Rare Earth Element and Isotopic Studies of Precambrian Chemical Sediments

本研究主要是研究Nd和Sr同位素的变化 元古宙和太古宙的稀土元素组成和丰度模式 化学沉积物 它的目的是追踪 元古代外源地球化学循环中的通量 并了解人类进化与 沉积层、海洋和大气层 时间段 我们将集中在钕和锶的测量 稀土元素丰度模式 元古宙海相沉积物。 以下具体项目 提出：1）测定元古宙~（143）Nd/~（144）Nd的变化 碳酸盐和页岩。2)条带状铁的稀土配分模式测定 地层年龄为-0.8 ~3.5Ga; 3)建模 外生地球化学的Sr、Nd同位素记录 过去3.5 Ga的循环，强调元古代。和 4)延长高精度锶同位素数据记录 中寒武世至-2.0 Ga前的碳酸盐岩， 来自维多利亚岛（N.W.T.， 加拿大）和澳大利亚的各种沉积盆地。 我们建议建立一个详细、准确的Sr和 2000 - 2005年间化学沉积物的Nd同位素变化 0.5 2.0G前 元古代海水Nd、Sr 预算似乎已经从主要是热液 输入（如在太古代）占主导地位的大陆（河流） 输入。 从这项研究中获得的数据将用于 限制了热液循环速率的变化， 大陆侵蚀速率和平均年龄的变化 整个元古代的大陆侵蚀产物。

This research is on variations in the Nd and Sr isotopic composition and REE abundance patterns in Proterozoic and Archean chemical sediments. It's purpose is to trace the major mass fluxes in the exogenic geochemical cycle through the Proterozoic and to understand the relationship between the evolution of the sedimentary reservoir, the oceans and the atmosphere during this time period. We will concentrate on measurements of Nd and Sr isotope variations and REE abundance patterns on samples of Proterozoic marine sediments. The following specific projects are proposed: 1) Determine 143Nd/144Nd variations in Proterozoic carbonates and shales.; 2) Determine REE patterns of banded iron formations ranging in age from - 0.8 Ga to 3.5 Ga.; 3) Modeling of the Sr and Nd isotope records of the exogenic geochemical cycle through the past 3.5 Ga, emphasizing the Proterozoic.; and 4) Extend the record of high precision Sr isotopic data of carbonates from the mid-Cambrian to - 2.0 Ga ago, using well dated and documented samples from Victoria Island (N.W.T., Canada), and various sedimentary basins in Australia. We propose to establish a detailed, precise record of Sr and Nd isotopic variations of chemical sediments for the time between 0.5 and 2.0 Ga ago. During the Proterozoic, seawater Nd and Sr budgets appear to have changed from dominantly hydrothermal inputs (as in the Archean) to dominantly continental (river) inputs. Data obtained from this research will be used to constrain the changes in rates of hydrothermal circulation, continental erosion rates and variations in the mean age of continental erosion products through the Proterozoic.