Download or read book Hydrogen and Oxygen Isotope Fractionation in Hydrous Minerals as Indicators of Fluid Source in Modern and Fossil Metasomatic Environments written by Emily Catherine Pope and published by Stanford University. This book was released on 2011 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxygen and hydrogen isotope properties of hydrous silicate minerals formed by weathering, hydrothermal, metamorphic and igneous processes provide a record of fluid-rock interaction. We utilize this isotopic record to 1) determine the source of geothermal fluids in two active geothermal systems in Iceland, and to evaluate the consequences of fluid-rock interaction on host rock, fluid and magma chemistry, and 2) to better characterize Earth's surface environments during the early Archaean. Geothermal systems within the active volcanic zone of Iceland provide a unique natural laboratory for studying fluid-rock interaction in magma-hydrothermal systems where the Mid-Atlantic ridge emerges onto land. The fluids of the Reykjanes geothermal system in southwest Iceland are derived from hydrothermally modified seawater. The anomalously low hydrogen isotope composition of these fluids is not due to mixing with local meteoric fluids, as previously supposed, but to diffusional exchange with relict hydrous alteration minerals, such as epidote, which retain an isotopic signature of glacially derived Ice Age fluids that existed early in the evolution of the geothermal system. In contrast, the meteoric-water dominated Krafla geothermal system, in northeast Iceland, displays wide isotopic heterogeneities in modern geothermal fluids and hydrothermal epidote that reflects a complex fluid evolution involving boiling, condensation and contamination by magmatic volatiles. A silicic melt that intruded the Iceland Deep Drilling Project drillhole IDDP-1 within the Krafla geothermal system appears to be largely derived from partial melting of hydrothermal alteration minerals, given the almost identical hydrogen isotope composition of glass sampled from drill cuttings and hydrothermal epidote. The oxygen isotope values of the rhyolite glass show the characteristically low-[lowercase Delta]18O values typical of Icelandic lavas, and result from mixing of a dominant mantle-derived basalt source and a lesser contribution of lighter oxygen from the incongruent melting of hydrothermally altered basalts within the Krafla caldera. The oxygen and hydrogen isotope characteristics of metamorphic fluids recorded in alteration minerals have applications to fossil metasomatic systems as well as modern ones. Serpentinites from the [greater than or equal to] 3.8 Ga Isua Supracrustal Belt (ISB) of West Greenland locally preserve isotope characteristics of their original formation by seawater alteration of ocean crust and suggest that the early Archaean oceans had oxygen isotopes comparable to modern day seawater, but a hydrogen isotope composition that is lower than modern seawater by 25 ± 5%. The hydrogen isotopes of Archaean oceans places mass balance constraints on the extent of hydrogen escape before the rise of atmospheric oxygen ~2.5 Ga, and by extension the maximum atmospheric methane levels during the early Archaean. The oxygen isotope composition predicted by these serpentinites suggests that the ocean was isotopically buffered by hydrothermal interaction with ocean crust by 3.8 Ga. Finally, chromian muscovite-quartz-carbonate veins in the ISB have oxygen and hydrogen stable isotope, elemental and mineralogical characteristics that are genetically similar to orogenic gold deposits in the fore-arc regions of Phanerozoic accretionary margins. We show that in both modern orogens and in the supracrustal sequence at Isua, these veins are the result of seawater-derived fluids liberated from subducting lithosphere interacting with ultramafic rocks in the mantle wedge and lower crust, before migrating up crustal-scale vertical fracture zones. The presence of these veins in the ISB and other Archaean-age deposits indicates that plate tectonic processes comparable to modern-day subduction existed as early as 3.8 Ga.
Download or read book Hydrogen and Oxygen Isotope Fractionation in Hydrous Minerals as Indicators of Fluid Source in Modern and Fossil Metasomatic Environments written by Emily Catherine Pope and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Oxygen and hydrogen isotope properties of hydrous silicate minerals formed by weathering, hydrothermal, metamorphic and igneous processes provide a record of fluid-rock interaction. We utilize this isotopic record to 1) determine the source of geothermal fluids in two active geothermal systems in Iceland, and to evaluate the consequences of fluid-rock interaction on host rock, fluid and magma chemistry, and 2) to better characterize Earth's surface environments during the early Archaean. Geothermal systems within the active volcanic zone of Iceland provide a unique natural laboratory for studying fluid-rock interaction in magma-hydrothermal systems where the Mid-Atlantic ridge emerges onto land. The fluids of the Reykjanes geothermal system in southwest Iceland are derived from hydrothermally modified seawater. The anomalously low hydrogen isotope composition of these fluids is not due to mixing with local meteoric fluids, as previously supposed, but to diffusional exchange with relict hydrous alteration minerals, such as epidote, which retain an isotopic signature of glacially derived Ice Age fluids that existed early in the evolution of the geothermal system. In contrast, the meteoric-water dominated Krafla geothermal system, in northeast Iceland, displays wide isotopic heterogeneities in modern geothermal fluids and hydrothermal epidote that reflects a complex fluid evolution involving boiling, condensation and contamination by magmatic volatiles. A silicic melt that intruded the Iceland Deep Drilling Project drillhole IDDP-1 within the Krafla geothermal system appears to be largely derived from partial melting of hydrothermal alteration minerals, given the almost identical hydrogen isotope composition of glass sampled from drill cuttings and hydrothermal epidote. The oxygen isotope values of the rhyolite glass show the characteristically low-[lowercase Delta]18O values typical of Icelandic lavas, and result from mixing of a dominant mantle-derived basalt source and a lesser contribution of lighter oxygen from the incongruent melting of hydrothermally altered basalts within the Krafla caldera. The oxygen and hydrogen isotope characteristics of metamorphic