Discrimination study on fluid-rock interaction between metallogenic and non-metallogenic sections in a shear zone
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Discriminations in a local chemical, fluidal, mechanical and thermal processes in a shear zone will lead to metallogenic differentiation in a local section. This paper, based on the general geological setting of the Shibangou gold deposit in Xixia, Henan, deals with petrological and petrochemical samples of altered rocks in the metallogenic section and of mylonites in the non-metallogenic section of a selected shear zone. The discriminations in fluid-rock interaction and petrological mass balance between altered rocks near the orebody and mylonites in the shear zone are discussed as well. The results show that the petrological volume of altered rocks in the metallogenic section of the shear zone is almost always dilatant and the mylonite volume in the non-metallogenic section is almost always lost. Major elements in altered rocks from the metallogenic section and in mylonites from the non-metallogenic section always show a tendency of being enriched and depleted, respectively. Fluid-rock ratios in the mylonites (Nu=93.68−468.40) are larger than those of the altered rocks (Nc (IV) 3 =36.11−216.67). The gain and loss of major and trace elements from the altered rocks and mylonites in the shear zone are a composite process to be imported and exported by percolating fluids as well as of the loss and dilatancy of rock volume.
Key wordsshear zone altered rock mylonite fluid-rock ratio
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