| Geological Survey,prospecting and Current Situation in Tumengela Coalfield are analyzed and comprehended comprehensively on the basis of systematic collection of pre-existing regional geological survey and coal geological survey, with induction of problems and insufficient in the former coalfield geology, generalizing including:(1) accuracy of regional geological survey is insufficient; (2)survey and exploration is too limited, accordingly the valuation of the whole coal field is not completed, (3)division and correlation of coal bearing formation system in coalfield is not a final conclusion;(4)insufficient survey and study of the main coal-controlling factor and coal-controlling structure lead to ambiguous cognition on coal-controlling structure model;(5)study on sedimentary facies,sedimentary environment and sedimentation basin haven't been developed, accordingly the coal-bearing basin type and formation-evolution are not explicit;(6)insufficient cognition of coal accumulating pattern heavily restrict the valuation to coal resources potential of the coal field. In consideration, the six provide the necessity of the Master's thesis.With significant research approach and technical route, regional geological conditions,coal-bearing formation,coal bed and distribution features are well studied, referring to pre-existing geological survey,coal geological survey and other researches, combining with the latest Tibet Plateau 1:250000 scale regional geological survey and relevant coal geologic dissertation. This paper takes geotectonics evolution of coal-accumulating basin,controlling sedimentary basin types and depositional filling sequence as the main line, and applies lithostratigraphy,biostratigraphy,chronostratigraphy and sequence stratigraphy combining together. Though System Analysis of coal measures sedimentary profile structure and sequence stratigraphic characters, this paper comprehensively sums up the tectonic geologic feature,coal sequence stratigraphy,sedimentary facies and sedimentary environment,sedimentary geochemistry and coal petrography. After lithostratigraphic framework is built up, the late Triassic structure- lithofacies paleogeography structure. On the basis of serious research of coal-controlling factor of Tumengela Coalfield, especially coal-controlling sedimentary environment and coal-controlling structure model , taking surface exposed or controlled coal bed as the reason, it majorly discusses the influence of main tectonic activity which induced by later geological events, to coal bed, and dissects the main coal accumulation in this coal field, which mainly considers the transforming and destructive actions, the later tectonics to coal measure strata and coal bed. Applying tectonic coal-controlling theory, the minimum coal-bearing prospect prediction area is made, and makes division on the reliable degree of prediction area and potential resources grade, then the valuation applying volume method in deep Tumengela Coalfield and circumjacent potential resources.On the stratigraphic area , Tumengela Coalfield located on Longmucuo- Shuanghu-Leiwuqi structure formation zone, while according to the tectonic, it belong to the northen of Bangonghu- Shuanghu- Nujiang butt zone. This paper were based on the previous geological survey reports of Tumengela Coalfield and the many relation study results of structural geology,deposition and lithofacies palaeogeography. By the features of chronostratigraphy and biostratigraphy, and in association with systematic division and contrast of lithostratigraphic, stratum of Tumengela Coalfield was objectively divided and compared. Tumengela Coalfield was located in Tumengela group, which consists of first section of Tumengela group (T3tm1) and second section of Tumengela group(T3tm2) by lithologic features and coaled features, and in the coalfield, from the bottom up, the other exposed stratums followed as Quemocuo group (J2q), Buqu group (J2b), Xiali group (J3x) , Suowa group (J3s), Bailongbinghe group (J3b), Xueshan group (J3 K1x) and Abushan group (K2a).According to the materials of Tumengela Coalfield deposition profiles and drillings, by identification and validation to deposition interface of depositional sequence in South Qiangtang Basin Late Triassic, lithofacies and spatial distribution of ancient geography in different stages of evolution in Tumengela Coal Basin late Triassic were systematically studied and analyzed, and features of basin filled sediments in different stages of evolution were generalized. The first section of Tumengela group primarily belongs to carbonate rocks, while the second section of Tumengela group primarily is clastic coal and deposition of coal line. By dividing sedimentary sequence of Tumengela group, it was found that Tumen coal is an incompletely developed construction-sedimentary sequence. Thus, by identifying pivotal sedimentary discontinuity, it could divided complete construction-sedimentary sequences, which are incomplete two super-sequences and five sequences.In Late Triassic, sedimentary facies in Tumengela Coalfield accumulating basin mainly develops terrigenous clastic delta,clastic-tidal flat facies,peat-swamp facies,and delta faceies can divide to delta plain facies,delta front facies;then developing carbonate-open platform facies, among them, peat-swamp face from clastic-tidal flat facies and delta plain facies is coal-accumulating sedimentary facies, gradatim forming 71 coal bed and coal streak. According to the current materials including coal seam thickness,coal seam stability and coal quality and coal type in Tumengela Coalfield, coal bed in Tumengela Coalfield is generally thin; the Paleomagnetic Tests in Qiangtang basin indicates that Qiangtang-Changdu block when coal forms locates at the Southern Hemisphere, with flourish vegetation, which although is good for the coal-forming environment, the sedimentary environment locates at high water level system tract through the whole coal-forming course, determining that the coal bed in Tumengela Coalfield is generally thin.Though the interrelation discussion of tectonic subsidence- depositional filling-sea level change and tectonic uplift- depositional hiatus- sea-level change of sedimentation basin, combining with structure-magma event analysis, in late Triassic, Qiangtang-Changdu block entirely locate at pull apart environment, North qiangtang-Changdu block and South qiangtang-Baoshan block both occur depression sedimentation in succession , while the central massif formed by Longmucuo-Shuanghu ophiolite melange belt, divided the Qiangtang basin into southern and northern two different sedimentation basin. In late Triassic, Tumengela Coalfield locates at the edge of northern south Qiangtang basin,in the late Triassic South qiangtang marginal relict basin which locates at the southern Tanggula paleo uplift denudation area, and experience the late Triassic evolvement of passive continental margin depression basin, which early-middle Jurassic paleogeography inherit the structure. This is the first time to present that Tumen coal formed in norian the late Triassic, which coal accumulating basin type belong to coal accumulating beneficial passive continental margin depression basin in south Qiangtang relict basin, has a stable coal-forming paleogeography pattern, extremely good for development of peat swamps environment, composing a well coal-forming environment in Tumengela area , with paleoclimate evolving from moist to arid environment gradually. The coal spatial distribution and occurrence status in Tumengela Coalfield were mainly controlled by deposition after coal accumulation and construction deformation. After multistage tectonic activities, the feature of Tumengela Coalfield was strong and complex deformation. In this thesis, the reformed effects of every structural form to coal after coal accumulation were discussed, such as the effect of reverse faults, normal faults, strike-slip faults and folds to coal. That were basis to deeply understand the distribution and occurrence status in Tumengela Coalfield and to forecast the deeper and periphery coal.In the paper, according to system understanding of space exhibition of coal measures and comprehensive analysis of coal accumulating pattern, combining with influence of later structure to the coal measure strata and coal bed, applying structure-controlling theory, the minimum coal-bearing prospect prediction area is made and divided into three: favorable(Ⅰ),secondary favorable(Ⅱ)and unfavorable(Ⅲ); then furtherly,refer to forecast reliability degree, the potential resource is divided into three: forecast reliability(334-1),forecast probable(334-2),forecast conjectural(334-3).According to coal-controlling structure and depositional features in forecast area of Tumengela, three minimum predicting areas are made, that is northern predicting area,centre predicting area and southern predicting area, and 10 forecast section; finally, using volume method to estimate resource extent, and choosing the reasonable and corresponding the specifications of resource exploration forecast parameters to estimate, the total resource extent is 308.1183 million tons. |
PDF Full Text Request