Speaker: Dr. Jeff Gillow, Principal Geochemist, ARCADIS, Highlands Ranch, CO. (SME Henry Krumb Lecture Series Speaker)


Subject:
Characterization of Arsenic Geochemistry in the Mojave Mining District of California

Background: Dr. Gillow is currently a Principal Geochemist at ARCADIS, U.S., Inc. and is focused on serving clients in the mining and industrial sectors with innovative, and technical based solutions to complex environmental issues. He has over 20 years of experience working on source control and water quality at mine sites, environmental stewardship of the nuclear fuel cycle, and management of energy byproducts. Dr. Gillow has a PhD. in Environmental Science & Engineering, Colorado School of Mines, an MS in Environmental Science, State University of New York, and a BS in Aquatic Chemistry, Southampton College. Prior to joining ARCADIS, Dr. Gillow was an Associate Chemist at Brookhaven National laboratory performing research and development on technologies for management of mine, energy, and nuclear waste materials. His expertise is arsenic and chromium geochemistry, as well as prevention and treatment of acid rock damage and associated metals. His practical experience centers on geochemical investigations and baseline water quality studies as well as control and treatment of sources of metals and acidity. He has worked on geochemical stabilization of arsenopyrite to prevent acid and arsenic release in oxidizing environments, and has investigated the basis for arsenic stabilization under anoxic conditions. He is principal scientist on current projects including the optimization on in-situ reductive precipitation of chromium in aquifer systems, as well as bio-geochemical approaches for treatment of uranium and sulfate in groundwater. He has employed sophisticated analytical chemistry methods to understand the mineralogy and geochemistry of metals and metalloids in ore, waste rock, and environmental samples. These include electron microprobe and x-ray spectroscopy as well as sequential selective chemical extraction. His approach to evaluation of source control involves detailed characterization, conceptual model development, and fate and transport assessment. He is well versed in all of these aspects of environmental evaluation for mining projects.

Summary:
Past mining activities in the Mojave Mining District have resulted in the accumulation of historical tailings from the recovery of precious metals. Rock types in the District include rhyolite, rhyolite porphyry, quartz latite, and pyroclastics with ore present as epithermal fissure veins containing gold and silver minerals, as well as minor pyrite, galena, and chalcopyrite. The Mojave area is characterized by arid conditions, and the rock has a very low acid generation potential; water-rock interactions are not of paramount concern. Prior to new mining activities in the area, a baseline study was performed to characterize the historical tailings and the occurrence of arsenic in order to understand its form and environmental mobility. The study included comprehensive sampling and analysis of ore, waste rock, tailings and soil, as well as advanced mineralogical analyses. A conceptual geochemical model was prepared to describe the forms of arsenic in association with iron oxyhydroxide weathering products. The model was validated through mineralogical characterization, including leaching testing and ion-beam microprobe analysis to examine the association of arsenic with forms of sulfur and iron. This characterization of previous mined areas, prior to new mining operations, as well as materials from host rock and leached ore, provides a comprehensive understanding of arsenic, its chemical form, and environmental stability.

Meeting Format: Social hour is from 6:00 pm to 7:00 pm, Buffet Dinner begins about 7:00 pm. After the dinner, section business is attended to, a raffle of several bottles of wind is conducted and the presentation is given. Proceeds from the raffle support the GEM Committee activities.

Summary: Doug and Dinah Shumway will lead a one day field trip to visit and view the geology and mines of Lucerne and Johnson Valleys in San Bernardino County. Points of interest will include the Helendale Fault, Blackhawk Landslide, Old Woman Springs Fault, Landers Fault Scarp, Morris Lode Iron deposit, Bessemer Iron Mine, and the collection of skarn minerals. Box lunches will be provided at a cost of approximately $15 each. Four wheel drive vehicles will be preferred. Reservations for the field trip will be required, call SEPOR @ 310-830-6601.

Background: NA

Meeting Format: We will meet in Apple Valley at the Lowe’s Home Improvement Center at Bear Valley Road and Apple Valley Road and be ready to start the field trip promptly at 9:00 am. Directions to Lowe’s: Take I-15 north to Victorville, exit Bear Valley Road to the east (right). Travel approximately 6 miles to Apple Valley Road (major intersection with stoplight), turn left and Lowe’s is on the right. The field trip will take approximately 6 hours. There are several excellent motels in Victorville along I-15 for those who want to travel to the Victorville area on Friday evening.  
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