Abstract
Most gold deposits are genetically controlled by shear zones, which are called shear zone type gold deposits (SZTGD). A better understanding of kinematics of shear zones and its constraint on the ore-forming process is critical to reveal the genetic mechanism of the SZTGD and favorable to mineral exploration. By conducting detailed structural analysis including field and microscopic observations and electron backscatter diffraction (EBSD) and fractal dimension analysis in the Muping-Rushan shear zone (MR) as well as several gold deposits, the kinematic characteristics of the MR are well recognized and the metallogenic process of the SZTGD are discussed. The main conclusions are as follows: (1) petrology, geometry, kinematics, macro- and micro-structures imply that the MR has experienced a progressive shearing history exhumed via middle crust to subsurface level under the NW-SE extensional regime from late Jurassic to early Cretaceous; (2) in the MR, gold may precipitate both in the brittle fractures at middle crust level and brittle deformation part at shallow crust level during the stress-chemical process and (3) comparison of gold deposits between the MR and other areas show that the SZTGD has a uniform metallogenic mechanism, which is from (multi-stage) pluton emplacement, hydrothermal fluid action, shearing action, brittle fracturing, sudden reduction of fluid pressure, flash vaporization to (gold) mineralization.
Highlights
Shear zones are one type of strain localization structures [1], which are widely developed in various structural environments
We choose the Muping-Rushan metallogenic belt as a study target and present detailed structural studies both at macro and micro scales to characterize the shearing activity in the Muping-Rushan shear zone (MR) and its constraint on gold formation
It has been widely proposed that North China Craton (NCC) has undergone large-scale lithosphere thinning in the extensional regime since late Mesozoic [29,67,79]
Summary
Shear zones are one type of strain localization structures [1], which are widely developed in various structural environments. To unveil the genetic mechanism of SZTGD, the best way is to investigate widely local structures developed during gold mineralization covering as many deposits as possible to get enough data and make regional comparison From this view, this study chooses Jiaodong Peninsula as a unique opportunity to better understand this type of metallogenetic framework. We choose the Muping-Rushan metallogenic belt as a study target and present detailed structural studies both at macro and micro scales to characterize the shearing activity in the Muping-Rushan shear zone (MR) and its constraint on gold formation Based on these results and combining with previous studies of gold deposits all over the world, this paper improves the genetic mechanism of the SZTGD from macroscopic shearing activities to physical-chemical process intrinsically
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