楚雄盆地砂岩铜矿容矿岩石胶结物与铜矿化     

俞国芬  张淑芸  郑庆鳌  王维贤 《云南地质》2008,27(4):477-482

砂岩铜矿的含铜矿物较简单,为典型的溶蚀交代岩石组构。含铜砂岩中胶结物主要有碳酸盐类、硅质、泥质和铁质四种,胶结类型有孔隙式、接触式、基底式三种;与矿化关系密切的是碳酸盐类胶结物;矿化强度与铁白云石和孔隙式、接触式胶结类型关系密切。  相似文献   

“中国山水画原本”—祝张家界国家地质公园诞生     

谢文安  胡能勇等 《湖南地质》2001,20(4):256-258

座落在张家界市的国家地质公园,面积约3600km^2,迷人的奇特石英砂岩峰林地貌景观为其精萃,已成为闻名遐迩的风景名胜区和旅游胜地,一代宗师吴冠中先生赞誉张家界为“中国山水画原本”。经过亿万年地质历史的发展演化,距今3亿多年的上泥盆统云台观组石英砂岩在流水侵蚀、风化剥蚀、地壳的掀斜抬升等内外地质营力作用下,最终形成现代迷人的砂岩峰林景观,被誉为“国之瑰宝,世界明珠”。  相似文献   

云冈石窟砂岩中碳酸盐胶结物化学风化及相关文物病害研究   总被引：1，自引：0，他引：1  

马在平  黄继忠  张洪 《中国岩溶》2005,24(1):71-76

云冈石窟地区云冈组上段砂岩中碳酸盐胶结物的含量普遍在10%以上,其主要矿物成分为含铁方解石和含铁白云石。在碳酸盐胶结物化学风化过程中发生的化学反应包括碳酸盐矿物溶解、Fe2+ 离子氧化及Fe3+ 离子水解,以及石膏、泻利盐、水碳镁石、球碳镁石等矿物结晶。水、砂岩中裂隙和层理发育、大气污染等是影响碳酸盐胶结物化学风化的主要外因。碳酸盐胶结物化学风化引发了多种文物病害,对云冈石窟的文物价值造成严重破坏。   相似文献   

Be data from meltwater channels suggest that Jameson Land, east Greenland, was ice-covered during the last glacial maximum     

Lena Håkansson  Jason P. Briner  Ala Aldahan  Göran Possnert 《Quaternary Research》2011,76(3):452-459

Along the northeast Greenland continental margin, bedrock on interfjord plateaus is highly weathered, whereas rock surfaces in fjord troughs are characterized by glacial scour. Based on the intense bedrock weathering and lack of glacial deposits from the last glaciation, interfjord plateaus have long been thought to be ice-free throughout the last glacial maximum (LGM). In recent years there is growing evidence from shelf and fjord settings that the northeast Greenland continental margin was more extensively glaciated during the LGM than previously thought. However, little is still known from interfjord settings. We present cosmogenic ¹⁰Be data from meltwater channels and weathered sandstone outcrops on Jameson Land, an interfjord highland north of Scoresby Sund. The mean exposure age of samples from channel beds (n = 3) constrains on the onset of deglaciation on interior Jameson Land to 18.5 ± 1.3–21.4 ± 1.9 ka (for erosion conditions of 0–10 mm/ka, respectively). This finding adds to growing evidence that the northeast Greenland continental margin was more heavily glaciated during the LGM than previously thought.  相似文献   

滇南南坡铜矿成矿条件及矿床成因     

吕晓宏  张搜  周仕雄  坚润堂 《云南地质》2011,30(4):411-414

南坡铜矿床是在原来沉积铜矿的基础上,经地下水作用次生富集而成的富矿体。  相似文献   

The Green Castle Sandstone Formation: A new name for the Cwmffrwd Formation (Old Red Sandstone) preoccupied by an Ordovician Member     

John C.W. Cope 《Proceedings of the Geologists' Association. Geologists' Association》2018,129(1):89-91

The Geological Survey’s Framework Report on the Old Red Sandstone of the Anglo-Welsh region includes a proposal for a new formational name, the Cwmffrwd Formation, for the basal formation of the Daugleddau Group in Carmarthenshire, S. Wales.The name is preoccupied by the Early Ordovician Cwmffrwd Member of the Carmarthen Formation and a new name, the Green Castle Sandstone Formation is proposed for the Cwmffrwd Formation.  相似文献   

Anatomy of falling‐stage deltas in the Turonian Ferron Sandstone of the western Henry Mountains Syncline,Utah: Growth faults,slope failures and mass transport complexes          下载免费PDF全文

