REU: Miocene to Recent Sedimentary Conditions on the Peruvian Margin: Apatite Formation, Fluid Circulation, and Diagenesis

秘鲁近海有三种主要类型的磷岩：(1)易碎的浅色纹层，包括小球粒和结核；(2)以球粒为主的磷酸盐砂体；(3)通常较暗的、岩化良好的致密结核和坚硬的地面。在大洋钻探项目第112阶段中发现的岩心包含所有三种类型的磷岩，并允许将关于老新生代许多方面的现有信息扩展到该地区的第四纪沉积物。因此，该项目的主要目的是：(1)提高对控制地质记录中磷岩幕式沉积的海洋和沉积学因素的了解；(2)发展可以区分原始沉积环境中的原生属性和修饰属性的地球化学和同位素标准，受地下咸水影响或在后来的埋藏成岩作用中获得的，或通过沉积学过程重新加工和浓缩而获得的。大陆边缘的磷矿是一种有趣的、潜在的经济矿床。这项研究将探讨这些矿床形成的控制因素。来自秘鲁边缘钻探岩心的沉积物将通过各种地球化学技术进行检查，以寻找气候对地层的影响以及流体流动和成岩作用的沉积后效应的线索。

Three major types of phosphorites occur off Peru: (1) friable light-colored laminae, including small peloids and nodules, (2) phosphatic sands dominated by peloids, and (3) generally darker, well lithified dense nodules and hard-grounds. The cores recovered during Ocean Drilling Project (ODP) Leg 112 contain all three phosphorite types and allow expansion of the existing information on many aspects of the older Cenozoic to Quaternary sediments of this region. Accordingly, the primary aims of this project are to (1) improve the understanding of oceanographic and sedimentologic factors which control the episodic deposition of phosphorites in the geologic record, and (2) to develop geochemical and isotopic criteria which may distinguish primary properites derived in the original depositional environment, from modified properties, those acquired by the influence of a subsurface saline brine or during later burial diagenesis, or by reworking and concentration through sedimentologic processes. %%% Phosphorites on continental margins are an interesting and potentially economical mineral deposit. This study will examine the controlling factors for the formation of these deposits. Sediments from drill cores on the Peruvian margin will be examined by a variety of geochemical techniques for clues to the climatic influences on formation as well as the post- depositional effects of fluid flow and diagenesis.