Metallogenic model and dynamics process of ore magma of cryptoexplosive breccia type in Dongji gold (silver)deposit,Zhenghe,Fujian
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    Abstract:

    This research described the geological characteristics of the Zhenghe Dongji gold (silver) deposit, established a mineralization model of the deposit, demonstrated the mechanical process of the material transport and movement of the deposit, and explored the source of ore formation.Methods:The mine has undergone systematic exploration and mining. The ore body from the surface at 580m~620m to -200m underground was thoroughly exposed by drilling and exploration. Using conventional and reliable geological argumentation methods, the first- hand information has been comprehensively collected. This study also equipped with macro and micro rock and mineral identification and partial electronic probe analysis for comprehensive discussion.Results: From top to bottom, Breccia pipe of the ore deposit can be divided into 5 facies belts: fissure facies belt,shattered facies belt, cryptoexplosive facies, upper channel facies and lower channel facies. Based on a series of phenomena such as the structural characteristics of the ore, the contact relationship of the ore body intrusive surrounding rock, the characteristics of the breccia, and the composition of the cement, the deposit is the origin of the ore magma. The silicon- rich and iron- rich magma originated from the separation and differentiation of acidic magma in the deep crust—mantle transition zone. The former(silicon- rich magma) invaded upwards to form large- scale volcanic eruptions and sub- volcanic intrusion, while the latter (iron- rich magma) remained in the “source” and captured the sulfide droplets. The iron- rich magma then accumulated and formed a mixed ore magma. The physical properties and the mechanical characteristics of transport and movement indicate that under the external driving force, the ore magma invaded upwards along the quartz porphyry “magma thermal field channel”. Accumulation, concealed explosion, positioning and mineralization were undergone at 2.0~2.5 km below the paleo- surface, under the quartz porphyry silicon cap barrier.Conclusions:The Zhenghe Dongji gold (silver) mine is a ore magma cryptoexplosive breccia type deposit. Quartz porphyry is ore- hosting wall rock, which has a close temporal and spatial relationship with the deposit but has nothing to do with its genesis. Deep drilling confirmed that the tail of the cryptoexplosive breccia tube converged in the quartz porphyry followed by the termination of mineralization. The “ore magma cryptoexplosion” is a novel type of Cryptoexplosive breccia type gold deposit and has not been published elsewhere. The discovery of this type provide a real- life example of the theory of intermediate—acid magmatic melting separation and mineralization, and is of great significance to the prospecting of the same type of gold deposit in the Mesozoic continental volcanic rock area in the south- eastern coast of China.

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ZHU Yulin, MAO Guangwu, YAN Xieping.2021. Metallogenic model and dynamics process of ore magma of cryptoexplosive breccia type in Dongji gold (silver)deposit,Zhenghe, Fujian[J]. Geological Review,67(1):99-115.

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History
  • Received:July 18,2020
  • Revised:October 23,2020
  • Adopted:
  • Online: January 19,2021
  • Published: