CAREER: Investigating the tectono-magmatic response to a transitioning plate boundary: a case study of the California Borderlands

加州边境地带是南加州和下墨西哥西部的一个被淹没的地区。该地区的不同寻常之处在于它有多个盆地（500-200米深）和山脊（有些到达海面，形成了海峡群岛）。在过去的3000万年里，它经历了断裂、旋转和火山活动，而沿着北美构造板块西部边界的大约1200公里的构造边界从俯冲向走滑方向过渡。为什么重要的断裂、旋转、火山活动和一个新的三重连接的形成都局限于加利福尼亚南部和巴哈北部的地区，人们还不太清楚。该项目旨在了解是什么导致了加利福尼亚边境地区的火山活动，以及它与从俯冲到走滑的变化有何关系。更广泛的影响包括为多个研究生和本科生提供研究机会，为从代表性不足的群体招募的学生提供长期强化指导计划，支持URM早期职业研究员，与世界一流的分析设施合作，以及向K-12学校推广。该项目的目标是：(1)调查火山和构造过程，这些过程不容易用标准板块边界或热点动力学来解释。(2)指导和培养加州州立大学长滩分校海洋和地球科学专业的本科生和研究生。(3)激励和激励K-12诺沃克学区的新一代STEM专业人士。PI建议定义火山活动的时间和地球化学特征，这些活动与南加州海岸边缘地区独特记录的过程有关，包括扩张中心的俯冲和从俯冲到转换边界的过渡。虽然这一淹没区域的独特地质记录了这些很少观测到的事件，但目前有限的时间和地球化学限制缺乏通过火山反馈来表征这些复杂构造事件所需的覆盖范围。在这里，PI提出了一个基于现代运动学的新的区域构造模型，表明边界地区在30 Ma和18 Ma时可能受到脊-沟相互作用的影响。该提案旨在分析先前检索到的海底火山样本，以测试新构造模型的预测结果。该项目将利用该地区的这些和其他有价值的样本来回答关于板块边界转变之前，期间和之后的火山反应的变革性问题。该项目还将培训加州州立大学长滩分校的本科生科学家。这项科学工作是支持多名本科生和研究生研究人员的理想选择，因为它可以从火成岩的观察和详细表征扩展到更先进的化学分析程序。该项目旨在通过实施更长期（与典型的夏季研究经验相比为一年半）的强化指导计划，利用队列模型来提高保留率。拟议的研究和教育活动是协同的，因为它们将(1)使用整个拟议的研究作为本科生和研究生的研究项目；(2)从本科生研究项目中招募研究生；(3)纳入每周的实验室会议，讨论研究进展，同时建立支持网络并提供指导。PI支持的本科生研究人员将以社区科学家的身份访问当地的几所K-12学校，吸引学生，并为争取STEM职业树立榜样。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The California Borderlands is a submerged region directly west of Southern California and Baja Mexico. The region is unusual for its multiple basins (500-200 m deep) and ridges (some reach the surface and form the Channel Islands). It has experienced faulting, rotation, and volcanism over the past 30 million years while the approximate 1200 km tectonic boundary along the western limit of the North American tectonic plate transitioned from a subduction to a strike-slip orientation. It is not well understood why significant faulting, rotation, volcanism, and the formation of a new triple junction are localized to the region off southern California and northern Baja. This project seeks to understand what caused the California Borderlands volcanism and how it is related to a change from subduction to strike-slip. Broader impacts include research opportunities for multiple graduate and undergraduate students, a long-term intensive mentoring program for students recruited from underrepresented groups, support for a URM early-career researcher, collaborations with world-class analytical facilities, and outreach to K-12 schools.The goals of the project are to (1) investigate volcanic and tectonic processes not readily explained by standard plate boundary or hotspot dynamics. (2) Mentor and train a diverse pool of California State University Long Beach undergraduate and graduate students in ocean and geosciences. (3) Inspire and motivate a new generation of STEM professionals in the K-12 Norwalk School District. The PI proposes to define the timing and geochemical character of volcanic activity associated with processes uniquely recorded in the Borderland area off the coast of southern California that include the subduction of spreading centers and the transitioning from a subduction to transform boundary. While the unique geology of this submerged region records these rarely observed events, the limited temporal and geochemical constraints currently available lack coverage required to characterize these complex tectonic events via their resulting volcanic feedbacks. Here the PI presents a new regional tectonic model based on modern kinematics that indicate the Borderland region would have been affected by ridge-trench interaction at 30 Ma and 18 Ma. This proposal seeks to analyze previously retrieved seafloor volcanic samples to test the predictive consequences of the new tectonic model. This project will make use of these and other valuable samples from this area to answer transformative questions about the volcanic response prior to, during and after a plate boundary transition. The project will also train undergraduate student scientists from California State University Long Beach. The scientific work is ideal for supporting multiple undergraduate and graduate researchers because it scales from observations and detailed characterization of igneous rocks to more advanced procedures of chemical analyses. The program is designed to increase retention through the implementation of a longer term (one and half years as compared to a typical summer research experience) intensive mentorship program utilizing the cohort model. The proposed research and education activities are synergetic because they will (1) use the entirety of the proposed research as both undergraduate and graduate research projects (2) recruit graduate students from the undergraduate research program (3) incorporate weekly lab meetings to discuss research progress while also building a support network and providing mentorship. The undergraduate researchers supported by the PI will visit several local K-12 schools as community scientists to engage students and serve as role models striving for STEM careers.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.