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2006 Philadelphia Annual Meeting (22–25 October 2006)

Paper No. 2
Presentation Time: 1:30 PM-5:30 PM

GRADIENTS IN MINERALOGY AND ELEMENT COMPOSITION AT THE BEDROCK-REGOLITH INTERFACE RECORD MINERAL REACTION AND TRANSPORT RATES


HAUSRATH, Elisabeth M., Geosciences, Pennsylvania State University, 302 Hosler Building, University Park, PA 16802, SAK, Peter, Dickinson College, Carlisle, PA, NAVARRE-SITCHLER, Alexis K., Geosciences, The Pennsylvania State University, 315 Hosler Building, University Park, PA 16802, WILLIAMS, Jennifer Zan, Center for Environmental Kinetics Analysis, Pennsylvania State University, 218 Deike Building, University Park, PA 16802, CABRET, Eduardo J., Geology, The University of Puerto Rico at Mayaguez, Mayaguez, PR 00681 and BRANTLEY, Susan L., Earth and Environmental Systems Institute, Pennsylvania State University, 2217 Earth and Engineering Building, University Park, PA 16802, emh191@psu.edu

Basalt is the most common volcanic rock in the Earth's crust, and due to its quickly dissolving nature plays an important role in the composition of the Earth's waters. Additionally, about one third of the carbon dioxide currently being removed from the atmosphere by weathering silicate rocks is removed by weathering basalt. Basalt is also important to our understanding of the surface of Mars. However, despite its importance on both Earth and Mars, basalt weathering rates remain poorly understood.

We have studied elemental weathering profiles formed on basaltic parent material in three field weathering environments: tropical Costa Rica, temperate Pennsylvania, and arctic Svalbard (Norway). The gradients formed at these interfaces between parent rock and weathered rind or soil allow a comparison of basalt weathering under different climate regimes, duration of weathering, and physical erosion. The reaction front thickness over which primary minerals disappear from these profiles ranges from microns (Svalbard) to centimeters (Pennsylvania).

We also compare global mineral persistence data from soil environments to the studied weathering profiles. We present a compilation of field weathering rates for 8 common rock-forming phases (plagioclase, volcanic glass, quartz, feldspar, micas, pyroxene, amphibole, and olivine) collected from dated chronosequences representing a wide climatic spectrum ranging from -10°C to 30°C mean annual temperature and 400 mm to 4500 mm mean annual precipitation. This compilation helps constrain the rates at which primary phases weather under field conditions.

Understanding and interpreting basalt weathering profiles as well as mineral persistence in field environments allows us to better understand basalt weathering rates. This will help inform geochemical modeling, and enhance our understanding of the surface and aqueous history of both Earth and Mars.

Session No. 59--Booth# 140

T68. Gradients at Hydrologic Interfaces as Indicators of Key Earth-Surface ("Critical-Zone") Processes (Posters)
Sunday, 22 October 2006: 1:30 PM-5:30 PM
Geological Society of America Abstracts with Programs. Vol. 38, No. 7, p.159
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