Oxygen isotopes and major and trace element geochemistry have been used to evaluate the geochemical and tectonic history of a Franciscan hornblende-amphibolite and a eclogite block from Ring Mountain, Tiburon and three eclogite/blueschist blocks from Jenner Beach, California, all blocks have experienced varying amounts of retrogression. Relative to the presumed basaltic protolith, enrichments in large ion lithophile elements (LILEs) indicate interaction with sediment derived fluids in the retrograde eclogite and retrograde blueschist samples and high Mg, Cr, and Ni in actinolite rind indicate interaction with ultramafic rock. The [delta]¹⁸O values of chlorite from the Ring Mountain hornblende-amphibolite and the eclogite block have a narrow range of [delta]¹⁸O values (+7.7-8.2%₀, n=8) and actinolite from actinolite rind on the eclogite block from Ring Mountain and the blueschist/eclogite blocks from Jenner Beach are (+7.8-8.5%₀, n=5). Chlorite-actinolite geothermometry yields temperatures of 200-280°C for actinolite rind formation. Additionally, the [delta]¹⁸O values of both chlorite and actinolite at these temperatures indicates equilibrium with the measured value of Tiburon serpentinites, (7.6 to 8.1%₀, n = 3 Wenner and Taylor, 1974). Oxygen isotope analyses of garnet mineral separates from the eclogite and hornblende-amphibolite from Ring Mountain have [delta]¹⁸O values of +6.8±0.3%₀ (n=7), and +8.2±0.2%₀ (n=7), respectively. Garnets from the three eclogite/blueschist blocks at Jenner Beach have a [delta]¹⁸O value of +9.8±0.7%₀, (n=23). The difference in [delta]¹⁸O values of garnets between the high-grade blocks is likely due to in situ hydrothermal alteration of the seafloor basalt prior to subduction. The geochemical trends can be explained by a model in which during the early stages of subduction pieces of altered oceanic crust are detached from the downgoing slab and incorporated into the mantle wedge soon after reaching peak eclogite or amphibolite facies conditions. As subduction continues, the hanging wall cools and fluids released from subducted sediments infiltrate the overlying mantle wedge. As the blocks cool they develop a retrograde blueschist facies overprint under relatively static conditions. With cooling of the hanging wall and infiltration of sedimentary fluids, serpentinization induces reaction between the blocks and surrounding mantle wedge and Mg-rich actinolite rind is formed. The blocks are then plucked from the mantle wedge and incorporated into the subduction channel where they flow back to the surface via corner flow. / text

No description available.

No description available.

No description available.

The large amount of turquoise artifacts recovered from archaeological sites in the American Southwest and Mesoamerica suggests that turquoise was an important commodity in pre-Columbian trade networks. However, the spatial and temporal patterns of turquoise exchange networks and the provenance regions of the turquoise in the southwestern United States and Mesoamerica are poorly understood. Turquoise (CuAl6(PO4)4(OH)8•4(H2O)) is a supergene mineral that forms from meteoric water along fractures that are often associated with copper porphyry deposits. This copper-rich mineral can range in color and chemistry within a single sample or deposit. The ability to identify the turquoise resource areas of turquoise artifacts using the stable isotopes of hydrogen (2H/1H) and copper (65Cu/63Cu) has overcome many of the limitations of trace element analyses of complex minerals such as turquoise. The geography and geology of turquoise deposits dictate the isotopic composition of turquoise. Employing the Secondary Ion Mass Spectrometry (SIMS) technique to measure the hydrogen and copper stable isotope ratios in turquoise samples, a comparative reference database consisting of 876 analyses from 21 turquoise resource areas in the western United States was established. Sixty-two turquoise artifacts recovered from Aztec Ruin, Salmon Ruin, and nine sites in Chaco Canyon were analyzed and their isotopic signatures were compared to the reference database identifying the turquoise resource areas of 35 artifacts. These results were compared to pre-existing models of trade and exchange in the American Southwest and models that explain the complex culture history of the inhabitants of these sites. The results showed that turquoise was obtained from several different turquoise provenance regions across the western United States and there are notable differences in the turquoise procurement patterns between the three major great houses and between Pueblo Bonito and the small sites within Chaco Canyon. The results from this study improved the understanding of turquoise trade and relationships among the occupants of important Ancestral Puebloan sites in northwestern New Mexico. The development of the turquoise comparative reference database established the foundation of future research for reconstruction of ancient turquoise trade networks and investigation of turquoise procurement strategies in the American Southwest and Mesoamerica.

