共查询到20条相似文献，搜索用时 822 毫秒
1.
地球化学块体与大型矿集区的关系——以东天山为例 总被引：11，自引：5，他引：11
通过在东天山15万km2的战略性深穿透地球化学调查共圈出大于1000km2以上的地球化学块体18处,其中铜-铅-锌-银地球化学块体5处,铜地球化学块体3处,铜-镍地球化学块体1处,金的地球化学块体4处,铀的地球化学块体3处,铂-钯地球化学块体1处,钨地球化学块体1处。有6处地球化学块体与已知矿集区相对应,新圈定的地球化学块体12处,其中有3处发现了新的矿床。根据这些块体与矿集区的对比得出如下结论:所有的已知矿集区都位于地球化学块体的范围之内,地球化学块体为矿集区的形成提供了丰富的物质基础;有矿集区的存在一定有地球化学块体的存在,但反过来有地球化学块体的存在不一定有矿集区的存在,地球化学块体是客观存在的,而矿集区是已经发现了一系列矿床并勘探到一定程度才能称作矿集区,因此,地球化学块体内可能会存在潜在的矿集区,这为利用地球化学块体预测新的矿集区提供了依据。 相似文献
2.
Classification and mineralization potential of the pegmatites of the Eastern Brazilian Pegmatite Province 总被引：1，自引：0，他引：1
The potential for Nb, Ta, Li, Sn-mineralization as well as for precious stones for the Eastern Brazilian Pegmatite Province (EBPP) has been evaluated on the basis of 530 K-feldspar and 550 muscovite major and trace element analyses. The EBPP is situated mainly in the State of Minas Gerais, but encompasses also parts of the States of Bahia, Espírito Santo and Rio de Janeiro. The EBPP is the largest pegmatite province of South America. It was divided into the pegmatite districts of Itambé, Araçuaí, Safira, Nova Era, Aimorés and Espera Feliz. This was done to test whether the pegmatites of these districts differ in their mineralization potential and how geotectonic setting influences mineralization potential. The fractionation diagrams such as Cs, Zn, Li, Be, Ba versus K/Rb, Cs versus Ta/(Ta + Nb), and U, Na2O versus K/Cs for the pegmatite districts of Araçuaí and Safira show the widest range in fractionation. These pegmatite districts are leaders in the production of gem-quality tourmaline, aquamarine, morganite, and contain abundant spodumene, tantalite and columbite. In contrast, the Espera Feliz and Aimorés pegmatite districts are the most primitive districts examined and have a corresponding lack of rare-element mineralization. Literature data indicate that all studied pegmatites are of Brasiliano age, i.e., formed between 600 and 480?Ma. The pegmatites of Transamazonic age (1.9?Ga), found rarely in the study area, are of economic importance in the context of emerald mineralization, but seem to be of less importance for rare metal and other gemstone mineralization. 相似文献
3.
Babar Ali Shah 《Arabian Journal of Geosciences》2014,7(9):3525-3536
A groundwater arsenic (As) survey in Mirzapur, Varanasi, Ghazipur, Ballia, Buxar, Ara, Patna, and Vaishali districts of UP and Bihar shows that people from these districts are drinking As-contaminated groundwater (max. 1,300 μg/l). About 66 % of tubewells from Buxar to Mirzapur areas and 89 % of tubewells from Patna to Ballia areas have As?>?10 μg/l (WHO guideline). Moreover, 36 % of tubewells from Buxar to Mirzapur areas and 50 % of tubewells from Patna to Ballia areas have As above 50 μg/l. Most of the As-affected villages are located close to abandoned or present meander channels of the Ganga River. In contrast, tubewells located in Mirzapur, Chunar, Varanasi, Saidpur, Ghazipur, Muhammadabad, Ballia, Buxar, Ara, Chhapra, Patna, and Hazipur towns are As-safe in groundwater because of their positions on the Pleistocene Older Alluvium upland surfaces. The iron (Fe) content in tubewell water samples varies from 0.1 to 12.93 mg/l. About 77 % As-contaminated tubewells are located within the depth of 21 to 40 m in the Holocene Newer Alluvium aquifers. The potential source of As in sediments carried through the rivers from the Himalayas. Maximum As concentrations in the Older and Newer Alluvium sediments are 13.73 and 30.91 mg/kg, respectively. The Himalayas rivers, i.e. Yamuna, Ganga, Gomati, Ghaghara, Gondak, Buri Gandak, and Kosi rivers carrying suspended sediments have high content of As (max. 10.59 mg/kg). 相似文献
4.
