This study presents mineralogic and stable isotopic records generated for piston cores and Ocean Drilling Program holes recovered from intermediate water depths (500 to 2500 meters) near carbonate platforms around the world. Study areas included the Bahamas (western North Atlantic Ocean), the Nicaragua Rise (Caribbean Sea), the Maldives (north equatorial Indian Ocean), and the Queensland Plateau (southwest Pacific Ocean). Mineralogic data includes percent fine aragonite content, percent fine Mg calcite content, pteropod (aragonitic holoplanktonic gastropods) abundance, percent whole pteropods, and for some cores, percent clear pteropods. Carbonate data were interpreted both in terms of carbonate input from the nearby banks and in terms of seafloor dissolution. Planktic foraminiferal $\delta\sp{18}$O records were used as the primary chronostratigraphic tool for all sites. Statistical analyses of four metastable CaCO$\sb3$ dissolution proxies yielded a composite dissolution index (CDI) that displays different dissolution histories for Bahama and Nicaragua Rise sediments over the last 200,000 years. These differences are not predicted by intermediate to deep water nutrient fractionation models (e.g., Boyle, 1988). A good correlation is observed between the Caribbean CDI record (this study) and CaCO$\sb3$ dissolution and benthic $\delta\sp{13}$C records from 4641 meters in the Venezuela Basin, Caribbean Sea (Cofer-Shabica, 1987). It is concluded that during the last 200,000 years, variable cross-equatorial flux of Antarctic Intermediate Water has strongly influenced Caribbean carbon chemistry at water depths greater than 1100 meters. The assumption, therefore, that deep Caribbean sediment cores reliably record nutrient and (CO$\sb3\sp{=}$) variations of average mid-depth Atlantic water may need re-evaluation. Over longer time scales, CaCO$\sb3$ dissolution records from intermediate water depths near the Bahamas, Maldives, and Queensland Plateau are similar to deep-water dissolution records. Dissolution occurred from thermocline to abyssal depths from 500,000 to 300,000 years ago (during the middle Brunhes Chron) and between 1,000,000 and 900,000 years ago revealing that whole-ocean changes in carbonate chemistry have occurred during the Quaternary. Enhanced CaCO$\sb3$ dissolution may be related to decreased Ca$\sp{2+}$ flux to the ocean (decreased glacial weathering) and increased neritic CaCO$\sb3$ production and accumulation during periods of elevated interglacial sea-level highstands.

Thermodynamics of mixing for solids and liquids in the anhydrous apatite system Ca$\sb3$(PO$\sb4)\sb2$ - CaF$\sb2$ - Ca(OH)$\sb2$ - CaCl$\sb2$ are quantified using mathematical modeling of new and existing experimental data. These data apply to apatite experiments or to understanding natural apatites. Fluorapatites (FAp) are hexagonal, although hydroxyapatite and chlorapatite (ClAp) are monoclinic. Although the monoclinic and hexagonal endmembers are believed to be immiscible, no evidence of immiscibility exists. Miscibility is achieved by movement of the anions away from the sites occupied in the end member and by expansion of the apatite lattice. Anion-anion interaction and lattice deformation may lead to possible nonideal mixing of the endmembers. Thermodynamic treatment of experimental data gathered above 475$\sp\circ$C shows that apatite solid solutions may be considered ideal. Standard state data for chlorapatite are derived. Thermodynamic modeling of the molten mixtures uses a stoichiometric approach with Ca$\sb{1.5}$PO$\sb4$ and Ca$\sb{0.5}$X (X = F, OH, Cl) liquid phase components. New data are presented for joins Ca(OH)$\sb2$ - CaCl$\sb2$ and CaF$\sb2$ - Ca(OH)$\sb2$. Molten mixtures on the join CaF$\sb2$ - CaCl$\sb2$ are ideal. Ca(OH)$\sb2$ - CaCl$\sb2$ and CaF$\sb2$ - Ca(OH)$\sb2$ molten mixtures show positive enthalpies of mixing typical of common cation-mixed anion systems. The phosphate-salt joins show small positive entropies of mixing due to formation of polymeric species in the phosphate melt not explicitly considered in the model. Heats of fusion for solids and standard state data for the liquid phase components, CaClF, CaOHCl and Ca$\sb2$PO$\sb4$Cl are derived. The apatite thermodynamic data are applied to existing data for the Bishop Tuff (BT) and new data for the Fish Canyon Tuff (FCT). Results show that both magmas were saturated with a fluid phase prior to eruption, in agreement with earlier studies. Apatite inclusions in FCT phenocrysts preserve the pressure- temperature path of the magma, requiring a higher pressure for plagioclase crystallization than for hornblendes. Similar treatment of the BT shows that the pressure paradox observed by earlier workers is also found in the apatite chemistry. Applications are limited currently by analytical problems, but the ratio of X$\sb{\rm FAp}$/X$\sb{\rm ClAp}$ is probably accurate.

Metasedimentary and metabasaltic rocks of the Pelona schist of Sierra Pelona, southern California, preserve a relatively high P/T inverted metamorphic gradient (Graham and Powell, 1984) and provide an opportunity to study possible compositional changes in an oceanic slab progressively metamorphosed under P-T conditions similar to those in shallow parts of some subduction zones. Progressive metamorphism resulted in continuous major element compositional change in plagioclase, white mica, amphibole, and epidote. Variations in whole-rock compositions do not correlate with increasing metamorphic grade and largely appear to reflect protolith heterogeneity. Loss of H$\sb2$O-rich fluid during chlorite breakdown reactions largely accounts for the decrease in weight percent LOI and H content with increasing metamorphic grade. Comparison with unmetamorphosed equivalents and lower temperature, high-pressure metamorphic rocks (including metabasaltic samples from the Shuksan schist and the Franciscan Complex) suggest that As and Sb may be lost from metasedimentary rocks and that B may be lost from metabasaltic rocks at temperatures less than 450$\sp\circ$C. Trace element analyses obtained by ion microprobe for minerals in the Pelona, Catalina, and Shuksan schists document the mineral residencies of trace elements and the redistribution of trace elements among minerals as modal abundances vary. Boron, Ba, Li, Rb, and Cs are strongly concentrated in micas. In samples with coexisting white mica and biotite, higher concentrations of B, Ba, and Sr are observed in white mica, relative to Li, Rb, and Cs, which preferentially substitute into biotite. Cesium and Rb partition in a relatively constant ratio between white mica and biotite. Strontium is strongly concentrated in epidote, but is increasingly incorporated into white mica and plagioclase as the modal abundance of epidote decreases and as plagioclase compositions become more calcic. Similarly, Li appears to be repartitioned into amphibole as chlorite decreases in modal abundance. These observations support a model of gradual release of fluid-mobile trace elements during progressive metamorphism (as from subducted slabs). Prograde continuous reactions involving mica may particularly control the mobility of alkali and alkaline earth elements enriched in arc magmas and provide a mechanism for fractionating incompatible element ratios (e.g. B/Cs) during subduction zone metamorphism.

The Caribbean carbonate crash was a time of increased regional carbonate dissolution at the middle to late Miocene transition. It is marked by five dissolution episodes, occurring from 12-10 Ma, characterized by significant reductions in carbonate mass accumulation rates (CO$\sb3$ MAR). We determined carbonate content and CO$\sb3$ MAR for sites 998-1000 over the middle to late Miocene interval. Stable isotope composition of benthic foraminifers is used to track changes in deep water masses. Carbonate mineralogies are determined for the shallow site 1000 (927 m water depth) to detect dissolution of metastable carbonates at sub-thermocline depths. The geochemical changes during the carbonate period are similar to those that occur during the Caribbean Quaternary interglacial stages, times when Antarctic Intermediate Water (AAIW) filled the Caribbean to abyssal depths. The initiation of North Atlantic Deep Water (NADW) production during this period, possibly caused by the partial closing of the Isthmus of Panama and the opening of Pedro Channel (northern Nicaragua Rise), led to reorganization of global thermohaline circulation. The increase of return flow that passes through the Caribbean may have brought corrosive AAIW into the Caribbean, causing dissolution of carbonate sediment at the sea floor.

An investigation of the petrography, mineralogy and chemistry of primitive basalts found in a E-W transect of southern Washington and northern Oregon provides constraints concerning the thermal structure and composition of the mantle wedge beneath the Cascadia subduction zone. The Cascades represents a warm, slowly subducting end-member of subduction zone types. Chemical and petrographical characteristics of basalts from a transect across southern Washington representing at least six variants of primitive melts can be recognized. Estimates of magma temperature and depth based on mineral and whole-rock chemistry provide estimations on the Cascadia subduction zone's thermal structure. Mineral chemistry and whole-rock trace element chemistry are further used to interpret the mantle chemistry and the processes involved in producing subduction zone basalts. The results can be explained by multiple sources found within the subduction zone mantle, melting at various depths and temperatures.

Fluorine is abundant in the oceans, and carbonate fluorapatite precipitation in marine sediment is a significant removal mechanism. A paucity of data has led to several misconceptions of fluorine geochemistry and carbonate fluorapatite (CFA) diagenesis, a fluorine and carbonate substituted apatite (Ca10 (PO4)5.74(CO3)0.26F 2.26). This thesis will revise and expand our understanding of fluorine and CFA in deep sediment by proving fluorine's availability, documenting CFA precipitation, and demonstrating alkalinity controls on fluorine and CFA. Because CFA is the main mineral phase of economic phosphorite deposits, its development has warranted much study. However, previous research focused on PO43- and F concentrations in pore waters of shallow sediment (<10 meters) and is incomplete. Here, previous work is improved by directly measuring fluorine concentrations in sediments and pore waters from deep cores (>100 meters) near the upwelling zone of the Peru margin. These results are then related to CFA diagenesis.

