| The study area is located in the Hebukesaier Mongolian Autonomous County, Xinjiang and it is one of the rare late Paleozoic volcanic-type uranium-polymetallic metallogenic belt located in the West Junggar Paleozoic accretionary orogen and in the ancient Asian metallogenic domain.By studying geological and geochemical characteristics of the Xuexisitan uranium-polymetallic metallogenic belt, this thesis summarized uranium mineralization geological conditions of the area and the main ore-controlling factors, and analysed the geochemical characteristics of the main ore-controlling structure and fluid’s geochemistry. There has discussed the Xuemisitan’s volcanic belt prospecting, and cleared uranium and other multi-metal prospecting direction. Finally, the knowledge achieved as follows:(1) Fracture is a channel of both a magmatic,hydrothermal rising and migration,and precipitation of uranium space for their relationships.There has obvious characteristics of ore-controlling grading structure,that is, different levels of structure are respectively controlled uranium mineralization zone(first grading), uranium-ore field(second grading),uranium-ore deposits(mineral occurrence) and ore bodies(third,fourth grading and small cracks or fissures zone).(2) Compared with tectonic rock and country rock of the main fault, the enrichment of trace elements of ore-bearing tectonic rock has obvious characteristics.It has enriched many kinds of trace elements, and bigger strength. With greater broken degree of the fracture, there has the higher degree of enrichment. Almost all work area have a significant enrichment of Mo, secondly, Pb and Sb in most regions also enrich less significantly, so Mo, Pb and Sb of ore-bearing fracture can serve as iconic elements.(3) Compared with tectonic rock and wall-rock of the main fault,∑REE of ore-bearing tectonic rock increased mostly significantly, suggesting uranium mineralization and alteration processes brought into REE enrichment. REE geochemistry of ore-bearing fracture has mostly significant negative Eu anomaly characteristics.(4) Trace element characteristics of the tectonic fluid can initially be seen, uranium mineralization related to NW trending calcite, quartz ore-forming fluid in the Shiyue work area. Uranium mineralization associated with calcite, quartz veins with abnormally high U, Mo, Pb content, and a variety of metal enrichment.and NE trending veins also have a high uranium content and a variety of enrichment of trace elements in the entire study area, suggesting that tectonic fluid of the direction of NE trending related to uranium mineralization closely may be ore-leading structure. EW trending veins (may be relevant to the main EW fault of Xuemisitan) generally have a low content of trace elements, which is mostly consistent with macroscopic characteristics of lower secondary fracture of ore-controlling in relevant with uranium-polymetallic mineralization.(5) The main trace elements in the rocks(ores) are Cu、Sb、V together with U and mainly Pb, Li, Re, Sc, Bi, Cs, W and other elements cluster into Be group.This outcome suggests that uranium, beryllium mineralization has significantly different characteristics of the element association, showing that the two groups are different periods and have different products of hydrothermal origin.Mainly Mo, Cd in the quartz veins cluster into U group, and mainly Pb, In, W, Sc, Tl together with Be, suggesting that U, Be ore-forming fluids may have significantly different sources.(6) Mo, Cd were positively correlated with uranium in the quartz veins, where U-Mo showed a significant positive correlation between the logarithm, of which were consistent with U-Mo relations in the rocks (ores) and species of trace elements enrichment of ores&altered rocks (in the ore-bearing tectonic fracture), reflecting that uranium mineralization and silicification is a close genetic relationship.(7) Tectonic fluids formed in the tectonic environment which is the low temperature (107～324℃), the shallow(0.412～1.064km), the low-pressure(10.3～26.6Mpa). Overall, the tectonic environment is conducive to uranium mineralization.With these achievements on Xuemisitan volcanic belt, there has important guiding significance for uranium-polymetallic prospecting. |
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