| 其他摘要 | The Turpan-Hami basin is located in the east portion of Kazakhstan Plate, and is within the Mid-Asian Orogenic-Metallogeni Belt together with the ISL sandstone type uranium productive basins in abroad vicinity of North West China. Since the discovery of Shihongtan sandstone type uranium deposit in Turpan-Hami Basin, the basin has become the second exploration base for In-Situ Leach (ISL) amenable sandstone type uranium resources in China. In order to promote the potential of ISL amenable uranium resource, it is necessary to get a comprehensive understanding of the basin, include the geological settings, tectonic evolution and sedimentary histories of the basin. But the most interests have been attracted by the study of the host sedimentary rocks in Shihongtan uranium mineralized district, the uranium metallogenetic process and the definition of the analogical site in the basin as a whole. Therefor, some research projects have been conducted to recognize the types of the host sedimentary formation, the Lower-Mid Jurassic Shuixigou Formation. And various results have been derived from the projects research.
The host rock is the base for the uranium mineralization of sandstone type uranium ore deposits. So, it is necessary to get a better understanding in the features of Shuixigou Formation at first, including components, textures, structures, and sedimentary processes and depositional system types of the formation. Afterwards, searching for the most favorable depositional system type for uranium mineralization, the analogs and the distribution is the main target of this study.
By means of the field investigation, borehole core examination, lithologic study, rare earth elements and trace elements geochemical analyses, and multi geological information integration, main results of this dissertation are as follows,
1. The types of depositional system of Shuixigou Formation can be distinguished as alluvial, alluvial-braided, braided, braided delta and lacustrine depositional system. The most important host rock of Shihongtan sandstone type uranium ore deposit is the sedimentary sandbodies of braided delta depositional system. And it indicates that the most favorable sandstone distributed locally, and is limited far beyond continuously regional distribution.
2. The sandbodies as the host rock in Shihongtan uranium mineralized district lie down nearly from south to north, and cross with the stratum of Shuixigou Formation. It is similar to the status in Wyoming Basin. The occurrences of the sandstones control the direction, velocity and bound of the migration of uranium bearing fluid-flow.
3. The strata deformations are various along the Aiding Lake Slope Belt. Strata deformation of J2x3 in the east part of the belt show intro-bed faults, while J2x1 and J2x2in the middle and west part of the belt show folds respectively.
Several episodes of structure reform and fluid-flow alteration in the host rock can be recognized by the deformation of the strata in the Shuixigou Formation, micro cracks in quartz, detrital feldspar, and the filling of carbonate in the splits and holes in the host sandstone.
4. The detrital components of the host sandstones are mainly consist of quartz, feldspar, mica, and fragments of igneous rock, metamorphic rock. The cements are usually clay minerals, carbonates. Some minerals or mineral assemblage, such as microcrystal biotite, chlorite-epidot-quartz and even the remelting of quartz, indicate the results of tectonic and hydro metamorphism.
5.Whole-rock rare earth elements and trace elements geochemical data on the samples from zk32-11-2、zk96-4、zk96-7、zk80-6 are used to confirm the characteristics of the sandstones. The REE patterns of all most all sandstone samples of the four borehole are very similar, and all most the same as the source rocks. But the eigen values of rare earth elements, include δEu, δCe and TE（1，3）of the samples, indicate the differences among different types of sandstone. The values of δEu of the distributaries channel sandbodies are lower than that of braided delta sandstone. And the values of δCe and TE（1，3）of the front delta sandstones are all most the same with each other as a whole. The various values of δEu, δCe and TE（1，3）show the the different depositional system types of the sandstones.
6. Compared with the sandstone type uranium ore deposits productive basins of Mid-Asian and Wyoming, USA, the Turpan-Hami basin is located in the same plate and has similar tectonic evolution histories with the basins of Mid-Asian area. But the tectonic type of the Turpan-Hami basin is the same as Wyoming basins, and as well as the characters of the host rocks.
7. Based on the multi geological information integration and spatial analyses, some analogs of Shihongtan sandstone uranium mineralized district, characterized by the braided delta depositional system, regional redox condition can be defined. They are Alagoukou, Ke’erjian in the western portion of the basin, and the Shanshan-Xiaocaohu zone in the east of Shihongtan district. |
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