.
Download or read book Mantle Xenoliths written by Peter H. Nixon and published by John Wiley & Sons. This book was released on 1987 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt: The eruption of deep-seated xenoliths in basaltic, alnoitic, kimberlitic, etc volcanoes provides the geologist with an important direct means of examining the fragments of the earth's mantle and lower crust.
Download or read book Trace Elements in Magmas written by Denis M. Shaw and published by Cambridge University Press. This book was released on 2006-03-09 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book brings together the essential theory required to understand the behaviour of trace elements in magmas and magma-derived rocks.
Download or read book Trace Elements in Igneous Petrology written by C.J. Allègre and published by Elsevier. This book was released on 2013-10-22 with total page 285 pages. Available in PDF, EPUB and Kindle. Book excerpt: Trace Elements in Igneous Petrology, 5: Developments in Petrology: A Volume in Memory of Paul W. Gast focuses on the contributions and influence of Gast in petrology, including crystallization, magmatic processes, isotopic composition, and ocean ridge basalt chemistry. The selection first takes a look at quantitative models of trace element behavior in magmatic processes; application of trace elements to the petrogenesis of igneous rocks of granitic composition; and an assessment of local and regional isotopic equilibrium in the mantle. Discussions focus on evidence derived from time constraints, scale of isotopic disequilibrium, fractional crystallization, trace element modeling, geodynamics and tectonic setting, partition coefficients, quantitative models for trace elements, and parameter determination and inverse-problem solution. The publication then examines the isotopic composition of lead in oceanic basalt and its implication to mantle evolution; strontium isotopes in basalts from the Pacific Ocean basin; and trace elements in ocean ridge basalts. Concerns cover variations in ocean ridge basalt chemistry, trace elements in ocean ridge basalts, disequilibrium partial melting, seawater alteration, background for lead isotope tracer studies, and uranium, thorium, and lead concentrations in basalts. The book examines trace elements and anorthosite genesis, lead isotopes in Archaean plutonic rocks, early Archaean rocks and geochemical evolution of the earth's crust, and factors controlling the noble gas abundance patterns of deep-sea basalts. The selection is a valuable source of data for researchers interested in petrology.
Download or read book The Mantle and Core written by R.W. Carlson and published by Elsevier. This book was released on 2005-11-22 with total page 609 pages. Available in PDF, EPUB and Kindle. Book excerpt: Though largely inaccessible, the geochemistry of Earth's mantle and core can be examined through a wide variety of approaches. Volume 2 focuses first on "remote" sensing using evidence from cosmochemical, seismic, petrologic and geochemical approaches. Mantle composition is then examined in detail through descriptions of mantle samples brought to Earth's surface through tectonic, volcanic, and volatile-outgassing processes. The volume concludes with examination of processes that modify the composition of the mantle and core including an early magma ocean, partial melting, element partitioning between minerals and melts, and physical mixing caused by plate subduction, mantle convection and mass exchange between mantle and core. Reprinted individual volume from the acclaimed Treatise on Geochemistry, (10 Volume Set, ISBN 0-08-043751-6, published in 2003) Comprehensive and authoritative scope and focus Reviews from renowned scientists across a range of subjects, providing both overviews and new data, supplemented by extensive bibliographies Extensive illustrations and examples from the field
Download or read book Treatise on Geochemistry The mantle and core written by Heinrich D. Holland and published by . This book was released on 2004 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt: Focuses first on remote sensing using evidence from cosmochemical, seismis, petrologic and geochemical approaches. Concludes with examination of processes that modify the composition of the mantle and core including an early magma ocean, partial melting, element partitioning between minerals and melts, etc.
