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81.
The environmental risk posed by small dumps of complex arsenic,antimony, nickel and cobalt sulphides
Mine waste dumps sited in the vicinity of mine workings typically consist of fragmented rock masses which in chemical terms may be defined as "complex systems", due to uncertainties in accurately simulating their behaviour, when water or aqueous solutions percolate through them. Remediation of the contamination problems created by abandoned mine dumps concerns many former mining areas from Europe to Africa. These dumps usually range in size from a few hundred thousand up to million cubic meters of rock defined as “waste” but which still contain significant amounts of potentially toxic elements. Although relatively small, they are often densely distributed in the territory impacting on surface and ground-water. This scenario is particularly applicable to the region of Sardinia, Italy, where several small dumps of uncommon sulphide minerals still exist on derelict mine sites. This paper reports on the results of a research project aimed at defining appropriate remedial measures of acid rock drainage. A dump of a Co–Ni–As–Sb complex sulphides mine was investigated and simulated in a laboratory leaching column. The column was irrigated with distilled water and a repetitive behaviour of the polluting elements concentrations in the effluents was observed for each run. Regardless of the campaign duration and the extent of the intervals between tests metal ions concentration peaks (250–50 ppm for Ni, 35–20 ppm for Co, 1.6–0.4 ppm for As, 20–15 ppm for Zn and 0.03–0.002 ppm for Sb) and acidic conditions (pH 2.5–3.5), on resumption of each irrigation, was noticed. As percolation continued, the ion concentrations decreased within the discharge limits after the replacement of only two pore volumes of the column material. This produces the conception that a sufficiently long rainfall period could remediate the polluting effects. Conception contradicted by field experiences: sporadic rainfall events, typical of the region, are not sufficient to completely leach out the metal ions. The repetitive nature of the leaching processes, both quantitatively and qualitatively, can be explained only by the activity of a microflora thriving in the rock mass even during long dry periods. Microbial tests and neutralisation campaigns confirmed this hypothesis and suggested that any effective remediation strategy must take into consideration the interaction between environmental factors with microbiological activities. 相似文献
82.
Patterns of basin fill in Triassic turbidites of the Nanpanjiang basin: implications for regional tectonics and impacts on carbonate‐platform evolution 下载免费PDF全文
Daniel J. Lehrmann Daniel H. Chaikin Paul Enos Marcello Minzoni Jonathan L. Payne Meiyi Yu Alexa Goers Tanner Wood Paula Richter Brian M. Kelley Xiaowei Li Yanjiao Qin Lingyun Liu Gang Lu 《Basin Research》2015,27(5):587-612
The Nanpanjiang Basin occurs in a key position for resolving controversies of basin tectonics and patterns of plate assembly at the junction between south China and Southeast Asian plates. Paleocurrent measurements indicate that siliciclastic turbidites in the basin were sourced by the Precambrian Jiangnan uplift to the northeast, the Precambrian Yunkai uplift to the southeast and the Triassic Songma suture to the south. Detrital zircon geochronology reveals Archean (2500 Ma), Paleoproterozoic (1800–1900 Ma), Neoproterozoic (900–1000 Ma) and Paleozoic (420–460 Ma) ages consistent with derivation from the Jiangnan and Yunkai uplifts. A large Permian‐Triassic peak of 250 Ma is present in the southern basin and attenuates northward suggesting derivation from an arc developed along the Songma suture. Sandstone QFL compositions average 65/12/23% and plot in the recycled orogen field except for a few samples in the southern basin that fall in the dissected arc field. The compositions are consistent with derivation from Precambrian basement that includes orogenic complexes. In the southern basin, Middle Triassic turbidites contain greater lithics and feldspars and Lower Triassic turbidites have volcaniclastic composition consistent with derivation from a southerly arc. Our preferred interpretation is evolution from remnant basin to a large peripheral foreland with southward subduction and convergence with Indochina along the Songma suture. The previously proposed Dian‐Qiong zone is not a suture as its map location places it within carbonate platforms bounded by identical stratigraphy. The Nan‐Uttaradit zone is too distant to have provided voluminous siliciclastic flux to the basin. The Nanpanjiang Basin provides an example of the evolution of an exceptionally large foreland with far‐field rejuvenation of Precambrian uplifts and carbonate platforms that were significantly influenced by siliciclastic flux. The timing and pattern of turbidite basin fill impacted platform evolution by enabling margin progradation in areas proximal to siliciclastic sources, whereas platforms distant from sources were driven to aggradation and extreme relief with large‐scale gravitational sector collapse. 相似文献
83.
84.
Ocean Dynamics - The sea level observations from satellite altimetry are characterised by a sparse spatial and temporal coverage. For this reason, along-track data are routinely interpolated into... 相似文献
85.
86.
