Spherule layers in the 2011 ICDP drilling in the Barberton Mountain Land: Early impact record on Earth

2011 年巴伯顿山区 ICDP 钻探中的小球层：对地球的早期撞击记录

• 批准号: 235479303
• 负责人: Professor Dr. Wolf Uwe Reimold
• 金额: --
• 依托单位: Museum für Naturkunde - Leibniz-Institut für Evolutions- und Biodiversitätsforschung (MfN)
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2016-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/235479303?language=en
• 关键词: Spherule; layers; 2011; ICDP; drilling

The 2011 ICDP drilling “Barberton Mountain Land” drilled relatively unweathered rare late Archean volcanic and sedimentary rocks including the oldest known impact ejecta layers on Earth. The chemical signature (high Iridium concentrations, Chromium isotopic ratios) of some of these up to tens of cm thick Archean spherule layers advocate that these ejecta deposits formed dominantly from extraterrestrial material. The ejecta layers contain millimeter sized spherules that are larger and form thicker layers compared to any impact ejecta layer known from Phanerozoic sediments, including the global ejecta layer of the Chicxulub impact catering event that terminated the Mesozoic era of Earth’s history. We propose to conduct 1) bulk chemical analyses of major and trace elements, 2) petrographic, micro-chemical and mineralogical characterization of the impact ejecta layers, and 3) LA-ICP-MS elemental mapping of platinum group element (PGE) distributions. This aims at 1) characterization of the ejecta layers, 2) identification of the phases hosting the extraterrestrial PGE signature, 3) discrimination of the primary geological evidence of the impact event from those characteristics that resulted from syn- and post-sedimentary alteration. We want to exploit the geological evidence for extracting key information regarding size, type and frequency of projectiles impacting the Archean Earth.

2011 年 ICDP 钻探“巴伯顿山地”钻探了相对未风化的稀有晚太古代火山岩和沉积岩，包括地球上已知最古老的撞击喷射物层。其中一些厚达数十厘米的太古宙小球层的化学特征（高铱浓度、铬同位素比）表明这些喷射物沉积物主要由外星物质形成。喷射物层包含毫米大小的球体，与显生宙沉积物中已知的任何撞击喷射物层相比，这些球体更大且形成更厚的层，包括结束地球历史中生代时代的希克苏鲁伯撞击餐饮事件的全球喷射物层。我们建议进行 1) 主要和微量元素的大量化学分析，2) 撞击喷射物层的岩相、微化学和矿物学表征，以及 3) 铂族元素 (PGE) 分布的 LA-ICP-MS 元素测绘。其目的是 1) 喷射物层的特征，2) 识别包含地外 PGE 特征的相，3) 从同沉积和沉积后蚀变产生的特征中区分撞击事件的主要地质证据。我们希望利用地质证据来提取有关影响太古代地球的射弹的大小、类型和频率的关键信息。