Download or read book Using Geochemical Data written by Hugh Rollinson and published by Cambridge University Press. This book was released on 2021-05-06 with total page 359 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook is a complete rewrite, and expansion of Hugh Rollinson's highly successful 1993 book Using Geochemical Data: Evaluation, Presentation, Interpretation. Rollinson and Pease's new book covers the explosion in geochemical thinking over the past three decades, as new instruments and techniques have come online. It provides a comprehensive overview of how modern geochemical data are used in the understanding of geological and petrological processes. It covers major element, trace element, and radiogenic and stable isotope geochemistry. It explains the potential of many geochemical techniques, provides examples of their application, and emphasizes how to interpret the resulting data. Additional topics covered include the critical statistical analysis of geochemical data, current geochemical techniques, effective display of geochemical data, and the application of data in problem solving and identifying petrogenetic processes within a geological context. It will be invaluable for all graduate students, researchers, and professionals using geochemical techniques.
Download or read book Flow Over Finite Isolated Topography written by LuAnne Thompson and published by . This book was released on 1990 with total page 722 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Isotope Geochemistry of Abyssal Peridotites and Related Rocks written by Jonathan E. Snow and published by . This book was released on 1993 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation studies several aspects of the formation of the Earth's oceanic mantle and crust, using a variety of geologic techniques, principally major elements, radiogenic isotopes and trace elements, but including petrography, mineral chemistry, x-ray diffraction, seafloor geomorphology, and analysis of the tectonics of fracture zones. The first chapter is an introduction to the problems to be addressed in this work. The second chapter examines the composition of basalts erupted near the Atlantis II Fracture Zone on the Southwest Indian Ridge. Trends in major element compositions of those basalts can be related directly to the nearby presence of the fracture zone. The effects of mantle composition and crustal level lateral transport of magma in the rift system can be ruled out by the analysis of isotopes and the geomorphology of the fracture zone floor. This is the best demonstration to date of a transform fault effect on basalt compositions. In trying to quantify putative transform fault effects documented at other fracture zones, no systematic correlation of transform offset age with mantle temperature change can be found, suggesting that mantle composition and lateral transport phenomena play a larger than expected role in the evolution of those areas. The third chapter relates to oceanic mantle rocks as they are altered at or near the Earth's surface. The major elements which make up abyssal peridotites are extensively redistributed by the alteration they have undergone. Mg is shown to be extracted from the peridotites, and a variety of trace elements added. This elemental redistribution is taken as evidence for extensive Mg transport by circulating waters. Since the solubility of Mg-bearing minerals in hydrothermal solutions is quite limited, much lower temperatures and much higher water /rock ratios are required to explain the major element compositions of the peridotites than had previously been assumed. The behavior of the Nd, Sr and Os isotopic systems during seafloor alteration was also studied. The isotope systematics of these rocks strongly support the hypothesis of high water /rock ratios in the formation of serpentinized abyssal peridotites. Nonetheless, Nd and Sr reside in a phase which is resistant to alteration (clinopyroxene) and the concentration of Os is high relative to that of seawater, so that it too appears resistant to alteration. Primary mantle isotopic signatures may be obtained from abyssal peridotites by careful analysis, even of extremely weathered rocks. Radiogenic strontium in excess of what could be introduced by seawater contamination or in situ radiogenic growth in a reasonable period of time was also found. These observations confirm earlier work which had been discredited for many years. The only plausible mechanism for the formation of this "orphan" S7Sr is that it is introduced as part of a sedimentary component which infiltrates the rock during metamorphism and/ or weathering. The 87Sr may be contained by or sorbed onto extremely fine clay particulates, or colloidal suspensions, as opposed to the dissolved ionic Sr which is normally thought of as characterizing the Sr isotopic composition of seawater. The high water/rock ratios required by the bulk isotopic analysis, as well as the pervasive elemental redistribution arguing for extensive near-surface weathering at high water /rock ra.tios strongly support this hypothesis. Given pervasive percolation of water throughout the samples, sufficient radiogenic, sediment-derived strontium may be drawn deep into the crust in the course of its weathering to cause such