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1.
For a mining operation to be successful, it is important to bring fundamental and applied science together. The mining engineer needs to understand the importance of geology, mineralogy and petrography, and how projects can benefit from the data collected during the exploration and pre-exploration stage. Geological scientists also need to understand the process of project development from the exploration stage through mine design and operation to mine closure. Kimberlite pipe or dyke emplacement, geology and petrology/mineralogy are three areas that illustrate how information obtained from the geological studies could directly influence the mining method selection and the project strategy and design. Kimberlite emplacement is one of the fundamental processes that rely on knowledge of the kimberlite body geology. Although the importance of the emplacement model is commonly recognized in the resource geology, mining engineers do not always appreciate its importance to the mine design. The knowledge of the orebody geometry, character of the contact zones, internal structures and distribution of inclusions could directly influence pit wall stability (thus strip ratio), underground mining method selection, dilution, treatability, and the dewatering strategy. Understanding the internal kimberlite geology mainly includes the geometry and character of individual phases, and the orientation and character of internal structures that transect the rock mass. For any mining method it is important to know “where the less and where the more competent rocks are located” to achieve stability. On the other hand, the detailed facies studies may not be important for the resource and mine design if the rock types have similar physical properties and diamond content. A good understanding of the kimberlite petrology and mineralogy could be crucial not only to the treatability (namely diamond damage and liberation), but also to the pit wall and underground excavation stability, support design, mine safety (mudrush risk assessment) and mine dewatering. There is no doubt that a better understanding of the kimberlite and country rock geology has a direct impact on the safety and economics of the mining operations. The process of mine design can start at the beginning of kimberlite discovery by incorporating the critical geological information without necessarily increasing the exploration budget. It is important to appreciate the usefulness of fundamental geological research and its impact on increased confidence in the mine design. Such studies should be viewed as worthwhile investments, not as cost items. 相似文献
2.
Field and Scott Smith [Field, M., Scott Smith, B.H., 1999. Contrasting geology and near-surface emplacement of kimberlite pipes in southern Africa and Canada. Proc. 7th Int. Kimb. Conf. (Eds. Gurney et al.) 1, 214–237.] propose that kimberlite pipes can be grouped into three types or classes. Classical or Class 1 pipes are the only class with characteristic low temperature, diatreme-facies kimberlite in addition to hypabyssal- and crater-facies kimberlite. Class 2 and 3 pipes are characterized only by hypabyssal-and crater-facies kimberlite. In an increasing number of Class 1 pipes a new kimberlite facies, transitional-facies kimberlite, is being found. In most cases this facies forms a zone several metres wide at the interface between the hypabyssal- and diatreme-facies. The transitional-facies exhibits textural and mineralogical features, which are continuously gradational between the hypabyssal and the diatreme types. The textural gradations are from a coherent magmatic texture to one where the rock becomes increasingly magmaclastic and this is accompanied by concomitant mineralogical gradations involving the decline and eventual elimination of primary calcite at the expense of microlitic diopside. Both transitional- and diatreme-facies kimberlites are considered to have formed in situ from intruding hypabyssal kimberlite magma as a consequence of exsolution of initially CO 2-rich volatiles from the volatile-rich kimberlite magma. The transitional-facies is initiated by volatile exsolution at depths of about 3 km below the original surface. With subsequent cracking through to the surface and resultant rapid decompression, the further catastrophic exsolution of volatiles and their expansion leads to the formation of the diatreme facies. Thus diatreme-facies kimberlite and Class 1 pipes are emplaced by essentially magmatic processes rather than by phreatomagmatism. Distinctly different petrographic features characterize crater-facies kimberlite in each of the three pipe classes. In crater-facies kimberlites of Class 1 pipes, small pelletal magmaclasts and abundant microlitic diopside are characteristic. These features appear to reflect the derivation of the crater-facies material from the underlying diatreme zone. Most Class 2 pipes have shallow craters and the crater-facies rocks are predominantly pyroclastic kimberlites with diagnostic amoeboid lapilli, which are sometimes welded and have vesicles as well as glass. Possible kimberlite lava also occurs at two Class 2 pipes in N Angola. The possible presence of lava as well as the features of the pyroclastic kimberlite is indicative of hot kimberlite magma being able to rise to levels close to the surface to form Class 2 pipes. Most Class 3 kimberlites have very steep craters and crater-facies rocks are predominantly resedimented volcaniclastic kimberlites, in some cases characterized by the presence of abundant angular magmaclasts, which are petrographically very similar to typical hypabyssal-facies kimberlite found in Class 1 pipes. The differences in crater-facies kimberlite of the three classes of pipe reflect different formation and depositional processes as well as differences in kimberlite composition, specifically volatile composition. Kimberlite forming pipe Classes 1 and 3 is thought to be relatively water-rich and is emplaced by processes involving magmatic exsolution of volatiles. The kimberlite magma forming Class 2 pipes is CO2-rich, can rise to shallow levels, and can initiate phreatomagmatic emplacement processes. 相似文献
3.
