Ductile shearing age of the south Altun fault and its tectonic implications

作者：Cui JunWen^*

来源：Acta Petrologica Sinica, 2011, 27(11): 3422-3434.

• South Altun fault
• Ductile shear
• Ar-40/Ar-39 geochromology
• Middle Ordovician-Silurian
• Tectonic

The South Altun fault, lying between the Neoarchean-Paleoproterozoic high-grade metamorphic rocks of the Altun Group and the Meso-Neoproterozoic low-grade metamorphic rocks in the Altun hinterland, is a roughly E-W-trending and slightly S-dipping high-angle large thrust fault. It has undergone two tectonic evolution stages, i. e. ductile deformation and fragile deformation. The ductile shear zone took shape in the Late Cambian, and shearing was intensive during the Middle Ordovician-Silurian (468.4 similar to 412.2Ma). In Early-Middle Devonian, Early Carboniferous, Late Permian and Early Jurassic periods, the shear zone entered the ductile deformation stage dominated by high and medium temperatures. With the elapse of time, the deformation temperature continued to decrease, and shearing was obviously weakened. After the Early Jurassic, the fault completely entered the tectonic evolution stage dominated by fragile deformation. However, it is indicated by the 491.3 +/- 4.6 similar to 413.8 +/- 8.0Ma calc-alkaline granites widely distributed north of the fault and the 500 +/- 10 similar to 519 +/- 37Ma eclogite and amphibole-mylonite exposed on the south side of the fault that there had been a lithosphere-scale subduction from south to north along the fault before a thrust-type ductile shearing of north polarity occurred. Therefore, this fault is an important convergance and collision zone of Early Paleozoic plates in the Altun hinterland.

• 出版日期2011-11
• 单位中国地质科学院