THE INFLUENCE OF RADIATION DAMAGE ON THE SOLUBILITY OF EPIDOTE-GROUP MINERALS DURING CHEMICAL WEATHERING

Millersville University, Millersville PA

Investigators

Abstract

The purpose of this proposed study is to determine the maximum radiation dose of detrital epidote-group minerals collected from large river delta sediments. Because these minerals are sufficiently resistant to chemical weathering and survive into delta sediments, the maximum radiation dose measured will reflect a threshold of solubility. Based on previous studies completed on zircon and epidote-group minerals, the hypothesis of this study is that detrital epidote-group mineral grains that have experienced radiation doses less than ~3.5 * 1015 α-decay mg-1 will be resistant to chemical weathering. Epidote-group mineral grains will be extracted from Nile and Yangtze River delta sediments as both sites contain significant quantities of epidote and allanite. The Nile and Yangtze Rivers possess two of the world?s largest watersheds. Because the delta sediments originated from large watersheds underlain by crystalline silicate bedrock of varying age and lithology, the suite of epidote-group minerals derived from these sediments should span the range of compositions and radiation damage commonly observed in nature for grains resistant to dissolution. The grains extracted from the delta sediments will be verified as being epidote-group by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). For each epidote-group mineral grain utilized in this proposed study, major and trace element analyses will be completed. Major element analyses will be determined by electron microprobe (EMPA), and trace elements (e.g., U, Th, REE) determined by laser-ablation microprobe-inductively coupled-mass spectrometry (LAM-ICP-MS). The α-decay damage in the individual epidote-group mineral grains will be calculated using their age and radionuclide concentration. The broader impacts of this proposed study will be addressed in three different ways. First, Millersville University is an undergraduate institution and as a result undergraduates will be actively involved in the project. Second, this project will permit establishment of a relationship between undergraduate Millersville University and the Ph.D.-granting Memorial University of Newfoundland, Canada. Third, there will be development of an exhibit at the Lancaster Science Factory, located approximately 6 km from Millersville University near downtown Lancaster, Pennsylvania. The Lancaster Science Factory provides numerous hands-on, interactive technology and science exhibits relating to the physical sciences, engineering, technology, and mathematics. The hands-on exhibit will be entitled ?Radiation in the Environment,? and will provide a digital Geiger counter with a wand that interfaces to a computer allowing for the detection of radioactivity among different materials. The materials will include rocks and minerals, including samples of epidote-group minerals, as well as more common household items such as pieces of granite countertop and ceramic bowls.