We will present petrophysical data for 489 meteoritic samples representing 368 different meteorites ranging from achondrites to chondrites and from stony-irons to irons. The data (susceptibility, density, NRM-intensity, Q-ratio) have been compiled into a database that has many potential applications in meteorite research, in space geophysics and in archaeology (to study the origin of metals in archaeological materials). For example, we have used it in classifying meteorites following the method by Kukkonen and Pesonen (1983). The rationale behind the method is the observation that the main classes (achondrites, chondrites, stony-irons and irons) and the groups (e.g., the LL-, L-, H- and E- chondrites) form distinct clusters when plotted on petrophysical relation diagrams, such as the susceptibility vs. density. Three factors, the FeNi-content, the grain size of the opaque minerals and the degree of metamorphism, are causing this behavior. The petrophysical classification method was tested successfully with 24 meteorite samples from Czechoslovakian, one sample from Australian and three samples from Swedish meteorite collections. When meteorites are compared with the terrestrial basic igneous rocks, the petrophysical properties of the terrestrial rocks are seen to overlap only the area of achondrites in the susceptibility-density diagram. Thus, it is possible to distinguish rapidly a meteorite from a terrestrial rock by petrophysical properties, except for achondrites. The role of grain size producing variations in petrophysical properties was verified with magnetic hysteresis measurements of 54 meteorites. We have also carried out paleointensity determinations for 16 meteorites using the Thellier double heating technique. Of these, only 6 yielded meaningful results. The results suggest a high magnetic field, ranging from 51 microteslas to 728 microteslas, during the formation or during the last metamorphism of these meteorites (or their parent bodies). Magnetic hysteresis data and the stability of NRM (natural remanence), IRM (isothermal remanence) and ARM (anhysteretic remanence) are of particular importance in selecting suitable samples for Thellier paleointensity determinations.
- Pub Date:
- July 1992