U、Th同位素在沉积物定年中的应用

全球气候变化已成为当前研究的热点问题,为预测未来气候的变化趋势,有必要对过去气候变化进行深入的研究,而这又基于可靠的年代学成果,故而年代尺度的高灵敏度、高精密度的测量成为当前迫切需要解决的课题之一。U-Th定年技术在14C年代测定(通常仅适用于39Ar/40Ar法或裂变径迹年代测定(一般用于>500 ka的火山堆积物)之间提供了一种年代测定的桥梁。U-Th定年技术在50~500 ka测年范围内是首选。主要介绍了国内外热电离质谱法(TIMS)U-Th定年技术、单接受器电感耦合等离子体质谱技术(SC ICP-MS)和多接受器电感耦合等离子体质谱法(MC ICP-MS)、U-Th定年法在沉积物领域中的研究概况,并对α谱仪、TIMS、SC ICP-MS、MC ICP-MS U-Th定年技术在测量时间、测量精度、样品需要量等方面进行比较。

APPLICATION OF U,TH ISOTOPES IN DATING YOUNG SEDIMENT

Further research on past climate change based on a reliable geochronogical framework is essential for predicting the future trend of climate change. High-sensitivity and high-precision measurement of age is one of the subjects urgent to solve. U-Th dating technique fills the gap between the 14C dating, which is only applicable to dating the sediments younger than 50 ka, and the 39Ar/40Ar method or fission-track thermorchronology, which is usually applicable to the dating of volcanic deposits older than 500 ka. Up to date, the U-Th dating technique is the first choice for the sediments in age of 50 ka to 500 ka. This paper mainly introduces the current status of the U-Th dating technique using thermal ionization mass spectrometry(TIMS)、single-collector inductively coupled plasma mass spectrometry(SC ICP-MS)and multi-collector inductively coupled plasma mass spectrometry(MC ICP-MS)respectively for sediments. Comparison of U-Th dating techniques with the methods of α-spectrometry,TIMS,SC ICP-MS and MC ICP-MS is also provided for time range,measurement precision and sample requirement.