Processes of Granulite Formation and Their Geochemical Signatures: A Study in the Wind River and Laramie Mountains,Wyoming

麻粒岩形成过程及其地球化学特征：怀俄明州风河和拉勒米山的研究

• 批准号: 8707296
• 负责人: Carol Frost
• 金额: $ 8万
• 依托单位: University of Wyoming
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1987
• 资助国家: 美国
• 起止时间: 1987-07-01 至 1990-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8707296&HistoricalAwards=false
• 关键词: Processes; Granulite; Formation; Their; Geochemical

The problem of the origin of granulites is of interest to a wide cross-section of Earth Scientists because present-day surface outcrops are believed to give clues to processes operating, past and present, in the lower crust. It is proposed to study the causes of granulite metamorphism and to identify the geochemical effects of hornblende breakdown. The breakdown will be studied in two places in the contact aureole of the Laramie Anorthosite. In one locality hornblende breakdown due to simple dehydration, while in other breakdown is in response to CO2-fluxing from adjacent marble. Both of these mechanisms of hornblende decomposition have been proposed as causes of granulite metamorphism. The results of the Laramie Anorthosite investigation will be applied to interpreting the origins of charnockites in the Wind River Mtns. An attempt will be made to determine the origin of granulite selvages in the country rock of charnockite dikes. Criteria will be established for distinguishing igneous charnockites from granulite gneisses metamorphosed in the granulite facies. The research will use field mapping, petrology, electron microprobe analyses, stable and radiogenic isotope analyses to deduce the processes of granulite formation and their geochemical signatures.

麻粒岩的起源问题引起了广泛领域的地球科学家的兴趣，因为今天的地表露头被认为为下地壳过去和现在的运作过程提供了线索。建议研究麻粒岩变质作用的成因，识别角闪石破裂的地球化学效应。将在拉勒米斜长岩接触光环的两个地方研究击穿。在一个地方，角闪石由于简单的脱水而破裂，而在另一个地方，角闪石的破裂是对相邻大理岩的二氧化碳熔融的反应。角闪石的这两种分解机制都被认为是麻粒岩变质的原因。拉勒米斜长岩的调查结果将被应用于解释风河山脉的沸石成因。试图确定紫苏花岗岩脉围岩中麻粒岩边沿的成因。将建立区分火成岩和麻粒岩相变质麻粒片麻岩的标准。这项研究将利用野外填图、岩石学、电子探针分析、稳定同位素和放射性同位素分析来推断麻粒岩的形成过程及其地球化学特征。