Petrogenesis of Massif Anorthosites

地块斜长岩的岩石成因

• 批准号: 8816977
• 负责人: Robert Dymek
• 金额: $ 5万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1989
• 资助国家: 美国
• 起止时间: 1989-02-15 至 1991-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8816977&HistoricalAwards=false
• 关键词: Petrogenesis; Massif; Anorthosites

Massif anorthosites are plutonic igneous rocks consisting almost entirely of plagioclase feldspar. Recurring problems in the study of these enigmatic rocks include the mechanisms that lead to such unusual concentrations of plagioclase on the scale of batholiths, the nature and source of their parental magmas, their relationship to associated iron-titanium oxide ores, their relationship to associated granitic igneous rocks of the admellite-charnockite-mangerite suite, and the crystallization - differentiation processes that link some or all of these rocks together as parts of single or repeated episodes of magmatism. The emplacement of massif anorthosites appears restricted in space and time to relatively narrow belts of mid-Proterozoic age. Accordingly, the formation of massif anorthosites and their associated rocks represents an important stage in the growth and development of the continental crust spanning only a short interval of Earth history. We will investigate the origin of massif anorthosite and associated rock types through an integrated field, petrological and geochemical study on the St. Urbain and Labrieville anorthosites, Quebec. Our study of St. Urbain is a continuation of work begun a number of years ago, whereas the study of Labrieville represents a new initiative. Each massif contains a range of rock types pertinent to a critical evaluation of the anorthosite problem within plutons that are small enough to be investigated in great detail. Our work will include the analysis of mineral compositions by electron microprobe methods, and the analysis of whole-rocks for major and selected trace elements by a combination of X-ray fluorescence (XRF) and instrumental neutron activation (INA) methods. We will establish a comprehensive petrological and geochemical data base that will allow us to develop quantitative models for the chemical assembly of the anorthositic rocks, to evaluate processes responsible for their magmatic differentiation, and to provide well-constrained estimates of their parental magma compositions.

块状斜长岩是深成火成岩， 几乎全是斜长石。 经常出现的问题 对这些神秘岩石的研究包括其机制， 导致斜长石的密度如此之高 岩基的性质和母岩浆的来源， 它们与伴生的铁-钛氧化物矿石的关系， 与相关花岗质火成岩的关系 辉橄榄岩-紫苏花岗岩-镁橄榄石岩组，以及结晶- 将这些岩石的一部分或全部联系起来的分异过程 一起作为单一或重复的岩浆活动的一部分。 斜长岩的侵位似乎局限于 空间和时间相对狭窄的带中元古界年龄。 因此，斜长岩的形成及其 共生岩是生长的重要阶段， 大陆地壳的发展只跨越了短短的 地球历史的一段时间。 我们将探讨斜长岩的成因， 通过综合领域，岩石学， 对圣乌尔班和拉布里维尔的地球化学研究 斜长岩，魁北克。 我们的研究圣乌尔班是一个延续 这项工作开始于几年前，而研究 Labrieville代表了一个新的倡议。 每一个bifs都包含一个 一系列岩石类型有关的一个关键的评价 岩体中的斜长岩问题， 详细调查过。 我们的工作将包括分析矿物成分 用电子探针法和全岩分析 主要和选定的微量元素的X射线组合 荧光（XRF）和仪器中子活化（INA） 方法. 我们将建立一个全面的岩石学和 地球化学数据库，这将使我们能够开发定量的 斜长岩化学组合模型， 评估导致其岩浆活动的过程 差异，并提供良好的约束估计 它们的母岩浆成分