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Gerald Pischinger Walter Kurz Martin Übleis Magdalena Egger Harald Fritz Franz Josef Brosch Karl Stingl 《Swiss Journal of Geoscience》2008,101(1):235-254
The Paleogene and Neogene evolution of Austroalpine basement units east of the Tauern Window is characterised by the formation of two major sets of faults: (1) ESE–WNW- to E–W-trending faults, associated with ENE- and NNW-trending conjugate structures and (2) N–S to NNE-SSW striking structures, mainly acting as high-angle normal faults, often associated with E-dipping low-angle normal faults along the western margin of the Styrian Basin.Together with the stratigraphic evolution of the Styrian and Lavanttal Basins and the related subsidence histories a tectonic evolution may be reconstructed for this part of the Eastern Alps. In the southern part of the Koralm Massif, WNW-trending fractures were activated as dextral strike-slip faults, associated with the evolution of WNW-trending troughs filled up with coarse block debris. W- to WNW-trending fractures were reactivated as normal faults, indicating N–S extension. It is assumed that these phases resulted in subsidence and block debris sedimentation in Karpatian and Badenian times (ca. 17–13 Ma).In the Western Styrian Basin no Sarmatian (13–11.5 Ma) sediments are observed; Pannonian (11.5 to 7.1 Ma) sediments are restricted to the Eastern Styrian Basin. This indicates, that the Koralm basement and the Western Styrian Basin were affected by post-Sarmatian uplift, coinciding with a re-activation of N-trending normal faults along the eastern margin of the Koralm Massif. Therefore, we suggest that the final uplift of the Koralm Complex, partly together with the Western Styrian Basin, occurred during the early Pannonian (at approximately 10 Ma). The elevation of clastic deposits indicates that the Koralm Complex was elevated by approximately 800 m during this phase, associated with an additional phase of E–W-directed extension accommodated by N–S striking normal faults. 相似文献
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The Seongsan district in the Jindo–Haenam basin of southwest Korea comprises Precambrian gneissic basement, overlain and intruded by Cretaceous volcanic (98–71 Ma) and plutonic (86–68 Ma) rocks, respectively. Haenam Formation volcanic and volcaniclastic rocks are the dominant rock type exposed in the district and are the main host to high-sulphidation (82–77 Ma) and low-sulphidation (79–73 Ma) epithermal deposits. The Eunsan and Moisan low-sulphidation epithermal deposits have similar vein mineralogy, zoned hydrothermal alteration mineral assemblages, structural framework and interpreted deformation events. These similarities suggest that they formed by district-scale hydrothermal fluid flow at about 77.5 Ma. At this time, ore fluid movement along subvertical WNW-trending faults was particularly focussed in dilatant fault bends, jogs, and at intersections with N-trending splays. At Eunsan, Au–Ag ore shoots coincide with these areas of structural complexity, whereas at Moisan, narrower ore zones correspond with several parallel, poorly connected veins. A secondary control on the location of ore zones is the intersection between mineralised WNW-striking structures and rocks of the Haenam Formation. The higher permeability and porosity of these rocks, in comparison with mudstones and siltstones of the underlying Uhangri Formation, resulted in the more efficient lateral migration of ore fluids away from subvertical faults and into wall rocks. The intersection between subvertical WNW-striking faults and the gently dipping Haenam Formation imparts a low angle SW plunge to both ore bodies. WNW-striking post-mineralisation faults displace ore zones up to 100 m and complicate the along-strike exploration and mining of WNW-trending ore zones. Future exploration strategies in the district involve the systematic testing of WNW-trending mineralised structures along strike from known deposits, with a particular emphasis on identifying structurally complex areas that experienced local dilation during the mineralisation event. Poorly exposed regions have historically been under-explored. However, based on the proposed exploration model for the Eunsan and Moisan deposits, these areas of poor outcrop are now considered important target areas for hidden ore bodies using ground-based geophysical exploration tools, such as seismic surveys. 相似文献
