1,721,235 research outputs found
College students Kimberley Nightingale, Andrea Harris, Michelle Dussault, and Ka
No full textCollege students Kimberley Nightingale, Andrea Harris, Michelle Dussault, and Karen Simard sued their landlord, Joe Soley. The four Portland roommates said Soley stole their property when they were soon to move out. Their apartment had been condemned and housed cockroaches and a dead cat. Details
The accretion of lower oceanic crust
No full textThe formation of new ocean lithosphere at mid-ocean ridges is a fundamental component of the plate tectonic cycle, and through hydrothermal interactions with seawater is a major control on the composition of the oceans, ocean crust, and upper mantle. Two complementary approaches are used to investigate the thermal implications of endmember theoretical models that describe the accretion of the lower oceanic crust at fast spreading rates. The first approach uses the record of hydrothermal alteration of the ocean crust, including Sr and O-isotopes, to investigate and quantify the role of hydrothermal circulation during the accretion of the ocean crust. The second method uses diffusion based geospeedometry techniques to determine cooling rates in the ocean crust. Samples from two locations of ocean crust formed at fast spreading rates at the East Pacific Rise are used in these investigations, ODP Hole 1256D and Hess Deep. Hole 1256D provides the first intact sampling of a complete section of upper oceanic crust formed at a fast spreading rate and recovered the first in situ sampling of the dike/-gabbro boundary. Hess Deep is a tectonic window where the westward propagation of the Cocos-Naza Ridge has rifted ocean crust formed at the EPR and exposed the lower ocean crust at the seafloor.The whole rock profile for Hole 1256D reveals Sr isotopes in the volcanic sequence to be only slightly shifted from primary MORB values (0.70284-0.703814 compared to 1256 MORB of 0.70283). In contrast, Sr isotopes in the sheeted dike complex (0.70294-0.70536) are strongly elevated towards hydrothermal fluid compositions (0.70505-0.70525). Rocks of the plutonic complex are characterised by elevated Sr ratios along igneous contacts (up to 0.70524) but only limited increases in Sr isotopes relative to MORB in the centres of the gabbro bodies (0.70290-0.70396). The complementary oxygen isotope profile records the downwards transition from low temperature to high temperature hydrothermal alteration but contains small scale variation associated with changes in secondary mineral abundances and local fluid/rock ratios. Both the detailed Sr and O isotope profiles document the importance of dike margins and other igneous contacts as focussed pathways for fluid flow through the crust. The time-integrated fluid flux required to cause the observed Sr isotope profile through the sheeted dike complex is 2.0 - 2.6 x 106 kg/m2 and is consistent with fluid fluxes calculated for other crustal locations (e.g, Hole 504B, Pito Deep, Hess Deep). The heat flux required to sustain this fluid flux is equivalent to half of the latent heat released during the crystallisation of the lower ocean crust. At Hole 1256D the removal of heat by hydrothermal fluids was efficient and demonstrates that the fluid flux in the sheeted dikes must have removed some portion of the heat flux out of the lower ocean crust. In order to remove all of the latent heat of crystallisation from the lower crust, there must be significant hydrothermal circulation in the lower ocean crust
Hydrothermal circulation and the dike-gabbro transition in the detachment mode of slow seafloor spreading
No full textOne of the most ubiquitous boundaries within our planet is between sheeted dikes and gabbros in fast-spreading ocean crust. This boundary marks the brittle-ductile transition at the ridge crest, and is localized by a decametric conductive boundary layer between hydrothermal circulation in the sheeted dike layer and a shallow quasi-steady-state melt lens. In contrast, at slow-spreading ridges, the crustal structure appears chaotic, with no consistent sheeted dike layer and widespread occurrences of gabbro and serpentinized peridotite on the seafloor. Recent work suggests that as much as 50% of the Atlantic Ocean crust formed by a detachment mode of seafloor spreading, including the formation of oceanic core complexes capped by long-lived, convex-upward detachment faults. These detachment faults are often associated with large hydrothermal systems in which the location of any magmatic heat source is uncertain. Here we show that detachment faults can act as thermal boundaries between gabbroic melt in the fault footwall and hydrothermal circulation in the fault zone and hanging wall, thus explaining the link between faulting and black smoker systems. We suggest that interaction between magmatism and hydrothermal circulation means that detachment faults can act as the dike-gabbro transition in the detachment mode of spreading, inevitably leading to exposure of gabbros on the seafloor through continued faulting. This concept provides a means of unifying apparently contrasting processes and crustal structures at different spreading rates
