Collaborative Research: RUI: Age, Petrology, and Tectonic Setting of Purported Taconic-aged plutons, Ashland-Wedowee-Emuckfaw Belt, Southern Appalachians

合作研究：RUI：南阿巴拉契亚山脉阿什兰-Wedowee-Emuckfaw 带的据称塔科尼年龄岩体的年龄、岩石学和构造背景

• 批准号: 1220540
• 负责人: Clinton Barineau
• 金额: $ 12.6万
• 依托单位: Columbus State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1220540&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Age; Petrology

This collaborative project between investigators at Columbus State University and the University of Florida aims to resolve conflicting interpretations of the tectonic origin and age of a number of metamorphosed granitoids in the Ashland-Wedowee-Emuckfaw belt (Eastern Blue Ridge) province of Alabama in the southernmost Appalachians. Traditionally attributed to latest Cambrian-Middle Ordovician magmatism associated with the Taconic orogeny, the Elkahatchee Quartz Diorite, Zana Gneiss, and Kowaliga Gneiss have been considered by some workers to be part of an obducted Taconic island or peri-Laurentian arc emplaced atop the subducting margin of North America. SHRIMP-RG results from the dominant quartz diorite component of the Elkahatchee, however, suggest an Upper Devonian emplacement age with considerable evidence for abundant xenocrystic inheritance which may have complicated the initial whole rock and multi-grain analyses completed over two decades ago. The potential for significant Acadian-aged magmatic components in the Elkahatchee calls into question its association with a Taconic arc; a question which can only be addressed by detailed isotopic analysis of the various lithologies typically assigned to this batholith. Furthermore, since both the Zana and Kowaliga gneisses were assigned ages using some of the same techniques as those used to assign a latest Cambrian age to the Elkahatchee, attribution of these plutons to Ordovician orogenesis is also suspect. Spatially resolved U-Pb analysis of these plutons will provide the best temporal context for examining the Lu-Hf systematics of zircon components and, in combination, will allow us to constrain the petrotectonic evolution of parental magma(s).Results from this project will shed new light on the tectonic evolution of the North American margin and the development of the Appalachian Mountains through the Paleozoic. Significantly, it will provide new constraints on fundamental questions regarding evolution of the southern Appalachian orogeny because of its bearing on the continuity and nature of subduction along the eastern margin of North America during the closure of the Iapetus and Rheic oceans. These results will also afford an improved understanding of the role of important plutonic elements in the evolution of the southern Appalachians, which will be of advantage to many institutions in the region for undergraduate and graduate instruction. Integration of student and faculty expertise and opportunities at these universities will have a significant impact on training professional geoscientists, who are critical to developing a strong national STEM workforce, and will provide valuable support for a faculty research program at a predominantly undergraduate institution through the Research in Undergraduate Institutions program (RUI). Finally, this project will afford a group of geology undergraduates an invaluable experience (from field to analytical) through participation in a geological research program, greatly enhancing their undergraduate education and enhancing the nation?s STEM workforce.

哥伦布州立大学和佛罗里达大学的这项合作项目旨在解决对阿巴拉契亚山脉最南端阿拉巴马州阿什兰-韦多维-艾默克福带(东部蓝岭)中一些变质花岗岩的构造起源和年龄的相互矛盾的解释。传统上被认为是与塔肯造山有关的寒武纪-中奥陶世晚期岩浆作用，埃尔卡哈奇石英闪长岩、扎纳片麻岩和科瓦利加片麻岩被一些工作人员认为是侵位在北美俯冲边缘之上的隐蔽的塔科尼岛或劳伦斯周弧的一部分。然而，SHRIMP-RG来自Elkahatchee的主要石英闪长岩成分，表明上泥盆统的侵位年龄具有丰富的捕虏晶遗产，这可能使20多年前完成的最初的全岩和多颗粒分析变得复杂。Elkahatchee中可能存在大量阿卡迪亚时代的岩浆成分，这让人怀疑它与Taconic弧的联系；这个问题只能通过对通常分配给该岩基的各种岩性进行详细的同位素分析来解决。此外，由于扎纳片麻岩和科瓦利加片麻岩都使用了一些与给埃尔卡哈奇岩确定最新寒武纪年龄的方法相同的方法来确定年龄，因此这些深成岩归因于奥陶纪的造山作用也是可疑的。这些岩体的空间分辨U-Pb分析将为研究Lu-Hf锆石系统学提供最佳的时间背景，并将使我们能够约束母岩浆(S)的岩石构造演化。这一项目的结果将为北美边缘的构造演化和阿巴拉契亚山脉在古生代的发展提供新的线索。值得注意的是，它将对有关阿巴拉契亚南部造山运动演化的基本问题提供新的制约，因为它影响到伊阿普图斯海和瑞西海关闭期间北美东部边缘俯冲的连续性和性质。这些结果还将使人们更好地了解重要的深成因素在阿巴拉契亚山脉南部演化中的作用，这将有利于该地区的许多机构进行本科生和研究生教学。这些大学的学生和教师的专业知识和机会的整合将对培养专业的地球科学家产生重大影响，他们对于发展强大的全国STEM劳动力队伍至关重要，并将通过本科院校研究计划(RUI)为以本科为主的机构的教师研究计划提供宝贵的支持。最后，该项目将为一群地质学本科生提供宝贵的经验(从野外到分析)，通过参与地质研究项目，极大地提高他们的本科教育，并增强国家-S科技劳动力。