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CHEN Bailin LI Zhongjian DONG Faxian Institute of Geomechanics Chinese Academy of Geological Sciences Beijing 《《地质学报》英文版》2001,75(1):94-100
The Qifengcha-Detiangou gold deposit is a medium-sized deposit recently found in Huairou County, Beijing. It belongs to the altered mylonite type with superimposed quartz vein type and is related to the early Yanshanian magmatic activity. Characterized by multiperiodic activity, the NE-trending Qifengcha fault is a regional ore-controlling structure in the area, and gold mineralization develops only in its southeastern part. Meanwhile, gold mineralization is controlled by the Yunmengshan metamorphic core complex. The nearly N-S- and E-W-trending low-angle detachment faults, reformed by the Qifengcha fault in the northwestern part of the core complex, are the main ore-bearing faults. All discovered gold deposits are located within an area 1.5-4.0 km away from the boundary of the upwelling centre. The N-S- (NNE-) and E-W-trending ore-bearing faults are ductile-brittle structural zones developing in shallow positions and subjected mainly to compressive deformation. The structural ore-controlling effects ar 相似文献
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通过对胶东金矿地质背景和成矿特征研究的总结与分析,依据热液矿床水相变控矿理论,探索胶东地区高密度聚集巨量金矿的原因。研究发现,两期次降压驱动成矿物质运动和临界水的（温度和压力都达到水临界值时的水,下同）特殊性质是两个重要因素。在此基础上,文章提出胶东巨量金聚集成矿的深大断裂-临界成矿机制,即"一饼加一刀"的成矿机制:老变质岩提供丰富的成矿物源是基础;早期大型点状降压形成酸性侵入杂岩体和各类岩脉等,其伴生的长时间、巨量临界水促使成矿物质活化迁移;晚期大型线状断裂降压造成较短时间内成矿物质的沉淀,若断裂是张开的不连续空间则矿石以充填结构为主,若破碎带是连续空间时矿石则以蚀变交代结构为主。丰富的金源,两期次不同性质的降压,临界水的独特性质,是胶东巨量金矿聚集的主要因素。 相似文献
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CAO Ye LI Shengrong XIONG Xianxiao LI Zhenzhen LIU Xiaobin YAO Meijuan ZHANG Huafeng 《《地质学报》英文版》2012,86(5):1211-1224
The Shihu gold deposit, situated in the Taihang Mesozoic orogen of the North China Craton (NCC), is hosted by ductile-brittle faults within Archean metamorphic core complex. The deposit is characterized by gold-bearing quartz-polymetallic sulfides veins. The Mapeng granitoids stock and intermediate-basic dikes intruded the metamorphic basement rocks, and are spatially related to gold mineralization. Detailed laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS) U-Pb zircon ages of the granitic rocks, dykes and mineralized quartz veins in the studied area reveal its magmatic and mineralized history. The mineralized quartz veins contain inherited zircons with ages of about 2.55 Ga and 1.84 Ga, probably coming from the basement. These two Precambrian events are coeval with those in other parts of the NCC. The Mapeng granitoid stock, the largest intrusion in the area, was emplaced at ca. 130 Ma, and is coeval with magmatic zircon populations from diorites and quartz diorite pophyrites in the same region. The ca. 130 Ma magmatism and gold mineralization were most likely related to an underplating event that took place in the Taihang orogen at Late Mesozoic. The timing of gold mineralization with respect to felsic magmatism in the area is similar to those observed in other major gold-producing provinces in the NCC. This episode is simultaneous with those in the eastern margin of NCC, indicative of a widespread late Yanshanian metallogenic event that was a response to the Early Cretaceous lithosphere in the eastern NCC, in which the mesothermal gold deposits were formed from similar tectono-magmatic environments. 相似文献
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Richard M. Vielreicher Noreen M. Vielreicher Steffen G. Hagemann Greg Jones 《Mineralium Deposita》2002,38(5):538-554
The Jian Cha Ling gold deposit is sited in folded and faulted Palaeoproterozoic rocks of the uplifted Mian-Lue-Yang block, adjacent to the Mianlue suture zone within the West Qinling mineral province, along the northern margin of the South China craton. Early Mesozoic gold mineralization at Jian Cha Ling, which has a pre-mined resource of about 536,000 oz Au, is controlled by the so-called F 1 45 fault. The fault is a generally steeply N-dipping, WNW-trending deformation zone that is the result of dislocation along bedding planes, early foliation and axial planar surfaces of regional folds. The fault zone marks the contact between serpentinized, lower greenschist-facies dunites, harzburgites and minor gabbroic units in the footwall, and a metasedimentary sequence in the hanging wall that is dominated by metadolomite, metalimestone and phyllitic schists. Brittle–ductile deformation, partitioning of strain along pre-existing zones