TIMS

1) 名称:热电离质谱仪

Name:Thermal Ionization Mass Spectrometer (TIMS)

型号: Triton Plus

Type: Triton Plus

制造商:美国赛默飞世尔科技有限公司

Manufacturer:Thermo Fisher Scientific Co.,Ltd

购置时间:2013

Purchasing time: April 2013

2) 主要功能

测定岩石全岩及单矿物的Sr、Nd 、Ca、Cr同位素

2)Major specialty

Measuring Sr、Nd 、Ca and Cr isotopes of bulk rocks and minerals

 

3)应用领域

Rb-Sr,Sm-Nd同位素体系,广泛用于地质年代学与同位素示踪。各地质储库因Rb/Sr和Sm/Nd不同,经长时间衰变积累而具有各自不同的Sr、Nd同位素比值。Sr、Nd同位素比值在短期地质过程中(如部分熔融、分离结晶等)不发生变化,因此可作为示踪岩石物源区的重要工具。在地质年代学方面,对于一些缺少锆石或其他适宜U-Pb定年矿物的岩石,Rb-Sr和Sm-Nd同位素体系可以提供较为精确的岩石形成年龄,比如岩浆结晶年龄或变质年龄。此外,由于Rb-Sr、Sm-Nd和U-Pb同位素体系的封闭温度不同,在一些变质岩研究中,多同位素体系联合定年被用来确定研究对象变质过程的P-T-t轨迹。

Ca同位素是新世纪研究比较多的金属稳定同位素。由于Ca是碳酸盐(方解石,白云石,文石等)中的主要元素之一,因此,绝大多数的Ca同位素研究都集中在与碳酸盐相关的领域中,在古海水Ca同位素演化,地层Ca同位素与大洋缺氧事件及生物大灭绝等方面有较多的应用。Ca同位素在岩浆演化方面也有少量的研究。

Cr同位素是近年来研究较多、发展较快的一种金属稳定同位素。在生物地球化学领域中主要用于古环境氧化还原条件变化的研究。Cr作为一种重金属,对环境,动物及人类的健康有较大危害,将Cr(VI)还原成Cr(III)可以有效的降低Cr对环境的危害,而在这个过程中会伴随着明显的Cr同位素质量相关分馏,因此在环境地球化学中可以利用Cr同位素来指示Cr污染的情况,比如Cr污染的来源及其传播过程。在宇宙化学中,由于53Mn是短半衰期的放射性核素,衰变产生53Cr,53Mn-53Cr同位素体系可以用来限制小行星分异的时间,以及为早期太阳系星体发生的更大规模作用提供信息,它已成为研究太阳系最初几个百万年演化史的最重要手段之一。

 

3)Applied Areas

Rb-Sr and Sm-Nd systematics have been widely used in geochronology and isotopic tracing. Geological reservoirs possess Sr, Nd isotopic ratios different among each other due to their different Rb/Sr and Sm/Nd ratios and long-term radiogenic accumulation. The Sr and Nd isotopic ratios do not change significantly during short-term geological processes, e.g., partial melting, fractional crystallization, and etc, and thus can be used as an important tracer for material sources of rocks. As for geochronology, for some rocks lack of zircons and other suitable minerals for U-Pb dating, Rb-Sr and Sm-Nd systematics can provide precise rock-formation ages, such as the crystallization or metamorphic age. Furthermore, due to different closure temperatures of Rb-Sr, Sm-Nd and U-Pb systems, multiple geochrons are used to reveal the P-T-t paths of metamorphic processes in some studies of metamorphic rocks.

Ca isotope has been one of the most focused metallic isotopes in the new century. Since Ca is one of the main elements in carbonates(calcite, dolomite, aragonite etc.), most of the Ca isotope research have been concentrated on the area about carbonates, including Ca isotope evolution of paleoocean, oceanic anoxic events and mass extinction in the past. Also, there are a few research focusing on the isotopic features during magmatic evolution, but more work needs do be done.

Cr isotopes also gain much attention during the first decade of the 21st century. Due to the variations of the valence of Cr, Cr isotope can used to tracing the redox state of paleoenvironmentin bio-geochemistry. Among one of the heavy metals, Cr is harmful to the environment, animals and humankind. The reduction of Cr(VI) can effectively reduce the harm to the environment, and this process will be accompanied by significant Cr isotopic fractionation. Therefore, Cr isotopes can be used to trace the pollution situation, such as the source and migration process of Cr pollutant in environmental geochemistry. Another significantly applied area of Cr isotope is cosmochemistry. Due to short-lived radionuclide 53Mn, 53Mn-53Cr systematics of bulk samples from a differentiated planetesimal can yield important constraints on its time of differentiation and valuable information on large scale processes within early solar system bodies. 53Mn-53Cr system has been becoming one of the most powerful method to analyze the evolution of solar system in the first few million years.