On strain characters of rocks and minerals within the ductile shear zone, it is calculated that the strain value is 1.24-2.32,the forming depth is 13-20km,the temperature is 450-650℃, the surrounding pressure is 325-550MPa, the biggest shear stress is 113-141MPa and the discrepant stress is 31-35MPa.
The mylonite and ultramylonite in the ductile shear zones yield whole-rock 40Ar/39Ar ages of 120. 48 Ma and 118. 75 Ma respectively, which suggest that large-scale sinistral displacement in the Tan-Lu fault zone took place in the Early Cretaceous.
After oreforming and orecontrolling structures analysed,listric ductile shear zones with E-W strike and high angle(80°~90°/N∠70°~85°) are found to be the main ore-forming and controlling structures in Huangtuliang field.
Therefore, as viewed from the tectonic evolution, the three types of gold deposits resulted from the sustained development of ductile shear zones during orogenesis, which is one of the important mineralization conditions.
The analyses of metallogenic enviroments, ore-controlling structures, ore deposit and its minerals, ductile shearing zone, isotopes, and fluid inclusions, as well as the genetic information provided by chemical compositions of pyrite, are taken to study the ore-containing and ore-controlling factors, the ore resources and the characteristics of ore fluid. It is revealed that the Dola gold deposit is a magmatic-metamorphic hydrothermal deposit of low to intermediate temperature.
According to the geological modes of occurrence, the mylonite in the Xiazhuang uranium orefield may be divided into two kinds, namely mylonite in the ductile shearing zone and that in silicic cataclastic rocks. The two kinds of mylonite have different characteristics, which reflect different geneses and formation environments.
Fluid participation in ductile shear zone: Evidence from geological, geochemical and13O/16O relations from south part of Tanchen
The large-scale ductile shear zone in Kuda, western Kunlun
Jingshan superlarge gold deposit is a typical deposit closely related to the ductile shear zone, developing the economic enrichment during the transition form the ductile deformation to the brittle deformation.
40Ar/39Ar geochronology and exhumation of mylonitized metamorphic complex in Changle-Nanao ductile shear zone
The40Ar/39 Ar plateau ages, K-Ar date of K-feldspar and other geochronologic information suggest that the exhumation rate of the ductile shear zone is about 0.18-1.12 mm/a in the range of 107-70 Ma, which is mainly influenced by tectonic extension.
In 180-150 Ma, the zone underwent ductile shear deformation and amphibolite facies metamorphism; and in 130-80 Ma, rose rapidly and collided with the Southeastern China continental margin volcanic rocks along the NE trending ductile shear belt.
These rocks occur exclusively in high-temperature ductile shear zones, which can develop either during the primary exhumation of rock complexes or during the overprinting by high-temperature dynamometamorphism.
Ductile shear zones developed in Archean granulite gneisses simultaneously with their exhumation, and, hence, their P-T trajectories are segments of decompression and/or isobaric cooling paths.
Straight gneisses in Proterozoic polymetamorphic complexes commonly compose high-temperature ductile shear zones overprinted on Archean granulite complexes, and the P-T paths of these rocks are Z-shaped.
Such ductile shear zones commonly have a strike-slip morphology and can be easily seen in aerial photographs and discerned during structural geological surveying.
The control of ductile shear zones over gold mineralization could be explained in view of pressure solution of gold-bearing miner als under shearing stress and the resultant mobilization of this metal.