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

该奖项将支持对 U1309D 洞（亚特兰蒂斯马西夫，位于北纬 30 度大西洋中脊西侧的辉长岩进行综合磁性和热测时研究。正常极性磁性叠印的分布（相对于火成岩接触）和温度稳定性将为侵入的空间尺度以及这些岩体就位时围岩的温度提供有价值的限制。 U-Pb 测年将确定在 IODP 孔 U1309D 上部 1250m 处发现的结壳熔体（包括淡色岩脉、氧化辉长岩和一些辉长岩）的侵位年龄，对锆石和磷灰石进行的闭合温度约为 200-70°C，将确定这些岩石的低温冷却和剥蚀历史。测时法和剩磁数据将用于限制由亚特兰蒂斯地块提出的低角度正断层引起的冷却/剥蚀的时间和速率。剩磁方向（特别是使用地层显微扫描仪图像重新定向的岩心片）将用于估计自获取剩磁以来的构造旋转量，并且可能有助于限制可能的旋转轴的范围。

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.