Cation export by overland flow in a recently burnt forest area in north-central Portugal
Ana Isabel MachadoDalila SerpaR.V. FerreiraM. L. Rodríguez‐BlancoRosana V. PintoMaria Isabel NunesMário CerqueiraJan Jacob Keizer
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The Wepawaug Schist, part of the Orange Milford Belt of southern Connecticut, consists dominantly of micaceous phyllites and schists. A progression in metamorphic zonation from chlorite through kyanite grade occurs within 3 km. There were previously no constraints on either the depositional age of the Wepawaug Schist or the time of metamorphism. Concordant U-Pb sphene ages of 457 [+-] 3 Ma for the Woodbridge granite, which cuts the Wepawaug Schist, mean that the metapelites are older than late Ordovician. Kyanite grade rocks contain two distinct monazite populations within a single outcrop: (1) Crystals from a graphitic schist are clear, round, and xenoblastic. They have [approximately]0.9 wt.% Th, Sm/Nd = 0.12--0.14, and display pronounced chemical zonation. These give normality discordant U-Pb ages that define an upper intercept age of 420 [+-] 12 Ma. (2) In a less graphitic schist they are light yellow, idioblastic, tabular crystals that cut muscovites. They have Sm/Nd = 0.16 and [approximately] 2.6 wt.% Th and give concordant U-Pb ages of 377 [+-] 3 Ma. The authors suggest that the Wepawaug Schist is older than 457 Ma and was affected by two events which resulted in monazite growth, one during the Middle Devonian (377 Ma) and onemore » in the Late Silurian (420 Ma).« less
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In the present paper, from the geological and geomorphological standpoints we discuss the landslides in the Sambagawa metamorphic belt in the Kawai area, the central part of Tokushima prefecture, which is one of the most famous landslide areas in Japan.In this area, the Sambagawa metamorphic belt is widely ditributed and its stratigraphic sequence in ascending order is as follows:Kashidaira formation; mainly composed of pelitic schist intercalated with basic schist, siliceous schist and calcareous schist.Nonowaki formation; mainly composed of pelitic schist and siliceous schist intercalated with basic schist.This belt is in contact on the south with the Mikabu green rocks or the Kenzan group, the Chichibu Palaeozoic formation, and by the Akui river fault or the Mikabu tectonic line.A large number of landslides in the area occur in the Sambagawa metamorphic belt. Their characteristics can be summarized as follows:(1) Most of the landslides occur in the pelitic schist area, and rarely occur in the siliceous schist area.(2) A sliding body is mainly composed of debris deposites derived from the basement schists.(3) Let θ denote the angle on a horizontal plane between the sliding direction of a landslide and the dip direction of a bedding schistosity plane. Then, most of the landslides move within the range 0°≤θ<90°, and are referred to as the “nagareban” structure type. The landslides within the range 0°≤θ<30° occur in the largest number, and the landslides within the range 60°≤θ<90° have the second highest frequency. On the other hand, there are a small number of landslides moving within the range 90°<θ≤180°, which are of the “ukeban” structure type.(4) The landslides belonging to the “nagareban” structure type are generally large in scale, but the landslides belonging to the “ukeban” structure type are generally small in scale.(5) The slope angles in the area are determined by the Horton method. The slopes in the landslide areas generally range between 25° and 30°, irrespective of the lithofacies of the basement schists.(6) The pelitic schist area often forms slopes of 25° to 30° in slope angle. On the other hand, in the siliceous schist area the slope angles are 35° to 50°, in general. Consequently, from the discussion of slope angle it is concluded that the pelitic schist area has many hazardous slopes appropriate for landslide activity.