high B7SrfB6Sr ratios. The fourth chapter deals exclusively with primary mantle isotopic information from abyssal peridotites. This is the first study which has attempted to relate the Os isotopic system in the oceanic mantle to other isotopic systems and to trace elements. It is possible, with some extreme assumptions, to model the range of Os isotopes in the oceanic mantle alone in a standard model of formation of the depleted mantle by extraction of the crust. The additional constraints provided by the study of Nd isotopes in depleted mantle rocks from the oceans show that partial melt extraction and the formation of a depleted reservoir alone are not sufficient to account for the range of both N d and Os isotopes in the Earth's mantle. Possible mechanisms for the decoupling of the Os and Nd isotopic systems include elemental fractionation via the porous flow of basalt through the mantle, mantle metasomatism, recycling of a subducted component in the mantle and core formation. The core extraction model is pursued in some detail. Such core extraction models can account for the distributions and isotopic compositions of compatible and incompatible trace elements in the Earth's mantle, but they are highly non-unique, and thus difficult to test
Download or read book Volcanism and Subduction written by John Eichelberger and published by John Wiley & Sons. This book was released on 2013-05-02 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 172 .The Kamchatka Peninsula and contiguous North Pacific Rim is among the most active regions in the world. Kamchatka itself contains 29 active volcanoes, 4 now in a state of semi-continuous eruption, and I has experienced 14 magnitude 7 or greater earthquakes since accurate recording began in 1962. At its heart is the uniquely acute subduction cusp where the Kamchatka and Aleutian Arcs and Emperor Seamount Chain meet. Volcanism and Subduction covers coupled magmatism and tectonics in this spectacular region, where the torn North Pacific slab dives into hot mantle. Senior Russian and American authors grapple with the dynamics of the cusp with perspectives from the west and east of it, respectively, while careful tephrostratigraphy yields a remarkably precise record of behavior of storied volcanoes such as Kliuchevskoi and Shiveluch. Towards the south, Japanese researchers elucidate subduction earthquake processes with unprecedented geodetic resolution. Looking eastward, new insights on caldera formation, monitoring, and magma ascent are presented for the Aleutians. This is one of the first books of its kind printed in the English language. Students and scientists beginning research in the region will find in this book a useful context and introduction to the region's scientific leaders. Others who wish to apply lessons learned in the North Pacific to their areas of interest will find the volume a valuable reference.
Download or read book Partitioning of Elements Between Silicate Melt and Salt Water at Mantle Conditions written by John C. Ayers and published by . This book was released on 1988 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Constraints on Mantle Melting from Major and Trace Element Systematics in Residual Abyssal Peridotites written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: AbstractThe generation of mid-ocean ridge basalts (MORB) is one of the most important mass transfer processes on Earth. Each year, more than twenty km3 of magmatic crust is produced along 75,000 km of ocean ridge, which is over ninety percent of the global magma production. Although ocean ridges and MORB are among the most studied geological features, several interlocking issues concerning melt generation at mid-ocean ridges are still not well understood. The most important of these are the role of geodynamic boundary conditions, such as spreading rate or vicinity to plumes and large transform offsets, as well as the absolute extent of melting or the depth at which melting initiates. This thesis examines these issues on the basis of mineral major and trace element compositions of oceanic mantle rocks. Geochemical characteristics of MORB suggest that melting begins in the stability field of garnet peridotite, at depths exceeding 80 km. Recent experiments, however, have shown that heavy rare earth elements (REE) are compatible in clinopyroxene (cpx) at the lherzolite solidus. This garnet-like partitioning behavior of cpx implies that garnet is no longer needed and that melting begins at significantly lower pressures. Therefore it is important to know, whether this hypothesis is consistent with compositional variations of abyssal peridotites. These fragments of the oceanic mantle are the residues of MORB melting and are now exposed on the ocean floor. Their mineral chemistry preserved the conditions at which melts were created in the mantle. Major and trace element data obtained by electron and ion microprobe on residual abyssal peridotite samples from the Central Indian Ridge (CIR) are compared to published data. Cpx in the CIR peridotites have very fractionated REE patterns, i.e. low Sm/Yb ratios, but high absolute Yb concentrations. Fractional melting models (which simulate the most extreme fractionation theoretically possible) of a spinel peridotite using commonly a.
