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Research On Depositional Feature And Mineralization Mechanism Of Manganese Deposit Of The Lower Triassic In Southwestern Guangxi Area

Posted on:2016-02-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:Q YinFull Text:PDF
GTID:1220330461956402Subject:Sedimentology
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The manganese deposits are mainly distributed in Southwestern Guangxi Area, which was regarded as one of the most predominant ore types in this area. A systematic research has been conducted on the sedimentary paleogeographic environment in the major mineralization period—the Early Triassic by analyzing sedimentology, cyclostratigraphic, geophysics and geochemistry to explain the manganese mineralization, characteristics of ore-bearing rock series, geochemical features as well as the ore-controlling factors of the sedimentary manganese deposits. The ore-forming materials, metallogenic regularity, prospecting criteria,genesis are discussed and summarized.The Early Triassic is one of the most important period in manganese deposition in Southwestern Guangxi area. The Lower Triassic can be devided into the non-Manganese-bearing Sequences and the Manganese-bearing Sequences. The non-Manganese-bearing Sequences which was named Majiaoling Formation is characterized by the massive carbonatite. The Manganese-bearing Sequences named Beisi Formation is characterized by siliceous rocks, cherty limestone and manganese ore. The manganese ore deposits only developed in the platforms basin facie,which is in the north of the Daxin shallow-water carbonate platform. The stage of alternate platform-basin developed in the study area and the platforms basin facie in the study area is in small size,which is distributed in Fuwan of Debao County-dongping in Tiandeng County-Jiangcheng of Tiandong County area. The trench elongated was existed between the carbonate platforms.The platforms basin facie was deep in sea water with low water energy.Morphological characteristics of logging curve are the synthetical reflection of lithology and physical property.The logging curve was used to divide the bearing strata also to study the corresponding relationship between logging curve and lithology. The continuous logging data of the four drilling in the Dongping Manganese Ore zones have been acquired.Typical geological structure is analyzed and identified by using logging data. The results shows that the natural gamma ray, sonic and resistivity logs have obvious response to lithology in the four holes. The main lithology can be efficiently identified by drawing sinusoid curve fit of logging lithology parameters. With the magnetic measurements as main method, the Lower Triassic Manganese Ore Deposit in Southwestern Guangxi area can be devided into some Manganese Ore zones. Different Manganese Ore zones have similar characteristics. The magnetic susceptibility of the manganese ore show a positive correlation with Mn and TFe content in the area. The higher Mn and TFe content is, the greater magnetic susceptibility will be; The lower Mn and TFe content is, the lower magnetic susceptibility will be. In the later prospecting work in Southwestern Guangxi area, the abnormal zone with high magnetic susceptibility of manganese ore are delineated to position the prospecting target area, which is an excellent prospecting method.The spectral analysis and filter methods can be adopted to divide cyclic sequence hierarchy and discuss depositional mechanism, and the cumulative residual curves from average amplitude variations of good logs are introduced and demonstrated as a valid graphical method to define depositional regime transformation and check boundary surfaces of cyclic sequences. The cumulative residual curves results shows the positive half waves and negative half waves of cumulative residual curves are respectively corresponds to upward-deepening and upward-shallowing sedimentary successions in low frequency cyclic sequences in a well interval. Transform points of positive half waves and negative half waves are calibrated to boundary surface depth of cyclic sequences. The GR log data from 0302 Well of Southwestern Guangxi Area as a case example,cumulative residual curves are calculated and constructed on well log data. The low and high frequency cyclic sequences are distinguished and its procedure and methods are illustrated in detail. The significance and interpretation of amplitudes and wavelength changes of sedimentary cycles is discussed in this paper. The Beisi Formation of the Lower Triassic can be divided into four forth-order sequences, and the manganese ore deposit developed in the regression cycle.By analyzing the rock samples of the Manganese-bearing Sequences in Beisi Formation of major elements, trace elements, rare earth elements and the isotope, the manganese ore contains hydrothermal origin and terrestrial sources were discussed. And the model of sedimentary manganese deposits is controlled by redox interface changes caused by the sea level changes.The trace elemental correlation conclusions have been reached that,the remarkable positive correlation between Mn、Ga、Co and Ni in the Manganese-bearing Sequences in Beisi Formation,which is an unique manganese deposits of the study area.And the correlation between Mn and Ga is greater than that between Co and Mn as well as Ni and Mn. Chemical exploration technique on deep manganese ore deposit could be applied well in this zone.A comprehensive discussion in the characteristic of geographical environment,the ore-forming materials,redox conditins and the sea-level change, a systematic research has been investigated on the main factors which affecting the development of the manganese deposits. The origin model of manganese ore can be divide in three stage:1.Sea-level fall-the oxidizing manganese is formation;2.Sea-level rise-the oxidizing manganese is transformed in manganese carbonate;3.The maximum flooding surface-a little manganese carbonate is formation.
Keywords/Search Tags:The Southwestern Guangxi area, the Lower Triassic, Beisi, Formation manganese ore deposition, Manganese-bearing Sequence, depositional feature, cyclostratigraphy, formation mechanisms
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