No description available.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. Johannesburg, December, 2013. / The Palaeoproterozoic southern Goren volcano-sedimentary belt of northeast Burkina Faso represents a sequence/package of rocks formed in a back-arc basin environment. Evidence is based on a conformable sequence of basalts that have geochemical affinities of normal mid-oceanic ridge style basalts (N-MORB) as well as arc-related magmas. Tholeiitic compositions, determined by major and trace element geochemistry, are exclusive to the study area, which is unique to northeast Burkina Faso. Flat, chondrite-normalised REE patterns suggest dominantly N-MORB compositions, with the occasional elevated Th and Al2O3 values, suggestive of arc basalts. Depleted chondrite-normalised concentrations of phosphorus (0.5-0.03 times lower than chondrite) and Ti (1-5 times chondrite) as well as anomalous concentrations of N-MORB-normalised Ta (80-120 times greater) are characteristic of the tholeiitic basalts of the Goren belt. The volcanic rocks are intercalated with a succession of volcanogenic manganese deposits, siltstone, volcaniclastite, volcanogenic greywacke and a discrete pyroclastic breccia deposit composed of lapilli- to bomb-sized volcanic debris, indicative of bimodal volcanism. The volcanic facies were established through field and petrographic interpretations. The subaqueous facies architecture consists of proximal, coherent and autoclastic basaltic flow units containing porphyritic, aphyric, amygdaloidal and hyaloclastic textures as well as pillowed, jointed and flow-banded basaltic lithofacies. Proximal to distal volcanogenic manganese deposits intercalated with basalt flows indicate a syn-volcanic genesis. A discrete pyroclastic interbed (~300 m thick) within a volcanogenic, marginal marine to offshore greywacke succession occupies a distal facies relative to the volcanic source and indicates a bimodal source of volcanism, i.e., mafic and intermediate. Volcanogenic manganese deposits are characterized by quartz-ankerite stockwork breccia, a braunite-ilmenite-magnetite-chalcopyrite-pyrite-(gold) mineral assemblage and increased Ba concentrations, indicating syn-volcanic seafloor-related hydrothermal activity. The Goren volcano-sedimentary belt presents potential for economic mineralisation in volcanogenic primary manganese and base metal deposits.

Mineralogical and geochemical effects of alteration were studied in three early Mesozoic diabase/host-rock systems: (1) the Rocky Ridge dike and aureole, Gettysburg basin, Maryland; (2) the West Gainesville and Nokesville diabase sheets and subjacent host rocks, Culpeper basin, Virginia; and (3) the East Gainesville diabase sheet and associated host rocks, Culpeper basin, Virginia. The Rocky Ridge diabase is relatively unaltered and its thermal aureole formed under predominately isochemical conditions. The West Gainesville/Nokesville system exhibits apparent isovolumetric, complementary exchange of volatiles and alkalis(?) from the host rocks with Si, Al, Fe(?), Mn, Mg, Ca, Co and V(?) from the diabase sheet. Mass-balance calculations for this system indicate that, except for loss of Si and gain of volatiles and perhaps alkalis, it behaved isochemically. The East Gainesville diabase sheet is characterized by multiple injection of two magma types from different mantle sources. Alteration in this system is more complex and aureole temperatures were lower than those in the West Gainesville/Nokesville system. / Observed mineral reactions in the diabase are consistent with relative mobilities; the dominant mechanisms for this mass transfer are apparently infiltration metasomatism and intergranular diffusion. Relative mobilities of cations can be correlated with ionic radius. Rare-earth elements and Zr were immobile with respect to the diabase sheets, but Ti, commonly used to distinguish magma types in these and other mafic rocks, was not. In all studies Si, Al, Fe, Ca, and V were lost from the diabase during metasomatism, whereas volatiles, Rb and K were gained. / Source: Dissertation Abstracts International, Volume: 55-04, Section: B, page: 1344. / Director: Paul C. Ragland. / Thesis (Ph.D.)--The Florida State University, 1994.

