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11.
The complex brecciation and shock history of amphoterite (LL-) chondrites is well reflected in their diverse natural magnetic remanence (NRM) behavior: Most LL-chondrites have a multicomponent, undemagnetizable NRM, analogous to that of lunar breccias. Only one meteorite among those studied, namely Dhurmsala (LL6), meets the criteria of NRM stability and directional coherence with progressive AF cleaning, indicative of a useful paleoremanence. Ancient field paleointensity determinations for Dhurmsala (LL6) of 0.03 and 0.1 Oe, agree well with our earlier estimates of 0.01 and 0.08 Oe for the LL6 Jelica and Vavilovka, respectively. In light of their petrographic structure, cooling rates, radiometric ages and shock indicators, it appears likely that the NRM may have been thermally imprinted, during cooling following shock-metamorphism. The closely similar saturation remanence (IRMs) behavior for LL-chondrites, in contrast to the intragroup scatter in NRM characteristics, implies that - although formed by similar process from the same starting material, - the LL-chondrites have suffered widely different degrees of shock/metamorphic reheating. 相似文献
12.
Fabien Magri Ulf Bayer Christoph Jahnke V. Clausnitzer H. J. Diersch J. Fuhrman P. Möller A. Pekdeger M. Tesmer H. J. Voigt 《International Journal of Earth Sciences》2005,94(5-6):1056-1069
In several areas of the North German Basin, saline water comes close to, or even reaches the surface. Available data from
wells indicate that brine stratification is under unstable conditions in the deeper underground. In order to analyse the possible
transport mechanisms, 3D thermohaline simulations have been carried out for two different scenarios. The 3D regional model
(230×330 km) indicates that salty water is driven to the surface by hydrostatical forces from the surrounding highlands. In
addition, a smaller scale model (10×10 km) has been constructed with a grid resolution accounting for possible convective
flow. The results indicate that convective flow may play a dominant role in areas with minor topography. In summary, the complex
pattern of near surface occurrences of saline water probably results from the interaction of hydrostatic and thermal forces. 相似文献