Collaborative Research: Laurentian and Non-Laurentian (Baltican) Components of Terranes in NW Washington?

古老的北美大陆(劳伦蒂亚)在古生代沿着其西缘的增长是由于当地和外来来源的物质的补充：来自大陆西侧的沉积停机坪(米地斜)，以及由来自地球其他地区的板块构造移位并断裂进入大陆的由聚积的地体组成的杂岩。这项研究的研究将考察华盛顿州西北部吸积的奇利瓦克地体的历史，初步研究表明，至少部分来自欧洲西北部。我们工作中的一个主要工具是获取火成岩和沉积岩中的锆石颗粒的U-Th-Pb年龄。奇利瓦克地体火成岩的初步数据得出的年龄在北美西部未知，但在古代斯堪的纳维亚半岛(波罗的海)很常见。在沉积岩中，锆石的年龄分布在一些类似北美的岩石中，而在其他岩石中，则指向一个异国(欧洲或其他)的故乡。更多的锆石年龄将澄清这些可能的相关性。进一步的锆石Hf同位素数据将被用来测试奇利瓦克地体部分来自原始大洋岛弧的可能性，特别是早古生代亚历山大弧地体结于阿拉斯加东南部，而不是演化的大陆地壳(劳伦斯或其他)。岩石单元的野外测绘将评估奇利瓦克地体具有北美与外来亲缘关系的部分之间的遗传和结构关系。该项目的基本目标是了解板块构造机制和活动大陆边缘的形成过程的基本知识。研究计划旨在解决上述科学问题，并加强学生的教育和培训，提高公众对太平洋西北地区地球历史的兴趣和了解。项目资金将支持本科生担任现场和实验室助理，并支付学生参加专业会议的费用。学生对该项目的研究可能会构成高级论文的基础。从这项研究中获得的知识将被纳入到课堂、实地考察和西华盛顿大学教授的太平洋西北地区校外实地考察课程中。至于更广泛的社区，除了技术出版物和讲座外，拟议的研究成果将被纳入并将加强美国地质学会、全国地质教师协会和西北地质学会等专业团体经常进行的实地考察。圣胡安群岛和喀斯喀德的公共土地是全球旅游目的地，通过公园内的地质展示和流行的地质文献提供了接触广泛受众的机会。在华盛顿西部展示的大陆边缘构造的规模，在任何知识水平上都是令人着迷的。

Growth of the ancient North American continent (Laurentia) along its western margin in Paleozoic times occurred by addition of materials of both local and exotic origins: a sedimentary apron derived from erosion of the western flank of the continent (the miogeocline), and also a complex of accreted terranes displaced by plate tectonics from other parts of the globe and faulted into the continent. Research of this study will examine the history of the accreted Chilliwack terrane in northwest Washington about which preliminary studies suggest that at least parts came from northwestern Europe. A primary tool in our work is acquisition of U-Th-Pb ages of zircon grains in igneous and sedimentary rocks. Preliminary data from igneous rocks in the Chilliwack terrane yield ages not known in western North America, but common in ancient Scandinavia (Baltica). In sedimentary rocks, age distributions of zircons are in some rocks similar to North America and in other rocks point to an exotic (European or other) homeland. Additional zircon ages will clarify these possible correlations. Further Hf isotopic data from zircons will be used to test possible derivation of parts of the Chilliwack terrane from a primitive oceanic island arc, specifically the early Paleozoic Alexander arc terrane accreted in southeast Alaska, as opposed to evolved continental crust (Laurentian or other). Field mapping of rock units will evaluate the genetic and structural relationship among parts of the Chilliwack terrane that have North American vs. exotic affinities. The fundamental goal of the project is basic knowledge of mechanisms of plate tectonics and processes of formation of an active continental margin.The research plan is designed to address the scientific issue described above, and also to enhance the education and training of students and elevate interest and understanding of earth history of the Pacific Northwest in the general public. Project funds will support undergraduate students as assistants in the field and laboratory, and pay for students to attend a professional meeting. Student research on the project will likely form the basis of senior theses. Knowledge gained from this study will be incorporated into course work in the classroom, on field trips, and off-campus Pacific Northwest field courses taught at Western Washington University. With respect to the broader community, and aside from technical publications and lectures, results of the proposed study will be integrated into and will enhance frequently occurring field trips for professional groups, such as the Geological Society of America, National Association of Geology Teachers, and Northwest Geological Society. The public lands of the San Juan Islands and Cascades are global tourist destinations, presenting opportunity for reaching a broad audience through geologic displays in parks and in popular geologic literature. The scale of continental margin tectonics on display in western Washington is fascinating at any level of knowledge.