Development and Calibration of Rutile (U-Th)/He Geo- and Thermochronometry

磷灰石、锆石、独居石和钛矿等磷酸盐和硅酸盐矿物的(U-Th)/He定年引起了相当大的兴趣；然而，含U和th的铁或钛氧化物尚未被系统地研究和开发为低t温度计。一种常见的氧化矿物是金红石（TiO2），它作为一种辅助矿物存在于许多岩浆岩中，也广泛存在于高变质岩中，特别是蓝片岩、榴辉岩和麻粒岩中。我们建议通过研究金红石(U-Th)/He的He扩散特性来发展和校准金红石(U-Th)/He地热时计；我们将考虑诸如粒度和化学成分等因素。此外，我们将在KTB超深井和Wassuk山脉西部盆地和山脉省的一个伸展断块中，对快冷火山岩以及更慢冷的样品阵列进行金红石(U-Th)/He测年。我们还将应用金红石(U-Th)/He热时测定法测定阿曼高压变质岩的冷却时间。金红石的(U-Th)/He校准将提供一种新的地质和温度计时器，将广泛适用，但对于高磷至超高磷样品的研究尤其有用，这些样品目前很难或不可能确定日期。在我们的研究过程中发展的科学成果和方法将通过发表研究论文和在国际会议上发表报告的方式传播给地球科学界。这项研究将对两名学生的教育产生重大影响，他们将在KU (U-Th)/He和TIMS实验室与pi一起工作，为他们提供主动学习的机会，并使他们接触到最先进的分析设备和新的研究方向。这种背景对学生的智力成长非常重要，并能让他们在合作和小组/团队的情况下工作。

(U-Th)/He dating of phosphate and silicate minerals such as apatite, zircon, monazite, and titanite has attracted considerable interest; however, U- and Th-bearing Fe- or Ti-oxides have not been systematically investigated and developed as low-T thermochronometers. A common oxide mineral is rutile (TiO2), which is present as an accessory mineral in many magmatic rocks and also occurs widely in high-grade metamorphic rocks, especially in blueschists, eclogites, and granulites. We propose to develop and calibrate rutile (U-Th)/He geo- and thermochronometry by investigating its He diffusion characteristics; we will include such factors as grain size and chemical composition. Furthermore, we will test rutile (U-Th)/He dating on fast-cooled volcanic rocks as well as more slowly-cooled sample arrays from the KTB ultra-deep borehole and an exhumed extensional fault block in the Wassuk Range, western Basin and Range province. We will also apply rutile (U-Th)/He thermochronometry to date the cooling of high-pressure metamorphic rocks from Oman. The (U-Th)/He calibration of rutile will provide a new geo- and thermochronometer that will be widely applicable, but should be especially useful for studies of high-P to ultrahigh-P samples that are notoriously difficult or impossible to date at the present. The scientific results and methodologies developed during our study will be disseminated to the geosciences community through publication of research papers and presentations at international meetings. The study will significantly impact the education of two students that will work with the PIs in the KU (U-Th)/He and TIMS laboratories, providing them the opportunity for active learning and exposing them to state-of-the-art analytical facilities and new research directions. This background will be important to the intellectual growth of the students and give them experience in working in collaborative and group/team situations.