Petrologic-Tectonic Evolution of the Lau Basin

劳盆地的岩石构造演化

• 批准号: 8716660
• 负责人: James Hawkins
• 金额: $ 31.42万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1988
• 资助国家: 美国
• 起止时间: 1988-10-15 至 1991-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8716660&HistoricalAwards=false
• 关键词: Petrologic; Tectonic; Evolution; Lau; Basin

The origin of backarc basins has been a topic of much interest and some controversy to marine geologists, geophysicists and petrologists for several decades. This interest stems in part because of their location close to island arcs where different magma types are erupted synchronously with formation of the backarc basin crust. The thermal and stress regimes of backarc basins are of interest because they represent extensional tectonics, steep thermal gradients and mantle upwelling and melting in regions which are dominated overall by compression and subduction of old and cold sediments and crustal rocks to considerable depth within the mantle. The present award will support a geologic and geochemical study of the formation of the Lau Basin which lies to the west of the Tonga Trench and Tonga Ridge in the southwest Pacific. The Lau Basin began rifting within the last few million years and has shown a progressive change in basalt chemistry from a dominance of island arc related basalts to more normal backarc basin basalts. Such a change implies an evolution in the mantle source region from which the basalts are erupted. The field program will examine both the transition regions where mixed basalts have been erupted and the spreading ridge where normal basin crust is presently being emplaced. Subsequent laboratory analyses of recovered samples should fully define the backarc melting regime and allow a comparison of the Lau Basin with the more fully studied Marianas back arc basin. Data from the field program will also aid in defining potential sites for ocean drilling.

弧后盆地的成因一直是一个备受关注的话题 引起了海洋地质学家、地球化学家、 几十年来，这种兴趣部分源于 因为它们靠近岛弧， 岩浆类型与火山岩的形成同步 弧后盆地地壳弧后热应力状态 盆地是令人感兴趣的，因为它们代表了伸展作用 构造，陡峭的热梯度和地幔上涌， 在总体上由压缩主导的区域中熔化， 古老而寒冷的沉积物和地壳岩石俯冲， 在地幔中有相当深的深度。 本奖项将支持地质和地球化学 研究位于香港以西的劳盆地的形成， 太平洋西南部的汤加海沟和汤加海岭。的 劳盆地在过去的几百万年里开始裂谷， 显示了玄武岩化学成分的逐渐变化， 岛弧玄武岩向更正常的弧后盆地演化 玄武岩这种变化意味着地幔源区的演化 玄武岩喷发的地区。外地方案将 研究混合玄武岩的过渡区域， 爆发和扩张的山脊，正常的盆地地壳 目前正在部署。随后的实验室分析 回收的样品应完全定义反弧熔化状态 并允许比较刘盆地与更全面的 研究了马里亚纳弧后盆地。现场项目的数据将 还有助于确定海洋钻探的潜在地点。