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

9315960 Gill PIS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)放射性核素在部分熔融期间的行为的数值模型；(3)大洋中脊(Siqueros变换，北纬36oS和南纬33oS，加拉帕戈斯扩张中心尖端860oW)、两个大陆边缘弧(日本和堪察加)和两个大洋弧背弧(伊豆中部的拉斑玄武岩和马里亚纳斯海北部的玄武岩)和两个化学分带大陆长英质体系(加利福尼亚州的Inyo-Mono和中国的白头山)的火山岩中的Th、U、Ra和Pa活动。其目的是在每种情况下区分时间的影响和开放制度的影响。除了克服困难的分析问题外，实现这一目标的关键是选择适合专题问题的岩石套件，并为此提供丰富的其他地质和地球化学信息。因此，本提案的重点是上面的第三点。

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.