采空塌陷是地下开采矿山主要的地质灾害之一,矿山关闭后采空区土地资源如何开发利用至关重要。以苏州小茅山矿山采空区勘查研究与应用为实例,从采空区的地质环境条件特征分析入手,采用系统搜集资料,实地地质测绘,地球物理勘探验证,综合研究分析评价的"四步骤"方法,对采空区场地土地适宜性进行了评价。 相似文献
4.
The need for storage caverns for oil and gas, and repositories for toxic chemical waste is increasing world-wide. Rock salt formations are particularly suitable for the construction of cavities for such purposes. Owing to its favourable geomechanical properties, rock salt remains stable over long periods of time without support, and it can be shown that the geological barrier of the host rock remains intact for a remarkably long time. Safety analysis must be made for each proposed site based on site-specific data. The methods of doing this are well known and related technical recommendations exist in Germany. These recommendations apply to the planning, construction, operation and post-operational management of salt caverns used for the underground disposal of hazardous wastes. In particular, geotechnical site-specific safety verification, as required by the government's technical regulations on wastes (TA-Abfall) under the section “Underground Disposal”, is required. This safety verification must cover the entire system comprising the waste, the cavern and the surrounding rocks. For this purpose geomechanical models have to be developed. The steps which must be taken when carrying out geological engineering site explorations and when determining geotechnical parameters are discussed. In addition, recommendations are made for the design and construction of underground repositories. For liquid-filled caverns, long-term sealing from the biosphere is of particular interest. In this instance it must be shown that the natural increase in pressure in the closed cavity due to long-term convergence does not exceed the fracture pressure. A special filled test (scale 1:1) has been performed to study this. 相似文献
5.
The problem of waste disposal in Germany has been solved by using a combination of above-ground and underground disposal. Site selection criteria and precise criteria for the performance assessment of various types of waste disposal are available. In view of long-term safety of disposal, it is necessary to include geological and hydrogeological viewpoints in addition to purely engineering viewpoints. In particular, the geotechnical site-specific safety assessment is described, as defined by the government in “Technical Regulations on Wastes” (TA-Abfall) in the section “Underground Disposal”. This safety assessment must cover the entire system comprising waste, cavern/mine and surrounding rock. For this purpose geo-mechanical models have to be developed. According to the multi-barrier principle, the geological setting must be able to contribute significantly to isolation of the waste over longer periods. The assessment of the integrity of the geological barrier can only be performed by making calculations with validated geomechanical models. Various engineering geological data are required for the selection of a site, for the design and construction of a repository, and for a safety analysis for the post-operational phase. These data can only be attained by the execution of a comprehensive site-specific geomechanical exploration and investigation program. The planning and design of an underground repository in rock salt layers are described, as an example for the various steps of this type of safety assessment. 相似文献
6.
