Influence of deformation mechanisms on deformation-induced resetting of radiogenic isotope systems (U-Pb, Rb-Sr, Sm-Nd) and homogenization on the grain-scale (TP15)

变质岩的直接测年变形过程仍然很困难，尽管近年来在测年技术方面已经取得了实质性的进展。特别是，原位技术有助于将放射性年龄与岩石学相关联，并选择同位素均一的样本量。对于不完全均质，年龄可能会在不同程度上偏离真实年龄。然而，同位素不均一性确实发生在纳米尺度上，因为纳米尺度总是小于原位测年技术的取样量，无法避免。因此，为了获得可靠和准确的变形年龄，了解变形过程如何影响同位素重置以及它们在矿物颗粒尺度上的作用距离是至关重要的。为此，我们将研究变形的天然岩石样品，这些样品表现出变形诱导的矿物反应和流体可获得性的微组构特征。我们的样品来自结构明确的构造环境，可以从颗粒尺度到地图尺度的现象进行外推。该项目的预期结果对确定地球动力学过程的时间、持续时间和速率具有重要影响。这些数据对于定量了解和模拟大陆规模的构造-变质过程，例如变质岩的埋藏和折返是必要的。

Direct dating deformation processes in metamorphic rocks still remains difficult, though substantial advances in geochronological dating techniques have been made in recent years. In particular in-situ techniques facilitate the correlation of radiometric ages to petrology, and the selection of isotopically homogeneous sample volumes. For incomplete homogenization, ages may diverge from the true age to variable extent. However, isotope heterogeneities do occur at the nano-scale being always smaller than sampling volumes for in-situ dating techniques and can not be avoided. Thus, to obtain reliable and accurate deformation ages, it is essential to understand how deformation processes influence isotopic resetting and over which distances on the mineral grain-scale they act. For this purpose, we will investigate deformed natural rock samples showing microfabrics characteristic for deformation-induced mineral reactions and fluid availability. Our samples from structurally well defined tectonic settings allow the extrapolation from grain-scale to map-scale phenomena. The expected results of this project have important implications for determining the timing, duration and rates of geodynamic processes. Such data are a requirement for the quantitative understanding and modelling continent-scale tectono–metamorphic processes, e.g. burial and exhumation of metamorphic rocks.