Proceedings of the Integrated Ocean Drilling Program Expedition, Volume 335: Superfast Spreading Rate Crust 4. Expedition 335 of the riserless drilling platform Puntarenas, Costa Rica, to Balboa, Panama, Site 1256 13 April–3 June 2011
No full textProceedings of the Integrated Ocean Drilling Program Expedition, Volume 327: Superfast Spreading Rate Crust 4. Juan de Fuca Ridge-Flank Hydrogeology, Expedition 327 of the riserless drilling platform from and to Victoria, British Columbia (Canada)Sites U1362, U1301, 1027, and U1363, 5 July–5 September 2010
No full textIntegrated Ocean Drilling Program Expedition 327 Preliminary Report: Juan de Fuca Ridge-Flank Hydrogeology The hydrogeologic architecture of basaltic oceanic crust: compartmentalization, anisotropy, microbiology, and crustal-scale properties on the eastern flank of Juan de Fuca Ridge, eastern Pacific Ocean, 5 July–5 September 2010
No full textIntegrated Ocean Drilling Program (IODP) Expedition 327 and related experiments focus on understanding fluid–rock interactions in young, upper ocean crust on the eastern flank of the Juan de Fuca Ridge, delineating the magnitude and distribution of hydrologic properties; the extent to which crustal compartments are connected or isolated (laterally and with depth); the rates and spatial extent of ridge-flank fluid circulation; and links between ridge-flank circulation, crustal alteration, and geomicrobial processes. Expedition 327 built on the achievements of IODP Expedition 301 and subsequent submersible and remotely operated vehicle (ROV) expeditions. Both drilling expeditions installed subseafloor borehole observatories ("CORKs") in basement holes to allow borehole conditions to recover to a more natural state after the dissipation of disturbances caused by drilling, casing, and other operations; provide a long-term monitoring and sampling presence for determining fluid pressure, temperature, composition, and microbiology; and facilitate the completion of active experiments to resolve crustal hydrogeologic conditions and processes.During Expedition 327, two basement holes were cored and drilled at Site U1362. Hole U1362A was cored and drilled to 528 meters below seafloor (mbsf) (292 meters subbasement [msb]), subjected to geophysical logging and hydrologic testing, and instrumented with a multilevel CORK observatory. Hole U1362B was drilled to 359 mbsf (117 msb), subjected to a 24 h pumping and tracer injection experiment, and instrumented with a single-level CORK observatory. Both CORK observatories include monitoring of pressure and temperature and downhole fluid and microbiology sampling. Wellhead samplers will be added and a long-term cross-hole test will be initiated during a postdrilling ROV expedition scheduled for Summer 2011. In addition, part of an instrument string deployed in Hole U1301B during Expedition 301 was recovered, and a replacement string of thermal sensors was installed. Finally, a program of shallow sediment coring was completed adjacent to Grizzly Bare outcrop, a suspected site of regional hydrothermal recharge. Thermal measurements and analyses of pore fluid and microbiological samples from a series of holes aligned radially from the outcrop edge will elucidate rates of fluid transport and evolution during the initial stages of ridge-flank hydrothermal circulation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Automated feature classification and knowledge extraction from wireline geophysical observations: big data potential for offshore resources assessment
No full textScientific drilling of the volcanic ocean crust recovers cores and undertakes downholewireline logging. However, because core recovery rates are typically low (<30%), interpreting thewireline data is essential to gain a complete understanding of the stratigraphy. Ocean Drilling ProgramHole 1256D samples 1500 m of in situ upper oceanic crust and has both core-derived lithostratigraphyand electrofacies classification based on geological interpretations of continuous downhole FormationMicroScanner imagery. We propose an automatic quantitative identification of electrofacies usingDecision Trees. The cores and existing electrofacies classification provide training and verification ofthe automated classification. The identification of various classes is a challenging problem due tomissing data, vertical shifts, horizontal misalignments, and multiclass unbalanced problem with 2classes representing 50% of the data. Additionally, the structure of the same class changes with depthleading to large intra-class variations. Distinctive features for each class were identified by observationof images based on texture/shapes, and Decision Tree classifier was trained. Classification accuracyabove 90% was achieved for the 3-classes for electrofacies with high recovery rates. In case of 9-classes, accuracy above 60% was achieved for some classes, though some challenges are remaineddue to strongly overlapped classes. A detailed analysis of the big data used for training the classifierand its performance is described. Combined analysis of drill cores and wireline geophysical data fromscientific boreholes into volcanic rocks provides excellent training opportunities to develop automatedrock classification methods for complex geological terranes that are of increasing interest to thehydrocarbons industry
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