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，高剥蚀率（高达1厘米/年）和快速的地形演变已被记录在案。 相比之下，自从主要的构造活动扰动了一些大陆内部以来，已经过去了数十亿年。然而，现在很清楚，即使是这些表面上稳定的地幔核也经历了低幅度的埋藏和去顶，与遥远的构造过程和板间耦合和地幔流的变化模式有关。在这个项目中，（U-Th）/He和4 He/3 He磷灰石热年代测定法的最新进展正在被用来调查加拿大西部地盾（丘吉尔省和奴隶克拉通）部分地区古生代埋藏和去顶的热年代学和地质证据，目前没有古生代盖层。最近对（U-Th）/He磷灰石测年辐射损害控制的认识，使人们有希望通过调查同一地壳水平上具有一系列闭合温度（目前的数据表明约为50-115摄氏度）的磷灰石，破译热历史的其他部分。4 He/3 He磷灰石热时计对温度较低（低至30-40摄氏度）的敏感度高于其他方法，因此可以检测到大陆内部可能保存的热状态的更微妙变化。这一综合办法将用于：1）在西部丘吉尔省进行有针对性的研究，以跟进关于古生代再埋藏和去顶的具有争议性的初步热年代学证据，和2）开始对奴隶克拉通进行勘察调查，以评估已知已发生的中生代再埋藏的热年代学特征，这是通过识别金伯利岩管中夹带的中生代盖层捕虏体来实现的。该项目将提供对大陆内部地表和岩石圈历史之间的联系的新的见解，这些联系传统上没有使用（U-Th）/He技术进行研究。表面的埋藏和侵蚀可能与金伯利岩管道从世界钻石的来源深处侵入有关，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去顶的原因，也可能提供有关北美东部中生代盆地序列发生的基本信息，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.