of weakness, and the formation of intrashear zone lozenges contributed to the development of a complex fault zone geometry. Variations in both dip and strike of discrete dislocation surfaces related to oblique, sinistral–reverse movement along the F 1 45 fault zone focussed auriferous hydrothermal fluids along three dominant structural orientations. Gold was preferentially deposited along shallowly NNE-dipping and shallowly to moderately NNW-dipping fault segments, and is also associated with shallowly WSW-dipping, dolomite-dominated vein sets. Disseminated, economic gold grades (>4 g/t Au) are restricted to the footwall ultramafic rocks to within about 5 to 10 m of the contact with the hanging wall. Gold is related to laminated, realgar- and orpiment- bearing sheeted veins and hydrothermal breccias, as well as slickolites and fault gouge. Gold-bearing vein sets are located within the relatively undeformed, ultramafic intrashear zone lozenges. Gold-related alteration is dominated by extremely fine-grained, arsenic-bearing sulphide minerals and dolomite, with additional white mica and clay minerals. The structural setting of the deposit, combined with published data on the geological evolution of the West Qinling mineral province, suggest that the Jian Cha Ling gold deposit developed in an uplifted basement block during the final phases of northward subduction and suturing of the South China craton with the South Qinling orogen along the Mianlue Suture Zone, during the changeover from a compressional to transpressional tectonic regime in Late Triassic to Middle Jurassic times. 相似文献
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马扎拉金矿位于藏南拆离断裂以北的特提斯喜马拉雅南部隆子逆冲推覆断裂南缘,是扎西康整装勘查区构造蚀变岩型金矿床的典型代表。本文在矿区外围30km2范围开展地质测量工作,重新厘定了矿区及外围的地层系统并新发现大量岩浆岩,重塑了矿区及外围的断裂构造格架并初步厘定了构造活动期次,结合地球物理剖面测量、区域地质新近调查研究成果和少量工程验证,初步构建了矿床的控矿构造几何模型并重新确立了矿区及外围在近东西向具有早期逆冲推覆、晚期伸展滑脱的前断坡和反冲断裂及其次级断裂中寻找构造蚀变岩型金矿的找矿方向,对进一步找矿工作的部署具有重要的指导意义。 相似文献
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Detailed geologic mapping of the San Andreas fault zone in Los Angeles County since 1972 has revealed evidence for diverse histories of displacement on branch and secondary faults near Palmdale. The main trace of the San Andreas fault is well defined by a variety of physiographic features. The geologic record supports the concept of many kilometers of lateral displacement on the main trace and on some secondary faults, especially when dealing with pre-Quaternary rocks. However, the distribution of upper Pleistocene rocks along branch and secondary faults suggests a strong vertical component of displacement and, in many locations, Holocene displacement appears to be primarily vertical. The most recent movement on many secondary and some branch faults has been either high-angle (reverse and normal) or thrust. This is in contrast to the abundant evidence for lateral movement seen along the main San Andreas fault. We suggest that this change in the sense of displacement is more common than has been previously recognized.The branch and secondary faults described here have geomorphic features along them that are as fresh as similar features visible along the most recent trace of the San Andreas fault. From this we infer that surface rupture occurred on these faults in 1857, as it did on the main San Andreas fault. Branch faults commonly form “Riedel” and “thrust” shear configurations adjacent to the main San Andreas fault and affect a zone less than a few hundred meters wide. Holocene and upper Pleistocene deposits have been repeatedly offset along faults that also separate contrasting older rocks. Secondary faults are located up to 1500 m on either side of the San Andreas fault and trend subparallel to it. Moreover, our mapping indicates that some portions of these secondary faults appear to have been “inactive” throughout much of Quaternary time, even though Holocene and upper Pleistocene deposits have been repeatedly offset along other parts of these same faults. For example, near 37th Street E. and Barrel Springs Road, a limited stretch of the Nadeau fault has a very fresh normal scarp, in one place as much as 3 m high, which breaks upper Pleistocene or Holocene deposits. This scarp has two bevelled surfaces, the upper surface sloping significantly less than the lower, suggesting at least two periods of recent movement. Other exposures along this fault show undisturbed Quaternary deposits overlying the fault. The Cemetery and Little Rock faults also exhibit selected reactivation of isolated segments separated by “inactive” stretches.Activity on branch and secondary faults, as outlined above, is presumed to be the result of sympathetic movement on limited segments of older faults in response to major movement on the San Andreas fault. The recognition that Holocene activity is possible on faults where much of the evidence suggests prolonged inactivity emphasizes the need for regional, as well as detailed site studies to evaluate adequately the hazard of any fault trace in a major fault zone. Similar problems may be encountered when geodetic or other studies, Which depend on stable sites, are conducted in the vicinity of major faults. 相似文献
