HR: 0800h
AN: V51C-0596    [Abstracts]
TI: In-situ Production Rates of $^{53}$Mn in Antarctic Rocks
AU: * Serefiddin, F
EM: serefif@rutchem.rutgers.edu
AF: Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08901 United States
AU: Faestermann, T
EM: Thomas.Faestermann@physik.tu-muenchen.de
AF: Physik Department E15, Technische Universitaet Muenchen, Garching, 85747 Germany
AU: Herzog, G F
EM: herzog@rutchem.rutgers.edu
AF: Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, NJ 08901 United States
AU: Knie, K
EM: klaus.knie@ph.tum.de
AF: Physik Department E15, Technische Universitaet Muenchen, Garching, 85747 Germany
AU: Korschinek, G
EM: Gunther.Korschinek@ph.tum.de
AF: Physik Department E15, Technische Universitaet Muenchen, Garching, 85747 Germany
AU: Masarik, J
EM: masarik@fmph.uniba.sk
AF: Department of Nuclear Physics, Comenius University , Bratislava, 842 48 Slovakia (Slovak Republic)
AU: Poutivtsev, M
EM: mpouti@ph.tum.de
AF: Physik Department E15, Technische Universitaet Muenchen, Garching, 85747 Germany
AU: Sch\, J M
AF: Geochemistry, Lamont-Doherty Earth Observatory, Palisades, NY 10964
AB: We present first successful measurements of terrestrial $^{53}$Mn from whole rock and pyroxene separates from surfaces with long-term exposure in the Antarctic Dry Valleys. The half-life for $^{53}$Mn (t$_{1/2}$ $\sim$3.7 Myr)is much longer compared to $^{36}$Cl (t$_{1/2}$ $\sim$301 Kyr), $^{10}$Be (t$_{1/2}$ $\sim$1.5 Myr) and $^{26}$Al ($_{1/2}$ $\sim$720 Kyr). Previous surface exposure ages based on $^{3}$He, $^{21}$Ne and $^{10}$Be from these rocks can be used to cross-calibrate the $^{53}$Mn production rate (PR) with modeled $^{53}$Mn production rates. With its half-life of $\sim$3.7 Myr and ubiquitous parent element (Fe), $^{53}$Mn may soon find a broad application to surface dating. Due to its long half-life, $^{53}$Mn is a valuable tool to quantify earth surface processes on time scales up to 10 Myr. $^{53}$Mn is a single target (Fe) product, therefore the production pathway and thus the PR model calculations are relatively simple. Because Fe is abundant in most rocks, whole rock samples can be processed on time scales exceeding the $^{36}$Cl method. Furthermore, the chemical separation of $^{53}$Mn from rocks is simple and fast compared to other cosmogenic nuclide methods such as $^{10}$Be, $^{26}$Al and $^{36}$Cl. Relatively high energies and advanced detector systems are indispensable for separating $^{53}$Mn from its isobar $^{53}$Cr. Furthermore, low production rates in terrestrial systems require a high analytical sensitivity. Recent advances at the tandem accelerator of the TUM and LMU in Munich have allowed an efficient suppression of $^{53}$Mn's interfering isobar, $^{53}$Cr, and reduced the detection limit for the $^{53}$Mn/$^{55}$Mn ratio to 10$^{-14}$. Our measurements confirm that the measurements of $^{53}$Mn are possible. All $^{53}$Mn data are normalized to a well-known meteorite standard. First results for six measurements in four Antarctic dolerites give promising results. The samples were taken from dolerite boulders or bedrock surfaces at elevations ranging from 1145 to 2555 m altitude. The Fe and Mn concentrations, used for activity calculations, were measured by atomic absorption spectroscopy or spectrophotometry. The terrestrial $^{53}$Mn activity of the whole rock sample and a pyroxene separate from the same rock are strikingly consistent with one another, demonstrating that $^{53}$Mn surface exposure dating (SED) is feasible for whole rock samples. Two independent chemical preparations of pyroxene sample from the same rock agree, suggesting that with increased counting times, the uncertainties of the $^{53}$Mn determinations should be reducible to about 10% or less. The modeled value for production rates in pyroxenes at 2555 m altitude is 1.7 dpm/kg Fe. This agrees well with the measured production rate of 1.66 dpm/kg Fe.
DE: 9310 Antarctica
DE: 9604 Cenozoic
DE: 3344 Paleoclimatology
DE: 1035 Geochronology
DE: 1040 Isotopic composition/chemistry
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting