Kenneth F. Sprenke

Metal content of charcoal in mining-impacted wetland sediments

Charcoal is well known to accumulate contaminants, but its association with metals and other toxic elements in natural settings has not been well studied. Association of contaminants with charcoal in soil and sediment may affect their mobility, bioavailability, and fate in the environment. In this paper, natural wildfire charcoal samples collected from a wetland site that has been heavily contaminated by mine waste were analyzed for elemental contents and compared to the surrounding soil. Results showed that the charcoal particles were enriched over the host soils by factors of two to 40 times in all contaminant elements analyzed. Principal component analysis was carried out on the data to determine whether element enrichment patterns in the soil profile charcoal are related to those in the soils. The results suggest that manganese and zinc concentrations in charcoal are controlled by geochemical processes in the surrounding soil, whereas the concentrations of arsenic, lead, zinc, iron, phosphorus, and sulfur in charcoal are unrelated to those in the surrounding soil. This study shows evidence that charcoal in soils can have a distinct and important role in controlling contaminant speciation and fate in the environment.

Improvements in Mining Induced Microseismic Source Locations at the Lucky Friday Mine Using an Automated Whole-waveform Analysis System

For years, severe rockburst problems at the Lucky Friday mine in northern Idaho have been a persistent safety hazard and an impediment to production. An MP250 based microseismic monitoring system, which uses simple voltage threshold picking of first arrivals, has been used in this mine since 1973 to provide source locations and energy estimates of seismic events. Recently, interest has been expressed in developing a whole waveform microseismic monitoring system for the mine to provide more accurate source locations and information about source characteristics. For this study, we have developed a prototype whole-waveform microseismic monitoring system based on a 80386 computer equipped with a 50 kHz analog-digital convertor board. The software developed includes a data collection program, a data analysis program, and an event detection program. Whole-waveform data collected and analyzed using this system during a three-day test have been employed to investigate sources of error in the hypocenter location process and to develop an automatic phase picker appropriate for microseismic events.Comparison of hypocenter estimates produced by the MP250 system to those produced by the whole-waveform system shows that significant timing errors are common in the MP250 system and that these errors caused a large part of the scatter evident in the daily activity plots produced at the mine. Simulations and analysis of blast data show that analytical control over the solutions is strongly influenced by the array geometry. Within the geophone array, large errors in the velocity model or moderate timing errors may result in small changes in the solution, but outside the array, the solution is very sensitive to small changes in the data.Our whole-waveform detection program picks event onset times and determines event durations by analysis of a segmented envelope function (SEF) derived from the microseismic signal. The detection program has been tested by comparing its arrival time picks to those generated by human analysis of the data set. The program picked 87% of the channels that were picked by hand with a standard error of 0.75 milliseconds. Source locations calculated using times provided by our entire waveform detection program were similar to those calculated using hand-picked arrival times. In particular, they show far less scatter than source locations calculated using arrival times based on simple voltage threshold picking of first arrivals.

Efficient terrain corrections: A geostatistical analysis

The farther out that terrain corrections for gravity surveys are computed, the more they cost. The conventionally recommended practice is to compute corrections out to a distance of 167 km. Explorationists, however, do not always require this much accuracy. Terrain corrections can be made cost-effective by optimizing the distance to which they are carried in any given study area. First, the terrain is simulated by a mathematical model with the same statistical properties as the topography in the study area. Geostatistical procedures are then used to estimate the errors in carrying out terrain corrections to distances less than 167 km. As an example of the process, terrain corrections for the central Cascade Mountains of Washington were analyzed. In this type of terrain, terrain corrections within 1 mGal, on the average, of the 167 km standard can be obtained either by carrying corrections out to 21 km and then simply truncating them or by carrying corrections out to 3.5 km and making an analytic adjustment for the more distant terrain. Corresponding results were obtained for other accuracies. The geostatistical method used to obtain these error estimates is universal and can be applied to any region for which the mean elevation and the covariance of elevations can be calculated.

