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Geoscience ›› 2024, Vol. 38 ›› Issue (04): 873-891.DOI: 10.19657/j.geoscience.1000-8527.2024.092

• Theories and Methods of Tectono-physicochemistry • Previous Articles     Next Articles

Migration and Emplacement of Ore-forming Fluids and Their Structural Controlling Mechanisms: An Example from Jiaojia Gold Belt in Jiaodong Peninsula

ZHANG Longxiao1,2(), YANG Liqiang1,2,3,4(), YANG Wei1,2, XIE Dong1,2   

  1. 1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences(Beijing),Beijing 100083, China
    2. Frontiers Science Center for Deep Time Digital Earth, China University of Geosciences(Beijing), Beijing 100083, China
    3. Ministry of Natural Resources Key Laboratory of Gold Mineralization Processes and Resources Utilization,Shandong Institute of Geological Sciences, Jinan,Shandong 250013, China
    4. Key Laboratory of Metallogenic-Geologic Processes and Comprehensive Utilization of Minerals Resources in Shandong Province, Shandong Institute of Geological Sciences, Jinan,Shandong 250013, China
  • Online:2024-08-10 Published:2024-10-16
  • Contact: YANG Liqiang

Abstract:

Hydrothermal ore-forming system can be controlled by the migration and placement of ore-forming fluids induced by tectonic movement.Structure is the primary ore-controlling factor, and the migration and placement of ore-forming fluids are the core theory of tectonic ore-controlling.Multiple or single dominant factors, such as fluid pressure differences, integrated hydraulic gradients, and heat conduction, drive fluid migration within transport channels formed by faults, cracks, and pores in the surrounding rocks.Chemical reactions of fluids in structural cracks or pores, fluid mixing and immiscibility, and fluid boiling lead to changes in the physical and chemical properties of the fluids, resulting in the precipitation of ore-forming materials.Fluid migration patterns affect the form of mineralization.Fluid migrating through macroscopic faults and fractures, resembling pipeline flow, primarily forms large vein ore bodies with high mineralization.However, permeation flow, which widely develops in micron-scale cracks and pores of surrounding rock, mostly forms fine veins and disseminated ore bodies with stable mineralization grade and medium scale.The dynamic coupling between tectonic deformation, fluid pressure, and stress state leads to the temporal and spatial occurrence of the ore body.The fault valve-pumping mechanism is the most representative tectonic-fluid coupling model to explain orogenic gold mineralization.The formation and distribution of deposits in the Jiaojia gold belt are controlled by three-order fault structures.The compression-shear Jiaojia fault is a first-order ore-controlling structure, which governs the extensive hydrothermal alteration dominated by sericitization and the placement of altered rock type gold ore bodies within fracture zones.The Wangershan fault, a tensile shear structure in its footwall, serves as a secondary ore-controlling structure, where hydrothermal alteration is relatively weaker, resulting in the development transitional gold ore-body.The third-order ore-controlling structure consists of dozens of tensile-shear faults and joint systems dominated by the Baoli fault, which exhibits the weakest degree of alteration and mineralization.This structure mainly controls the occurrence of quartz vein-type gold orebodies.The study of the three-dimensional geometry of the ore-body in Sizhuang gold deposit shows that the morphological flatness of the ore-body group increase from No.I ore body to No.Ⅲ ore body.This indicates the spatial evolution of ore-forming fluid transport from infiltration to pipeline flow, and the differences in ore-body occurrence reflect changes in ore-forming fluid migration directions.Further research needs to integrate results from multidisciplinary studies, especially conducting in-depth analysis of the coupling relationship between micro-ultra-microscopic deformation fabric and ore-forming fluid behaviors.This includes constructing a multi-scale structure-fluid coupling ore-forming model that closely mimics reality and reveals the intricate processes and mechanisms of hydrothermal ore-forming system.

Key words: hydrothermal ore-forming system, migration and emplacement of ore-forming fluids, structural ore-controlling, structure-fluid metallogenic dynamics, Jiaojia gold belt

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