Structural analysis, interpretation of seismic reflection lines, and apatite fission-track analysis in the Western Serrania del Interior fold and thrust belt and in the Guarico basin of north-central Venezuela indicate that the area underwent Mesozoic and Tertiary-to-Recent deformation. Mesozoic deformation, related to the breakup of Pangea, resulted in the formation of the Espino graben in the southernmost portion of the Guarico basin and in the formation of the Proto-Caribbean lithosphere between the diverging North and South American plates. The northern margin of Venezuela became a northward facing passive margin. Minor normal faults formed in the Guarico basin. The most intense deformation took place in the Neogene when the Leeward Antilles volcanic island arc collided obliquely with South America. The inception of the basal foredeep unconformity in the Late Eocene-Early Oligocene marks the formation of a perisutural basin on top of a buried graben system. It is coeval with minor extension and possible reactivation of Cretaceous normal faults in the Guarico basin. It marks the deepening of the foredeep. Cooling ages derived from apatite fission-tracks suggest that the obduction of the fold and thrust belt in the study area occurred in the Late Oligocene through the Middle Miocene. Field data and seismic interpretations suggest also that contractional deformation began during the Neogene, and specifically during the Miocene. The most surprising results of the detrital apatite fission-track study are the ages acquired in the sedimentary rocks of the easternmost part of the study area in the foreland fold and thrust belt. They indicate an Eocene thermal event. This event may be related to the Eocene NW-SE convergence of the North and South American plates that must have caused the Proto-Caribbean lithosphere to be shortened. This event is not related to the collision of the arc with South America, as the arc was far to the west during the Eocene.

Fouling is the drop in permeate flux per unit of applied pressure due to the accumulation of materials in the pores and on the surface of the membrane. Dissolved organic matter (DOM) in natural waters is often an important factor in irreversible fouling of membranes. This work characterizes fouling of nanofiltration and ultrafiltration membranes by compounds selected as models for the polysaccharide, polyhydroxyaromatic: and proteinaceous fractions of DOM commonly obtained by pyrolysis-GC/MS. Polygalacturonic acid, rosolic acid and bovine serum albumin were selected as model compounds. Although proteins have been observed to foul membranes, pyrolysis-GC/MS analysis alone of DOM extracted from foulant cakes on membranes yields relatively little proteinaceous material. It was hypothesized that proteins are more significant foulants than is indicated by pyrolysis-GC/MS analysis of the foulant cakes. It was also hypothesized that mixtures of organic molecules would not foul the membrane to the same extent as they will separately and that these flux-reducing foulants were both in the pores and on the surface. Membranes were employed in a dead-end filtration configuration. Surface topology was characterized using atomic force microscopy, the data from which was used to calculate surface roughness by a multifractal analysis algorithm. Foulant location was investigated using infrared spectroscopy with attenuated total reflectance. These laboratory data were compared to pilot plant data collected at the San Patricio Municipal Water District (SPMWD). Long-chain PgA molecules and BSA had the strongest influence on fouling. Mixing the different DOM fractions enhanced fouling. Combinations of the different organic molecules produced more fouling than would be predicted from the sum of each compound's fouling potential. The degree to which the organic molecules fouled the membranes was influenced by both the nature of the membrane materials and by their MWCOs. The fouling effect per millimole foulant was higher in the UF range, likely due to greater pore fouling. Results from the laboratory experiments and from the pilot plant at the SPMWD were not strictly comparable, but do indicate that the presence of a substantial deposit on the membrane surface does not necessarily account for an observed reduction in permeate flux.

Multiple isotopic and geochemical tracers were employed to unravel the complex history of recent environmental variability at Cocos Island. Downcore variations in delta18O, U/Ca, Sr/Ca, and Ba/Ca within coral skeletal aragonite correlate with environmental parameters such as temperature, precipitation, and advection of surface waters. U/Ca and Sr/Ca ratios were evaluated as potential paleothermometers in conjunction with delta 18O, and indicate a combined influence of temperature and precipitation on delta18O. Ba/Ca records indicate that this tracer may be a useful tracer for the advection of coastal waters from the Gulf of Panama and the strength of the NECC. Information regarding large-scale atmospheric and oceanic processes is also embedded within the records. Long-term trends are reproducible in coral records throughout the eastern Pacific and indicate significant changes in the tropical climate system. Records developed from Cocos Island suggest an increase in rainfall in conjunction with localized cooling during the past 100 years.

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