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Abbas Babaahmadi Mohammad MohajjelAbbas Eftekhari Ali Reza Davoudian 《Journal of Asian Earth Sciences》2012,43(1):77-88
The NW-SE trending Sanandaj-Sirjan Zone (SSZ) is the internal part of the Zagros continental collision zone, which mainly consists of metamorphic rocks deformed in a dextral transpressional zone. This dextral transpression is attributed to brittle deformation related to late Cenozoic Arabia-Eurasia oblique continental collision. Major NW-trending faults, including the Dalan, Garmdareh, Yasechah, Sheida, and Ben faults, are reverse faults with a dextral strike-slip component. These faults were displaced by NW-trending synthetic and NE-trending antithetic faults. There are also E-trending thrusts and N-trending normal faults developing in directions that are, respectively, almost normal and parallel to the major shortening direction. The NW-trending Ben, Yasechah, and Sheida faults are NE-dipping faults, and the Dalan and Garmdareh faults are SW-dipping faults. These faults indicate the presence of a transpressive flower structure zone that probably led to the exhumation of Jurassic high-grade metamorphic rocks, such as eclogite, in the central part of the study area. 相似文献
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Frank P. Bierlein Finbarr C. Murphy Roberto F. Weinberg Terry Lees 《Mineralium Deposita》2006,41(2):107-126
A quantitative spatial analysis of mineral deposit distributions in relation to their proximity to a variety of structural elements is used to define parameters that can influence metal endowment, deposit location and the resource potential of a region. Using orogenic gold deposits as an example, geostatistical techniques are applied in a geographic-information-systems-based regional-scale analysis in the high-data-density Yilgarn Craton of Western Australia. Metal endowment (gold production and gold ‘rank’ per square kilometer) is measured in incremental buffer regions created in relation to vector lines, such as faults. The greatest metal tonnages are related to intersections of major faults with regional anticlines and to fault jogs, particularly those of dilatant geometry. Using fault length in parameter search, there is a strong association between crustal-scale shear zones/faults and deposits. Nonetheless, it is the small-scale faults that are marginal or peripheral to the larger-scale features that are more prospective. Gravity gradients (depicted as multiscale edges or gravity ‘worms’) show a clear association to faults that host gold deposits. Long wavelength/long strikelength edges, interpreted as dominantly fault-related, have greater metal endowment and provide a first-order area selection filter for exploration, particularly in areas of poor exposure. Statistical analysis of fault, fold and gravity gradient patterns mainly affirms empirical exploration criteria for orogenic gold deposits, such as associations with crustal-scale faults, anticlinal hinge zones, dilational jogs, elevated fault roughness, strong rheological contrasts and medium metamorphic grade rocks. The presence and concurrence of these parameters determine the metallogenic endowment of a given fault system and segments within the system. By quantifying such parameters, the search area for exploration can be significantly reduced by an order of magnitude, while increasing the chance of discovery. 相似文献