fluids recorded in alteration minerals have applications to fossil metasomatic systems as well as modern ones. Serpentinites from the [greater than or equal to] 3.8 Ga Isua Supracrustal Belt (ISB) of West Greenland locally preserve isotope characteristics of their original formation by seawater alteration of ocean crust and suggest that the early Archaean oceans had oxygen isotopes comparable to modern day seawater, but a hydrogen isotope composition that is lower than modern seawater by 25 ± 5%. The hydrogen isotopes of Archaean oceans places mass balance constraints on the extent of hydrogen escape before the rise of atmospheric oxygen ~2.5 Ga, and by extension the maximum atmospheric methane levels during the early Archaean. The oxygen isotope composition predicted by these serpentinites suggests that the ocean was isotopically buffered by hydrothermal interaction with ocean crust by 3.8 Ga. Finally, chromian muscovite-quartz-carbonate veins in the ISB have oxygen and hydrogen stable isotope, elemental and mineralogical characteristics that are genetically similar to orogenic gold deposits in the fore-arc regions of Phanerozoic accretionary margins. We show that in both modern orogens and in the supracrustal sequence at Isua, these veins are the result of seawater-derived fluids liberated from subducting lithosphere interacting with ultramafic rocks in the mantle wedge and lower crust, before migrating up crustal-scale vertical fracture zones. The presence of these veins in the ISB and other Archaean-age deposits indicates that plate tectonic processes comparable to modern-day subduction existed as early as 3.8 Ga.
Download or read book Analysis of Hydrogen Isotope Ratios by SIMS and Application to Determining Mineral fluid Isotope Fractionation Factors written by and published by . This book was released on 1997 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the large mass difference between the two isotopes, D/H ratios can be strongly affected by chemical processes. Thus, they can be sensitive monitors of fluid source, temperature, and fluid-rock interactions in geologic settings. The lack of confidence in fractionation factors has significantly hindered realization of the potential of D/H ratios in geochemical studies. The authors describe a new experimental method, relying on SIMS analysis, that allows the precise determination of mineral-water D/H fractionation factors, and the analytical considerations that are required to make both precise and accurate measurements. The development of this method is based on the fact that diffusion rates are markedly anisotropic in many hydrous minerals, varying by over five orders of magnitude depending on the crystallographic orientation. The diffusion rates can be determined by conducting controlled exchange experiments of fixed duration using isotopically labeled waters that are enriched (strongly) with D, and then measuring the depth profile by SIMS.
Download or read book Oxygen and Hydrogen Isotope Ratios in Sedimentary Rocks and Minerals written by Samuel Marvin Savin and published by . This book was released on 1967 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Stable Oxygen Hydrogen and Carbon Isotope Fractionation of Gases and Minerals in Geology written by Mark Schmidt and published by . This book was released on 2005 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stable Isotopes and Fluid Processes in Mineralization written by and published by . This book was released on 1990 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oxygen and Hydrogen Isotopic Fractionation Factors Determined in Experimental Clay water Systems written by Jean Bryna Kulla and published by . This book was released on 1984 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oxygen Isotope Fractionation Studies in Mineral Systems written by James R. O'Neil and published by . This book was released on 1963 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fluid Pathways in the Subducting Crust Insights from Oxygen Isotope Records in Metamorphic Minerals written by Alice Vho and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Role of Hydrous Minerals in Determining Trace Element and Isotope Geochemistry at Subduction Zones written by Maureen Diana Feineman and published by . This book was released on 2004 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Environmental Isotopes in the Hydrosphere written by Vasiliĭ Ivanovich Ferronskiĭ and published by . This book was released on 1982 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oxygen Isotope Fractionation in Monazite and Zircon written by Allistair L. Sessions and published by . This book was released on 1996 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Oxygen Isotope Fractionation Between Rutile and Water written by Sunit K. Addy and published by . This book was released on 1974 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Possible Evidence for Fluid rock Oxygen Isotope Disequilibrium in Hydrothermal Systems written by and published by . This book was released on 1992 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is ample evidence from geothermal systems that isotope temperatures estimated from the oxygen isotope fractionation between alteration phases and coexisting aquifer fluids agree closely with measured bore-hole temperatures. Similar, but limited evidence is found in epithermal vein deposits where isotopes temperature agree well with fluid inclusion homogenization temperature. Conversely, many hydrothermal systems exhibit varying degrees of fluid-rock oxygen isotope equilibration. There appears to be a crude relationship between increasing degree of equilibrium and increasing temperature and salinity. The observed variations in the degree of exchange may have resulted from local, self-sealing of the fracture network prior to equilibration. The ability for fracture to remain open or to propogate allowing continued fluid flow may be the deciding factor in the attainment of isotopic equilibration.
Download or read book Radiolytic fractionation of the hydrogen and oxygen isotopes of water in the earth s crust written by I. F. Vovk and published by . This book was released on 1982 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Evaluation of the Effectiveness of Hydrogen and Oxygen Isotopes Used in Concert with Chemical Water quality Parameters as Indicators of Subsurface Water Movement and Source written by Timothy W. Thurnblad and published by . This book was released on 1982 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:
