A Darcian Model for the Flow of Big Spring and the hydraulic head in the Ozark aquifer, Missouri, USA

The complex discharge hydrographfor Big Spring, Missouri, can be described as the sum of two terms governed by Darcy’s Law. The dominant, long-term component is proportional to the regional hydraulic gradient, and constitutes about 80% of the average flow of 12.6 m3/s. Superimposed on this is a tran­sient component witha time-constant of about 1.5 days that represents the Darcian response to sharp, rainfall-driven pulses on the head of the shallow groundwater system. This tran­sient component delivers about 20% of the average total flow, but over short intervals can exceed the long-term component. However, the long-term component is so large that the ratio of record highflows to the average flow is only about 4x for Big Spring, and 1.5 to 4.5x for most other large Ozark springs; for comparison, this ratio is 10 to 3000x for most surface streams in Missouri. The strong correlation between the discharge of the large springs and the head in the Ozark aquifer permits the extension of the Darcian rainfall-runoff model to predict groundwater levels in wells

Enhanced Stage Variability on the Lower Missouri River as Benchmarked by Lewis and Clark: Implications for Ecosystem Restoration

Because lower Missouri River management began in the early 1800s, a challenge for present-day ecosystem restoration efforts is a lack of quantitative data on pre-management river hydrology and long-term (100+ yr.) river response to changing management practice and intensity. We address this challenge and report new results from a study spanning 200 years of lower Missouri River hydrology, encompassing natural, channelization-only, and channelization with reservoir release regimes (Ehlmann & Criss, Geology, forthcoming, Nov/Dec 2006)

Tertiary Meteoric Hydrothermal Systems and their Relation to Ore Deposition, Northwestern United States and Southern British Columbia

Tertiary meteoric hydrothermal systems have altered the rocks exposed over more than 5 % of the land surface of the northwestern United States and southern British Columbia, including at least 25,000 km^2 in Idaho. The systems typically involved convective circulation of fluid derived from ordinary meteoric groundwaters around crystallizing, calc-alkaline, epizonal plutons emplaced into coeval volcanic cover rocks. These individual systems had widely ranging “lifetimes” of 10^3 to 10^6 years and operated locally throughout the Cenozoic, although the most profound development of such activity occurred during Eocene time. Individual systems varied in size from a few tens of square kilometers (Yankee Fork, Idaho) or less to several thousand square kilometers (Sawtooth and Castro ring zones, Idaho) Typically, regional propylitization aacompanied the fluid circulation, although the higher-temperature alteration assemblages were developed locally, as were intense alteration effects (e.g., silicification, sericitization, etc.) near some veins and in mining districts. A significant amount, probably 25–50%, of the mineral production and potential in the region is closely related to Tertiary meteoric hydrothermal systems. Oxygen and hydrogen isotopic data clearly demonstrate the close geologic association of meteoric hydrothermal systems and mineralization in (1) the Paleocene, Cu-Zn-Pb-Mn Main Stage mineralization at Butte, Montana; (2) numerous Eocene epithermal deposits principally valued for Au and Ag but also including significant deposits of Cu, Pb, Zn, F, Sb, etc., as at Republic, Washington, and in several mining districts in the Idaho batholith and the Challis volcanic field; (3) several Eocene skarn deposits valued for W (Ima, Idaho) and Cu (Mackay, Idaho); (4) important lead-silver vein and replacement deposits of Tertiary (Bluebell, British Columbia) and of probable Cretaceous and early Tertiary age (Wood River, Idaho); (5) several potentially economic Mo-, Be-, and U-bearing Eocene “porphyry” plutons; and (6) Miocene epithermal deposits, most prominently the Au and Ag bearing veins at Silver City and DeLamar, Idaho, the Hg deposits at the McDermitt caldera, Nevada and Oregon, and at Weiser, Idaho, and Au deposits in the Western Cascade Range and Lake County, Oregon. A close spatial association has been demonstrated between ore deposits and rocks having anomalous δ^(18)O values and low δD values. The most important deposits are associated with relatively small (generally 5–300 km^2) zones of low δ^(18)O values, and they are particularly closely linked with zones of very steep ^(18)O/^(16)O gradients in the altered rocks. These associations hold much promise for the use of δ^(18)O and δD contour maps in future exploration efforts

Implications of ^(18)O/^(16)O and D/H Data on Hydrothermally-Altered Terranes to the Deep-Level and Long-Term Characteristics of Caldera·Related Hydrothermal Systems

Eroded hydrothermally-altered terranes provide much information about the inaccessible deep levels and long-term characteristics of modern geothermal systems. Detailed isotopic maps of large (12 to 60 km dia.) Challis (Geology, 12, 331-334) and San Juan volcanic fields (J. Volc. Geotherm. Res., 30, 47-82) prove that I) the ground- water circulation pattern was affected over lateral distances of 50 km or more; 2) vertical I so gradients were produced in the crust, with fluid penetrating to depths of at least 5 to 10 km; 3) fluid temperatures were mostly 150° to 350°C; 4) isotopic disequilibrium between coexisting minerals was ubiquitous, consistent with system lifetimes of 10^5 to 10^6 years; This page may be freely copied. 5) regional fluid/rock ratios were typically -1, such that a large ^(18)O shift of the deep fluid occurs; and 6) the highest fluid-rock ratios (>>1), as integrated over the lifetimes of the systems, occurred along the ring fracture zones and adjacent to resurgent intrusions. Analogous zones in modern systems are clearly excellent drilling targets for geothermal resources

Mechanical properties of α-tricalcium phosphate-based bone cements incorporating regenerative biomaterials for filling bone defects exposed to low mechanical loads

Calcium phosphate-based cements with enhanced regenerative potential are promising biomaterials for the healing of bone defects. With a view to the use of such cements for low load bearing applications such as sinus augmentation or filling extraction sites, we have prepared α-tricalcium phosphate (α-TCP)-based bone cements including materials that we would expect to improve their regenerative potential, and describe the mechanical properities of the resulting formulations herein. Formulations incorporated α-TCP, hydroxyapatite, biopolymer-thickened wetting agents, sutures, and platelet poor plasma. The mechanical properties of the composites were composition dependent, and optimized formulations had clinically relevant mechanical properties. Such calcium phosphate-based cements have potential as replacements for cements such as those based on polymethylmethacrylate (PMMA)

Hydrologic and isotopic modeling of Alpine Lake Waiau, Mauna Kea, Hawai'i

Analysis of hydrologic, meteorologic, and isotopic data collected over 3 yr quantifies and explains the enormous variability and isotopic enrichment (δ18O = +16.9, δD = +50.0) of alpine Lake Waiau, a culturally and ecologically significant perched lake near the summit of Mauna Kea, Hawai'i. Further, a simple one-dimensional hydrologic model was developed that couples standard water budget modeling with modeling of δD and δ18O isotopic composition to provide daily predictions of lake volume and chemistry. Data analysis and modeling show that winter storms are the primary source of water for the lake, adding a distinctively light isotopic signature appropriate for high-altitude precipitation. Evaporation at the windy, dry summit is the primary loss mechanism for most of the year, greatly enriching the lake in heavy isotopes