Petrotectonic Evolution of High-Pressure and Suspected Ultrahigh Pressure Granulites and Eclogites in Neoproterozoic Nappes of South-East Brazil

巴西东南部新元古代推覆体高压和疑似超高压麻粒岩和榴辉岩的岩石构造演化

• 批准号: 0125867
• 负责人: Christopher Parkinson
• 金额: $ 12.8万
• 依托单位: University South Carolina Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2003-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0125867&HistoricalAwards=false
• 关键词: Petrotectonic; Evolution; Pressure; Suspected; Ultrahigh

AbstractEAR-0125867ParkinsonUniversity of South CarolinaThe primary objective of this proposal is to document the petrological characteristics and tectonic significance of high- to ultrahigh-pressure metamorphism (HP-UHPM) of Pan-African nappes in Minas Gerais State, southeast Brazil. The crystalline nappes are components of the Tocantins orogen, which extends along strike for around 1000 km, and records Neoproterozoic convergence, subduction and collision between the Sao Francisco craton and Rio de la Plata plate. Techniques to be applied will include: [1] X-ray compositional mapping of major and trace elements in garnets, [2] identification of inclusion species in garnet and zircon by micro-Raman spectroscopy, [3] textural and compositional characterization of exsolution lamellae and integration of precursor phase compositions, [4] SHRIMP U-Pb geochronology of zircon zonal domains. These studies will be complemented by conventional analyses of reaction textures and petrofabrics. The observation of coesite-grade metamorphism in the Americas not only impacts local studies of the Brasiliano-Pan African tectonic framework, but also provides a comparison between deep burial in the Proterozoic (at c. 630 Ma) and better studied Cainozoic orogenic analogues. This proposal, which addresses directly ancient convergent margin orogenesis, provides critical detail field, geochemical, and geochronological data of deeply buried rocks now exposed at the surface. The newly derived P-T-time data for this 630 Ma terrane will be incorporated into regional geodynamic models for the evolution of the South American orogen.

摘要本文的主要目的是研究巴西东南部米纳斯吉拉斯州泛非推覆体的高-超高压变质作用（HP-UHPM）的岩石学特征及其构造意义。结晶推覆体是Tocantins造山带的组成部分，沿走向延伸约1000公里，记录了新元古代圣弗朗西斯科克拉通与里约热内卢de la Plata板块之间的辐合、俯冲和碰撞。应用的技术将包括：[1]石榴石中主要和微量元素的x射线成分制图，[2]用微拉曼光谱鉴定石榴石和锆石中的包裹体物种，[3]脱溶层片的结构和成分表征以及前驱体成分的整合，[4]SHRIMP锆石带域U-Pb地质年代学。这些研究将由反应织构和岩石织构的常规分析加以补充。美洲地区榴辉岩级变质作用的观察不仅影响了当地对巴西利亚-泛非构造格局的研究，而且提供了元古代（约630 Ma）深埋与较好研究的新生代造山类似物之间的比较。这一建议直接解决了古代收敛边缘造山作用，提供了现在暴露在地表的深埋岩石的关键细节、地球化学和地质年代学数据。新获得的630 Ma地块的P-T-time数据将被纳入南美造山带演化的区域地球动力学模型。