Collaborative Research: The Rosario Segment of the Cretaceous Alisitos Oceanic Arc (Baja California, Mexico): An Outstanding Field Analog to the Izu Bonin Arc

合作研究：白垩纪阿利西托斯大洋弧的罗萨里奥段（墨西哥下加利福尼亚州）：与伊豆博宁弧的杰出野外模拟

• 批准号: 1347794
• 负责人: Susan DeBari
• 金额: $ 19.3万
• 依托单位: Western Washington University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-03-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1347794&HistoricalAwards=false
• 关键词: Collaborative; Research; Rosario; Segment; Cretaceous

This collaborative research project will interface closely with the IODP projects in the Izu-Bonin-Mariana (IBM) arc by fully characterizing what is probably its best field analog on Earth: the Rosario segment of the Alisitos arc. DeBari has been deeply involved in the IBM proposals, and Busby is co-chief scientist on IODP Expedition 350. Exhumed rocks from arc crustal sections have the unique ability to inform studies of active subduction zones by "ground-truthing" the assumptions that go into models, experiments, and interpretive geophysics and geochemistry. Some of the questions we will ask, highly complementary to the IBM work, are: How is arc middle crust constructed? What is the relationship and proportion between volcanic and plutonic rocks in juvenile arc crust? What is the tempo of constructing arc crust? How does arc crust composition change with time? Is there any older crust that makes up significant parts of the Alisitos arc? What can we learn about convergent margin mineralization by comparing the Alsitos arc to the Izu Bonin arc? How does the crustal structure of the Alisitos arc compare with seismic velocity profiles in modern arcs? Can surface and borehole heat flow measurements in modern arcs be related to features preserved in the geologic record of ancient arcs?This research furthers the careers of two female scientists (DeBari at WWU and Busby at UCSB) and their respective graduate students. Training of these graduate students is collaborative so that both students will become skilled at the integration of field geology, petrology and geochronology. Scientific interaction between US scientists at WWU and UCSB and international colleagues at UNAM in Mexico will broaden the perspectives of all participants, and enhance research and training outcomes. The proposed project is of interest to the broader science community, as it addresses some of the foremost questions in the NSF GeoPRISMS science plan on the growth and evolution of continental crust through study of island arcs (http://www.geoprisms.org/science-plan.html#science-plan), as well as research envisioned by the GeoPRISMS ExTerra initiative (http://www.geoprisms.org/scd/exterra.html). One of the main products, a web-based ?Island Arc Crust Virtual Field Model?, will be used by scientists as a reference model for IBM drilling outcomes, and in curriculum for both undergraduate and graduate students. A field workshop in the Alisitos arc, ideally held in conjunction with Expeditions 350-352 post-expedition meetings and before IBM-4 drilling begins, will provide invaluable context for IBM drilling participants.The Rosario segment of the Cretaceous Alisitos arc in Baja California is an outstanding field analog for the Izu-Bonin-Mariana (IBM) volcanic arc. The IBM arc is under intense study by the International Ocean Drilling Program (IODP) as an in-situ example of present-day formation of nascent continental crust. Earth is the only planet in the solar system with extensive felsic (Si-rich, Mg-poor) continental crust. The rocky planets and the Moon have basaltic (Mg-rich) crusts formed early in the history of the solar system. The volume of continental crust on Earth has grown over time due to plate tectonic processes, dominantly because of accretion of felsic to intermediate volcanic arcs at convergent margins. However, the processes that produce this felsic to intermediate crust are not well characterized in situ. The Rosario segment has superior three-dimensional exposures of an upper- to middle-crustal section through an extensional oceanic arc. Previous mapping of this 60-km-long segment of the Alisitos arc, done in the 1990?s (Busby et al., 2006), will provide a framework for the proposed study; however, that study focused mainly on field descriptions of the volcanic rocks, with limited geochronology, and no geochemistry. The proposed study will determine in detail the relationships between rock types at all stratigraphic levels in the arc, using field, geochemical, and geochronological data. This collaborative research project will interface closely with IODP Expeditions 350-352 (in 2014) and a fourth ambitious proposal to drill to the arc middle crust (IODP Proposal 698 at site IBM-4, awaiting scheduling. These data will be used to construct an ?Island Arc Crust Virtual Field Model? to be used by scientists as a reference model for IBM drilling outcomes.

