Collaborative Proposal: Spatial and temporal scales of crustal accretion in slow spreading crust - IODP Site U1309

该奖项将支持对大西洋中脊西侧30度处的U1309D洞（Atlantis Masif）的辉长岩进行综合磁性和热时计研究。正极性磁叠印的分布（相对于火成岩接触）和温度稳定性将对侵入的空间尺度以及这些岩体就位时的围岩温度提供有价值的约束。单锆石U-Pb定年将确定在IODP U1309D孔上部1250m处发现的地壳形成熔体（包括白岩脉、氧化辉长岩和部分辉长岩）的侵位年龄。锆石和磷灰石的(U-Th)/He热年代学表明，闭合温度在~200 ~ 70℃之间，可以确定这些岩石的低温冷却和剥蚀历史。结合U/Pb测时和剩磁数据将用于限制亚特兰蒂斯地块低角度正断层导致的冷却/剥蚀的时间和速率。剩余物方向（特别是利用地层微扫描仪图像重新定位的岩心碎片）将用于估计获得剩余物后的构造旋转量，并有助于限制可能的旋转轴范围。这项研究涉及国际合作和研究生的参与。

This award will support an integrated magnetic and thermochronometric study of gabbroic rocks from Hole U1309D (Atlantis Masif, on the western flank of the Mid-Atlantic Ridge at 30degreesN. The distribution (relative to igneous contacts) and temperature stability of the normal polarity magnetic overprints will give valuable constraints on the spatial scales of intrusions as well as the temperature of the country rock when these plutons were emplaced. Single zircon U-Pb dating will define the emplacement age of crust forming melts (including leucocratic dikes, oxide gabbro and some gabbro) found throughout the upper 1250m of IODP Hole U1309D. (U-Th)/He thermochronometry on zircon and apatite, with closure temperatures between ~200- 70degreesC, will delimit the low temperature cooling and denudation history of these rocks. The combined U/Pb chronometry and remanent magnetic data will be used to constrain the timing and rate of cooling/denudation resulting from low-angle normal faulting as proposed for Atlantis Massif. Remanence directions (particularly from core pieces reoriented using formation microscanner images) will be used to estimate the amount of tectonic rotation since the remanence was acquired and where may help constrain the range of possible rotation axes. The study involves international collaboration and the participation of graduate students.