Investigation of metasedimentary and metaigneous units of the northern Alabama Piedmont has revealed the following evidence: (1) stratigraphic continuity exists between previously uncorrelated lithotectonic blocks, (2) petrogenesis of synmetamorphic Rockford-type granite was controlled by the anatectic melting of metasedimentary units of greywacke composition producing S-type geochemical signatures, (3) estimates of pressure and temperature from metamorphic mineral assemblages yield Barrovian-type geothermal gradient terminated by a subsequent near-isothermal decompression event producing a clockwise P-T-time path in P-T space, and (4) estimates of the fluid composition in equilibrium with mineral assemblages of metasedimentary compositions indicate a metamorphic fluid composed of 0.90 H$\sb2$O, and 0.05 CO$\sb2$ and CH$\sb4,$ with the other fluid phases CO, COH, S$\sb2,$ O$\sb2,$ S$\sb8,$ H$\sb2$S being present in trace quantities. Metamorphic total fluid pressure was essentially equivalent to lithostatic pressure during peak metamorphic conditions (P$\sb{\rm T}$ = P$\sb{\rm F}).$ / Analysis of micro-, meso- and megascopic structural relationships has revealed 5 phases of deformation. Previous investigations have established the internal stratigraphy of structural blocks composing the northern Alabama Piedmont. This study identifies the conformable relationships between stratigraphy of the Coosa and Tallapoosa blocks. Because of thermal and structural correlation across the eastern-western Blue Ridge boundary (Hollins Line fault), the Ashland-Wedowee belt may have been proximal to the North American margin prior to the Acadian dynamothermal events. / Source: Dissertation Abstracts International, Volume: 53-09, Section: B, page: 4552. / Major Professor: James F. Tull. / Thesis (Ph.D.)--The Florida State University, 1992.

The Greenland Ice Sheet (GrIS) is melting at an alarming rate. Supraglacial melt water flows into moulins that drain to the base of the ice sheet, and enhances basal flow. Ultimately, large quantities of melt water are expelled into the ocean contributing to rising sea level, as well as nutrient fertilization of the North Atlantic Ocean. The presence of residual melt water in a warm-based polythermal glacier creates conditions for chemical weathering of the subglacial till which is expected to lead to a higher dissolved load in the basal melt water. Supraglacial melt arriving during the start of the melting season flushes out the basal melt water. Despite this important window, little work has been done to measure trace element concentrations in the early melt season. To examine the effect of supraglacial melt water input on the chemistry of basal melt waters, we performed a time series of supraglacial and proglacial sampling collected daily for four weeks at the start of the melt season in 2016 in southwest Greenland following GEOTRACES trace element-clean protocols. Briefly, glacial melt water samples were vacuum-filtered through 0.45 um acid-washed Supor filters under Class-10 HEPA-filtered laminar air flow and analyzed for major and trace element concentrations by High Resolution Inductively Coupled Plasma Mass Spectrometry (HR-ICP-MS). The daily sampling regime captured trace element concentrations throughout the first seasonal pulse of melt water discharge. Concentrations of a variety of trace elements, including Ba, Mg, Mn, and Sr, closely followed the melt water discharge pulse, increasing in concentration during the main pulse event (which lasted <5 days). The abundances of REEs and Fe exhibited no discernable temporal relationship, however Fe concentrations fell between 15-120 ppb, below a recent study implying that the melting GrIS is a significant source of bioavailable Fe. Also notable is that toxic metals never exceeded EPA primary and secondary drinking water quality standards, even during the pulse peak, demonstrating the potential of seasonal glacial melt waters as viable sources of drinking water. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the Master of Science. / Summer Semester 2017. / July 19, 2017. / Chemistry, Greenland, Pulse, Seasonal, Water, Weathering / Includes bibliographical references. / Munir Humayun, Professor Co-Directing Thesis; Peter Morton, Professor Co-Directing Thesis; Vincent Salters, Committee Member; Robert Spencer, Committee Member.