Download or read book Subduction Zone Magmatism written by Yashiyuki Tatsumi and published by Wiley. This book was released on 1995-06-15 with total page 224 pages. Available in PDF, EPUB and Kindle. Book excerpt: Subduction zones are major sites of volcanism on the Earth. As one crustal plate sinks or is pushed beneath another, hot magma is produced and the resultant magma flux is fundamental to both the thermal evolution and chemical differentiation of the mantle and the Earth itself. To understand these evolutionary processes, we need to understand the physical and chemical consequences of all aspects of the subduction process. In this book, the authors present a simple, current and comprehensive model that explains the dominant geological processes at work in subduction zones. Structuring the book around the model, the authors describe the physical characteristics and geochemical dynamics of subduction zones, arc magma generation, and the dynamics and flow in the mantle. Students and researchers alike will find this book of immense value in understanding this most complex of subjects.
Download or read book Deep Carbon written by Beth N. Orcutt and published by Cambridge University Press. This book was released on 2019-10-17 with total page 687 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive guide to carbon inside Earth - its quantities, movements, forms, origins, changes over time and impact on planetary processes. This title is also available as Open Access on Cambridge Core.
Download or read book Abstracts of Manuscripts Submitted in 1989 for Publication written by and published by . This book was released on 1990 with total page 1086 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Treatise on Geochemistry written by and published by Newnes. This book was released on 2013-10-19 with total page 14787 pages. Available in PDF, EPUB and Kindle. Book excerpt: This extensively updated new edition of the widely acclaimed Treatise on Geochemistry has increased its coverage beyond the wide range of geochemical subject areas in the first edition, with five new volumes which include: the history of the atmosphere, geochemistry of mineral deposits, archaeology and anthropology, organic geochemistry and analytical geochemistry. In addition, the original Volume 1 on "Meteorites, Comets, and Planets" was expanded into two separate volumes dealing with meteorites and planets, respectively. These additions increased the number of volumes in the Treatise from 9 to 15 with the index/appendices volume remaining as the last volume (Volume 16). Each of the original volumes was scrutinized by the appropriate volume editors, with respect to necessary revisions as well as additions and deletions. As a result, 27% were republished without major changes, 66% were revised and 126 new chapters were added. In a many-faceted field such as Geochemistry, explaining and understanding how one sub-field relates to another is key. Instructors will find the complete overviews with extensive cross-referencing useful additions to their course packs and students will benefit from the contextual organization of the subject matter Six new volumes added and 66% updated from 1st edition. The Editors of this work have taken every measure to include the many suggestions received from readers and ensure comprehensiveness of coverage and added value in this 2nd edition The esteemed Board of Volume Editors and Editors-in-Chief worked cohesively to ensure a uniform and consistent approach to the content, which is an amazing accomplishment for a 15-volume work (16 volumes including index volume)!
Download or read book Readings from the Treatise on Geochemistry written by Heinrich D Holland and published by Academic Press. This book was released on 2010-05-25 with total page 681 pages. Available in PDF, EPUB and Kindle. Book excerpt: Readings from the Treatise on Geochemistry offers an interdisciplinary reference for scientists, researchers and upper undergraduate and graduate level geochemistry students that is more affordable than the full Treatise. For professionals, this volume will provide an overview of the field as a whole. For students, it will provide more in-depth introductory content than is found in broad-based geochemistry textbooks. Articles were selected from chapters across all volumes of the full Treatise, and include: The Origin and Earliest History of the Earth, Compositional Evolution of the Mantle, Evolution of Sedimentary Rocks, Soil Formation, Geochemistry of Groundwater, Geologic History of Seawater, Hydrothermal Processes, and Biogeochemistry of Primary Production in the Sea. Comprehensive, interdisciplinary and authoritative content selected by leading subject experts Robust illustrations, figures and tables Affordably priced sampling of content from the full Treatise on Geochemistry
