Collaborative Research: Geochemistry and Tectonics of Cretaceous Gateway Closure in the Central American Isthmus

合作研究：中美洲地峡白垩​​纪门户闭合的地球化学和构造

• 批准号: 1019382
• 负责人: Jonathan Snow
• 金额: $ 11.17万
• 依托单位: University of Houston
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1019382&HistoricalAwards=false
• 关键词: Collaborative; Research; Geochemistry; Tectonics; Cretaceous

Planet Earth is divided in three main layers at great depth, the core, the mantle and the crust. The dynamics of the mantle exerts significant control over the evolution of the crust, which in turn shapes the morphology of the surface we see today. Although rare, exposed mantle is found where dramatic tectonic events such as continental collisions have taken place, and these places are essentially windows into our planet. This study will focus on the Santa Elena Peninsula, Costa Rica, a practically unexplored segment of exposed mantle. The observations on the surface will provide valuable information about processes that result in volcanic activity. One goal is to link the Central American geologic history to the development of land-bridges and seaway closures that affected the evolution of global circulation, climate and ecology. These researchers will explore the paleogeography and tectonic evolution of the region through geochemical, petrologic and structural analysis of mantle and associated volcanic rocks of the Santa Elena Peninsula, Costa Rica. This will be the first time the Santa Elena mantle section will be studied with modern analytical techniques. The objectives are to constrain the timing and tectonic environment of formation and consolidation of this terrane. To address these questions the investigators will map the different lithologies and conduct detailed structural analysis. Selected samples of mantle peridotites and other ultramafic lithologies will be studied with electron-microprobe and in-situ laser ablation ICP-MS. Samples from the volcanic units will be analyzed for major, trace element and radiogenic isotope compositions. The analyses will constrain the age of the different lithologies and also the tectonic events that amalgamated the Santa Elena complex. The identification of the complex with a fore-arc, back-arc or mid-ocean ridge tectonic setting will help constrain the large-scale tectonic geometry that led to the closure of the first Central American Gateway during the Cretaceous.

地球在深处分为三个主要层：地核、地幔和地壳。地幔的动力学对地壳的演化发挥着重要的控制作用，这反过来又塑造了我们今天所看到的地表的形态。 尽管罕见，但在发生大陆碰撞等剧烈构造事件的地方发现了裸露的地幔，这些地方本质上是了解我们星球的窗口。这项研究将重点关注哥斯达黎加的圣埃琳娜半岛，这是一块几乎未经勘探的裸露地幔部分。地表观测将提供有关导致火山活动的过程的宝贵信息。目标之一是将中美洲地质历史与影响全球环流、气候和生态演变的陆桥和海道封闭的发展联系起来。这些研究人员将通过对哥斯达黎加圣埃琳娜半岛的地幔和相关火山岩进行地球化学、岩石学和结构分析，探索该地区的古地理和构造演化。这将是首次利用现代分析技术研究圣埃琳娜地幔部分。目的是限制该地体形成和巩固的时间和构造环境。为了解决这些问题，研究人员将绘制不同岩性图并进行详细的结构分析。将使用电子微探针和原位激光烧蚀ICP-MS 对选定的地幔橄榄岩和其他超镁铁岩岩性样本进行研究。 将对火山单元的样品进行主量元素、微量元素和放射性同位素组成的分析。这些分析将限制不同岩性的年龄以及合并圣埃琳娜复合体的构造事件。确定该复合体具有弧前、弧后或洋中脊构造环境将有助于限制导致白垩纪第一个中美洲门户关闭的大规模构造几何形状。