Intra-crater glacial processes in central Utopia Planitia, Mars     

Geoffrey Pearce  Gordon R. Osinski  Richard J. Soare 《Icarus》2011,212(1):86-95

We describe and interpret a series of previously unidentified glacial-like lobes (34-43°N; 107-125°E) that were discovered as part of a survey of large (D > 5 km) impact craters in Utopia Planitia, one of the great northern plains of Mars. The lobes have characteristics that are consistent with a glacial origin. Evidence includes curvilinearity of form, lineations and ridges, and surface textures that are thought to form by the sublimation of near-surface volatiles. The lobes display morphologies that range from wedge-shaped to near-circular to elongate. The flow directions are towards the northern walls in the case of craters with large single lobes, and in all directions in the case of the largest (D > 30 km) craters. Concentric crater fill is also interspersed within craters of our study region, with such craters having much higher filling rates than those with flow lobes. We suggest that the impact crater population in south-west Utopia Planitia demonstrates a spectrum of glacial modifications, from low levels of filling in the case of craters with elongate lobes at one extreme, to concentric crater fill in highly-filled craters at the other.  相似文献   

Measurement of LNAPL flow using single-well tracer dilution techniques   总被引：1，自引：0，他引：1  

Sale T  Taylor GR  Iltis G  Lyverse M 《Ground water》2007,45(5):569-578

This paper describes the use of single-well tracer dilution techniques to resolve the rate of light nonaqueous phase liquid (LNAPL) flow through wells and the adjacent geologic formation. Laboratory studies are presented in which a fluorescing tracer is added to LNAPL in wells. An in-well mixer keeps the tracer well mixed in the LNAPL. Tracer concentrations in LNAPL are measured through time using a fiber optic cable and a spectrometer. Results indicate that the rate of tracer depletion is proportional to the rate of LNAPL flow through the well and the adjacent formation. Tracer dilution methods are demonstrated for vertically averaged LNAPL Darcy velocities of 0.00048 to 0.11 m/d and LNAPL thicknesses of 9 to 24 cm. Over the range of conditions studied, results agree closely with steady-state LNAPL flow rates imposed by pumping. A key parameter for estimating LNAPL flow rates in the formation is the flow convergence factor alpha. Measured convergence factors for 0.030-inch wire wrap, 0.030-inch-slotted polyvinyl chloride (PVC), and 0.010-inch-slotted PVC are 1.7, 0.91, and 0.79, respectively. In addition, methods for using tracer dilution data to determine formation transmissivity to LNAPL are presented. Results suggest that single-well tracer dilution techniques are a viable approach for measuring in situ LNAPL flow and formation transmissivity to LNAPL.  相似文献   

Role of Hydrology in the Formation of Co-rich Mn Crusts from the Equatorial N Pacific,Equatorial S Indian Ocean and the NE Atlantic Ocean     

Geoffrey P. Glasby  Bruce Mountain  Theckethottathil C. Vineesh  Virupaxa Banakar  Ramesh Rajani  Xiangwen Ren 《Resource Geology》2010,60(2):165-177

Co-rich Mn crusts from four different locations of the world ocean have been studied to understand the role of dissolved oxygen of the ambient seawater in the formation of Co-rich Mn crusts. WOCE (World Ocean Circulation Experiment) oxygen profiles of modern seawater in the Equatorial North Pacific Ocean, Equatorial South Indian Ocean and the North East Atlantic Ocean have been evaluated with respect to the occurrence of Co-rich Mn crusts at depths ranging from 1500 to 3200 m. The oxygen content at these depths varied from ∼90–240 µmol/kg. The oxygen minimum zone (OMZ), with oxygen contents in the range ∼45–100 µmol/kg, is located in the depth range 800–900 m in these regions. The age of the ocean crust on which seamounts formed is in the range 80.3–180 Ma. Profiles of the oxygen contents of seawater with depth in the oceans are shown to be extremely useful in establishing the optimum conditions for the formation of Co-rich Mn crusts. The use of WOCE oxygen profiles to study geochemical processes in the oceans is highly recommended.  相似文献   

Incorporation of Transition and Platinum Group Elements (PGE) in Co-rich Mn Crusts at Afanasiy-Nikitin Seamount (AFS) in the Equatorial S Indian Ocean     

Geoffrey P. Glasby 《Resource Geology》2010,60(2):212-215

Of the 12 elements enriched in Co-rich Mn crusts from the Afanasiy-Nikitin Seamount in the Equatorial S Indian Ocean, Mn, Fe and Co are enriched by a factor of ~10⁹ compared to their concentrations in seawater whereas Ni and Cu are enriched by a factor of ~10⁷ and the PGE and Au by a factor of ~10⁵ to 10⁷ compared to their concentrations in seawater. The relatively high concentration of Pt in the crusts reflects its occurrence as fine-grained particles in the crusts rather than adsorption of the elements from seawater.  相似文献   

Measurements of the Henry's Law Coefficients of 2-Methyl-3-buten-2-ol, Methacrolein, and Methylvinyl Ketone   总被引：1，自引：0，他引：1  

Laura T. Iraci  Bradly M. Baker  Geoffrey S. Tyndall  John J. Orlando 《Journal of Atmospheric Chemistry》1999,33(3):321-330

Using an equilibrium headspace technique, Henry's law coefficients were measured for methacrolein (H = 6.5 ± 0.7 M atm-1) and methylvinyl ketone (41 ± 7.0 M atm-1) in water at 25 °C. In addition, 2-methyl-3-buten-2-ol was studied at 30 °C in water and in an aqueous ionic solution representative of plant tissue. Similar values were found in deionized water (65 ± 3.5 M atm-1) and in a 0.05 mol kg-1 Ca2+, K+, NO3-, SO42- solution (62 ± 0.8 M atm-1). These Henry's Law coefficients are too small to allow for significant partitioning of methacrolein, methylvinyl ketone or methylbutenol into cloud water under equilibrium conditions.  相似文献