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

古北美大陆（劳伦西亚）在古生代沿着其西部边缘的生长是由本地和外来物质的添加而发生的：一个由大陆西侧翼的侵蚀而形成的沉积围裙（洋地槽），以及一个由地球其他地区的板块构造位移并断裂进入大陆的增生地体的复合物。这项研究的研究将检查华盛顿西北部的奇利瓦克地形的历史，初步研究表明，至少部分来自欧洲西北部。我们工作的主要工具是获取火成岩和沉积岩中锆石颗粒的U-Th-Pb年龄。来自奇利瓦克地体火成岩的初步数据显示，北美西部地区的年龄未知，但在古斯堪的纳维亚（波罗的海）地区很常见。在沉积岩中，锆石的年龄分布在一些岩石中与北美相似，而在另一些岩石中则指向异国（欧洲或其他）故乡。更多的锆石将澄清这些可能的相关性。进一步的锆石Hf同位素数据将用于测试Chilliwack地体的部分可能来源于原始海洋岛弧，特别是阿拉斯加东南部增生的早古生代亚历山大弧地体，而不是演化的大陆地壳（Laurentian或其他）。岩石单元的现场测绘将评估Chilliwack地块中具有北美和异国亲和力的部分之间的成因和结构关系。该项目的基本目标是板块构造机制和活动大陆边缘形成过程的基本知识。该研究计划旨在解决上述科学问题，并加强对学生的教育和培训，提高公众对太平洋西北地区地球史的兴趣和了解。项目资金将支持本科生在现场和实验室担任助理，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形成高级论文的基础。从本研究中获得的知识将被纳入西华盛顿大学的课堂作业、实地考察和校外太平洋西北地区实地考察课程中。就更广泛的社区而言，除了技术出版物和讲座之外，拟议研究的结果将纳入并将加强专业团体经常进行的实地考察，如美国地质学会、全国地质教师协会和西北地质学会。圣胡安群岛和喀斯喀特的公共土地是全球旅游目的地，通过公园的地质展览和流行的地质文献，为广大观众提供了机会。在华盛顿西部展出的大陆边缘构造的规模在任何知识水平上都是迷人的。

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.