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

地球在很深的地方分为三个主要层：地核、地幔和地壳。地幔的动力学对地壳的演化有着重要的控制作用，而地壳的演化又塑造了我们今天所看到的地表形态。 虽然罕见，但暴露的地幔是在发生大陆碰撞等剧烈构造事件的地方发现的，这些地方基本上是我们地球的窗口。这项研究将集中在哥斯达黎加的圣埃莱纳半岛，这是一个实际上尚未勘探的暴露地幔段。对地面的观测将提供有关导致火山活动的过程的宝贵信息。一个目标是将中美洲地质历史与陆桥和海道关闭的发展联系起来，这些发展影响到全球环流、气候和生态的演变。这些研究人员将通过对哥斯达黎加圣埃莱纳半岛地幔和相关火山岩的地球化学、岩石学和结构分析，探索该地区的古地理和构造演化。这将是第一次用现代分析技术研究圣埃莱纳地幔部分。其目的是为了确定该岩体形成和固结的时间和构造环境。为了解决这些问题，调查人员将绘制不同的岩性，并进行详细的结构分析。将用电子微探针和现场激光烧蚀ICP-MS研究地幔橄榄岩和其他超镁铁质岩石的选定样品。将分析火山单位的样品的主要、微量元素和放射性同位素组成。这些分析将限制不同岩性的年龄以及合并圣埃莱纳杂岩的构造事件。确定该复合体具有弧前、弧后或洋中脊构造背景，将有助于限制导致第一个中美洲门户在白垩纪关闭的大规模构造几何学。

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.