The Cauvery Shear Zone (CSZ) is a crustal-scale shear system within the Southern Granulite Terrain along the southern margin of the Archaean Dharwar craton. Structural interpretation of satellite data and field observations reveal four major shear zones within the CSZ system. They show dextral shear kinematics synchronous with a major Neoproterozoic tectono-metamorphic event (D2) associated with intracrustal melting and migmatisation. The disposition, geometry and contemporaneity of shear fabrics of the CSZ system are modelled in terms of a crustal-scale flower structure akin to transpressional and collisional orogens. In the light of recent seismic evidence for a displaced Moho structure and a mid- to lower-crustal low velocity zone, the flower structure across the CSZ may extend to mantle depths. 相似文献
Multi-equilibrium thermobarometry shows that low-grade metapelites (Cubito-Moura schists) from the Ossa–Morena Zone underwent HP–LT metamorphism from 340–370 °C at 1.0–0.9 GPa to 400–450 °C at 0.8–0.7 GPa. These HP–LT equilibriums were reached by parageneses including white K mica, chlorite and chloritoid, which define the earliest schistosity (S1) in these rocks. The main foliation in the schists is a crenulation cleavage (S2), which developed during decompression from 0.8–0.7 to 0.4–0.3 GPa at increasing temperatures from 400–450 °C to 440–465 °C. Fe3+ in chlorite decreased greatly during prograde metamorphism from molar fractions of 0.4 determined in syn-S1 chlorites down to 0.1 in syn-S2 chlorites. These new data add to previous findings of eclogites in the Moura schists indicating that a pile of allochtonous rocks situated next to the Beja-Acebuches oceanic amphibolites underwent HP–LT metamorphism during the Variscan orogeny. To cite this article: G. Booth-Rea et al., C. R. Geoscience 338 (2006).相似文献
From July 1996 to August 1997 the TOR project operated 130 seismographs in North Germany, Denmark and South Sweden, with the aim of collecting signals from local, regional and teleseismic earthquakes. This data set is particularly interesting since the seismic antenna crosses the most significant geological boundary in Europe, the Tornquist Zone, which in the northern part is the border between the Baltic Shield and the younger European lithosphere. Previous studies have shown significant physical changes in the crust and upper mantle across this transition zone, including two independent teleseismic tomographic studies of the TOR data set. But these two studies disagree on the orientation of the slope of the transition. Both studies used an iterative linearized inversion method. We will in this work Preprint submitted to Elsevier Science 27 July 2005 present an inversion based on Bayesian statistics, where the solution space is examined in order to study a very large number of tomographic solutions and to examine the solution uniqueness and uncertainty. The method is applied to measurements of 3345 relative teleseismic P-phase travel times from 48 teleseismic earthquakes with good azimuthal coverage with respect to the great circle arc of the TOR array. We find the lithospheric transition to be a north east inclination of around 30° to 45° off vertical. 相似文献
Twenty-nine water samples were collected from different river channels of the Pearl River Delta Economic Zone, China. An inductively
coupled plasma-mass spectromonitor (ICP-MS) was used to measure concentrations of the trace elements in these samples. The
results suggest that the average concentrations of rare earth elements in river water show an increasing trend from the West
River, the North River, the rivers of the Pearl River Delta, and the Shenzhen River to the East River. Relatively high concentrations
of heavy metals appear in the East River, the rivers of the Pearl River Delta and the Shenzhen River, while the West River
and the North River have relatively low heavy metal concentrations. Trace element concentrations in samples collected near
urban or industrial areas are much higher than those of samples collected from distant areas, away from urban and industrial
areas. After natural conditions, human activities have significant influence on the trace element concentrations in river
water. This trace element concentration’s spatial distribution in the river water from the Pearl River Delta Economic Zone
is actually an integrated effect of natural conditions and human activity. 相似文献
As a result of the collapse of the Aznalcollar mine tailings dam, a large extension of the Guadiamar valley in SW Spain was covered with a layer of pyrite sludge. Although most of the sludge was removed, a small amount remains in the soil, constituting a potential source of water pollution. A column experiment was carried out in order to determine the rate of sludge oxidation in the soil, and the existence of metal retention processes. The column was filled with a mixture of sludge and a sandy soil common in the region. At different time intervals, the column was leached with water and the resulting solution analysed.
The pH of the water dropped to values around 2 after 260 days and then remained constant due to the buffering role of silicate dissolution. The concentration of Zn, Cd and Co in the leachates matched the expected values from flow-through experiments at atmospheric oxygen pressure. This indicates that oxygen diffusion in the pores was complete. Moreover, no efficient processes existed for retaining Zn, Cd and Co, which formed soluble salts and were entirely incorporated into the infiltrating water. During the first 2 months of the experiment, when pH was higher than 4.5, the concentrations of Fe and Al were very low. Saturation indices showed that the solution was in equilibrium with amorphous Fe(OH)3 and Al(OH)3. Subsequently, at lower pH values, jarosite [(Na,K)Fe3(SO4)2(OH)6] formed. This solid phase was identified by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). Jarosite was also responsible for the depletion of As, Pb, Sb and probably Tl in the water resulting from infiltration. 相似文献