New Rb–Sr age determinations using macrocrystal phlogopite are presented for 27 kimberlites from the Ekati property of the Lac de Gras region, Slave Province, Canada. These new data show that kimberlite magmatism at Ekati ranges in age from at least Late Paleocene (61 Ma) to Middle Eocene time (45 Ma). Older, perovskite-bearing kimberlites from Ekati extend this age range to Late Cretaceous time (74 Ma). Within this age range, emplacement episodes at 48, 51–53, 55–56 and 59–61 Ma can be recognized. Middle Eocene kimberlite magmatism of the previously dated Mark kimberlite (47.5 Ma) is shown to include four other pipes from the east-central Ekati property. A single kimberlite (Aaron) may be younger than the 47.5 Ma Mark kimberlite. The economically important Panda kimberlite is precisely dated in this study to be 53.3±0.6 Ma using the phlogopite isochron method, and up to six additional kimberlites from the central Ekati property have Early Eocene ages indistinguishable from that of Panda, including the Koala and Koala North occurrences. Late Paleocene 55–56 Ma kimberlite magmatism, represented by the Diavik kimberlite pipes adjacent to the southeastern Ekati property, is shown to extend onto the southeastern Ekati property and includes three, and possibly four, kimberlites. A precise eight-point phlogopite isochron for the Cobra South kimberlite yields an emplacement age of 59.7±0.4 Ma; eight other kimberlites from across the Ekati property have similar Late Paleocene Rb–Sr model ages. The addition of 27 new emplacement ages for kimberlites from the Ekati property confirms that kimberlite magmatism from the central Slave Province is geologically young, despite ages ranging back to Cambrian time from elsewhere in the Slave Province. With the available geochronologic database, Lac de Gras kimberlites with the highest diamond potential are currently restricted to the 51–53 and 55–56 Ma periods of kimberlite magmatism. 相似文献
7.
About one quarter of the coal produced in Australia is by underground mining methods. The most commonly used underground coal
mining methods in Australia are longwall, and room and pillar. This paper provides a detailed review of the two methods, including
their advantages and disadvantages, the major geotechnical and operational issues, and the factors that need to be considered
regarding their choice, including the varying geological and geotechnical conditions suited to a particular method. Factors
and issues such as capital cost, productivity, recovery, versatility and mine safety associated with the two methods are discussed
and compared. The major advantages of the longwall mining method include its suitability for mining at greater depth, higher
recovery, and higher production rate compared to room and pillar. The main disadvantages of the room and pillar method are
the higher risks of roof and pillar collapse, higher capital costs incurred as well as lower recovery rate. 相似文献
8.
Metasomatism accompanying kimberlite emplacement is a worldwide phenomenon, although infrequently described or recognised. At the Cambrian-aged Murowa and Sese kimberlite clusters located within the Archean Zimbabwe Craton just north of the boundary with the Limpopo Mobile Zone in southern central Zimbabwe, the metasomatism is intense and well exposed and the processes can be readily studied. Dykes, sills and the root zones of pipes are exposed at the current erosion level. Kimberlite lithologies present are hypabyssal macrocrystic kimberlite (“HMK”), HMK breccia, and tuffisitic kimberlite breccia (“TKB”) including minor lithic tuffisitic kimberlite breccia (“LTKB”). Country rocks are 2.6 Ga Chibi and Zimbabwe granite batholiths emplaced into 2.6–2.9 Ga or earlier Archean tonalitic gneiss and greenstones. During initial metasomatism, the granites become spotted with green chlorite, needles of alkaline amphiboles (winchite, riebeckite, arfvedsonite) and pyroxenes (aegirine–augite) with minor carbonate and felts of talc. Oligoclase feldspar becomes converted to albite, extensively altered, dusted and reddened with hematite, whereas K-feldspar remains unaffected. The granites become converted to syenite through removal of quartz. More intense metasomatism at Murowa and Sese results in veins of green metasomatite which cut and disrupt the granite. Progressive disruption entrains granite blocks, breaking down the granite still further, spalling off needle-like granite slivers, and so giving rise to LTKB. This process of disruption and entrainment appears to be the manner of initial development of the pipe structure. The chemistry of the metasomatite is intermediate between granite and kimberlite. Compared to granite country rock it has markedly higher Mg, Cr, Ni, CO 2 and H 2O+, higher Ca, Mn, Nb, Sr, P, Fe 3+/Fe 2+ ratio, U, Co, and Cu, approximately equal TiO 2, K 2O, Na 2O, La, Ta, Rb, Zr, Zn and resultant lower SiO 2, Al 2O 3, Ga and Y. The metasomatite Na 2O/K 2O ratio is slightly higher than that of the granite. The metasomatic process is broadly analogous to fenitisation of granitic wall rock accompanying carbonatite complex emplacement. The metasomatism at Murowa and Sese was caused by fluids from the rising but confined proto-kimberlite melt penetrating into cracks and matrix of granite country rock and reacting with it. These fluids were CO 2-rich, hydrous, oxidising, enhanced in ultramafic elements and carried low levels of Na. 相似文献
9.
