Quantifying the Stability of Continents Using Advances in (U/Th)/He, 4He/3He and U/Pb Apatite Thermochronometry

在活动板块边缘，记录了高剥蚀率(高达1厘米/年)和快速地形演化。相比之下，自从主要的构造活动扰乱了一些大陆内部以来，已经过去了数十亿年。然而，现在清楚的是，即使是这些表面上稳定的克拉通岩芯，也经历了低幅度的埋藏和剥离，这与遥远的构造过程和板间耦合和地幔流动模式的变化有关。在这个项目中，(U-Th)/He和4He/3He磷灰石测年的最新进展正在被用来调查加拿大西部盾体(丘吉尔省和奴隶克拉通)部分地区显生界埋藏和去顶的温度年代学和地质证据，该地区目前没有显生宙盖层。最近对(U-Th)/He磷灰石年代辐射损害控制的认识，有望通过研究同一地壳水平闭合温度范围(当前数据显示约50-115摄氏度)的磷灰石来破译热历史的其他部分。与其他方法相比，4He/3He磷灰石温度计时器对较低的温度(低至30-40摄氏度)很敏感，因此可以探测到可能保存在大陆内部的更细微的热状况变化。这一综合方法将用于：1)在西部丘吉尔省开展一项有针对性的研究，以跟进显生代重新埋藏和去顶的挑衅性初步热年代学证据，以及2)开始对奴隶克拉通进行勘察调查，以评估已知的显生代重新埋葬的热年代学特征，这是通过识别携带在金伯利岩管道中的显生代盖层包裹体而发生的。该项目的结果将为传统上未使用(U-Th)/He技术研究的大陆内部地表和岩石圈历史之间的联系提供新的见解。地表的埋藏和侵蚀事件可能与金伯利岩管从深处侵入有关，金伯利岩是世界钻石的来源，这取决于神秘的金伯利岩成因的地球动力学驱动因素。了解大陆内部埋藏和剥落屋顶的原因也可能提供有关北美克拉通地区显生宙盆地序列产状的基本信息，这些盆地序列是化石燃料的重要来源。

At active plate margins, high denudation rates (up to 1 cm/yr) and rapid topographic evolution have been documented. In contrast, billions of years have passed since major tectonic activity perturbed some continental interiors. However, it is now clear that even these apparently stable cratonic cores undergo low amplitude episodes of burial and unroofing, linked to distant tectonic processes and changing patterns of interplate coupling and mantle flow. In this project, recent advances in (U-Th)/He and 4He/3He apatite thermochronometry are being used to investigate thermochronological and geological evidence for Phanerozoic burial and unroofing in portions of the western Canadian shield (Churchill province and Slave craton), which is currently devoid of Phanerozoic cover. Recent recognition of radiation damage control on (U-Th)/He apatite dates holds the promise of deciphering additional portions of the thermal history by investigating apatites with a range of closure temperatures (current data suggests approximately 50-115 degrees C) from the same crustal level. The 4He/3He apatite thermochronometer is sensitive to temperatures lower (down to 30-40 degrees C) than those accessible by other methods, and thus can detect the more subtle changes in thermal regimes that may be preserved within continental interiors. This integrated approach will be used to: 1) carry out a targeted study in the western Churchill province to follow up on provocative preliminary thermochronological evidence for Phanerozoic reburial and unroofing, and 2) commence a reconnaissance investigation of the Slave craton to evaluate the thermochronologic signature of Phanerozoic reburial known to have occurred by recognition of xenoliths of Phanerozoic cover entrained in kimberlite pipes.The results of this project will provide fresh insight into links between surface and lithospheric histories in continental interiors that have not been traditionally investigated using (U-Th)/He techniques. Burial and erosional episodes at the surface may correlate with the intrusion of kimberlite pipes from great depths that are the source of the world's diamonds, depending on the geodynamic driver for enigmatic kimberlite genesis. Understanding the causes of burial and unroofing in continental interiors also may provide basic information about the occurrence of Phanerozoic basinal sequences within cratonic North America that are an important source of fossil fuels.