Anticlockwise pressure–temperature paths record Variscan upper‐plate exhumation: Example from micaschists of the Porto Vecchio region,Corsica 下载免费PDF全文
Hans‐Joachim Massonne Gabriele Cruciani Marcello Franceschelli Giovanni Musumeci 《Journal of Metamorphic Geology》2018,36(1):55-77
To better understand the evolution of deep‐seated crust of the Variscan orogen in the Sardinia‐Corsica region, we studied garnet‐bearing micaschists which were sampled 3 km east and 15 km northeast of Porto Vecchio, south‐eastern Corsica. After a careful investigation of the textural relations and compositions of minerals, especially of zoned garnet, a P–T path was reconstructed using contoured P–T pseudosections. U–Th–Pb dating of monazite in the micaschists was undertaken with the electron microprobe. The micaschists from both localities were formed along similar anticlockwise P–T paths. The prograde branch of these paths starts at 3 kbar close to 600°C in the P–T field of sillimanite and reaches peak conditions at 7 kbar and 600 (15 km NE of Porto Vecchio) to 630°C (3 km E of Porto Vecchio). The metamorphism at peak P–T conditions happened c. 340 Ma based on low‐Y (<0.65 wt% Y2O3) monazite. Ages of monazite with high‐Y contents (>2 wt% Y2O3), which probably have formed before garnet, scatter around 362 Ma. The retrograde branch of the P–T paths passes through 4 kbar at ~550°C. We conclude that the micaschists belong to a common metasedimentary sequence, which extends over the Porto Vecchio region and is separated from other metamorphic rock sequences in the north and the south by major tectonic boundaries. This sequence had experienced peak pressures which are lower than those determined for metamorphic rocks, such as micaschist and gneiss, from north‐eastern Sardinia. At present, we favour a continent–continent collisional scenario with the studied metasedimentary sequence buried during the collisional event as part of the upper plate. The contemporaneous high‐P metamorphic rocks from NE Sardinia were part of the upper portion of the lower plate. The addressed rocks from both plates were exhumed in an exhumation channel. 相似文献
87.
88.
Raymond E. Arvidson Marcello Coradini A. Carusi A. Coradini M. Fulchignoni C. Federico R. Funiciello M. Salomone 《Icarus》1976,27(4):503-516
Wind erosion seems to be the dominant process eroding crater ejecta deposits and sorrounding materials on Mars. In the equatorial zone, ejecta deposits are eroded back by scarp recession, where scarp heights appear to be approximately equivalent to ejecta thickness. In mantled areas, escarpments develop by relatively rapid deflation of sorrounding aeolian debris, leaving the ejecta deposit (continuous deposit and zone of high density of secondary craters) standing high above sorrounding terrain. If the rate of scarp recession is controlled by the rate of aeolian undercutting of escarpment bases, then recession rates may scale roughly as the inverse with respect to scarp height. Thus, preferential preservation of ejecta deposits emplaced in thickest aeolian debris may occur. An empirical model developed for wind erosion of ejecta deposits in nonmantled areas suggests that removal of ejecta materials on the average is exceedingly slow (~10?5m/yr for 10m high scarp). On the other hand, rapid deflation of aeolian debris around crater ejecta is implied. Results suggest high differential aeolian erosion rates that are a function of both grain sizes and large-scale surface roughness. Aeolian activity on Mars has probably been dominated by rapid recycling of fine-grained debris, the bulk of which formed under more erosive conditions prevalent in the early history of Mars. 相似文献
89.
Marcello Carapezza P. Mario Nuccio Mariano Valenza 《Meteoritics & planetary science》1976,11(3):195-205
The fall occurred near Piancaldoli, Florence, Italy, at 19.14 U.T. on the 10th August 1968. The fireball broke up in the atmosphere producing a cloud like a balloon. The trajectory and the terminal point were calculated, leading to the recovery of three small meteoritic fragments, found on the roof of a house. Chemical analysis gave the following results: SiO2 40.80; TiO2 0.15; Al2O3 2. 70; Cr2O3 0.47; FeO 17.20; MnO 0.07; MgO 25.18; CaO 1.95; Na2O 0.64; K2O 0.07; P2O5 0.20; NiS 0.93; FeS 6.24; Fe° 2.40; Ni° 0.40; Co 0.05; sum 99.45. In the lithic portion of the meteorite the following minerals were found: both clino and orthopyroxenes (En = 76 to 98%), olivines (Fo = 66 to 98%), troilite, pyrrhotite, pentlandite, kamacite, ilmenite, apatite, merillite, schreibersite, chromite and Henderson phase. From all the mineralogical and petrological data, we conclude that the Piancaldoli meteorite is an “unequilibrated ordinary chondrite,” LL3. The microbrecciated structure of the rock and some shock features were observed, while the rock as a whole is unshocked, suggesting that these features were caused by impact events which took place during the accretion of the parent body. 相似文献
90.
Pino González-Riancho Marcello Sanò Raúl Medina Oscar García-Aguilar Jurgi Areizaga 《Ocean & Coastal Management》2009,52(11):545-558
The purpose of this paper is to assess the level of implementation of Integrated Coastal Zone Management (ICZM) principles in the Mediterranean developing countries at the moment of signing the protocol on ICZM for the Mediterranean, in the framework of the UNEP Mediterranean Action Plan of the Barcelona Convention. This assessment is based on the results of two advanced seminars on ICZM promoted by the Azahar programme of the Spanish Agency for International Cooperation for the Development (Ministry of Foreign Affairs and International Cooperation). The contribution of the participants of the seminar, who are representatives of national agencies related with ICZM in different Mediterranean countries, have been collected through a questionnaire including: (i) a ranking of the main coastal sectors and the main coastal issues of each country; (ii) significant initiatives for the sustainable development of the Mediterranean coastal zones; and (iii) the evaluation of the ICZM progress. The state of the coast, the level of implementation of ICZM and the main problems faced to apply it, have been detected for each country. None of the consulted countries have a full implemented integrated coastal zone management, the major problems being: (i) the lack of financial commitment for the implementation of ICZM; (ii) the lack of an assessment and monitoring system; (iii) the lack of knowledge regarding the coastal system; (iv) the lack of qualified human resources; and (v) the lack of public participation and administrative integration strategies based on information. From these conclusions, some recommendations to improve ICZM are also provided. The work presented in this paper is the starting point to assess the evolution and the reference from which ICZM will be improved through the protocol on ICZM for the Mediterranean. 相似文献