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.

地球被划分为深度的三个主要层，核心，地幔和地壳。地幔的动力学对地壳的演变产生了重大控制，这又塑造了我们今天看到的表面的形态。 尽管很少见，但在发生戏剧性的构造事件（例如大陆碰撞）的地方发现了裸露的地幔，这些地方本质上是进入我们星球的窗户。这项研究将重点介绍圣塔埃琳娜半岛哥斯达黎加，这实际上未开发裸露的地幔。表面上的观察结果将提供有关导致火山活动的过程的有价值的信息。一个目标是将中美洲地质历史与影响全球循环，气候和生态学进化的土地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塔埃琳娜半岛的地幔和相关火山岩的地震，岩石学和结构分析来探索该地区的古地理和构造演化。这将是第一次使用现代分析技术研究圣埃琳娜·曼特（Santa Elena Mantle）部分。这些目标是限制形成和整合该地层的时机和构造环境。为了解决这些问题，研究人员将绘制不同的岩性并进行详细的结构分析。将使用电子 - 微探针和原位激光消融ICP-MS研究地幔橄榄岩和其他超镁质岩性样品的选定样品。 将分析来自火山单元的样品，分析主要，痕量元素和放射性同位素组成。分析将限制不同岩性的年龄，并限制与圣埃琳娜综合体合并的构造事件。用前弧，后弧或中山山脊构造设置对复合物的识别将有助于限制大规模的构造几何形状，从而导致白垩纪期间第一个美国中部门户闭合。