Atomic lifetimes of selected levels in Neon I and Argon I were measured using a method of delayed coincidence. Pulsed rf was used to excite a discharge tube containing the neon and argon gas. The radiation emitted from the excited atoms of the gas was passed through a monochromator so only the desired wavelength would be observed. Each time an excitation pulse ended, the decay of light intensity was detected by a photomultiplier tube. By measuring the decay time of the light intensity using the delayed coincidence technique, the average lifetime of the desired level was determined. The values of lifetimes determined in this study were found to contain considerable error. Several factors contributing to these errors were thought to be the shape of the rf pulses and an effort known as cascading which was caused by the use of rf for excitation of the gas.

Submerged caves, locally referred to as cenotes, can be found throughout the Yucatan Peninsula of Mexico. These nutrient poor, aphotic “underground estuaries” lack photosynthetic primary productivity, but are often found underlying high primary productivity areas such as mangroves and tropical forests. Adjacent ecosystems contribute organic carbon to the cave systems via percolation, where it is then utilized by the obligate, cave-dwelling fish and invertebrates. Another potential pathway through which organic carbon can enter the cave food web is through chemosynthesis. Chemoautotrophic sulfur-oxidizing or nitrifying bacteria have been found in the hydrogen sulfide layer or in the sediments of some anchialine caves. Our study utilizes 13C/12C and 15N/14N stable isotopes as well as 14C radiocarbon dating to determine and compare the sources of organic matter entering a coastal anchialine cave (Cenote Aak Kimin) versus an inland cave (Cenote Maya Blue) in the Yucatan Peninsula. Stable isotopes have long been employed in tropic investigations. This study, however, is the first to utilize radiocarbon isotopes in anchialine caves. The use of both stable and radiocarbon isotopes as source indicators provides greater discrimination in systems that contain numerous carbon sources or indistinct trophic levels, particularly to distinguish between chemoautotrophic versus photosynthetically derived carbon. Results indicate that chemosynthetically derived organic carbon contributes substantially to the diet of some crustaceans, such as the stygobitic shrimp Typhlatya, while other species remain dependent on detrital inputs. Depleted δ13C values and aged radiocarbon values (as low as -47.51‰ and 1840 yrs. for Typhlatya spp.) in comparison to particulate and sediment δ13C values (lowest -32.07‰ and -28.43‰, respectively). A comparison of isotopic values between Cenote Aak Kimin and Cenote Maya Blue suggests that the trophic web of the coastal cave incorporates more photosynthetic or detrital carbon, while the inland cave, with more depleted 13C and 14C values, relies more heavily on chemoautotrophic carbon. Within both systems, however, distinct photosynthetic and chemoautotrophic levels were identified. Water quality parameters, especially dissolved oxygen and pH, support the hypothesis of bacterial activity at the halocline. Anchialine systems in the Yucatan Peninsula are threatened due to increases in tourism, development, and pollution. Quantifying and qualifying the inputs of organic carbon is vital for the management and conservation of the area’s freshwater resources.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1977. / Bibliography: leaves 138-146. / Microfiche. / x, 146 leaves ill

The reef corals Pocillopora damicornis and Montipora verrucosa were cultured under various controlled temperatures and light conditions at Ulupau Head Microcosm facility. The skeletal carbonate deposited under different experimental regimes was analyzed for 13C and 18O. Coral skeletal 013C values varied with light dose and correlated with changes in zooxanthellar pigment. The o13C value of skeletal aragonite seems to be controlled by oxidation of photosynthetically produced organic matter. Functionally significant relationships between coral skeletal o18O values and temperature have been determined. The temperature coefficients of the o18O values (-4.20) are the same as the first order coefficient in the equilibrium paleotemperature equation, but the o18O values have species-specific offsets from equilibrium. These offsets may be attributed to the activity of the coral's zooxanthellae. Based upon the results of this study a model of coral skeletal isotopic incorporation is presented. / Typescript. Thesis (M. S.)--University of Hawaii at Manoa, 1979. Bibliography: leaves 94-102.

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Jeffrey P. Chanton, Florida State University, College of Arts and Sciences, Dept. of Oceanography. Title and description from dissertation home page (viewed Sept. 24, 2004). Includes bibliographical references.