Geochronology, Petrology, and Geochemistry of the Jurassic White Mountain Batholith, New Hampshire

新罕布什尔州的白色山脉由超大陆泛大陆形成期间形成的变质岩和随后大西洋开放期间侵位和喷发的火成岩组成。 火成岩包括花岗岩（新罕布什尔州被称为花岗岩之州）和火山岩，形成壮观的悬崖面，如弗兰科尼亚峡谷州立公园标志性的“山中老人”。 然而，这一阶段岩浆活动的地质触发因素在很大程度上仍然未知。 PI将培训塔夫茨大学的本科生对整个地区的岩石进行采样，以获得化学和年龄信息，这些信息可用于将岩浆活动与导致我们今天看到的新罕布什尔州的特定地质过程联系起来。 研究结果将在一系列同行评审的期刊文章和专业科学会议上传播。作为该项目的顶点，PI和学生将在新罕布什尔州普利茅斯的白色山脉博物馆举办一个专门的夏季展览，以便将结果传达给公众。 展览将包括岩石和矿物的例子（包括大规模的石板和显微镜载玻片），在大西洋开放期间构造板块运动的视频，地质测年技术的入门，以及有兴趣了解更多关于白色山脉地质的徒步旅行者的步道指南。在这个项目中，塔夫茨大学的PI和本科生将专注于建立白色山岩浆系列（WMMS）中岩浆活动主要阶段的详细地质年代学、岩石学和地球化学数据集，即白色山玄武岩。 白色山玄武岩（WMB）由一系列斑状正长岩、角闪花岗岩、黑云母花岗岩和富钠流纹岩凝灰岩组成。Kinney等人（2022）最近发表的年龄显示，WMB不是一个单一的岩体，而是由两个不同的岩浆中心组成：西部岩基和东部岩基。 岩浆活动首先开始于岩基的西部（198 - 190 Ma），然后似乎在大约1000万年后（184 - 180 Ma）跳跃到东部。 研究人员的工作将确定各单元和岩体之间的侵位时间、侵位深度以及各单元之间的成岩关系。 本科生培训是这项工作的中心重点，PI将在三年内为塔夫茨大学的六名本科生进行科研项目培训。 学生将获得高精度的U-Pb锆石年龄的关键样品地点在整个岩基，以限制侵位的时间，以及获得整个岩石的主要和微量元素成分和Rb-Sr和Sm-Nd同位素组成的每个岩性单元在西部，东部和中部岩基。 他们的结果将是区分WMMS起源的各种地球动力学情景的重要的第一步。 在白色山脉博物馆（普利茅斯，新罕布什尔州）举办的一个为期一个夏天的专门展览和相关的公共讲座系列将为该项目提供一个顶点，并允许PI和学生将他们的结果传达给公众。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

The White Mountains of New Hampshire are composed of metamorphic rocks formed during the formation of the supercontinent Pangea and igneous rocks emplaced and erupted during the subsequent opening of the Atlantic Ocean. The igneous rocks include granites (New Hampshire is known as the Granite State) and volcanic rocks that form spectacular cliff faces such as the iconic 'Old Man of the Mountain' in Franconia Notch State Park. The geologic trigger for this phase of magmatism, however, remains largely unknown. The PI will train undergraduate students at Tufts University to sample the rocks throughout the region in order to obtain chemical and age information that can be used to link the magmatism to a particular geologic process that gave rise to the New Hampshire we see today. The results will be disseminated in a series of peer-reviewed journal articles, and at professional scientific conferences. As a capstone to the project, the PI and students will develop a dedicated summer-long exhibition at the Museum of the White Mountains in Plymouth, New Hampshire in order to communicate the results to the general public. The exhibit will include examples of rocks and minerals (both large-scale slabs and microscope slides) that are typical of the region, videos of tectonic plate motions during the opening of the Atlantic, primers on geologic dating techniques, and trail guides for hikers interested in learning more about geology in the White Mountains.In this project, the PI and undergraduate students at Tufts University will focus on establishing a detailed geochronologic, petrologic, and geochemical dataset for the main phase of magmatism in the White Mountain Magma Series (WMMS), the White Mountain Batholith. The White Mountain Batholith (WMB) is composed of a series of porphyritic syenites, hornblende granites, biotite granites, and comendite (Na-rich rhyolite) tuffs. Recently published ages from Kinney et al. (2022) reveal that the WMB is not a monolithic pluton, but is instead composed of two distinct magmatic centers: the western batholith and the eastern batholith. Magmatism first initiated in the western portions of the batholith (198 -190 Ma) and then appears to jump to the eastern portions approximately 10 Myr later (184 - 180 Ma). The researcher's work will establish the timing of emplacement between various units and plutons, the depths of emplacement, and the petrogenetic relationships between each unit. Undergraduate student training is a central focus of this work and the PI will train a total of six undergraduate students at Tufts University on scientific research projects over the three year period. Students will obtain high precision U-Pb zircon ages for key sample localities across the batholith to constrain the timing of emplacement, as well as obtain whole rock major and trace element compositions and Rb-Sr and Sm-Nd isotopic compositions for each lithological unit in the western, eastern, and central batholiths. Their results will be an essential first step in distinguishing between various geodynamic scenarios for the origin of the WMMS. A summer-long dedicated exhibition at the Museum of the White Mountains (Plymouth, NH), and associated public lecture series, will provide a capstone to the project and allow the PI and students to communicate their results to the general public.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.