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We localized crustal earthquakes in the Andean arc, between 35°S and 36°S, from December 2009 to May 2010. This research shows a seismicity increase, in a narrow longitudinal area, of more than nine times after the great Mw 8.8 Maule earthquake.The localized seismicity defines an area of ∼80 km long and ∼18 km wide and NNW to NNE trend. The Md magnitudes varied from 0.7 to 3.1 except for two earthquakes with Mw of 3.9 and 4.5, located in the northern end of the area. The focal mechanisms for these two last events were normal/strike-slip and strike-slip respectively.During 2011, a network of 13 temporary stations was installed in the trasarc region in Malargüe, Argentina. Sixty earthquakes were localized in the study region during an 8 month period.We explored how changes in Coulomb conditions associated with the mega-thrust earthquake triggered subsequent upper-plate events in the arc region. We assumed the major proposed structures as receiver faults and used previously published earthquake source parameters and slip distribution for the Maule quake. The largest contribution to static stress change, up to 5 bars, derives from unclamping resulting consistent with co-seismic dilatational deformation inferred from GPS observations in the region and subsidence in nearby volcanoes caused by magma migration.Three different Quaternary tectonic settings–extensional, strike-slip and compressional-have been proposed for the arc region at these latitudes. We found that the unclamping produced by the Maule quake could temporarily change the local regime to normal/strike-slip, or at least it would favor the activation of Quaternary NNE to N-trending dextral strike-slip faults with dextral transtensional movement. 相似文献
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This paper describes the geology and tectonics of the Paleoproterozoic Kumasi Basin, Ghana, West Africa, as applied to predictive mapping of prospectivity for orogenic gold mineral systems within the basin. The main objective of the study was to identify the most prospective ground for orogenic gold deposits within the Paleoproterozoic Kumasi Basin. A knowledge-driven, two-stage fuzzy inference system (FIS) was used for prospectivity modelling. The spatial proxies that served as input to the FIS were derived based on a conceptual model of gold mineral systems in the Kumasi Basin. As a first step, key components of the mineral system were predictively modelled using a Mamdani-type FIS. The second step involved combining the individual FIS outputs using a conjunction (product) operator to produce a continuous-scale prospectivity map. Using a cumulative area fuzzy favourability (CAFF) curve approach, this map was reclassified into a ternary prospectivity map divided into high-prospectivity, moderate-prospectivity and low-prospectivity areas, respectively. The spatial distribution of the known gold deposits within the study area relative to that of the prospective and non-prospective areas served as a means for evaluating the capture efficiency of our model. Approximately 99% of the known gold deposits and occurrences fall within high- and moderate-prospectivity areas that occupy 31% of the total study area. The high- and moderate-prospectivity areas illustrated by the prospectivity map are elongate features that are spatially coincident with areas of structural complexity along and reactivation during D4 of NE–SW-striking D2 thrust faults and subsidiary structures, implying a strong structural control on gold mineralization in the Kumasi Basin. In conclusion, our FIS approach to mapping gold prospectivity, which was based entirely on the conceptual reasoning of expert geologists and ignored the spatial distribution of known gold deposits for prospectivity estimation, effectively captured the main mineralized trends. As such, this study also demonstrates the effectiveness of FIS in capturing the linguistic reasoning of expert knowledge by exploration geologists. In spite of using a large number of variables, the curse of dimensionality was precluded because no training data are required for parameter estimation. 相似文献
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东峰顶金矿主要赋存于近SN向断裂破碎带中,呈脉状产出。矿石类型主要为硫化物（黄铁矿）-石英金矿石、褐铁矿-石英金矿石、褐铁矿金矿石等,矿石氧化率达86．2％,氧化矿石含金量高,以中粗粒表生自然金为主。成矿分原生热液成矿期和表生成矿期,原生热液成矿期具多阶段性,表生成矿期使金进一步富集。包裹体、铅和硫同位素、原生金成色以及黄铁矿中微量元素等特征研究表明：成矿溶液以岩浆水为主,可能混有地下热卤水,是一种低盐度、中低密度的流体,成矿物质来自于基底老变质岩（矿源层）,成矿温度在148℃～395℃之间,矿床形成距今年龄值约100Ma左右,属中温、中深岩浆热液型金矿床。矿床形成过程为：矿源层中金的活化-热液中金的迁移、沉淀-表生作用下金的再富集。 相似文献
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Allison L. Dugdale Christopher J. L. Wilson Lawrence D. Leader Jamie A. Robinson L. Jonathon Dugdale 《Mineralium Deposita》2009,44(2):205-219
Historically, carbonate spots have been identified as an indicator of gold mineralization throughout central Victoria, Australia.
