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

阿拉斯加北极地区晚元古代岩石中碎屑锆石的 U-Pb 分析：对加拿大盆地和邻近极地边缘构造演化的启示

• 批准号: 9423534
• 负责人: William McClelland
• 金额: $ 13.15万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-07-01 至 1998-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9423534&HistoricalAwards=false
• 关键词: Pb; Analysis; Detrital; Zircons; Late

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.

该奖项支持一个研究北极构造演化的项目，该项目通过为加拿大盆地开放的力学模型提供古地理约束来研究北极构造演化。这些模型所依据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），不能提供独特的解决方案（例如，地层和盆地轴的相关性），或者由于在较年轻的造山运动期间的叠印（例如，构造关系）而保持解释性。最适合贫乏数据库的两种模式调用了(1)北极阿拉斯加-楚科奇从罗蒙诺索夫海岭的裂谷，然后沿着加拿大北极岛边缘的左旋平移，或者(2)北极阿拉斯加从加拿大北极群岛的裂谷和旋转。这些模型在假定的阿拉斯加北部白垩纪前的古地理位置上存在差异。因此，旨在限制北极阿拉斯加古地理起源的同位素研究可能为加拿大盆地的演化提供重要的见解。钕同位素分析已成功地用于提供古地理模型的一般约束。将Nd数据与单个碎屑锆石的U-Pb同位素分析相结合，可以区分特定的年龄群体，为位移层序及其源区的对比提供了有力的工具。本研究将对阿拉斯加北极地区4个地点的元古代元碎屑岩进行U/Pb碎屑锆石研究，以提供对其古地理起源的额外限制。为了确定原始克拉通特征，并为北极阿拉斯加地区古生代和更年轻地层的类似碎屑研究建立基线，将以元古代岩石为目标。将得到的同位素数据与来自加拿大北极和科迪勒拉边缘的已知碎屑特征进行比较，将直接影响对加拿大盆地构造演化当前模式的关键评估。此外，本研究的结果将解决前密西西比时期地体的存在与否，阿拉斯加北部元古代岩石2.0 Ga Nd模式年龄在均匀源与多组分混合方面的意义，元古代碎屑岩样本的沉积年龄，以及阿拉斯加北极与科迪勒拉板块外地壳碎片（Yukon-Tanana和Ruby地体）的潜在相关性。