Investigation of Ultra-18O Depleted "Slushball" Earth Rocks from Karelia, Russia and the Timing of Paleoproterozoic Glaciations and the Great Oxidation Event

俄罗斯卡雷利亚超18O贫化“泥球”地球岩石的调查及古元古代冰川和大氧化事件的时间本提案寻求支持，以调查和解释俄罗斯卡雷利亚的古元古代岩石，这些岩石相对于氧18异常贫化(这些岩石具有世界上已知的最低值)。18O如此贫乏的岩石需要在泛全球冰川作用期间与冰川融水相互作用而产生。这些亏损现在分布在一条450公里长的带上的11个地点，并在空间上与冰下裂谷环境带中形成的2.45-2.2Ga镁铁质侵入体有关。由于卡雷利亚在整个古元古代都位于赤道纬度附近，这些岩石提供了低纬度冰的同位素证据，并提供了一个强大的水文循环，其中低纬度海洋保持未冻结状态(“泥球”气候状态)。由于在2.45-2.2Ga之间有三次泛全球冰川，利用卡累利亚冰下超贫化的大气热液特征准确确定镁铁质侵入体的年龄，将为这些全球冰川的形成提供最直接的限制。此外，这项研究可能会限制哪些冰川先于大气氧的上升和硫同位素与质量无关的分馏消失。该项目的范围将包括在异常贫化地区进行实地测绘和样品采集，随后进行同位素分析以确定典型的大气热液特征，通过原位和溶液地质年代学测定这种贫化的时间，对这些独特的热液蚀变趋势进行地球化学模拟，并在全球氧化事件的背景下调查未变质的同世早古元古代萨里奥利亚和维特尼带的苏美式火山和沉积序列。该提案将促进国际合作，让包括传统上在地球科学中代表性不足的学生在内的学生参与并支持他们，继续让大量本科生和社区大学生参与地球化学、地质年代学和稳定同位素研究，并让他们接触科学和国际合作。该提案将通过国际和平研究所以及研究小组成员和合作者所做的工作，支持最近建立的稳定同位素实验室的分析基础设施。派将继续他的外展活动、公开讲座和在流行期刊上发表文章。

Investigation of Ultra-18-O Depleted "Slushball" Earth Rocks from Karelia, Russia and the Timing of Paleoproterozoic Glaciations and the Great Oxidation EventThis proposal seeks support to investigate and interpret the Paleoproterozoic rocks from Karelia, Russia, which are extraordinarily depleted with respect to oxygen 18 (these rocks have the world's lowest known values). Rocks with such depleted 18O require derivation from interaction with glacial meltwaters during panglobal glaciation. These depletions now characterize 11 localities along a 450 km long belt and are spatially associated with the 2.45-2.2 Ga mafic intrusions formed in subglacial rifting environment zones. Since Karelia was located near equatorial latitudes throughout the Paleoproterizoic, these rocks provide isotopic evidence of ice at low latitudes, and a robust hydrologic cycle, in which low latitude oceans remained unfrozen (a "Slushball" climate state). As there were three panglobal glaciations between 2.45 and 2.2 Ga, precise determination of age of the mafic intrusions with the subglacial ultra-depleted meteoric hydrothermal features in Karelia will provide the most direct constraints on the timing of these global glaciations. Furthermore, this research may constrain which of the glaciations preceded the rise of atmospheric oxygen and disappearance of mass-independent fractionation of sulfur isotopes. The scope of this project will include mapping and sample collection in the field at the anomalously depleted areas, subsequent isotope analysis to identify the characteristic bulls-eyes meteoric hydrothermal features, dating the timing of such depletion by in situ and solution geochronology, geochemical modeling of these unique hydrothermal alteration trends, and investigation of the unmetamorphosed coeval early Paleoproterozoic Sariolian, and Sumian volcanic and sedimentary sequences of the Vetreny Belt in the context of the global oxidation event. The proposal will promote international collaboration, involve and support students including those traditionally underrepresented in geosciences, continue to involve large number of undergraduate and community college students into geochemical, geochronologic, and stable isotope research and expose them to science and international collaboration. The proposal will support the analytical infrastructure of the recently established stable isotope lab through work done by the PI and members of the research group and collaborators. PI will continue his outreach activities, public lectures and articles to popular journals.