Origin of Granite and Mafic-felsic Magma Interaction in the Lower Crust: Athabasca Granulite Terrane, CA

下地壳中花岗岩和镁铁质-长英质岩浆相互作用的起源：加利福尼亚州阿萨巴斯卡麻粒岩地体

• 批准号: 0911421
• 负责人: Michael Williams
• 金额: $ 19.16万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-15 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0911421&HistoricalAwards=false
• 关键词: Origin; Granite; Mafic; felsic; Magma

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Intellectual Merit. The Athabasca granulite terrane, Saskatchewan, Canada is one of Earth's largest exposures of intact lower continental crust, and offers the opportunity to see first-hand the complexity of magmatic processes that contributed to formation of the deep crust. In this terrane are unique exposures of heterogeneous lower crust comprising igneous rocks ranging from mafic to felsic compositions. Contrary to common belief that the lower crust is very poor in H2O, many of these rocks host abundant hydrous phases. The eastern part of the terrane is dominated by the 3.3 Ga Chipman tonalite and the 2.6 Ga Fehr granite/granodiorite. Prior to 1.9 Ga, these rocks made up the stable deep crust of the Rae Province. At 1.9 Ga, the Chipman mafic dike swarm intruded both the tonalite and the granite. The tonalite and some of the already crystallized mafic dikes were melted to a small extent. The Fehr granite underwent extensive partial melting, producing true granitic magmas. Over an area of tens of km2, brush-fired cleaned pavement exposures record the partial melting process and a stunning array of mixing and mingling textures between partial melt of Fehr granite and the Chipman dike mafic magma. It is hypothesized that the heterogeneity of the deep crust makes it a fertile source for a variety of melt compositions and that magma interaction processes so well documented in shallow crustal exposures elsewhere are also common at near-mantle depths as well. Funds are requested to carry out comprehensive petrologic characterization of these rocks. Field relationships, textures, and fabrics will be described along a north to south gradient/transect from minimal to extensive partial melting. Major, trace and isotopic analyses will establish the origin of end-member and hybrid rocks as well as source rocks and mid-crustal equivalents of melts identified in the lower crust.Broader Impacts. This grant will support the training of a Ph.D. student and the enrichment of the undergraduate mineralogy, petrology, and structural geology courses. In addition, the field work will provide an opportunity for outreach, through presentations and discussions, to a people who live in a very remote area, but whose livelihoods are generally based on the natural resources of the area. The work will help to lay the groundwork for a planned field forum for geologists and geophysicists to discuss the implications of the heterogeneous lower crust, and finally the project will involve the development of web resources for teachers and researchers about this special exposure of deep continental crust.

“该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。“智力优势。加拿大萨斯喀彻温省的阿萨巴斯卡麻粒岩是地球上最大的完整下陆壳暴露之一，并提供了第一手的机会来了解导致地壳深部形成的岩浆过程的复杂性。在这片岩石中，有独特的非均匀下地壳出露，包括从镁铁质到长英质成分的火成岩。与下地壳含水量非常低的普遍看法相反，许多这些岩石含有丰富的含水相。东部主要为3.3 Ga的奇普曼英云闪长岩和2.6 Ga的Fehr花岗岩/花岗闪长岩。在1.9 Ga之前，这些岩石构成了Rae省稳定的深地壳。在1.9 Ga，奇普曼基性岩墙群侵入英云闪长岩和花岗岩。英云闪长岩和一些已经结晶的基性岩脉在很小程度上被熔融。费尔花岗岩经历了广泛的部分熔融，产生真正的花岗岩岩浆。在数十平方公里的区域内，刷火清洁路面暴露记录了部分熔融过程和Fehr花岗岩部分熔融与奇普曼脉基性岩浆之间令人惊叹的混合和混合纹理。据推测，地壳深部的异质性，使其成为一个肥沃的来源，为各种熔体成分和岩浆相互作用过程，以便在其他地方的地壳暴露浅也很常见，在近地幔深处。要求提供资金对这些岩石进行全面的岩石学鉴定。场的关系，纹理，和织物将被描述沿着从北到南的梯度/样带从最小到广泛的部分熔化。主要、微量和同位素分析将确定端元和混合岩的起源，以及源岩和下地壳中已查明的熔体的中地壳等价物。这笔赠款将支持培养一名博士。学生和丰富的本科矿物学，岩石学和构造地质学课程。此外，实地工作将提供一个机会，通过介绍和讨论，与生活在非常偏远地区、但其生计通常依赖该地区自然资源的人民进行外联。这项工作将有助于为计划中的地质学家和地球物理学家实地论坛奠定基础，以讨论不均匀下地壳的影响，最后，该项目将涉及为教师和研究人员开发关于大陆地壳深部这种特殊暴露的网络资源。