El Valle is the easternmost volcano in the Central American Volcanic Arc, and is characterized by two periods of volcanic activity, an Old Group from 10-5 Ma and a Young Group from 3-0.03 Ma. Both the Old and Young Group’s are calc-alkaline in nature. However, the Old Group is dominantly andesitic, has flat REE patterns, low Sr-Y ratios and contains plagioclase and pyroxene phenocrysts. A subgroup of the older samples also contains biotite. In contrast, the younger group is dominantly dacitic, hornblende-bearing, has low HREE content, high Sr/Y ratios and overall exhibits adakitic characteristics. The transition between the two geochemical groups occurs gradually between 10-3 Ma, at which point the adakitic signature is fully developed. The modern El Valle volcanic edifice is dominated by voluminous Young Group eruptive products (e.g. the El Hato Ignimbrite) with adakitic-like characteristics. El Valle is also characterized by a large 40-50 mGal negative Bouguer Gravity anomaly that is apparent in both surficial and satellite gravity measurements. Initial surficial data indicates Bouguer anomalies vary from 40 mGal at the edge of the volcano to -10 mGal in its central caldera. Field lithologic observations paired with the gravity measurements and modeling suggest that the negative gravity anomaly is primarily due to a low-density batholith beneath the volcano. Samples collected during the gravity survey where geochemically analyzed to distinguish between the various proposed petrogenetic/tectonic models in southern Panamá (e.g. the existence of a slab window, oblique subduction, slab-melting or subduction erosion of Galapagos material). One significant quandary is that geochemical evidence suggests the existence of subduction whereas geophysical data shows a lack of a pronounced Benioff Zone. Modeling suggest that the geochemical signatures can be reproduced via the partial melting of Cretaceous-Early Tertiary lower crustal arc rocks. / A Thesis submitted to the Department of Earth, Ocean, and Atmospheric Science in partial fulfillment of the requirements for the degree of Master of Science. / Spring Semester 2018. / March 8, 2018. / Geochemistry, Geophysics, Modeling, Volcanology / Includes bibliographical references. / James F. Tull, Professor Co-Directing Thesis; David W. Farris, Professor Co-Directing Thesis; Vincent J. M. Salters, Committee Member; Leroy Odom, Committee Member.

Solid state $\sp{13}$C NMR, Inverse Gas Chromatography and elemental analysis have been used to study the early diagenesis of organic matter of peat deposits from the Florida Everglades and to develop correlations between the structure of the organic matter and its affinity for non-polar organic compounds. / The structure of the sedimentary organic matter and its fraction was studied by solid state $\sp{13}$C NMR cross polarization and dipolar dephasing NMR experiments. The changes in the different polar, aliphatic and aromatic groups are used to discern the different chemical pathways that operate during early diagenesis. In addition, the degree of substitution of the aromatic structures of the sediments, and the effect of acid dissolution of minerals on the structure of sedimentary organic matter were studied. NMR methodology to provide reliable information about the functional group distributions of sedimentary organic matter as well as the various factors that affect the reliability of the NMR measurements are also discussed. / $\sp{13}$C NMR and elemental analysis of the sediments indicate that the carbohydrate is selectively degraded while aromatic structures were preserved. The structure of the organic matter becomes more reduced and crosslinked with age. / IGC was used to evaluate relative affinity of these peats and their fractions for a number of selected non-ionic organic compounds. The different fractions of the organic matter were used as stationary phases and non-ionic organic compounds are used as chromatographic probes. Their elution patterns and retention volumes were used to calculate activity coefficients. The relative affinity of the sedimentary organic matter and its fractions as a function of their chemical composition and origin was then investigated as well as the role of the different fractions of the organic matter in the total sorption process. Experimental results indicate that the lipid fraction plays a dominant role in the sorption process and that the affinity of intact sediments, humin and humic acid fractions is dominated by their relative distribution of polar, aliphatic and aromatic groups. Sorption-structure response surfaces were used to express the relationships between polarity and affinity in these organic sediments. / Source: Dissertation Abstracts International, Volume: 51-01, Section: B, page: 0110. / Major Professor: William Theophilus Cooper, III. / Thesis (Ph.D.)--The Florida State University, 1989.

