Reconstruction of ocean paleoproductivity and paleochemistry is paramount to understanding global biogeochemical cycles such as the carbon, oxygen and sulfur cycles and the responses of these cycles to changes in climate and tectonics. Paleo-reconstruction involves the application of various tracers that record seawater compositions, which in turn may be used to infer oceanic processes. Several important tracers are incorporated into pelagic barite, an authigenic mineral that forms in the water column. Here we summarize the utility of pelagic barite for the reconstruction of export production and as a recorder of seawater S, O, Sr, Ca and Ba.
Case Studies in Isotope Stratigraphy, Volume Four in the Advances in Sequence Stratigraphy series, covers current research across many stratigraphic disciplines, providing information on the most recent developments for the geoscientific research community. This fully commissioned review publication aims to foster and convey progress in stratigraphy, including geochronology, magnetostratigraphy, lithostratigraphy, event-stratigraphy, isotope stratigraphy, astrochronology, climatostratigraphy, seismic stratigraphy, biostratigraphy, ice core chronology, cyclostratigraphy, paleoceanography, sequence stratigraphy, and more. - Contains contributions from leading authorities in the field - Informs and updates on all the latest developments in the field - Aims to foster and convey progress in stratigraphy, including geochronology, magnetostratigraphy, lithostratigraphy, event-stratigraphy, and more
Volume 6 of Reviews in Mineralogy was originated from notes prepared for a short course on Marine Minerals held in La Jolla, California, November 2-3, 1979. Chapters in this volume are devoted to marine manganese oxide, iron oxide, silica polymorphs, zeolite, clay, phosphorite, barite, evaporite, and placer minerals. Carbonates are not included; coverage of this important mineral group warrants a separate monograph. The extremely interesting sulfide and hydrothermal mineral assemblages recently discovered at oceanic spreading centers are also not discussed here. Marine Minerals was first published in 1979 as Volume 6 of the series entitled Short course. In 1980 the Mineralogical Society of America changed the name of the series to Reviews in Mineralogy, and for that reason this, the second printing of Marine Minerals has been reissued under the new banner. Only minor corrections have been made.
Volume 40 of Reviews in Mineralogy and Geochemistry compiles and synthesizes current information on sulfate minerals from a variety of perspectives, including crystallography, geochemical properties, geological environments of formation, thermodynamic stability relations, kinetics of formation and dissolution, and environmental aspects. The first two chapters cover crystallography (Chapter 1) and spectroscopy (Chapter 2). Environments with alkali and alkaline earth sulfates are described in the next three chapters, on evaporites (Chapter 3), barite-celestine deposits (Chapter 4), and the kinetics of precipitation and dissolution of gypsum, barite, and celestine (Chapter 5). Acidic environments are the theme for the next four chapters, which cover soluble metal salts from sulfide oxidation (Chapter 6), iron and aluminum hydroxysulfates (Chapter 7), jarosites in hydrometallugy (Chapter 8), and alunite-jarosite crystallography, thermodynamics, and geochronology (Chapter 9). The next two chapters discuss thermodynamic modeling of sulfate systems from the perspectives of predicting sulfate-mineral solubilities in waters covering a wide range in composition and concentration (Chapter 10) and predicting interactions between sulfate solid solutions and aqueous solutions (Chapter 11). The concluding chapter on stable-isotope systematics (Chapter 12) discusses the utility of sulfate minerals in understanding the geological and geochemical processes in both high- and low-temperature environments, and in unraveling the past evolution of natural systems through paleoclimate studies. The review chapters in this volume were the basis for a short course on sulfate minerals sponsored by the Mineralogical Society of America (MSA) November 11-12, 2000 in Tahoe City, California, prior to the Annual Meeting of MSA, the Geological Society of America, and other associated societies in nearby Reno, Nevada. The conveners of the course (and editors of this volume of Reviews in Mineralogy and Geochemistry), Alpers, John Jambor, and Kirk Nordstrom, also organized related topical sessions at the GSA meeting on sulfate minerals in both hydrothermal and low-temperature environments.
In the modern marine environment, barium isotope (δ138Ba) variations are primarily driven by barite cycling—barite incorporates 'light' Ba isotopes from solution, rendering the residual Ba reservoir enriched in 'heavy' Ba isotopes by a complementary amount. Since the processes of barite precipitation and dissolution are vertically segregated and spatially heterogeneous, barite cycling drives systematic variations in the barium isotope composition of seawater and sediments. This Element examines these variations; evaluates their global, regional, local, and geological controls; and, explores how δ138Ba can be exploited to constrain the origin of enigmatic sedimentary sulfates and to study marine biogeochemistry over Earth's history.
Molybdenum (Mo) is a widely used trace metal for investigating redox conditions. However, unanswered questions remain that concentration and bulk isotopic analysis cannot specially answer. Improvements can be made by combining new geochemical techniques to traditional methods of Mo analysis. In this Element, we propose a refinement of Mo geochemistry within aquatic systems, ancient rocks, and modern sediments through molecular geochemistry (systematically combining concentration, isotope ratio, elemental mapping, and speciation analyses). Specifically, to intermediate sulfide concentrations governing Mo behavior below the 'switch-point' and dominant sequestration pathways in low oxygen conditions. The aim of this work is to 1) aid and improve the breadth of Mo paleoproxy interpretations by considering Mo speciation and 2) address outstanding research gaps concerning Mo systematics (cycling, partitioning, sequestration, etc.). The Mo paleoproxy has potential to solve ever complex research questions. By using molecular geochemical recommendations, improved Mo paleoproxy interpretations and reconstruction can be achieved.
Ancient iron formations - iron and silica-rich chemical sedimentary rocks that formed throughout the Precambrian eons - provide a significant part of the evidence for the modern scientific understanding of palaeoenvironmental conditions in Archaean (4.0–2.5 billion years ago) and Proterozoic (2.5–0.539 billion years ago) times. Despite controversies regarding their formation mechanisms, iron formations are a testament to the influence of the Precambrian biosphere on early ocean chemistry. As many iron formations are pure chemical sediments that reflect the composition of the waters from which they precipitated, they can also serve as nuanced geochemical archives for the study of ancient marine temperatures, redox states, and elemental cycling, if proper care is taken to understand their sedimentological context.
