Orchid Jinding Lead-zinc Mine Area Features And Formation Mechanism Of The Salt Dome Structure Development

Because of its ultra-large-scale and complex ore-forming causes of Jinding Pb-Zn deposits in Lanping Basin, the understanding of its ore-forming process is a hot topic in mineral deposition, but there are many different opinions. Mining area has withstood intense compressional deformation under the Himalayan tectonic movement during Late Cenozoic period. During the formation of a series of nape structure, lots of salt domes are developed in the sandstone and limestone, which is found within the Yunlong group (E1y), the Jingxing group (K1j), the Maichuqing group (T3m) and the Sanhedong group (T3s). Local has formed puncture construct, contains large amounts of gypsum, rock salt, asphalt, accompanied by strong sulfate and metal supine mineralization, it proves that the salt domes are closely related with the Pb-Zn mineralization. Therefore, as the starting point of the salt domes. Through systematical studying of the development characteristics and deformation mechanisms of salt tectonics under the slip or nape tectonic setting, it is aim to identify the ore-forming controlling of salt domes, and provide an important basis to reveal the metalligenesis of Jinding Pb-Zn deposits. In this paper, on the basis of a large number of geological survey and construction and facies mapping, using the methods of structural analysis, spectrographic and geochemical tracing, a detailed analysis on the nine typical salt domes is carried out, and identify the geological characteristics of forming mechanism of salt domes. We obtained the following results and understanding in this thesis.There happened two large-scale thrust-nappe tectonic movements in Lanping basin during the Himalayan period, which also is clearly reflected in Jinding ore field. Among them, on the grounds west to east nappe in the first time, and the grounds of the northeast to southwest nappe in the second. Two nappe role and related tectonic deformation on the development of the mining area of the salt dome structure play a decisive control.Mining area salt dome structure was formed due to the difference of the occurrence of wall rock stratum, lithology and structure presents a distinctly different developmental characteristic. Among them, mudstone in the salt dome are mostly pillow, mushroom-shaped internal and structure is relatively simple occurrence in Yunlong Group. The internal structure is relatively simple and the flow structure is obvious. Breccia is brick-red mudstone gravel and there is a subangular, salt mound and contact with wall rock is significantly. Most of the salt dome in the sandstone (mudstone-sandy) like pillow. More obvious from internal to external structure, Performance of the zonation as, pure gypsum with white limestone gravelâ†'limonite of gypsumâ†'gray muddy containing plasterâ†'gypsum and pyrite mixed cement(containing limestone breccia) or pyrite crustâ†'mineralized sandstone. However, it showed varying degrees absence due to later tectonic and fluid activities, breccia composed of sandstone, limestone and gypsum. The overall stress direction is NE-SW, with the second phase of nappe role. Limestone of the salt dome structure is more obvious. From internal to external performance as gypsum of strongly Limonite and hematite, muddy mixed cement plaster bodyâ†'pyrite crustâ†'limestone of sulfate, carbonate. Breccia composed of limestone, containing sandstone breccia limestone, first nappe with the formation of salt domes.Limestone of salt domes early in the development of salt domes in sandstone. Relatively little resistance in the driving force for the formation of sandstone in salt domes. Inadequate supply of resources, resulting diapirism in salt domes along the joints or level. Gypsum in the salt dome activity acts as a lubricating layer, Salt domes occur in the contact surface as a whole in jingxing group (Klj) and maichuqing group (T3m. Strong the driving force for the formation of limestone in the salt dome, Resulting in salt dome diapirs the destruction of the surrounding rock in the limestone. The salt layers in the formation of salt domes of stampeding group in the salt dome formation process only perform for diapirism. This leads to the salt domes in the limestone mainly in the internal activities of the Sanhedong group.The salt domes of sandstone and limestone in the late deformation are mainly from the cream solubilization. After the formation of salt domes gypsum occurrence of a strong chemical reaction with the surface water and brine, resulting in cream melting collapse. Anhydrite in sandstone melting effect salt domes are mainly distributed in Jingxing and Maichuqing group,and the gypsum in limestone melting phenomenon is generally developed.Development features and formation of the mine salt tectonics are directly controlled by the tectonic. and impact of the corresponding structure in place. Tectonic movement of deformation (before the nappe tectonic movement) from early deep to shallow rock and the initial salt dome diapers in sanhedong group. The first phase of nappe tectonic movements cause the Sanhedong salt layer along the thrust fault rise and development of Sanhedong internal salt dome structure while promoting the salt body with brine system in Sanhedong and get the occurrence of space for the salt dome. Salt body early in the second phase of nappe played the role of the devolvement layer, late to pierce the overlying wall rock, cause the diaper structure. Among them, internal salt dome of Yunlong group development mechanism is relatively simple, by the first nape tectonic activity, as well as the first nape tectonic movement. Mainly for the formation of the layer of salt mounds, the salt dome of limestone diapers moved in the first nape tectonic movement. Mainly experienced three stages of evolution, the occurrence formation of the second type of salt domes in the Yunlong group and salt dome of limestone. Salt dome of the sandstone formation in the second nape movement, also experienced three stages of the movement. The salt dome of limestone and sandstone structures were formed through gypsum deformation stage of melt to form the recent structure of salt diapir.