Direct measurement of strain rates in ductile shear zones: A new method based on syntectonic dikes
Direct measurement of strain rates in ductile shear zones: A new method based on syntectonic dikes
复制标题
DOI：
10.1029/2008jb005597
复制
发表时间：
2009-01
期刊：
影响因子：
--
通讯作者：
Caroline Sassier;P. Leloup;D. Rubatto;Olivier Galland;Y. Yue;D. Lin
中科院分区：
文献类型：
--
作者：
Caroline Sassier;P. Leloup;D. Rubatto;Olivier Galland;Y. Yue;D. Lin
我们描述了一种新的方法，直接估计韧性应变率在露头规模的变形岩脉内的剪切带。该方法在一个约束良好的剪切带中进行了测试：哀牢山-红河剪切带，其全球应变率可以从公布的断层速率计算。应变速率是通过独立测量岩脉记录的剪切应变（γ）和岩脉侵位年龄（t）来确定的。通过三种不同的方法，考虑到无论是拉伸的堤坝或变形过程中的角度变化，或两者兼而有之的剪切应变进行量化。最小剪应变的值范围为0.2和9.7之间的最小变形的堤坝，分别。通过独居石的高分辨离子探针（SHRIMP）测年，获得了脉岩侵位的年龄。获得了三组年龄：年轻年龄为22.55 ± 0.25Ma，中间年龄为26.81 ± 0.66Ma，最老年龄为29.89 ± 0.46Ma和29.93 ± 0.38Ma。地质年代学数据与构造数据一致，变形最大的岩脉是最古老的。从这些测量中推断出的最小应变速率为3至4 × 10−14 s−1，这与之前对韧性剪切带地质应变速率的估计一致。
We describe a new method to estimate directly ductile strain rates at an outcrop scale from the deformation of dikes emplaced within a shear zone. The method is tested in a well‐constrained shear zone: the Ailao Shan–Red River shear zone, for which global strain rates can be calculated from published fault rates. The strain rate was determined by measuring independently the shear strain (γ) recorded by the dikes and the age (t) of dikes emplacement. The shear strain was quantified by three different methods that take into account either the stretching of the dikes or their angle variations during deformation or both of them. The values of minimum shear strains range between 0.2 and 9.7 for the less to the most deformed dikes, respectively. The ages of dike emplacement were obtained by Th‐Pb sensitive high‐resolution ion microprobe (SHRIMP) dating of monazites. We obtained three groups of ages: the younger age is 22.55 ± 0.25 Ma, the intermediate age is 26.81 ± 0.66 Ma, and the oldest ages are 29.89 ± 0.46 Ma and 29.93 ± 0.38 Ma. The geochronological data are in agreement with the structural data, the most deformed dikes being the oldest. The minimum strain rates deduced from these measurements are 3 to 4 × 10−14 s−1, which is consistent with previous estimates of geological strain rates in ductile shear zones.