该合作研究项目将与伊豆-博南-马里亚纳 (IBM) 弧线的 IODP 项目紧密结合，充分描述可能是地球上最好的现场模拟：阿利西托斯弧线的罗萨里奥段。 DeBari 深入参与了 IBM 的提案，Busby 是 IODP Expedition 350 的联合首席科学家。从弧地壳部分挖出的岩石具有独特的能力，可以通过“地面验证”相关假设来为活动俯冲带的研究提供信息。模型、实验以及解释地球物理学和地球化学。我们将提出的一些问题与 IBM 的工作高度互补，包括：弧形中地壳是如何构造的？新生弧地壳中火山岩和深成岩之间的关系和比例是怎样的？弧壳的构建速度是怎样的？弧壳成分如何随时间变化？是否有更古老的地壳构成了阿利西托斯弧的重要部分？通过比较阿尔西托斯岛弧和伊豆博宁岛弧，我们可以了解有关汇聚边缘矿化的什么信息？阿利西托斯弧的地壳结构与现代弧的地震速度剖面相比如何？现代弧中的地表和钻孔热流测量是否与古代弧的地质记录中保存的特征相关？这项研究进一步推动了两位女科学家（WWU 的 DeBari 和 UCSB 的 Busby）及其各自研究生的职业生涯。这些研究生的培训是协作性的，以便两名学生都能熟练掌握现场地质学、岩石学和地质年代学的整合。 WWU 和 UCSB 的美国科学家与墨西哥 UNAM 的国际同事之间的科学互动将拓宽所有参与者的视野，并提高研究和培训成果。拟议的项目引起了更广泛的科学界的兴趣，因为它通过研究岛弧解决了 NSF GeoPRISMS 科学计划中关于大陆地壳生长和演化的一些最重要的问题 (http://www.geoprisms.org/ science-plan.html#science-plan），以及 GeoPRISMS ExTerra 计划设想的研究 (http://www.geoprisms.org/scd/exterra.html)。 主要产品之一是基于网络的“岛弧地壳虚拟现场模型”，科学家将使用它作为 IBM 钻探成果的参考模型，并用于本科生和研究生的课程。 Alisitos 弧的现场研讨会最好与 Expeditions 350-352 探险后会议以及 IBM-4 钻探开始之前一起举行，将为 IBM 钻探参与者提供宝贵的背景信息。位于下加利福尼亚州的白垩纪 Alisitos 弧的 Rosario 段是伊豆-小博宁-马里亚纳 (IBM) 火山弧的出色现场模拟。国际海洋钻探计划 (IODP) 正在对 IBM 弧进行深入研究，将其作为当今新生大陆地壳形成的现场实例。地球是太阳系中唯一拥有广泛的长英质（富硅、贫镁）大陆地壳的行星。岩石行星和月球具有在太阳系历史早期形成的玄武岩（富含镁）地壳。 由于板块构造过程，地球上大陆地壳的体积随着时间的推移而增加，主要是由于长英质到中间火山弧在会聚边缘的增生。然而，产生这种长英质到中地壳的过程尚未得到很好的现场表征。罗萨里奥段通过伸展的海洋弧对上中地壳部分具有卓越的三维曝光。之前在 1990 年代绘制的 Alisitos 弧段 60 公里长的地图（Busby 等人，2006 年）将为拟议的研究提供一个框架；然而，该研究主要侧重于火山岩的实地描述，地质年代学有限，没有地球化学。拟议的研究将利用现场、地球化学和地质年代学数据，详细确定弧内所有地层层面岩石类型之间的关系。该合作研究项目将与 IODP 探险 350-352（2014 年）和第四个雄心勃勃的钻探弧形中地壳的提案（位于 IBM-4 的 IODP 提案 698，正在等待安排）紧密结合。这些数据将用于构建一个“岛弧地壳虚拟现场模型”将被科学家用作 IBM 钻探结果的参考模型。