Th Isotope and U-Series Disequilibria in Volcanic Rocks: Ridges, Arcs, and Zoned Eruptions

9315960 Gill PI提出了一项为期四年的综合研究：（1）Th，U和Ra的分配系数;（2）部分熔融期间放射性核素行为的数值模型;洋中脊段火山岩中Th、U、Ra和Pa的活度（Siqueros变换，大西洋中脊36 oN和33 oS，加拉帕戈斯扩张中心的扩展尖端位于86 oW），两个大陆边缘弧（日本和堪察加半岛）和两个大洋弧-后弧（伊豆中部拉斑玄武岩和北方马里亚纳的钾玄岩）和两个化学分带的大陆长英质岩系（加州的Inyo-Mono和中国的白头山）。 其目的是在每种情况下区分时间的影响和开放系统的影响。 实现这一目标的关键，除了克服困难的分析问题，是选择岩石套件非常适合的专题问题，并为丰富的其他地质和地球化学信息将是可用的。 因此，本建议侧重于上述#3。

9315960 Gill The PIs propose an integrated four year study of: (1) the partition coefficients of Th, U, and Ra; (2) numerical models of the behavior of radionuclides during partial melting; and (3) Th, U, Ra, and Pa activities in volcanic rocks from mid-ocean ridge segments (Siqueros transform, 36oN and 33oS on the Mid Atlantic Ridge, and a propogating tip of the Galapagos Spreading Center at 86oW), two continental margin arcs (Japan and Kamchatka) and two oceanic arc-backarcs (tholeiites in central Izu and shoshonites in the northern Marianas), and two chemically- zoned continental felsic systems (Inyo-Mono in California and Baitoushan in China). The objective is to distinguish the effect of time from the effect of an open system in each case. The key to reaching this objective, apart from overcoming the difficult analytical problems, is choosing rock suites well-suited to thematic questions and for which abundant other geological and geochemical information will be available. Consequently, this proposal focuses on #3 above.