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通常在白垩纪-第三纪(K-T)界面沉积岩中所发现的黑色微球状磁性颗粒被认为是由于碰撞而熔化的产物,现已得知这些颗粒是引起意大利Petriccio地区K-T界面磁异常的主要原因.此外在几乎所有的深海钻探计划(DSDP)所获得的K-T界面的沉积岩岩心里都存在这种颗粒.这种磁性矿物的富集程度可以通过磁化率的测量来探测.因为磁化率与微球状磁性颗粒的含量之间存在着非常近似的正比例关系.通过下述几种岩石磁生研究技术,对提取的微状磁性颗粒进行磁性分析,即利用磁滞分析、等温剩磁测量、退磁和热磁测量等,认为微球状磁性粒中的磁性矿物几乎为磁铁矿结构的自然铁和具有“软的”多磁畴特性,这与以前均的非磁性研究的结果一致.反之,来自夏威夷的火山灰具有明显的“较硬”磁性,然而却意外地在其K-T界面上发现了众所周知的火山成因的铱异常.在此建议如果对K-T界面进行大量的剖面性磁化率测量的话,就会得出该边界在全球范围内明显的分布特征,该特征就可能涉及到碰撞/火山的位置,因为假定在这些位置附近微球状磁性颗粒比较富集,利用微球状磁性颗粒的分布特征圈定K-T边界比利用附着在尘埃上的铱有明显的优点,因为这种铱在沉降之前可能已经环绕地球飘扬几遍了,而大颗粒的(几百微米)微球状磁性颗粒相对飘扬的路程较短.
Black microspherical magnetic particles, usually found in sedimentary rocks of the Cretaceous-Tertiary (KT) interface, are believed to be products of melting due to collisions and are now known to be responsible for the magnetic anomalies at the KT interface in the Petriccio region of Italy In addition, these particles are found in sedimentary rock cores at the KT interface obtained by almost all deep-sea drilling programs (DSDPs), and the degree of enrichment of such magnetic minerals can be probed by measuring susceptibility because the magnetic susceptibility is inversely proportional to the microspherical There is a very approximate proportional relationship between the content of magnetic particles.The magnetic analysis of the extracted micrormagnetic particles is carried out by the following rock magnetism research techniques using the hysteresis analysis, isothermal remanent magnetization measurement, demagnetization and heat Magnetic measurement and the like, it is considered that the magnetic minerals in the microspheroidal magnetic grains are almost natural iron with a magnetite structure and have “soft” multi-domain properties in agreement with the results of the previous non-magnetic studies. Hawaii’s volcanic ash has a markedly “hard” magnetism, but unexpectedly discovered the well known volcanic iridium anomaly at its KT interface. It is proposed here that K -T interface for a large number of cross-sectional susceptibility measurements, it will be drawn in the border of the global distribution of the obvious characteristics of this feature may be involved in the collision / volcano location, because these sites are assumed to be microspheroidal magnetic particles Enriched, the use of the distribution characteristics of the microspheroidal magnetic particles to delineate the KT boundary has distinct advantages over the use of iridium attached to the dust, as the iridium may have flown around the earth several times before settling, whereas the large 100 microns) Microspherical magnetic particles relatively fly a short distance.