However, the exact timing relationships between the growth of carbonates, development of deformation fabrics, and the introduction
of gold has only been determined in more recent times through isolated studies on individual gold deposits. Detailed examination
of the evolution of hydrothermal alteration associated with the Magdala gold deposit at Stawell recognized the fact that there
were at least two generations of carbonate growth, an early rounded ankerite phase that predated gold mineralization and a
later euhedral siderite phase coincident with gold mineralization. This pattern of carbonate growth is repeated in the majority
of significant gold deposits, including Bendigo and Ballarat, throughout central Victoria. Timing relationships within the
carbonates suggest that a fluid was introduced along bedding planes and early deformation fabrics prior to the main upright
folding events that significantly modified the original sedimentary basin. It is suggested that the early rounded carbonates
may have formed as a result of anaerobic oxidation of methane, derived from the sediments and advected along normal growth
faults within the sedimentary basin, through interaction with downward diffusing seawater sulfate. Although the growth of
the early carbonates is not related to gold mineralization, the change in the speciation of the carbonate during the later
carbonate event is critical and can be tracked using a simple geochemical index that can be used not only in areas of outcrop
but also in conjunction with exploration undercover. 相似文献
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Nyankanga is the largest gold deposit in the Geita Greenstone Belt of the northern Tanzania Craton. The deposit is hosted within an Archean volcano-sedimentary package dominated by ironstones and intruded by a large diorite complex, the Nyankanga Intrusive Complex. The supracrustal package is now included within the intrusive complex as roof pendants. The ironstone fragments contain evidence of multiple folding events that occurred prior to intrusion. The supracrustal package and Nyankanga Intrusive Complex are cut by a series of NE–SW trending, moderately NW dipping fault zones with a dominant reverse component of movement but showing multiple reactivation events with both oblique and normal movement components. The deposit is cut by a series of NW trending strike slip faults and ~ E–W trending late normal faults. The Nyankanga Fault Zone is a major NW dipping deformation zone developed mainly along the ironstone–diorite contacts that is mineralised over its entire length. The gold mineralization is hosted within the damage zone associated with Nyankanga Fault Zone by both diorite and ironstone with higher grades typically occurring in ironstone. Ore shoots dip more steeply than the Nyankanga Fault Zone. The mineralization is associated with sulfidation fronts and replacement textures in ironstones and is mostly contained as disseminated sulphides in diorite. The close spatial relationship between gold mineralization and the ironstone/diorite contact suggests that the reaction between the mineralising fluid and iron rich lithotypes played an important role in precipitating gold. Intense brecciation and veining, mainly in the footwall of Nyankanga Fault Zone, indicates that the fault zone increased permeability and allowed the access of mineralising fluids. The steeper dip of the ore shoots is consistent with mineralization during normal reactivation of the Nyankanga Fault Zone. 相似文献
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桂西巴马料屯金矿床成矿年代上限的确定——对滇黔桂“金三角”卡林型金矿年代学研究的启示 总被引：1，自引：0，他引：1
广西巴马料屯金矿床是较为典型的卡林型金矿床,金矿体与燕山晚期石英斑岩脉空间上相关。矿床勘查成果和野外露头观察均表明石英斑岩脉切割金矿体,说明岩浆岩形成于矿体之后。成矿元素地球化学测量结果表明,Au、As元素沿石英斑岩脉走向出现明显的分异,表现为在导矿和容矿断层区段Au、As质量分数高,局部形成矿（化）体;远离矿体的砂泥岩和灰岩围岩地段,则逐渐降低至正常背景值,说明石英斑岩侵位过程中切割早期的矿体或含矿断层,萃取了矿（化）体中成矿元素Au、As,从而在这些断层之间形成一定宽度的高值带。成矿元素地球化学测量支持岩浆岩形成于矿体之后的结论。石英斑岩脉白云母斑晶的40Ar/39Ar坪年龄为（95.5±0.7） Ma,代表了岩浆侵位年龄,由于岩脉形成于矿体之后,此年龄可以作为成矿年代的上限年龄。本矿床及滇黔桂"金三角"其他卡林型金矿的确切成矿年代,尚需更多高精度直接成矿年龄数据的约束。 相似文献