Growth of Early Continental Crust and Chemical Evolution of Cratonic Lithosphere

早期陆壳的生长与克拉通岩石圈的化学演化

• 批准号: 0440235
• 负责人: Robert Rapp
• 金额: $ 26.73万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-02-01 至 2008-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0440235&HistoricalAwards=false
• 关键词: Growth; Early; Continental; Crust; Chemical

The oldest rocks on Earth occur within the continents are of Archean age (~3.0-4.0 Ga), and are comprised of granitoid ("TTG") rocks that form the physical nucleus, or craton, of these continents. The cratons are underlain by mantle peridotites of the continental lithosphere, which possess unique chemical and physical properties that are responsible for their long-term stability since the Archean. Amongst the terrestrial planets of our solar system, the Earth appears to be unique in possessing extensive, highly-differentiated continental crust (or cratons). This study considers the origins of the oldest continental crust, and addresses how crustal growth in the Archean was related to the chemical evolution of the cratonic lithosphere. Laboratory experiments, to be performed at pressures and temperatures relevant to those of the subcratonic lithosphere, will consider to what extent and by what chemical mechanisms Archean granitoid (TTG) magmas interacted with peridotite rocks in evolving cratonic roots. These experiments will produce variable proportions of melt ("magma") and crystalline (mineral) phases as a function of pressure, temperature and other variables, and the detailed chemical features of the experimental melts and minerals will be compared with appropriate natural samples (respectively, Archean granitoids, and samples of the subcratonic lithosphere brought to the surface in kimberlite eruptions, in the form of peridotite "xenoliths, or as minute mineral "inclusions" in diamonds). Geometrically, modern subduction zones consist of a "wedge" of mantle lithosphere (peridotite) overlying a "slab" of subducting oceanic lithosphere. Questions for Archean crustal evolution, which this project will address, include whether or not a conventional mantle wedge-subducting slab geometry is appropriate for the early Earth, or if some unique style of tectonism was operative, and at what point in time did modern-style, plate tectonic processes take over? A better understanding of the genetic relationship between granitoid magmatism on the early Earth and the development of deep roots or "keels" for the cratons in the underlying mantle is an important prerequisite for on-site studies of crusts on the other terrestrial planets (e.g., Mars and Venus), and for the search for Earth-like planets beyond our solar system.

地球上最古老的岩石出现在大陆内，是太古代（~3.0-4.0 Ga），由花岗岩类（“TTG”）岩石组成，形成这些大陆的物理核或克拉通。地幔橄榄岩是大陆岩石圈的地幔橄榄岩，具有独特的化学和物理性质，是负责他们的长期稳定，因为太古代。 在我们太阳系的类地行星中，地球似乎是独一无二的，拥有广泛的，高度分化的大陆地壳（或地壳）。这项研究认为，最古老的大陆地壳的起源，并解决如何在太古代地壳生长有关的岩石圈的化学演化。实验室实验，进行相关的压力和温度的subtenonic岩石圈，将考虑在何种程度上，并通过什么样的化学机制太古代花岗岩类（TTG）岩浆与橄榄岩岩石在不断发展的subtenonic根。这些实验将产生不同比例的熔体（“岩浆”）和结晶（矿物）相，作为压力、温度和其他变量的函数，实验熔体和矿物的详细化学特征将与适当的天然样品进行比较（分别是太古代花岗岩类和金伯利岩喷发时带至地表的次白垩纪岩石圈样品，以橄榄岩捕虏体的形式，或作为钻石中的微小矿物“内含物”）。从几何学上讲，现代俯冲带由地幔岩石圈（橄榄岩）的“楔”和俯冲洋壳岩石圈的“板”组成。太古代地壳演化的问题，这一项目将解决，包括是否传统的地幔楔俯冲板几何形状是适合早期地球，或者如果一些独特的风格的构造作用是有效的，在什么时候现代风格，板块构造过程接管？更好地了解早期地球上花岗岩类岩浆活动与下地幔中地幔岩深根或“龙骨”发育之间的成因关系，是现场研究其他类地行星上地壳的重要先决条件（例如，火星和金星），以及寻找太阳系以外的类地行星。