Cenozoic crustal genesis in SW Pacific arcs and backarcs

摘要0751600（吉尔）学术成就：这项研究考察了在没有预先存在的大陆地壳的情况下，地球的地幔和地壳是如何在一个大约5000万年的俯冲周期中从开始到消亡演变的。 它涉及西南太平洋Kermadec-Fiji-Tonga地区岩石的四个火成岩岩石学项目。利用火山岩的地球化学和同位素特征进行的测试将用于回答：（1）俯冲起始是否具有特征性的岩浆特征和原因;（2）弧后裂谷作用期间地幔楔中的岩浆成因是否从通量主导的熔融演化为减压主导的熔融;以及（3）原始弧岩浆活动的地球化学特征是否传递到具有大陆特征的第二阶段地壳。 地球化学计划包括广泛的微量元素和Nd-Hf-Sr-Pb同位素数据的生成和解释。 此外，将获得火成岩的U/Pb和Ar-Ar年龄，并将结果与北方的类似物进行比较。第一个项目的重点是斐济和汤加最古老的岩石。第二个重点是在斐济爆发的玄武岩在3-5马，和那些在交叉链和裂谷盆地在哈弗海槽。第三个项目使用斐济不同年龄和成分的花岗岩体，包括（U-Th）/He双测年”。一个预期的影响将是评估地球上两个最大和研究最充分的海洋弧之间的过程的共同性：伊苏-马里亚纳群岛和克马德克-斐济-汤加。 所有这三个项目都直接补充了NSF资助的RIDGE 2000、MARGINS和IODP中的岛弧和弧后盆地研究重点。它们还涉及与日本和新西兰科学家的国际合作。 该项目为两名研究生和几名本科生提供教育/培训机会。公众宣传和传播将通过MARGINS教育和宣传计划进行，并将向史密森尼国家自然历史博物馆岛屿收藏品提供有充分记录的样本收藏品，在那里将无限期地进行策划。

ABSTRACT 0751600 (Gill)Intellectual Merit: This research examines how the mantle and crust of the Earth evolve from during one ~50 million year cycle of subduction, from initiation to demise, in the absence of pre-existing continental crust. It involves four igneous petrological projects on rocks from the Kermadec-Fiji-Tonga area of the SW Pacific. Test using the geochemical and isotopic signatures of volcanic rocks will be used to answer (1) whether subduction initiation has a characteristic magmatic signature and cause; (2) if magma genesis in the mantle wedge during back-arc rifting evolves from flux-dominated to decompression-dominated melting; and (3) whether geochemical features of primary arc magmatism get passed on to second stage" crust that is continental in character. The geochemical plan includes generation and interpretation of extensive trace element and Nd-Hf-Sr-Pb isotope data. In addition, U/Pb and Ar-Ar ages will be obtained for igneous rocks, and results compared to analogues in the northern hemisphere. The first project focuses on the oldest rocks in Fiji and Tonga. The second focuses on basalts erupted in Fiji during 3-5 Ma, and those in cross-chains and rift basins in the Havre Trough. The third uses the granitic plutons of different ages and compositions in Fiji and includes (U-Th)/He double-dating". One anticipated impact will be to assess the commonality of processes between Earth's two largest and best-studied oceanic arcs: Izu-Marianas, and Kermadec-Fiji-Tonga.Broader Impacts: All three projects directly complement the NSF-funded island arc and backarc basin research foci in RIDGE2000, MARGINS, and IODP. They also involve international collaboration with scientists in Japan and New Zealand. The project provides education/training opportunities for two graduate students and several undergraduates. Public outreach and dissemination will occur through the MARGINS Education and Outreach program and a well-documented sample collection will be provided to the Smithsonian National Museum of Natural History Islands" collection where it will be curated indefinitely.