Resolving mid- to upper-crustal exhumation through apatite petrochronology and thermochronology
Resolving mid- to upper-crustal exhumation through apatite petrochronology and thermochronology
复制标题
DOI：
10.1016/j.chemgeo.2021.120071
复制
发表时间：
2021-01
期刊：
影响因子：
3.9
通讯作者：
G. Jepson;B. Carrapa;S. George;A. Triantafyllou;S. M. Egan;K. Constenius;G. Gehrels;M. Ducea
中科院分区：
文献类型：
--
作者：
G. Jepson;B. Carrapa;S. George;A. Triantafyllou;S. M. Egan;K. Constenius;G. Gehrels;M. Ducea
使用磷灰石 U-Pb 和裂变径迹系统进行双重测年正在成为解决中上地壳冷却问题的越来越流行的方法。然而，由于两个系统之间的温度窗口差异较大（通常>250°C），这些测温仪限制了通常难以通过地质时间联系起来的日期。在这项研究中，我们将磷灰石 U-Pb、裂变径迹、磷灰石和全岩地球化学应用于科迪勒拉造山系统常见的四个构造域的 14 个样本：(1) 基底核隆起，(2) 侵入厚地壳柱的岩体，(3) 变质核复合体和相关的滑脱断层，以及 (4) 快速、喷出的火山冷却，以便在原位地球化学特征和冷却机制。磷灰石和整个岩石之间微量元素分配的比较提供了对初始磷灰石形成过程和/或后续改性的见解。磷灰石微量元素地球化学以及 Th/U 和 La/LuN 比率提供了工具来确定磷灰石是否是原生磷灰石并代表其母体熔体，或者是否在结晶后经历了地球化学扰动。此外，我们证明，通过使用磷灰石 U-Pb、FT、微量元素和全岩石地球化学相结合的方法，可以确定岩石自结晶以来是否经历过单调冷却、在中地壳中长期停留，并提供独特的结构信息，例如滑脱断层的历史。本文提供的见解为磷灰石热年代学提供了新的应用。
Double-dating using the apatite U-Pb and fission-track systems is becoming an increasingly popular method for resolving mid- to upper- crustal cooling. However, these thermochronometers constrain dates that are often difficult to link through geological time due to the large difference in temperature window between the two systems (typically >250 °C). In this study, we apply apatite U-Pb, fission-track, and apatite and whole rock geochemistry to fourteen samples from four tectonic domains common in Cordilleran orogenic systems: (1) basement-cored uplifts, (2) plutons intruded through a thick crustal column, (3) metamorphic core complexes and associated detachment faults, and (4) rapid, extrusive volcanic cooling, in order to provide a link between in situ geochemical signatures and cooling mechanisms. Comparisons of trace element partitioning between apatite and whole rock provide insights into initial apatite-forming processes and/or subsequent modification. Apatite trace element geochemistry and the Th/U and La/LuNratios provide tools to determine if an apatite is primary and representative of its parent melt or if it has undergone geochemical perturbation(s) after crystallization. Further, we demonstrate that by using a combined apatite U-Pb, FT, trace element, and whole rock geochemistry approach it is possible to determine if a rock has undergone monotonic cooling since crystallization, protracted residence in the middle crust, and provide unique structural information such as the history of detachment faulting. Insights provided herein offer new applications for apatite thermochronology.