通过对湘西上洞街煤矿区毛家寨段水文地质测绘、地质钻探及邻近生产矿井资料收集，综合分析研究认为：勘查区煤矿床主要充水主要为其顶、底板岩溶裂隙水，目前岩土工程地质条件比较简单，环境地质现状良好。煤矿开采后，因大量疏排岩溶地下水而导致的水、工、环不良地质问题将是今后矿区防治丁作的重点。 相似文献
10.
The Mwadui pipe represents the largest diamondiferous kimberlite ever mined and is an almost perfectly preserved example of a kimberlitic crater in-fill, albeit without the tuff ring. The geology of Mwadui can be subdivided into five geological units, viz. the primary pyroclastic kimberlite (PK), re-sedimented volcaniclastic kimberlite deposits (RVK), granite breccias (subdivided into two units), the turbidite deposits, and the yellow shales listed in approximate order of formation. The PK can be further subdivided into two units—lithic-rich ash and lapilli tuffs which dominate the succession, and lithic-poor juvenile-rich ash and lapilli tuffs. The lower crater is well bedded down to at least 684 m from present surface (extent of current drill data). The bedding is defined by the presence of juvenile-rich lapilli tuffs vs. lithic-rich lapilli tuffs, and the systematic variation in granite content and clast size within much of the lithic-rich lapilli tuffs. Four distinct types of bedding have been identified in the pyroclastic deposits. Diffuse zones characterised by increased granite abundance and size, and upward-fining units, represent the dominant types throughout the deposit. Lateral heterogeneity was observed, in addition to the vertical changes, suggesting that the eruption was quite heterogeneous, or that more than one vent may have been present. The continuous nature of the bedding in the pyroclastic material and the lack of ash-partings suggest deposition from a high concentration (ejecta), sustained eruption column at times, e.g. the massive, very diffusely stratified deposits. The paucity of tractional bed forms suggest near vertical particle trajectories, i.e. a clear air-fall component, but the poorly sorted, matrix-supported nature of the deposits suggest that pyroclastic flow and/or surge processes may also have been active during the eruption. Available diamond sampling data were examined and correlated with the geology. Data derive from the old 120 (37 m), 200 (61 m), 300 (92 m) and 1200 ft (366 m) levels, pits sunk during historical mining operations, drill logs, as well as more recent bench mapping. Correlating macro-diamond sample data and geology shows a clear relationship between diamond grade and lithology. Localised enrichment and dilution of the primary diamond grade has taken place in the upper reworked volcaniclastic deposits due to post-eruptive sedimentary in-fill processes. Clear distinction can be drawn between upper (re-sedimented) and lower (pyroclastic) crater deposits at Mwadui, both from a geological and diamond grade perspective. Finally, an emplacement model for the Mwadui kimberlite is proposed. Geological evidence suggests that little or no sedimentary cover existed at the time of emplacement. The nature of the bedding within the pyroclastic deposits and the continuity of the bedding in the vertical dimension suggest that the eruption was continuous, but that the eruption column may have been heterogeneous, both petrologically as well as geometrically. Volcanic activity appears to have ceased thereafter and the crater was gradually filled with granite debris from the unstable crater walls and re-sedimented volcaniclastic material derived from the tuff ring. The Mwadui kimberlite exhibits marked similarities compared to the Orapa kimberlite in Botswana. 相似文献
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