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The Ehime mine is situated about 5., 5km to the south of Niihama., Crystalline schists of the Sambagawa Group outcrop in the district., The crystalline schists of the district are composed of black-schists, originated from argillaceous rocks, sandstone-schists, derived from arenaceous rocks, siliceous schists from quartzose rocks, and green-schists, accompanied by serpentinite., The schistosity planes generally coincide with the original planes of stratification, and they dip mainly to the north., The crystalline schists can be divided litbologically into four formations, as tabulated below in the seemingly descending order., Formation Component rocks S Sandstone-schist and black-schist, interbedded with thin beds of green-schist and siliceous schist., R Black-schist, sandstone-schist, and five beds of conspicuous green-schist with siliceous schist., Q Mainly composed of black-schist., P Thick beds of green-schist, intercalated with thin beds of black-schist and siliceous schist., Structurally, areas may be divided into several blocks, among which the block composed of formation P, and the block formed by formations R and S, are discontinuous., The former belongs to the northern wing of the Sasagamine-Kampuzan anticline, while the latter is the block thrust over the former from the north., Formation Q should be interpreted as the shear zone between these two blocks., The Ehime ore body is deposited in the lowest part of the overthrust mass and is conformable to the foliation planes of the siliceous schist, which extends E-W., Albite porphyroblasts or spots are generally developed in formations R and S, but the spots are not uniform in size throughout the block., The heterogeneous development of spots might have been related to the heterogeneity of the original rock and differences in the amount of deformation., The albitization related to the formation of albite spots was controlled by the modes of deformation and by tectonic transport of the different parts of the deforming block at some stage in the process of the metamorphism of the crystalline schists., Albite spots were enriched in the parts of least componental differential movement., Metasomatizing agents moved through the passage which was formed in the parts of strong componental differential movement.,
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The main purpose of this contribution is to increase the knowledge of the geological resources of “Tras-os-Montes e Alto Douro” (TMAD) region, in particular of it “Schist” (slate, phyllite, Schist and quartzite), considering its economic and social impact. The target area is characterized by the abundant occurrence of different types of “Schist”, from the Hercynian basement, belonging to Galiza Tras-os-Montes Zone (GTMZ) and to the Central Iberian Zone (CIZ). The main outcome of this work was to improve the knowledge about mineralogy, fabric, chemistry and technology of the “Schist”, which can promote their exploitation and use as a natural stone. It was possible to identify the main factors that have an influence on the mechanical behaviour of the schists, conditioning their use as natural stone. This work also contributed to increase the knowledge about lithology and it allowed to show how the relationship between the metamorphic grade and the deformation intensity have a great influence on the stone properties and consequently on the type and size of the exploration site.
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Northwest Hubei province is located in Mount Wudang metamorphic zone, where the geological conditions are very complex. The carbonaceous schist is relatively rare in this area, however, compared with other schists, it has some quite special characteristics. This paper focuses on lithologic features, physical and mechanical characteristics of carbonaceous schist, and Huashigou tunnel is researched as the engineering background. Analysis of carbonaceous schist shows that it has typical rheological, anisotropic and water-sensitive properties. Through a large number of monitoring measurement data analysis, deformation law of carbonaceous schist are summarized.
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Crystalline schists in the district consist of sandstone-schists, black-schists of pelitic origin, green-schists of basic tuff and lava origin, and quartz-schists of chert origin., The formation of crystalline schists in the district is tabulated in the descending order as follows : Minawa formation comprises four beds of green-schists anb two beds of sandstone-schists; the other members are pinkish quartz -schists, and black-schists 1000∼300Om., Koboke formation is mainly sandstone-schists inter-bedded with black-schists and green-schists 300∼50Om., Kawaguchi formation is mainly composed of black-schists, interbedded with green-schists 100∼200m., Oboke formation almost exclusively consists of sandstone-schists 30∼50m., The ore-deposit of the Shingu Mine lies in the lowermost, non-spotted green-schists of Minawa formation., The ore-deposit is a "Kieslager" in type, having a pole-like form., The foot-wall of the ore body is green-schists, characterized by the presence of quartz, carbonate and hematite, and the hanging-wall is massive green-schists, characterized by the abundance of epidote, and parallel seams or veinlets of hamatite-quartz, chlorite, stilpnomelane, magnetite., In the green-schists near the contact with ore bodies are impregnated granules or pyrite and chalcopyrite, forming sinuated seams., The axis of sinuation coincides with that of the lineation of green-schists.,
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In a paper published some eight years ago, Prof. T. G. Bonney discriminated between the dominant characteristics of quartz schists from the Alps and quartzites modified by pressure. The distinctions as therein pointed out may be thus summed up.
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