Trace Element Diffusion Kinetics in Garnet and Clinopyroxene

我们提出了Sm、ND等稀土元素在石榴石(Ce、Gd、Yb)和单斜辉石(Ce、Yb)中的扩散动力学，以及Hf在石榴石中的扩散动力学随T、P和fO2的变化。扩散实验将通过示踪同位素技术进行，诱导的同位素剖面将主要通过离子探测器(SIMS)中的深度剖面进行分析。如果预算限制，将按照既定程序确定单斜辉石的各向异性扩散张量，这将对扩散机制有基本的了解。扩散数据将被用来模拟火成岩中稀土元素的动态演化，这些岩石是地幔部分熔融的产物，说明了微量元素从固体进入部分熔体的动力学。Hf扩散数据将被用来解释前寒武纪花岗岩和流纹岩中的Hf同位素数据，即石榴石在源区的参与。将建立矿物中微量组分缓慢扩散的闭合温度的理论公式，并将其冷却年龄与冷却速率相关联，并应用于石榴石中的Sm-ND和Lu-Hf衰变系统。

9805232GangulyWe proposed to determine the diffusion kinetics of Sm, Nd and other selected REE in garnet (Ce, Gd, Yb) and clinopyroxene (Ce, Yb), and also of Hf in garnet as functions of T, P and fO2. The diffusion experiments will be conducted by tracer isotope techniques, and the induced isotopic profiles will be analyzed primarily by depth profiling in an Ion probe (SIMS).If the budgetary constraints, the anisotropic diffusion tensor of clinopyroxene will be determined following established procedures, which should yield fundamental insight about the diffusion mechanism. The diffusion data will be applied to model the dynamic evolution of REE in igneous rocks, which are products of partial melting of the Earth's mantle, accounting for the kinetics ofincorporation of the trace elements from the solids into the partial melt. The Hf diffusion data will be applied to the interpretation of the Hf isotopic data in the Precambrian granites and rhyolites in terms of the involvement of garnet in the source region.Theoretical formulation will be developed for the closure temperature of slowly diffusing trace components in minerals, and to relate their cooling ages to the cooling rates, and applied to the Sm-Nd and Lu-Hf decay systems in garnet.