Earth Sciences Division
Fundamental and Exploratory Research Program
Annual Report 1998-1999
The Center for Isotope Geochemistry The Center for Isotope observed and simulated climate feaGeochemistry (CIG) was established tures suggests that the RCMS is capaDonald J. DePaolo in 1988 with three major goals. The ble of long-term regional climate simfirst is to maintain a state-of-the-art ulation. Another project couples genContact: Donald J. DePaolo analytical facility for the measurement eral circulation models, which simu(510) 643-5064, djdepaolo@lbl.gov of the concentrations and isotopic late global climate change scenarios, compositions of elements in rocks, with Califo rnia Department of minerals, fluids and gases in the earth’s crust, oceans and atmosForestry wildfire models to predict the impact of future climate phere.The second is to develop new ways of using isotope ratio change on the occurrence and magnitude of wildfires at a local measurements to study earth processes. This involves improvescale.The average insured cost of wildfires in the United States is ments in analytical techniques, as well as exploration of the natabout $300 million dollars per year. Insurers and climatologists ural isotopic variations of key elements and development of conhave long known that fire danger is intimately linked to climate. ceptual models relating isotopic variations to earth processes. For instance, local and regional droughts linked to the recent El The third objective is to apply well-known isotopic and chemiNiño led to devastating fires in Florida, Indonesia and elsewhere. cal approaches to specific energy and environmental problems, In most cases, climate change driven by a two-fold increase in such as groundwater contamination and remediation, geotheratmospheric carbon dioxide would lead to dramatic increases in mal resource development, nuclear waste isolation and global cliboth the area of land burned by California wildfires and the nummate change. ber of potentially catastrophic fires. The Center’s lab facilities include laboratory and field equipIn many natural systems, fracture permeability exerts a dominant influence on fluid flow. A simple model is under development for oceanographic studies, a stable isotope laboratory, a ment to test the feasibility of using the isotopic compositions of noble gas laboratory, a cosmogenic isotope laboratory, a soil carelement pairs in fluids to constrain fracture-matrix geometry and bon laboratory and an analytical chemistry laboratory.There is a spacing. Fluids acquire heat from matrix blocks by conduction thermal ionization mass spectro m e t ry lab o ra t o ry on the and solubility and ionic diffusivity limits the exchange of chemiUniversity of California’s Berkeley campus. In the coming year cal and isotopic constituents. Therefore, the thermal, chemical the Center will obtain a multiple-collector, magnetic sector mass and isotopic evolution of fluids flowing through fractured rock spectrometer with a plasma ion source, which will greatly depends strongly on fracture geometry and spacing. Reservoir expand its analytical capabilities. ESD researchers have estabmodeling relies on geometric information from rock outcrops lished the Regional Climate Center (RCC) and are associated and core, but the geometry of the reservoir fractures carrying with the Center for Isotope Geochemistry to take advantage of the bulk of the fluid is generally not known.The sensitivity of isothe overlap in research interests. The RCC specializes in a topic ratios to matrix block size (or average fracture spacing) is Regional Climate System Model (RCSM) that downscales global related to the differing solubility and diffusivity of the elements. model information to provide research information, climate predictions and impact assessments on a regional scale.The model The degree to which a matrix block is isolated from a fracture can be applied to weather forecasting, soil water content, river fluid decreases with increasing solubility and diffusivity. flow, hydrology at a waterR e s e a rchers measure d shed scale, climatic trends, helium, carbon and oxygen water re s o u rces, crop isotopes in samples fro m responses and ecological fault zone gouge, breccia and and environmental impacts. host rock of the San Andreas A pressing question in cliFault. Their study confirms matology is what the impact that a significant fraction of of future climate change will the helium in the fault zone be on regional and local fluids has come from the scales. Climate researchers, mantle and is accompanied using a re gional cl i m a t e by deep crustal or metamorhindcast, are evaluating the phic water and carbon dioxeffectiveness of the Regional ide. This supports their earClimate System Model and lier work that suggested fluits various components, such ids are entering the fault as the Mesoscale from the mantle and acting Atmospheric Simulation and to lubricate the fault, which S o i l - P l a n t - S n ow models, to would explain the we l l reproduce western U.S. cliknown dearth of friction on Figure 1. Mono Lake, California. Photo by Roy Kaltschmidt, LBNL. mate. Agreement between the San Andreas Fault. In a 29