Christopher R. Fielding 《Sedimentology》2015,62(1):1-26

Falling‐stage deltas are predicted by sequence stratigraphic models, yet few reliable criteria are available to diagnose falling‐stage deltaic systems in surface exposures. Recent work on the Upper Cretaceous (Turonian) Ferron Sandstone in the western Henry Mountains Syncline of south‐central Utah has established its environment of deposition as a series of modest‐sized (5 to 20 km wide), probably asymmetrical, mixed‐influence deltas (‘Ferron Notom Delta’) that dispersed sediment eastwards from the rising Sevier orogenic hinterland into the Western Cordilleran Foreland Basin. Analysis of sandstone body stacking patterns in a 67 km long, depositional strike‐parallel (north–south) transect indicates that the growth of successive deltas was strongly forced by synsedimentary growth of a long wavelength (ca 100 km), 50 m amplitude fold structure. Herein, two discrete areas within this transect, superbly exposed in three dimensions, are documented in order to determine the details of stratal stacking patterns in the depositional dip direction, and thereby to assess the stratigraphic context of the Ferron Notom Delta. In the two study areas, dip transects expose facies representing river mouth bar to distal delta front environments over distances of 2 to 4 km. Key stratal packages are clinothems that offlap, downlap, and describe descending regressive trajectories with respective to basal and top datums; they are interpreted as the product of relative sea‐level fall. The vertical extent of clinoforms suggests that deltas prograded into <30 m of water. Furthermore, these deltaic successions preserve abundant evidence of delta front slope failure, growth faulting, and incision and filling of deep (<15 m) slope gullies. Gully fills are composed of chaotic intraformational breccia and/or massive sandstone, and constitute linear, ‘shoestring’ sandbodies in the distal portions of individual palaeodelta systems. They are interpreted to have been cut and filled during the late falling‐stage and lowstand of relative sea‐level cycles. The north–south distribution of the stratal style described above seems to be focused on the flanks of the growth anticline, and so the numerous falling‐stage systems tracts preserved within the Ferron Notom Delta probably owe their origin to synsedimentary structural growth, and the unstable fluid pressure regime that this growth imposed on the sea floor and shallow subsurface.  相似文献   

Quartzite development in early Palaeozoic nearshore marine environments     

David J. Went 《Sedimentology》2013,60(4):1036-1058

Quartzites are especially characteristic of Proterozoic and Cambro‐Ordovician shallow marine strata, whereas equivalent age fluvial deposits are commonly arkosic. The absence of land vegetation in the pre‐Silurian influenced weathering processes and styles of fluvial deposition. It may also have had an impact on shallow marine sedimentation. Two field studies from the English Channel region are presented to investigate the processes leading to quartzite formation. On Alderney, nearshore marine and fluvial facies occur interbedded on a metre scale and are interpreted to represent deposition on the lower reaches of an alluvial plain, and in beach and upper shoreface environments. The marine and fluvial sandstones display marked differences in textural and mineralogical maturity, pointing to a process of sediment maturation by the destruction of feldspar and labile grains at the shoreline. At Erquy, fully mature, marine quartzites occur bounded above and below by alluvial deposits via sharp or erosional surfaces, and are interpreted to represent high energy, storm and tidally influenced lower shoreface and inner shelf deposits. A model for quartzite development is proposed where, under a cool climate, frequent storms in un‐vegetated, tectonically rejuvenated uplands provided an abundance of arkosic sand to fluvial basins and clastic shorelines. The model proposes that the marine basins were subject to high wave energies, frequent storm events and tidal currents. These were conditions conducive to transforming arkosic sand to quartz‐rich sand by the attrition of feldspar at the shoreline and in the shallow marine environment. On sediment burial, further feldspar destruction occurred during diagenesis. The proposed model highlights the potential for a step change in sediment maturity to occur at the shoreline in early Palaeozoic depositional systems tracts.  相似文献   

Discovery of an outcropping Mass Transport Deposit (MTD) in the Palaeogene subalpine synclines of southeastern France: Implications on flexural sub-basin deformation     

《Comptes Rendus Geoscience》2014,346(1-2):37-44

We document the sedimentary facies of a large Mass Transport Deposit (MTD) within the sand-rich sediment gravity flow-dominated deposits of the Eocene–Oligocene south-western Alpine forelands (Annot Sandstone system). The MTD with an approximated volume of several hundreds of cubic kilometres fills a sub-basin located in the Mont-Tournairet confined sub-basin. Autochthonous facies are very typical sediment gravity-flow deposits (thin-bedded classical turbidites and thick-bedded hyperconcentrated to concentrated flow deposits) that stratigraphically belong to the Annot Sandstone infill. Slumps and internal metre-large fold axes of the deformed stratigraphic intervals indicate a main transport direction towards the northwest. The seafloor instability that led to the mass-flow events within the Mont-Tournairet sub-basin could have been favoured by high sedimentation rates in a small, confined and tectonically active sub-basin, possibly enhanced by local structural deformation associated with the Triassic evaporites on the eastern side of the Mont-Tournairet confined basin. The presence of the MTD suggests that a period of increased flexural subsidence rate and basin deformation occurred in this portion of the subalpine foreland basin. Therefore, the MTD forms a stratigraphic marker of a period of tectonic activity.  相似文献   

Largest Ediacaran discs from the Jodhpur Sandstone,Marwar Supergroup,India: Their palaeobiological signi?cance     

Purnima Srivastava 《地学前缘(英文版)》2014,5(2):183-191

Ediacaran discs from the Jodhpur Sandstone of the Marwar Supergroup, Rajasthan, exhibit a wide size ranging from a few millimetres to 75 cm in diameter. Exceptionally large size of the discs in these rocks represent the largest reported so far from any Ediacaran assemblage. Although, larger medu-soid discs have been reported from USA, they are from the middle Cambrian and even younger rocks. Presence of microbial mats and weed-like structures with well preserved hold fasts and horizontal rhizome-like structures in association with some of these large-sized discs support their animal affinity, which probably feed on this weed-like vegetations. This association also supports their benthic habitat. Unlike the general trend of sudden increase in size of organisms in Ediacaran period and further decrease in size during Cambrian, these discs continued increasing in size in Cambrian also.  相似文献