Tracing on-axis diffuse fluids by chalcophile elements distribution in upper oceanic crust at Pito Deep, East Pacific Rise

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dc.contributor.authorTian, Zhu
dc.contributor.supervisorCoogan, Laurence
dc.date.accessioned2016-11-29T23:15:59Z
dc.date.available2016-11-29T23:15:59Z
dc.date.copyright2016en_US
dc.date.issued2016-11-29
dc.degree.departmentSchool of Earth and Ocean Sciences
dc.degree.levelMaster of Science M.Sc.en_US
dc.description.abstractMid-ocean ridge hydrothermal systems play an important role in the cycling of energy and mass between the solid earth and oceans. The on-axis low-temperature diffuse fluids (temperature lower than ~100 °C) carry ~90% of the on-axis heat fluxes, but diffuse fluids generation is poorly constrained. This study uses the abundance of the chalcophile elements, which form metal-sulphides in the rock record, to test models for diffuse fluids generation. These include mixing between seawater and high-temperature hydrothermal fluids and conductive cooling of high- temperature hydrothermal fluids. This thesis determined the concentrations of the elements of interest (As, Mo, Ag, Cd, Sn, and Tl) in geological reference materials using standard addition method in ICP-MS. These values were used to calibrate the analysis of samples from Pito Deep to trace the abundance of these elements within the upper oceanic crust. The results show that the Zn, Cu, As, Ag, Cd, Tl, and Pb are generally depleted in sheeted dikes and enriched in the lava unit and/or the transition zone, which is consistent with previous studies on fast-spreading EPR crust at Hole 504B, Hess Deep and Hole 1256D. The enrichment of these elements in the lava unit and/or the transition zone suggests that cooling high-temperature hydrothermal fluids to form diffuse fluids occurred in this iii iv area of the oceanic crust. Molybdenum and Sb are added into all units of the crust by recharging seawater. The concentrations of chalcophile elements in diffuse fluids were calculated by a mass balance. The results of this study favored a diffuse fluids generation model that involves mixing of seawater and high-temperature hydrothermal fluids. Results also show that the observed concentrations of Mo and Sb requires extra input source besides recharging seawater and oceanic crust, possibly particulates in seawater.en_US
dc.description.proquestemailjuliatian2013@gmail.comen_US
dc.description.scholarlevelGraduateen_US
dc.identifier.urihttp://hdl.handle.net/1828/7646
dc.languageEnglisheng
dc.language.isoenen_US
dc.rightsAvailable to the World Wide Weben_US
dc.subjectoceanic hydrothermal systemen_US
dc.subjectchalcophile elementen_US
dc.subjectgeochemistryen_US
dc.subjectdiffuse fluidsen_US
dc.subjectEast Pacific Riseen_US
dc.subjectfast-spreading ridgeen_US
dc.subjectICPMS analytical methoden_US
dc.subjectmetal-sulphide precipitationen_US
dc.subjectPito Deepen_US
dc.titleTracing on-axis diffuse fluids by chalcophile elements distribution in upper oceanic crust at Pito Deep, East Pacific Riseen_US
dc.typeThesisen_US

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