The solution speciation and solid-phase suspended particulate fractionation of the trace metals Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb were investigated in the Black Sea, the world's largest anoxic basin. Sequential filtration/ion-exchange and selective leaching techniques were developed for the determination of dissolved and solid-phase trace metal fractionation. Field measurements were compared with the results of a thermodynamic equilibrium model. The transition metals (Mn, Fe, and Co) were controlled by changes in redox state across the oxic/suboxic/anoxic boundary and by metal-sulfide precipitation in the anoxic deep waters. Dissolved transition metal concentrations were low in the surface waters, increased to maxima in the upper anoxic zone, then decreased again into the deep waters. Dissolved Mn and Fe approached saturation with respect to MnS$\sb2$ (haurite) and to FeS (mackinawite) or Fe$\sb3$S$\sb4$ (greigite) in the deep waters. Dissolved Co was best explained in terms of a scavenging/regeneration cycle with Mn-oxyhydroxides across the sulfide interface and coprecipitation of Co with Fe-sulfides in the deep waters. Dissolved Ni was nearly constant with depth. / The Class B metals (Cu, Zn, Cd, and Pb) were high in the surface waters and decreased rapidly across the sulfide interface, consistent with metal-sulfide precipitation below the interface. The dissolved metal fractionation was dominated in the oxic zone by "free" metal species, shifting to dissolved metal-sulfide complexes below the interface. / With the exceptions of Al and Fe, the suspended matter trace metal fractionation was dominated by weak-acid soluble forms. Strong-acid leachable forms, probably metal-sulfide phases, were important in the deep waters for Mn, Fe, and Co. / Source: Dissertation Abstracts International, Volume: 52-02, Section: B, page: 0705. / Major Professor: William M. Landing. / Thesis (Ph.D.)--The Florida State University, 1990.

No description available.

Measurements of radiogenic isotopes can in principle constrain the melting, melt migration, and solid state convection that occurs in the Earth's mantle, but to do so requires suitable quantitative models. A new statistical model is introduced to better understand the observed heterogeneity in isotopic ratios 143Nd/144Nd, 87Sr/86Sr, 176Hf/177Hf,208Pb/204Pb, 206Pb/204Pb and 207Pb/204Pb measured on mid-ocean ridge basalt. The model is highly idealised, analytically tractable, and contains the essential physical processes involved: radioactive decay, the stirring and recycling of mantle convection, partial melting, and the mixing of melts. Comparison of the modelled heterogeneity with that observed constrains model parameters, which in turn constrains aspects of mantle convection and melting. The model provides a new interpretation of the 2.0 Ga lead-lead pseudo-isochron age in terms of an age distribution of mantle material. Simple equations relate the pseudo-isochron age to the rate of melting and decay constants. These equations are different from, but related to and more general than, those found previously for standard geochemical box models. The results are in good agreement with numerical simulations of mantle convection. The 2.0 Ga pseudo-isochron age is shown to infer a 0.5 Ga average time scale for melting of mantle material. Geochemical and geological evidence suggests that melt travels to the surface via a network of channels under the ridge. Motivated by this, the fluid dynamical problem of a open melt conduit surrounded by a deformable porous medium is studied. Previous work has shown that the conduit supports solitary waves of elevation, with a region of trapped melt travelling with the wave. The new analysis comes to a different conclusion, showing that the solitary wave is instead one of depression, without a region of trapped melt.