HR: 1340h
AN: GP23A-0162    [Abstracts]
TI: Magnetic Properties of Santorini Volcanics and Archaeological Material From Northern Greece
AU: De Marco, E
EM: demarco@lemnos.geo.auth.gr
AF: Department of Geophysics, School of Geology, Aristotle University of Thessaloniki, P.O.Box, 352-1, Thessaloniki, GR-54124 Greece
AU: * Spassov, S
EM: simo.spassov@oma.be
AF: Department of Geophysics, School of Geology, Aristotle University of Thessaloniki, P.O.Box, 352-1, Thessaloniki, GR-54124 Greece
AU: * Spassov, S
EM: simo.spassov@oma.be
AF: Centre de Physique du Globe, Institut Royal M\'et\'eorologique, Dourbes, B-5670 Belgium
AU: Kondopoulou, D
EM: despi@geo.auth.gr
AF: Department of Geophysics, School of Geology, Aristotle University of Thessaloniki, P.O.Box, 352-1, Thessaloniki, GR-54124 Greece
AU: Zananiri, I
EM: izanan@lemnos.geo.auth.gr
AF: Department of Geophysics, School of Geology, Aristotle University of Thessaloniki, P.O.Box, 352-1, Thessaloniki, GR-54124 Greece
AB: Absolute palaeointensity determination is a long-winded and complicated procedure. The Thellier-Thellier technique, in particular, requires multiple heating and cooling steps. Magnetic minerals are often chemically unstable, and multiple heatings may cause oxidation, hence aiding the subsequent neo-formation of remanence carriers during the procedure. Samples from recent rhyodacitic lava flows on Santorini (Southern Greece)and archaeological material (burnt clay) from two Hellenistic pottery kilns at Katerini (Northern Greece) have been tested for their thermal stability. Small specimens were used to study the temperature dependence of magnetic low-field susceptibility, using a Thellier-Thellier like measurement sequence. The remanence properties were tested on palaeomagnetic standard sized samples by detailed alternating field (AF) demagnetisation of isothermal remanent magnetisation (IRM) and IRM acquisition at different annealing temperatures. The coercivity content was analysed using the method of Egli (2003, 2004). Two low coercivity ($<100$ $mT$) components were found in the lava samples, the individual contribution to the total magnetisation being unchanged after annealing up to $500$ $^{o}C$. The temperature dependence of susceptibility indicates also two components, which are both thermally stable. Heating and cooling cycles are almost undistinguishable up to $500$ $^{o}C$. In comparison to the lava, the burnt clay from the archaeological site seems to be slightly less resistant against multiple heatings as indicated by susceptibility and remanence behaviour. This is possibly due to the formation of chemical weathering products after the last burning. Temperature dependence of magnetic susceptibility in combination with coercivity spectra analysis at different annealing temperatures gives a reliable assessment about magnetic mineral alterations.
DE: 1503 Archeomagnetism
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting