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当火成碎屑沉积物在地磁场中在高温条件下沉降时,它们就能记忆自己的背景温度。这个背景温度值随沉积物类型的不同而改变,从大气层的一般温度(指从空中降落的火山灰的温度)到几百摄氏度(指浮岩流的温度)。这些温度值也随离开火山喷发口的距离远近而有很大变化。对于那些由于较老的地质事件而产生的火成碎屑沉积物来说,由于结晶作用或成岩过程产生的胶结作用,进行研究工作经常是困难的,因而要去探寻侵蚀喷发的中心。背景温度的精确评价既可以使我们查明沉积物的侵位过程及其性质,又可以通过绘制温度图来查明火山喷出的中心位置。到目前为止,研究碎屑沉积物背景温度的方法全是以分析沉没在岩流中的物质或是围岩物质为基础。当所研究的对象是燃烧过的木材或加热过的物体时,这种方法可能属于化学分析或者就象在分析陶瓷或岩石的情况那样以分析化石热剩余磁化强度为基础。然而这样的物体并不是经常能找到的,所以这儿提出的方法是分析来自沉积物自身的样品。方法的基本原理引自Thellier方法,它的要点是将样品在一个已知场中加热期间,天然磁化强度的损耗率与冷却期间总的热剩余磁化强度的损耗率进行比较。这个方法与Thellier方法最大的不同点是它可以在任何高温上直接得出剩余的磁化强度。这个方法只需要两次加热就可以得到结果,因此可使我们避免与磁相互作用有关的任何困难及减小矿物转换的影响。
As pyroclastic sediments settle in the geomagnetic field at high temperatures, they remember their own background temperature. The background temperature varies with the type of sediment, from the normal atmosphere temperature (the temperature of pozzolan falling from the sky) to a few hundred degrees Celsius (referring to the temperature of the pumice stream). These temperature values also vary greatly with the distance from the volcanic eruption opening. For pyroclastic sediments due to older geological events, research is often difficult due to crystallization or the cementation of the diagenesis process, so the center of erosion eruptions is explored. Accurate evaluation of the background temperature allows us to ascertain the emplacement process of sediment and its nature, but also can be drawn by mapping the volcano to ascertain the center of the volcano. So far, the method of studying the background temperature of clastic sediments has been based on the analysis of submerged matter or rock mass. When the object of study is burned wood or heated objects, this method may belong to chemical analysis or, as in the case of ceramic or rock analysis, based on an analysis of the thermal residual magnetization of the fossil. However, such objects are not always found, so the approach presented here is to analyze the samples from the sediment itself. The basic principle of the method is derived from the Thellier method and its point is to compare the rate of loss of natural magnetization with the rate of loss of total thermal residual magnetization during cooling during heating of the sample in a known field. The biggest difference between this method and the Thellier method is that it can directly derive the residual magnetization at any elevated temperature. This method requires only two heatings to get results, thus allowing us to avoid any difficulties associated with magnetic interactions and reduce the effects of mineral transformation.