The Petrogenesis of Cr-Poor and Cr-Rich "Megacrysts" in Mantle-Derived, Silica-Undersaturated Magmas

幔源二氧化硅不饱和岩浆中贫铬和富铬“巨晶体”的岩石成因

• 批准号: 9118128
• 负责人: Clive Neal
• 金额: $ 7.82万
• 依托单位: University of Notre Dame
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-03-15 至 1994-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9118128&HistoricalAwards=false
• 关键词: Petrogenesis; Cr; Poor; Rich; Megacrysts

The purpose of this research is to undertake a detailed geochemical examination of megacrysts suites from the Malaitan alnoite (Solomon Islands), and the Sloan-Nix kimberlite (Colorado). Samples will be gathered from existing collections and initially characterized by EMP analysis. Fractionation trends thus defined will allow critical samples to be selected for IMP analysis. Traverses will be carried out on samples forming end-member compositions to the apparent fractionation trends defined by EMP analyses. This approach will then pin-point samples for isotopic analysis (Sr, Nd, Pb, O), using micro-sampling techniques to investigate potential isotopic zonation within and between megacrysts. This integrated approach is required to: 1) determine the nature of the parental magma; 2) evaluate the mode of crystallization within the mantle regime; 3) determine whether the proposed igneous fractionation occurred in an open- or closed-system environment; 4) establish any link between megacryst crystallization and metasomatic processes; and 5) examine the relationship (if any) between Cr-rich and Cr- poor megacrysts.

这项研究的目的是对来自马来阿尔诺岩(所罗门群岛)和斯隆-尼克斯金伯利岩(科罗拉多州)的巨晶岩进行详细的地球化学检查。样品将从现有的样品中收集，并通过电磁脉冲分析进行初步表征。这样定义的分馏趋势将允许选择关键样品进行IMP分析。将对形成端元组成的样品进行遍历，以达到EMP分析定义的明显分馏趋势。然后，这种方法将点状样品用于同位素分析(锶、钕、铅、氧)，使用微采样技术调查巨晶内和巨晶之间潜在的同位素分带。这种综合的方法需要：1)确定母岩浆的性质；2)评估地幔体系内的结晶模式；3)确定所提出的火成岩分馏作用是发生在开放系统还是封闭系统环境中；4)建立巨晶结晶和交代过程之间的任何联系；以及5)研究富铬和贫铬巨晶之间的关系(如果有)。