Three-dimensional geological environment simulation of submarine exhalative sediments
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On the basis of the major metal grades from the super-large Bainiuchang Ag-rich polymetallic ore deposit, enrichment evolution processes were divided into three populations by using a new multiple time-series model. Population 1 shows the highest temporal/spatial autocorrelation with the ore-forming processes. Population 3 is considered to be a white noise process. The lithologies of populations 1 and 2 are closely related to submarine exhalative hydrothermal sedimentation. By using a semi-Markov process and a dynamic lithologic ratio parameter model, the paleogeographic environment of the bathyal basin in which the Bainiuchang Agrich polymetallic ore deposit formed was simulated. The result of the simulation suggests that four major submarine exhalation cycles occurred during basin evolution. Hydrothermal sedimentary metallization took place in the middle stage of each cycle. Hydrothermal sedimentation in each of the four cycles suggests an evolution from weak to strong to stronger to weak. Debris and turbidity currents related to syndepositional faulting along the northwestern margin of the basin and submarine hydrothermal exhalation originated from vents and flowed from northwest to southeast. A three-dimensional, finite-element method was used to simulate quantitatively the dynamic evolution of the temperature field of heat fluid circulation. A model is proposed that allows for the submarine heat fluid circulation from seawater that percolates downward, the upflow along a syndepositional falut to exhalation on the seafloor, and the formation of lenticular ore bodies in a single tectonic pulse. Comparison of the simulated temperature field and the mixing population of thermometric data of fluid inclusions suggests that the major submarine exhalation took about 35,000 years and that after 15,000 years from the initial establishment of the temperature field, the temperature of heat fluid circulation at the vents reached a maximum of 280°C.
Key wordsThree-dimensional geological environments submarine exhalative sedimentation heat fluid circulation dynamic evolution ALCAR time series model semi-Markov process computer simulation
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