金属矿区土壤重金属污染的植物修复研究现状 总被引：4，自引：0，他引：4
受矿业活动影响,金属矿区及周边土壤重金属污染已成为严重的环境问题之一。植物修复技术是近年来发展起来的清除土壤中重金属的一种有效、经济的生态技术。重金属污染土壤植物修复技术主要有植物固定、植物挥发和植物吸收等方式,植物固定技术是利用植物阻隔土壤中重金属的迁移,而植物挥发和植物吸收则是将土壤中的重金属移除。本文系统总结了迄今在金属矿区土壤重金属污染的植物固定和植物吸收修复技术研究方面的现状与进展,包括矿区超富集植物筛选、超耐受性植物筛选、提高重金属生物有效性的高效活化剂以及降低重金属迁移能力的化学钝化剂研究等。提出了当前相关领域研究中存在的主要问题,并提出了进一步研究的主要方向。 相似文献
5.
This study assesses the disparity in the level of material wellbeing between the rural and urban areas of various districts of West Bengal. To measure the level of material wellbeing three broad domains comprising of Housing index (HI), Basic Amenities Index (BAI) and Asset Index (AI) following which a composite index (Material Wellbeing Indexi.e. MWI) was computed for the urban and the rural areas for all the districts between the time frame of 2001–2011. A set of 14 sub-indicators were selected for the analysis. This paper takes into account the differentials between the urban and the rural areas of the state. The data was subjected to correlation analysis, ANOVA and PCA, intra-zonal analysis was also performed. The results show the presence of widespread levels of disparity between the various districts as well as within the districts. Over the course of the years this disparity has increased in case of the northern zone however intra and inter zonal disparity runs high. Among the different sub-indicators, BAI has recorded the highest decrease in the differentials whereas the AI has recorded the highest increase in the differentials. Among the districts eight of them have recorded a net increase in the differentials in MWI among which Maldah has recorded the highest decrease in the differentials whereas Dakshin Dinajpur has recorded the highest increase in the differentials.
相似文献6.
7.
Comparison of maps produced from publicly available data (drillers' logs, electrical logs and mine maps) provides a basis for inferring a deep-seated influence on the distribution of superposed deposits of thick coal (>1.4 m) in four Middle Pennsylvania (Desmoinesian Series) coal beds in three mining districts of west-central Indiana. Thick sandstone (>18 m) is common in areas between and around the mining districts, but less than 3 percent of the study area (consisting of 3200 km2) is underlain by both thick coal and thick sandstone. Only thick sandstone associated with the Survant Coal Member (Linton Formation), and informally referred to by us “Survant sandstone”, exists in all of the thin-coal areas. After comparison with published maps by other authors, it is inferred that distribution of the Survant sandstone, which was deposited immediately after a long period of slow deposition associated with the Colchester Coal Member (Linton Formation), may reflect topographic expression of long-term subsidence associated with differential thinning of much deeper Silurian strata (580 m below).Although the findings of this study provide the basis for a conceptual geologic model with a hypothetical structure that is amenable to statistical testing, such analysis should be undertaken only after the data are analyzed for randomness, spatial autocorrelation, linearity and normality. 相似文献
8.
Lionel F. Villarroel Jerry R. Miller Paul J. Lechler Dru Germanoski 《Environmental Geology》2006,51(2):283-299
An intense, but localized rainfall event in February 2003, led to the severe erosion and failure of a tailings disposal impoundment at the Abarόa Antimony Mine in southern Bolivia. The failure released approximately 5,500 m3 of contaminated tailings into the Rio Chilco-Rio Tupiza drainage system. The impacts of the event on sediment quality are examined and compared to contamination resulting from historic mining operations in the headwaters of the basin. Of primary concern are contaminated floodplain soils located along downstream reaches of the Rio Tupiza which were found to contain lead (Pb), zinc (Zn), and antimony (Sb) concentrations that locally exceed Canadian, German, and Dutch guidelines for agricultural use. Spatial patterns in sediment-borne trace metal concentrations, combined with Pb isotopic data, indicate that Pb, Zn, and Sb are derived from three tributary basins draining the Abarόa, Chilcobija, and Tatasi-Portugalete mining districts. Downstream of each tributary, geographical patterns in trace metal concentrations reflect local geomorphic changes throughout the drainage system. Trace metal concentrations within the Rio Chilco decrease rapidly downstream as a result of dilution by uncontaminated sediments and storage of metal enriched particles (e.g., sulfide minerals) in the channel bed as a result of ongoing aggradation. Storage in the floodplains is limited. These processes significantly reduced the dispersal and, thus, the relative environmental affects of tailings eroded from the Abarόa Mine during the 2003 flood. In contrast, storage of Pb, Zn, and Sb in floodplains along the Rio Tupiza is significant, the majority of which is derived from historic mining operations, particularly mining within the Tatasi-Portugalete district. 相似文献
9.
Wuzhen Huiwen Zhang Shiyin Liu Junyin Chen Dachen Tan 《Journal of the Geological Society of India》2018,91(4):457-466
Landslides commonly occurs in hilly areas and causes an enormous loss iof life and property every year. National highway-1D (NH-1D) is the only road link between the two districts (Kargil and Leh) of Ladakh region that connects these districts with Kashmir valley. The landslide failure record of the recent past along this sector of the highway is not available. The present study documents landslide susceptible zones and records occurrence of 60 landslides during the last 4 years showing an increasing trend in the occurrence of landslides over these years in this sector. The landslide susceptibility zonation map has been prepared based on the numerical rating of ten major factors viz. slope morphometry, lithology, structure, relative relief, land cover, landuse, rainfall, hydrological conditions, landslide incidences and Slope Erosion, categorised the area in different zones of instability based on the intensity of susceptibility. The landslide susceptibility map of the area encompassing 73.03 km2 is divided into 150 facets. Out of the total of 150 facets, 85 facets fall in low susceptibility zone covering 43.56 km2 which constitute about 59.65% of the total area under investigation with a record of 5 landslides; 40 facets fall in the moderate susceptibility zone covering 16.94km2 which constitutes about 23.19% of the study area with a record of 20 landslides; and 25 facets fall in the high susceptibility zone covering 12.53 km2 which constitute about 17.15% of the study area with a record of 35 landslides. Most of the facets which fall in HSZ are attributed to slope modification for road widening. 相似文献
10.
The Ohio and Mt. Baldy mining districts near Marysvale, Utah, are situated within a calc-alkalic rock assemblage of the Bullion Canyon Volcanics. The assemblage is divisible into three portions: 1) a lower laharic sequence of epiclastic breccias and autobreccias, 2) a middle portion containing mostly lava flows, including a dacite flow with cupola magma characteristics, and tuff and lapilli breccias, and 3) an upper portion containing a local volcanic vent complex and the ash-flow Delano Peak Tuff Member. Fissuring and veining accompanied magmatic doming. Vein types include: 1) early-stage quartz veins, 2) preproductive main-stage quartz veins, 3) productive main-stage quartz veins, and 4) alunite veins. Each vein of the latter two types is surrounded by advanced argillic, sericitic, argillic, and propylitic alteration halos. Environmental changes during vein fluid deposition account for a district wide zonation of vein types: 1) the boiling level accounts for bonanza precious metal deposits at shallower depths than base metal deposits, and 2) a change from an alkaline or neutral state to an acidic, oxygenated environment, near the paleo-water table, accounts for the presence of alunite veins at shallower depths than ore-bearing veins. Vein mineralogy and texture, wallrock alteration, and geologic structure suggest that an unexposed, ore-generating pluton underlies the area and that the districts represent fringe area mineralization and surface expression of a postulated, ore-bearing pluton. 相似文献
11.
This paper assesses the agricultural land resources of Guiyang City by means of GIS,on the basis of the pressure-state-response model in which soil heavy metal contamination is selected as a pressure indicatror.he results suggest that most of the agricultural land resources are of good quality,However,there are 17.11km^2 dry land and paddy field,which belong to the region of serious heavy metal contamination and are not fit for planting crops.At the same time,the high quality plowland,which is suitable for cultivation,has decreased nearly by 1/3 due to soil heavy metal contamination.These findings may improve our understanding that it is very important to prevent and cure heavy metal contamination of Guiyang City. 相似文献
12.
Tran Tuan Anh I.V. Gas’kov Tran Trong Hoa P.A. Nevol’ko Pham Thi Dung Pham Ngoc Can 《Russian Geology and Geophysics》2012,53(7):623-635
The Pb–Zn deposits in the Lo Gam structure, northeastern Vietnam, account for>80% of all the Pb and Zn resources of Vietnam. All the deposits make up four isolated ore districts (Thai Nguyen, Cho Don, Cho Dien, Na Son), which can be combined in one metallogenic zone extending for >100 km from southeast to northwest. The Pb–Zn deposits in all the ore districts show some similarity to stratiform (Mississippi-type) deposits: confinement to Devonian carbonate sediments; localization at the intersection of faults of different orientations; vein and stockwork (pocket-vein-disseminated) morphology of the mineralized zones; evidence for hydrothermal-metasomatic formation (carbonate-rock marbleization, quartz–carbonate veins, etc.); and low and moderate mineralization temperatures (<250 °C). On the other hand, some differences from stratiform deposits are observed: widespread occurrence of Permo-Triassic igneous rocks in the above ore districts; absent tabular orebodies, which are typical of stratiform deposits; large set of trace elements (In, Bi, Sb, Au, Ag, Cu, Cd) not typical of stratiform deposits; and an endogenic primary source, as evidenced by the isotope composition of sulfur (δS34= 2.68‰), which is close to meteoritic, and the set of trace elements, which are mainly of deep genesis. All this indicates that the above Pb–Zn deposits within the carbonate units are low-and moderate-temperature hydrothermal-metasomatic products associated with active magmatism which took place in this region in the Permo-Triassic.The differences in the mineral composition of the deposits, as well as in the trace-element set and contents at different deposits, clearly indicate an intricate ore formation process and the relation of the deposits with magmatism of different compositions. The simple mineral composition and the limited set of trace elements (Cd, Ag, Sb, As) at the Lang Hich deposit are closer to the characteristics of stratiform deposits. Also, manifestations of magmatism are almost absent here. On the contrary, unusually high (ppm) In (75.8), Sn (307.5), Cu (1080), Ag (157.7), Bi (99), and As (13,650) contents were observed at the deposits of the Cho Don and Cho Dien districts, with widespread granitoid magmatism in the Phia Bioc complex. Rare-earth mineralization (orthite) and high Mo, Re, and Rb contents at the deposits of the Na Son district are probably due to the widespread occurrence of stratified alkaline volcanics and their subvolcanic analogs, which belong to the Pla Ma complex (ξγPZ2 pm). 相似文献
13.
笔者应用因子克里格分析方法,研究了珠江口西部海域388个表层沉积物中7种重金属元素Cd, Ni,Cu,Zn,Pb,Cr和As的空间结构特征,识别并分离了重金属元素不同尺度的空间主成分及其分布特征,探讨了不同空间尺度重金属的物源及控制因素。结果显示,研究区7种重金属元素在空间上存在块金尺度、局部尺度(变程为60 km的球状结构)和区域尺度(变程为160 km的球状结构)3种尺度的空间变化。以迭代算法模拟了研究区重金属元素线性协同区域化模型。根据不同尺度上区域化因子的主成分得分分布特征可知:局部尺度上,F1因子(Zn,Cr,Ni,Cu)和F2因子(As)的高值区表现为"牛眼"状局部特征,并分布在陆地沿海的河口或者港湾区,指示了可能受人为污染成分影响的重金属区域。其中,雷州半岛东部沿海是最可能的重金属污染区,其空间分布主要受控于局部的地形、海流等因素。F2因子不同于F1的空间分布,主要在于As不同于Zn,Cr,Ni,Cu等的地球化学行为。区域尺度上,F1(Zn,Cr,Ni)和F2(As)因子主要反映了不同陆源母岩物质的影响。Zn,Cr,Ni等主要源于华南大陆陆源母岩物质,而As主要受到海南岛陆源母岩物质的控制。F1和F2因子得分高值区整体上表现为NNE向自陆地向较深海域延伸的"片状"分布特征,推测其主要受到海平面变化及NNE向区域性海洋环流的控制。 相似文献
14.
This paper presents a review of the available information on the significant porphyry, epithermal, and orogenic gold districts in Argentina, including the tectonic, geological, and structural settings of large deposits or deposits that have been exploited in the past. Based on this review of the geology and mineralization, targeting models are developed for epithermal and orogenic gold systems, in order to produce GIS-based prospectivity models. Using publically available digital geoscience data, weights of evidence and fuzzy logic prospectivity maps were generated for epithermal and orogenic gold mineralization in Argentina. The results of the prospectivity mapping highlight existing gold deposits within known mineralized districts throughout Argentina, as well as other highly prospective areas with no known deposits within these districts. Additionally, areas within Argentina that have no known gold mineralization (based on publically available information) were highlighted as being highly prospective based on the models used. 相似文献
15.
Survey responses from 76 public school districts in Mississippi and Alabama were analyzed along with county-level demographics, tornado-path data, and tornado warning data to investigate the emerging trend of early dismissals. No two districts had identical responses, but the concern of safety was consistently mentioned. The highest number of reported dismissals would have resulted in a loss of <2 % of total annual class time. The rates of dismissals reported by districts were compared with tornado warning days to identify potential over-dismissal, which was found in 51 % of districts. Rates of dismissal and over-dismissal were analyzed with variables from survey responses, tornado warning data, tornado-path data, and county census data to determine variables that influence differences among districts. Various stepwise models indicate that districts with higher poverty levels could be less likely to dismiss. Permutation tests and stepwise models show that early dismissal and over-dismissal are more likely when a district: (1) has a higher number of killer tornadoes in the last 5 years, (2) has a higher number of recent injury-causing tornadoes, (3) has a higher number of total killer tornadoes since 1950, (4) is in a smaller county, (5) has dismissal decisions made by a team, (6) is a county district rather than a city district, and (7) has a lower level of poverty. The inverse relationship with poverty suggests that schools in poorer areas may be holding students in school because they consider them to be safer there than at home, or it could be due to a lack of resources at the school. All of these are based on a district’s location and plans, things that can be determined before a potential dismissal. These indicators can be used to highlight districts most likely to dismiss and possibly reduce rates of over-dismissal by alerting districts to their predisposed tendencies. 相似文献
16.
Zhen Liu Chunming Liu Dezhi Huang Weijian Zhou Xia Teng 《International Geology Review》2018,60(11-14):1507-1528
ABSTRACTThe Ningwu Volcanic Basin (NVB), located in the Lower Yangtze Metallogenic Belt, is characterized by the widespread occurrence of porphyritic iron-ore deposits. These deposits are clustered in three areas within the basin: the northern, central, and southern districts. Our study shows that the differences are existed in geochemistry of the rocks and the mineralization of the deposits among these three districts. Though results of Sr–Nd isotopes indicate that the parental magma of the sub-volcanic rocks in NVB were derived from EMI and EMII, however, the sub-volcanic rocks from the northern and southern districts have higher εNd(t) values (t = 130 Ma) and lower initial 87Sr/86Sr ratios (t = 130 Ma) than those from middle district. The rocks from northern and southern districts are similar to EMI in geochemistry; in contrast, rocks from the middle district are close to EMII. Meanwhile, the deposits from different districts show some differences in mineralization. The magnetites from the northern ore deposits are rich in Cu, Mo, Zn, and Mg and poor in Ca, Al, and Ti, which probably indicates that the magnetites from the northern ore deposits closer to hydrothermal genesis than to magmatic genesis, but the magnetites from the centre are closer to both magmatic and hydrothermal geneses. Based on the fact that a part of the sub-volcanic rocks is closer to EMI and another part to EMII in geochemistry, we suggested that the incorporation of the lower and upper crustal materials into the source regions of the sub-volcanic rocks has taken place by different manner and processes. Integrated with analysis of the tectonic evolution of NVB, we come to the conclusion that the sub-volcanic rocks have recorded the geochemical imprints of the subduction of Yangtze block towards North China block during Indosinian Period and the delamination of the lower crust of Yangtze block during Yanshanian Period. 相似文献
17.
以长江中下游1∶20万铜区域地球化学数据为基础,研究了铜元素地球化学异常特征,认为不同尺度的地球化学异常图具有不同的研究意义:(1)1∶20万地球化学异常可以圈定矿床异常,用于大型矿床预测。研究区内13个大型矿床中有12个落在具有三层套合结构的地球化学异常中,已知矿床储量与异常面金属量、异常面积之间的相关系数分别为0.94、0.95,显示区域地球化学异常规模与储量之间的较好相关性。(2)1∶50万地球化学异常可以圈定矿区异常,用于在成矿带中预测有利成矿区。(3)1∶100万地球化学异常可以圈定大型矿集区或成矿带,用于矿集区预测。如果把研究区内面积大于1 000km2且含有3个以上已知矿床的异常作为矿集区的话,则长江中下游存在3个大型矿集区:马鞍山—南京矿集区、九江—瑞昌—大冶矿集区和德兴—黄山—安庆—铜陵矿集区(实际上包含德兴和铜陵2个矿集区)。大型矿床多产于多层套合的地球化学异常中,大型矿集区所形成的异常具有至少3层套合结构,浓集中心与大型矿床存在对应关系,这些规律的发现为在不同成矿域预测新的大型矿集区提供了重要地球化学标志。 相似文献
18.
《Applied Geochemistry》2001,16(11-12):1361-1368
Due to rapid urbanisation and scarcity of land, most of the urban parks and recreational areas in Hong Kong are built close to major roads or industrial areas, where they are subject to many potential pollution sources, including vehicle exhaust and industrial emissions. An extensive soil survey was conducted in urban parks of Hong Kong to study the current conditions of heavy metals contamination in soils. Soil samples and associated street dusts were collected from more than 60 parks and public amenity areas in old urban districts, industrial areas and New Towns of the territory. Soils were also sampled in the remote country parks to establish the baseline conditions. The total concentrations of heavy metals and major elements in the samples were determined. The results indicate that urban soils in Hong Kong have elevated concentrations of Cd, Cu, Pb and Zn. The parks with high metal concentrations are located in old urban commercial districts and industrial areas, indicating that the major contamination sources in these soils are traffic emissions and industrial activities. In addition, the application of Cd containing phosphate fertilizers may be an important source of Cd in urban park soils. The street dusts have highly elevated Zn concentration, particularly along the main trunk roads. The high Zn content in the street dusts may come from traffic sources, especially vehicle tyres. Selective soil and road dust samples were also analysed for potential chemical speciation by a sequential chemical extraction method. The chemical partitioning results show that Pb and Zn are mainly in the carbonate/adsorbed and Fe–Mn oxide phases, while Cu is largely associated with the organic and sulphide fractions. The high exchangeable Cd in urban soils and high concentration of Zn in street dusts need further investigation for their ecological and health implications. 相似文献
19.
渤海湾盆地莱州湾凹陷垦利油区沙三上亚段是目前中深层油气勘探开发的重点主力含油层系。综合研究区沉积背景,以三维地震资料、岩心及测井资料为依托,结合地震沉积学研究,开展了垦利油区沙三上亚段辫状河三角洲沉积特征及演化规律研究。结果表明,莱州湾凹陷垦利油区沙三上亚段沉积期,发育以莱北低凸起、垦东凸起及潜在物源区潍北低凸起供源形成的辫状河三角洲沉积体系。研究区辫状河三角洲平原砂体以细—中砂岩为主,前缘砂体以粉—细砂岩为主,分选性中等较好。牵引流性质的沉积构造十分发育,多见生物扰动构造,反映三角洲前缘动荡的水体环境。顺物源方向发育斜交前积反射地震相,垂直物源方向识别出多期丘状反射地震相。综合古地貌、沉积特征及振幅属性切片,明确研究区沙三上亚段以北部物源莱北低凸起供源为主导,沉积中块及沉积东块为主体沉积区,莱北低凸起供源的三角洲呈后退趋势,其展布面积大（95~130 km2）。沉积西块及东块为多物源供给区,来自垦东凸起的三角洲前缘沉积逐渐萎缩,来自潍北低凸起的三角洲区前缘沉积逐渐向湖盆中央推进。上述沉积展布及演化规律为进一步精细勘探开发提供了沉积地质基础。 相似文献
20.
Traditional models of urban development are no longer adequate to describe current metropolitan transformations. These are
now at the centre of a debate concerning management and administration. In Italy, delays in resolving problems of urban and
metropolitan government, despite the legal framework provided by Law 142/90, have weighed heavily on the larger urban areas
of the country: Rome, Naples, Milan, which have not been able to tackle the issue of metropolitan government. Recent legislation,
while not providing a pre-defined institutional solution, allows separate administrative districts to collectively establish
metropolitan institutions of `variable geometry'. The Milan urban area is not one city, but a system of mutually-dependent
cities, linked to each other and the rest of the world by a transport network still requiring much investment. The vitality
of its economic structure (especially its small firms) is held back by seriously inadequate infrastructure and low external
economic efficiency. The provincial capital may boast `historic centrality' but the most interesting potential for development
is to be found on the periphery and in the administrative districts immediately surrounding it, in the recovery of derelict
industrial areas and dormitory towns established in the 1950s and 1960s, especially to the north. Recovery of derelict areas,
green areas, and better transport links within the urban area and with the outside world are the key elements in the reorganization
of `Greater Milan'. In this situation of rapid transformation the most appropriate political strategies involve negotiated
planning.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献