Serpentinization-assisted deformation processes and characterization of hydrothermal fluxes at mid-ocean ridges
Başlık çevirisi mevcut değil.
- Tez No: 400107
- Danışmanlar: DR. LEONİD N. GERMANOVİCH
- Tez Türü: Doktora
- Konular: Çevre Mühendisliği, İnşaat Mühendisliği, Environmental Engineering, Civil Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2012
- Dil: İngilizce
- Üniversite: Georgıa Instıtute Of Technology
- Enstitü: Yurtdışı Enstitü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: Belirtilmemiş.
Özet
Özet yok.
Özet (Çeviri)
Seafloor hydrothermal systems play a significantly important role in Earth?senergy and geochemical budgets and support the existence and development ofcomplex biological ecosystems by providing nutrient and energy to microbial andmacrafaunal ecosystems through geochemical fluxes. Heat output and fluid flow are keyparameters which characterize hydrothermal systems at oceanic spreading centers byconstraining models of hydrothermal circulation. Although integrated measurements ofheat flux in plumes are critically important as well, quantification of heat flux at discretesources (vent orifices versus patches of seafloor shimmering diffuse flow) from directmeasurements is particularly essential for examining the partitioning of heat flow intofocused and diffuse components of venting and determining geochemical fluxes fromthese two modes of flow. Hydrothermal heat output also constrains the permeability ofyoung oceanic crust and thickness of the conductive boundary layer that separatesmagmatic heat source from overlying hydrothermal circulation. This dissertation will befundamentally focused on three main inter-connected topics: (1) the design anddevelopment of direct high- or low-temperature heat flow measuring devices forhydrothermal systems, (2) the collection of new heat output results on four cruisesbetween 2008 and 2010 at several distinct hydrothermal sites along mid-ocean ridges(MORs) to estimate total heat output from individual vent structures such as Dante,Hulk or the whole vent field (e.g., Main Endeavour Vent Field (MEF)), the partitioningbetween focused and diffuse hydrothermal venting in MEF, and determination of initialestimates of geochemical flux from diffuse hydrothermal fluids which may be influencedby the activity in subsurface biosphere and finally (3) the deformation and upliftassociated with serpentinization at MORs and subduction zones.Despite extensive efforts spent for the last couple of decades on heat flowmeasurement methods and techniques either in the plumes or right at sources, there isstill limited knowledge of direct estimates of heat discharge particularly at the vent scaleand reliable estimates of temporal variation in heat flux. Moreover, a few previouslyused tools to make discrete measurements were associated with mechanicalcomplications and/or problems mostly related to electronics or irrecoverable damagedue to environmental problems such as accumulation of sediments/particles fromhydrothermal fluids. In this dissertation we showed the stages of design, fabrication,calibration and in-situ deployment from DSV Alvin for two unique heat flow measuringseafloor instruments; cup anemometer and turbine flow meter. The devices haveproven to be robust, practical, and simple to maneuver and perform in both focusedand diffuse flow milieus. Field experiments showed that these self-contained devicesyielded a broad range of accurate heat flow estimates ranging from 2 cm/s to 200 cm/swith minimum required maintenance and much less on-station time compared toprevious designs.This dissertation reports 63 successful point measurements of focused anddiffuse fluid flow the majority of which were completed at the Main Endeavour, HighRise and Mothra hydrothermal vent fields along Endeavour Segment of Juan de FucaRidge. By coupling a fraction of our flow rate results with geochemical data (i.e. fluidvolatile concentrations) collected with in-situ mass spectrometer, direct geochemicalflux were estimated from both focused and diffuse flows.Heat and fluid flow results we have obtained complement our understanding ofserpentinization assisted deformation processes at Mid-Ocean Ridges and subductionzones. This dissertation also includes a simple mathematical model developed forcrustal deformation and seafloor uplift resulting from volume expansion associated withsubsurface serpentinization. Application of this model shows the apparent deformationat the central portion of the east wall of the axial valley at the TAG hydrothermal fieldand the Quaternary uplift of the Miyazaki Plain observed above the Kyushu-Palausubduction zone in the western Pacific. Our model suggests that observed topographicanomaly may have been produced in a relatively deep-seated region of serpentinizedmantle associated with a volume expansion (transformation strain) of 20 to 40% thatcould have possibly resulted into fracturing/faulting processes or only with 3% oftransformation strain respectively.
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