Seismic crustal structure and evolution of the Coast Mountains Batholith

海岸山脉岩基地震地壳结构与演化

• 批准号: 356263-2007
• 负责人: Spence, George
• 金额: $ 1.13万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Special Research Opportunity Program - Project
• 财政年份: 2011
• 资助国家: 加拿大
• 起止时间: 2011-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=483061
• 关键词: Seismic; crustal; structure; evolution; Coast

The Coast Mountain Batholith (CMB) of British Columbia is the largest batholith in the North American Cordillera. A batholith is a very large volume of previously molten rock in the deep subsurface that worked its way upward and solidified. The CMB is an ideal natural laboratory in which to address an outstanding problem in Earth Sciences. The average composition of the continental crust is represented by andesite [a volcanic rock intermediate between silicic (silicon oxides) and mafic (iron/magnesium oxides)]. However, melts derived from the mantle in all tectonic regimes are basaltic [a volcanic rock of mafic composition]. This discrepancy poses a fundamental problem for Earth Sciences: What processes generate an andesitic crust from basaltic rocks? We expect that the lighter silicic components fractionate and rise up, leaving a heavier ultramafic residue in the upper mantle. The residue may be so dense that it sank deeper into the mantle, or it may lay "hidden" below the crust-mantle boundary as a dense root. The BATHOLITHS project, primarily funded from U.S. sources ($4.6M over 5 years), investigates this problem through an integrated geological and geophysical study of the CMB. Seismic studies are among the most effective techniques for determining rock types in the deep crust and mantle. With NSERC funds of $286,500 over 3 years, Canadian scientists will participate as full partners in a major crustal-scale refraction / wide-angle-reflection (R/WAR) seismic program across the CMB. This contribution will bring nearly double our requested amount in U.S. funds to run the experiment, will provide access to the huge U.S. pool of seismometers (>2500 instruments), and will allow us to interact with U.S. and Canadian scientists from many Earth Science disciplines. We will share the significant discoveries to be made and promote the training of undergrad and graduate students who will become Earth scientists in industry, government and academia.

不列颠哥伦比亚省的海岸山岩基（CMB）是北美科迪勒拉山脉最大的岩基。岩基是地下深处大量先前熔化的岩石，向上移动并凝固。 CMB 是解决地球科学中突出问题的理想自然实验室。大陆地壳的平均成分以安山岩（介于硅质（氧化硅）和镁铁质（铁/镁氧化物）之间的火山岩）为代表。然而，在所有构造体系中，源自地幔的熔体都是玄武岩[镁铁质成分的火山岩]。这种差异给地球科学提出了一个基本问题：什么过程从玄武岩中产生了安山地壳？我们预计较轻的硅质成分会分馏并上升，在上地幔中留下较重的超镁铁质残留物。残留物可能非常致密，以至于更深地沉入地幔中，或者它可能作为致密的根“隐藏”在壳幔边界下方。 BATHOLITHS 项目主要由美国资助（5 年 460 万美元），通过对 CMB 进行综合地质和地球物理研究来调查这个问题。地震研究是确定深部地壳和地幔岩石类型的最有效技术之一。凭借 NSERC 三年内 286,500 美元的资金，加拿大科学家将作为全面合作伙伴参与整个 CMB 的主要地壳尺度折射/广角反射 (R/WAR) 地震计划。这笔捐款将使我们为运行该实验而请求的美国资金金额增加近一倍，将提供使用美国庞大的地震仪库（超过 2500 台仪器）的机会，并使我们能够与来自许多地球科学学科的美国和加拿大科学家进行互动。我们将分享即将取得的重大发现，并促进对本科生和研究生的培训，他们将成为工业界、政府和学术界的地球科学家。