Isotopic and palaeomagnetic evidence for rates of cooling, uplift and erosion
Isotopic and palaeomagnetic evidence for rates of cooling, uplift and erosion
复制标题
DOI：
10.1144/gsl.mem.1985.010.01.26
复制
发表时间：
1985
期刊：
影响因子：
--
通讯作者：
M. H. Dodson;E. McClelland-Brown
中科院分区：
文献类型：
--
作者：
M. H. Dodson;E. McClelland-Brown
总结使用同位素和磁阻塞温度来推断冷却历史的阻塞过程的动力学模型进行了审查。已发表的冷却和抬升（侵蚀）速率的同位素估计是基于（a）裂变径迹年龄的垂直梯度，（B）具有不同阻塞温度的同位素矿物系统之间的年龄差异和（c）39 Ar-40 Ar步进加热实验的动力学分析。古地磁冷却历史的方法取决于对单个样品的热退磁实验，从中可以将不同的阻断温度分配给具有已知年龄关系的不同磁化方向。连续的磁反转原则上可以使用，但只在快速的后造山冷却的地区。在冷却非常缓慢的地方，可以使用明显的极地漂移路径来推断冷却速率，如西格陵兰的中元古代。相反，在格伦维尔省，磁化的独特成分已经通过参考基于氩-39的冷却历史来确定年代。在苏格兰，一项对第三纪岩墙的热晕中的磁化作用的研究提供了它们被侵入时的环境温度估计。由此得出的冷却（侵蚀）速率在双峰上变化，从约2 x 107年的周期内每百万年约30°C（约1 km），到约2 x 108年的周期内每百万年约1°C（约30 m），并与沉积学估计大致一致。
Summary The use of isotopic and magnetic blocking temperatures to infer cooling history is reviewed in the light of kinetic models of the blocking process. Published isotopic estimates of cooling and uplift (erosion) rates are based upon (a) vertical gradients of fission track ages, (b) age differences amongst isotopic-mineral systems with different blocking temperatures and (c) kinetic analysis of 39Ar-40 Ar step-heating experiments. The palaeomagnetic approach to cooling history depends upon thermal demagnetization experiments upon individual samples, from which different blocking temperatures can be assigned to different directions of magnetization having known age relationships. Successive magnetic reversals might in principle be used but only in areas of rapid postorogenic cooling. Where cooling is very slow it may be possible to use apparent polar wander paths to infer cooling rates, as in the mid-Proterozoic of West Greenland. Conversely, in the Grenville Province distinctive components of magnetization have been dated by reference to a cooling history based upon argon-39. In Scotland a study of imposed magnetizations in thermal aureoles of Tertiary dykes provided estimates of ambient temperature at the times at which they were intruded. Cooling (erosion) rates so derived vary bimodally from ~ 30°C (~ 1 km) per million years over periods of ~ 2 x 107 years immediately following orogeny, to ~ 1°C (~ 30 m) per million years in cratonic areas over periods of ~ 2 x 108 years, and broadly agree with sedimentological estimates.