U-Pb Analysis of Detrital Zircons in Late Proterozoic Rocks of Arctic Alaska: Implications for Tectonic Evolution of the Canada Basin and Adjacent Polar Margins

摘要 该奖项支持了一个研究北极构造演化的项目，该项目通过为加拿大盆地的开放提出的力学模型提供古地理限制。这些模型所基于的当前地球物理和地质数据通常缺乏所需的细节和分辨率（例如， 地球物理数据），不提供唯一的解决方案（例如， 地层和盆地轴线相关性），或者由于在较年轻的造山作用期间的叠加而保持解释性（例如， 结构关系）。两个模型，最适合微薄的数据库调用（1）裂谷北极阿拉斯加楚科奇从罗蒙诺索夫海岭，然后左平移沿着加拿大北极岛屿边缘或（2）裂谷和旋转北极阿拉斯加从加拿大北极群岛。这些模型在假设的前白垩纪阿拉斯加北方的古地理位置不同。因此，旨在限制阿拉斯加北极的古地理起源的同位素研究可能会为加拿大盆地的演变提供重要的见解。 钕同位素分析已成功地用于提供古地理模型的一般约束。结合单颗粒碎屑锆石的Nd数据和U-Pb同位素分析，可以区分特定的年龄群体，提供了一个强有力的工具来对比移位地层序列和它们的源区。 这项研究将涉及一个U/Pb碎屑锆石的研究，元古代变质岩石在4个地点横跨北极阿拉斯加，努力提供额外的限制其古地理起源。 将以元古代岩石为目标，以确定主要的碎屑岩特征，并为阿拉斯加北极地区古生代和较年轻地层的类似碎屑岩研究建立基线。 由此产生的同位素数据与已知的碎屑签名从加拿大北极和科迪勒拉边缘的比较将直接承担目前的加拿大盆地的构造演化模型的关键评价。此外，这项研究的结果将解决前密西西比期碎屑岩的存在或不存在，阿拉斯加北方元古代岩石报告的2.0 Ga Nd模式年龄在同质源与多组分混合方面的意义，元古代碎屑岩取样的沉积年龄，和潜在的相关性，北极阿拉斯加与地壳碎片（育空-塔纳纳和红宝石）目前外侧的科迪勒拉moogeocline。

Abstract This award supports a project to study the tectonic evolution of the Arctic by providing paleogeographic constraints on mechanical models proposed for the opening of the Canada Basin. Current geophysical and geological data upon which these models are based typically lack the required detail and resolution (e.g., geophysical data), do not provide unique solutions (e.g., stratigraphic and basin axis correlations), or remain interpretive due to overprinting during younger orogenesis (e.g., structural relationships). The two models that best fit the meager data base invoke (1) rifting of Arctic Alaska-Chukotka from the Lomonosov Ridge followed by sinistral translation along the Canadian Arctic Island margin or (2) rifting and rotation of Arctic Alaska from the Canadian Arctic Islands. These models differ in the assumed pre-Cretaceous paleogeographic position of northern Alaska. Thus isotopic studies designed to constrain the paleogeographic origin of Arctic Alaska could potentially provide significant insights into the evolution of the Canada Basin. Nd isotopic analyses have been successfully utilized to provide general constraints on paleogeographic models. Combining Nd data with U-Pb isotopic analysis of single detrital zircons, which allow discrimination of specific age populations, provides a powerful tool for correlation of displaced stratal sequences and their source regions. This research will involve a U/Pb detrital zircon study of Proterozoic metaclastic rocks at 4 localities across Arctic Alaska in an effort to provide additional constraints on its paleogeographic origin. Proterozoic rocks will be targeted in order to determine the primary cratonal signature and establish a baseline for similar detrital studies in Paleozoic and younger strata of the Arctic Alaska region. Comparison of the resultant isotopic data with known detrital signatures from the Canadian Arctic and Cordilleran margins will bear directly on critical evaluation of current models for the tectonic evolution of the Canada Basin. In addition, results of this study will address the presence or absence of pre- Mississippian terranes, the significance of 2.0 Ga Nd model age reported for Proterozoic rocks in northern Alaska in terms of homogeneous source versus multicomponent mixing, depositional ages of the Proterozoic clastic rocks sampled, and potential correlation of Arctic Alaska with crustal fragments (Yukon-Tanana and Ruby terranes) presently outboard of the Cordilleran miogeocline.