Celadonite in continental flood basalts of the Columbia River Basalt Group

Abstract Celadonite is a common alteration product of basalts in marine environments. It has been argued that marine fluids are necessary for celadonite formation, possibly by providing a source of K and other dissolved cations. Laterally extensive deposits of celadonite occur in basalts of the Grande Ronde Basalt of the Columbia River Basalt Group. The celadonite is found in scoriaceous flow tops of layered basalt flows, where it fills vesicles and replaces the surrounding groundmass. Evolved interstitial glasses are present in the basalts and dissolution of these glasses may provide sufficient K for celadonite formation, whereas dissolution of groundmass augite provides a source of Mg and Fe. These observations show that alteration by seawater or any other external source of dissolved ions is not necessarily required for celadonite formation.

Radar detection of subglacial sulfides

Using an ice radar system, we detected anomalous reflection strengths over subglacial disseminated sulfide zones beneath the Mt. Henry Clay Glacier in southeast Alaska. The subglacial sulfide zones, which were verified by drill holes, were not detected by previous magnetic, helicopter EM, or ground‐based time‐domain EM surveys. The sulfide zones were mapped by measuring lateral variations in the strength of radar echoes from the ice‐bedrock interface at the base of the glacier. The reflected power from these disseminated occurrences ranged from 20 percent to 60 percent of the theoretically predicted reflected power from a perfect conductor at the base of the ice. The empirical results of this experiment suggest that ice radar may be a useful tool for direct mineral exploration in ice‐covered terrain.

A PC-based portable ice-radar receiver

We have assembled a low-cost portable ice-radar receiver that is based on a personal computer (PC). The unit consists of a digital storage oscilloscope controlled by a lap-top Pc. The total weight is 22 kg. The radar wave forms are digitized by the oscilloscope, displayed on the computer screen, and stored on a floppy diskette. All components are commercially available at a cost below

Analytic Geometry Formulas and Computer Routines for Stereonet Problems

2000 U.S. The radar receiver has proved to be very versatile because the computing capabilities of an IBM-compatible PC are available in the field to control s ignal acquisition, to display radar wave forms in near-real time, and to perform sophisticated signal processing as measurements are taken. The PC-based ice-radar receiver was used for ice-thickness and bedrock power-reflection coefficient surveys of Mount Estelle glacier in the Alaska Range, Alaska, in 1988.

Gravity modeling with Lotus 1-2-3

Stereonet solutions to three-dimensional geometric problems are time-consuming and subject to drawing errors. Analytic-geometry formulas provide exact solutions for such problems. The 29 FORTRAN routines listed in this paper constitute a fairly complete subroutine library for stereonet computations, and they provide a practical means for computing analytic solutions rapidly and accurately on a computer.

On: “A Method to minimize edge effects in two‐dimensional discrete Fourier transforms” by Yanick Ricard and Richard J. Blakely (GEOPHYSICS, 53, 1113–1117, August 1988).

Abstract Because of recent advances in microcomputer speed and memory, spreadsheet programs, such as Lotus 1-2-3, now can be used to solve highly technical exploration problems. One such application is interactive gravity modeling. The spreadsheet template GWIZ provides explorationists with a rapid and easy method for potential-field modeling. Using this template, many possible source solutions can be obtained for gravity profile data. This allows explorationists to apply their geologic experience to such problems in an efficient manner. Eighteen 2- and 2 1 2 - dimensional geometric models ranging from simple cylinders to complex polygonal prisms are supported. Parameter fitting can be performed manually or automatically. The advantage of using a spreadsheet, rather than conventional computer languages, for technical problems such as gravity modeling is that the spreadsheet program itself provides for screen graphics. input-output operations, and support for peripheral devices. This makes programming easier and user instructions simpler.

Field Trip to a Galaxy Far, Far Away

The authors of this paper have created a very valuable method for approximating the two‐dimensional continuous spectrum by repeatedly rotating a rectangular sampling grid and averaging the resulting spectra. The authors state that their rotational transform “eliminates artifacts associated with the orientation of the rectangular sampling window.” However, I believe that one aspect of their method, the interpolation process, actually creates artifacts: