Constraints of the Genesis of Continental Crust via Arc Magamatism: Geology, Geochemistry, Structure and Physical Properties of the Talkeetna Arc Section South Central Alaska

9910899 Kelemen这个项目是对塔尔基特纳岛弧(阿拉斯加)裸露的地壳部分进行的多年跨学科研究，以探讨会聚边缘大陆增长的速度和机制。Talkeetna弧段，特别是在NelChina-Tonsina地区，是一个地壳段，穿过与侏罗纪俯冲有关的增生岩浆弧，从顶部的火山岩、火山碎屑岩和沉积岩到底部的残余地幔橄榄岩。对裸露的岛弧剖面的详细研究可以在地球物理观测和地球化学蛇绿岩研究之间提供关键的联系。在建立海洋扩张脊处的地壳增长的完整图景、研究未来十年的弧岩浆作用和地壳成因方面，海洋地球物理和大洋中脊玄武岩的分析提供了理想的对应物。该项目解决了关于弧形过程的一个关键问题：汇聚边缘的大陆增长的速度和机制是什么？Talkeetna区段的工作可以对中、下弧壳的成分和吸积时间提供关键限制，这些地壳通常不暴露在活动弧中。P.I.S将探讨地壳成因的各个方面，应用各种分析技术：1)改进的地质填图；2)确定下地壳岩石的变形历史，寻找断层和缺失的部分；3)对该剖面中典型岩石的物理性质进行测量；4)详细调查地壳底部残留的地幔方辉橄榄岩和火成超镁铁质岩石；5)圈定弧形地壳段的液体下降线；6)岩石学和微量元素模拟；以及7)确定下地壳的P-T-T历史。

9910899KelemenThis project is for a multi-year, interdisciplinary study of the exposed crustal section of the Talkeetna island arc (Alaska) to address the rate and mechanism of continental growth at convergent margins. The Talkeetna arc section, particularly in the Nelchina-Tonsina region, is a crustal section through an accreted, Jurassic subduction-related magmatic arc, from volcanic, volcaniclastic and sedimentary rocks at the top to residual mantle peridotites at the base. Detailed studies of exposed, island arc sections can provide a crucial link between geophysical observations and geochemical ophiolite studies have provided an ideal counterpoint to both marine geophysics and analysis of mid-ocean ridge basalts in developing a complete picture of crustal accretion at oceanic spreading ridges, studies of arc magmatism and crustal genesis over the coming decade.The project addresses a key question regarding arc processes: What is the rate and mechanism of continental growth at convergent margins? Work on the Talkeetna section can provide crucial constraints on the composition and timing of accretion of the middle and lower arc crust, which are generally not exposed in active arcs. The P.I.s will address various aspects of crustal genesis, applying a variety of analytical techniques: 1) improved geological mapping; 2) determine deformation history of lower crustal rocks, look for faults and missing sections; 3) physical properties measurements on typical rocks in the section; 4) detailed investigations of residual mantle harzburgites and igneous utlramafic rocks at base of crust; 5) delineate liquid lines of descent in the arc crustal section; 6) petrological and trace element modeling; and 7) determine the P-T-t history of the lower crust.***