This paper mainly takes Zhacun goldmine as the research object and carries out research on the metallogenic system and genesis of the deposit in the area. The research methods are as follows: according to the geological characteristics of the metallogenic mining area in the Zhacun goldmine, combined with the comparative analysis of the metallogenic age, alteration characteristics and lithology between the Zhacun goldmine and the Lianhuashan alkali rich rock mass, and the analysis of the isotopic data in the Zhacun goldmine, this paper demonstrates that the magmatic activity of the Lianhuashan quartz monzonite porphyry plays an important role in the mineralization of this area, which is both an important ore source and fluid source. It is also the main heat source driving the circulation of ore-forming fluid. On this basis, through the analysis of the metallogenic elements in the area, the metallogenic system model of Zhacun goldmine is constructed. It is considered that under the action of long-term horizontal compressive stress, the atmospheric precipitation infiltrated into the formation continued to penetrate along the fractures and fissures to deep crust and finally mixed with the magmatic water sealed in the thick formation. During this period, a series of shallow and ultrashallow porphyry mass intruded, providing heat source and part of the ore-forming materials and resulting in incomplete homogenization under high temperature and high pressure, which formed highly mineralized mixed water. Under the combined action of long-term compressive stress and various deep thermal dynamics, these mineral fluids migrated along the buried deep faults near the core of the duplex anticline to the upper part of the crust. When the metal elements in these ore fluids migrated over long distances to the nappe fault zone of the gold-bearing fracture zone, the gold began to precipitate, and the native gold and the coarse-grained pyrite and quartz formed at the same time or earlier started to fill the fracture zone along the fissures and accumulate into minerals. Then, through the analysis of metallogenic conditions, gold mineralization process, and genetic mechanism of the deposit, it is proposed that the genetic type of the ore deposit in this area is magmatic mesothermal-epithermal gold deposit. The establishment of metallogenic system model in Zhacun goldmine will provide theoretical and practical guidance for deep and peripheral prospecting prediction in the area, carry out targeted and reasonable prediction, and improve prospecting effectiveness.
Winkler elastic foundation beam theory is often used to observe the influence of underground engineering construction on pipelines. Excavation under existing pipelines disturbs the lower strata to varying extent, which creates significant differences in the subgrade coefficients. Ignoring these differences can severely impact the accuracy of calculation results. A theoretical model of the effects of underground excavation on upper-level existing pipelines was developed in this study based on Winkler elastic foundation beam theory and considering the difference of subgrade coefficients under the existing pipeline. Methods for determining the subgrade coefficient under the influence of construction disturbance and other relevant parameters are proposed. The theoretical model can be used to calculate the settlement of an existing pipeline under the influence of underground excavation. The calculated settlement was compared with settlement measurements to find that the subgrade coefficient of the excavation section is the most important parameter in the calculation process. The suitable value range of the excavation subgrade coefficient is relatively large, as it has a relatively minor influence on the calculation result. When the value of subgrade coefficient of each section is appropriate, the calculated settlement curve is in close accordance with the measured settlement curve.
Single gold deposits are mainly found in the southern section of the Xuefeng Mountain metallogenic belt, and gold-antimony-tungsten polymetallic deposits are gradually found northward. Based on the causes of ore-forming differences between the southern and northern sections, this research studied fluid inclusion characteristics and hydrogen and oxygen isotopes of the main gold-bearing mineral quartz in both sections. The test results show that the cationic composition of quartz fluid inclusions in typical gold deposits in the southern section is Na + -Ca 2+ type, and the anionic composition is mainly SO4 2and Cl -, with K + /Na + <1 and F -/Cl -<1. The CO2 and N2 content in the gas phase composition is extremely low, especially with the maximum N2 content of only 0.025μg•g -1 . Hydrogen and oxygen isotope projection falls near the formation and metamorphic water, indicating that the ore-forming fluids do not come from magmatic water. The cationic content of quartz fluid inclusions in typical gold deposits in the northern section is relatively dispersed, including Ca + enriched type and Na + -K + -Ca 2+ type, and the anionic composition is mainly SO4 2-. The CO2 and N2 content indicating deep source in the gas phase composition is much higher than that of gold deposits in the southern section, and pure N2 inclusions are developed. Hydrogen and oxygen isotope projection mainly falls into the formation and metamorphic water and their overlap area. The geological and geochemical characteristics show that the ore-forming hydrothermal solution in the southern section mainly comes from groundwater, and that in the northern section comes from a mixture of magmatic rocks, metamorphic water, and groundwater.
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