Mesoproterozoic volcanosedimentary units and tectonic events occurring in the Río de la Plata Craton (RPC) are reviewed. A belt consisting of volcanosedimentary successions exhibiting greenschist-facies metamorphism is exposed in the eastern RPC (Nico Pérez Terrane) in Uruguay. The Parque UTE Group consists of basic volcanics and gabbros at the base (1,492?±?4?Ma, U?CPb on zircon), carbonates in its middle part and interbedded carbonates, shales and acid volcanics (1,429?±?21?Ma, U?CPb on zircon) at the top. The Mina Verdún Group is made up of rhyolites and acid pyroclastics at its base and top, and Conophyton-bearing limestones and massive dolostones in the middle. A U?CPb LA-ICP MS zircon age of 1,433?±?6?Ma is reported here for lapilli-tuffs at the base of the Mina Verdún Group (Cerro de las Víboras Formation). This age shows that the Mina Verdún Group immediately postdates the Parque UTE Group, a fact supported by carbon isotope chemostratigraphy. Both units were deformed and metamorphosed between 1.25 and 1.20?Ga, as shown by K?CAr and Ar?CAr ages. This tectonic event affected most of the RPC and led to the accretion of the Nico Pérez Terrane to the remainder of the RPC along the Sarandí del Yí megashear. We report a U?CPb LA-ICP MS zircon age (upper intercept) of 3,096?±?45?Ma for metatonalites of the La China Complex (Nico Pérez Terrane), which yield a lower intercept age of 1,252?Ma. A proto-Andean, Mesoproterozoic belt is envisaged to account for abundant Mesoproterozoic detrital zircon ages occurring in Ediacaran sandstones of the RPC. If the RPC is fringed at both sides by Mesoproterozoic, Grenville-aged belts it is likely that it occupied a rather central position in Rodinia. A possible location between Laurentia and the Kalahari Craton, and to the south of Amazonia, is suggested. 相似文献
As renewable energy, geothermal can contribute substantially to the energy transition. To generate electricity or to harvest heat, high-saline fluids are tapped by wells of a few kilometres and extracted from hydrothermal reservoirs. After the heat exchanger units have been passed by, these fluids are reinjected into the reservoir. Due to the pressure and temperature differences between the subsurface and the surface, as well as the cooling of the fluids in the power plant, unwanted chemical reactions can occur within the reservoir, in the borehole, and within the power plant itself. This can reduce the permeability of the reservoir as well as the output of the geothermal power plant. This study aims to simulate real subsurface reactions using batch and leaching experiments with sandstone or sandstone powder as solid phase, and deionised water or natural brine as liquid phase. It is demonstrated that fluid composition changes after only a few days. In particular, calcite, aragonite, clay minerals, and zinc phases precipitate from the natural brine. In contrast, in particular minerals containing potassium, arsenic, barium, and silica are dissolved. Due to the experimental set-up, these mineral reactions mainly took place on the surface of the samples, which is why no substantial changes in petrophysical properties could be observed. However, it is assumed that the observed reactions on the reservoir scale have a relevant influence on parameters such as permeability.
Since 1740 until now, the Book of Vine Branches encompasses beautiful pictorial representations of shoots and sprouts, collected every year on April 24th in the vineyards of the Hungarian town of K?szeg. A long time series (1740–2009) of sprouts phenological development coded with the BBCH scale is obtained through paintings visual inspection. Consequently, a model relating sprouts development with thermal resources accumulation is developed on the base of Wien daily air temperature series for the 1857–2009 period. Thermal resources is obtained with the Normal Heat Hours approach, a response curve method that takes into account the nonlinear response of phenological development to temperature. The model, calibrated and validated on the 1930–2009 period, shows an overestimation of thermal resources when applied to the 1857–1929, due to the more advanced phenology of that phase. Since this advance can be ascribed to genetics and management instead of more favorable thermal conditions, model outputs previous to 1930 are decreased by a constant factor. Finally, the 1740–2009 time series of grapevine spring thermal resources is obtained applying the model to the complete phenological time series. The analysis of the series highlights a first phase (1740–1780) characterized by high and stable availability of thermal resources during the 1740–1780, a second phase (1781–1820) with the lowest level of resources, a phase of intermediate availability (1821–1929) and a final present phase (1930–2009) with renewed high availability. The adopted method overcomes the lack of correlation for the post 1960 period shown by previous works. 相似文献
Selenium is a chemical element with major environmental implications, due to the extremely narrow range between essential and toxic concentrations. Volcanoes emit significant amounts of Se, which has an enormous impact on the Se cycle and potentially human and animal health. This paper presents a broad overview of the current state of knowledge of major aspects of volcanic derived Se, focussing on the processes in soils and aquifers. 相似文献
The cosmic ray modulation in the period 1965–70 is investigated by the comparison of the intensity data of groundbased stations with different response to primaries. The socalled step-like modulation, already observed by other authors, is found to be produced by the overlapping between the quasi-stationary solar cycle modulation and the Forbush decrease events. Moreover a good correlation between the cosmic-ray variance (Forbush decrease index) and the 5303 coronal intensity at middle heliolatitudes (17.5°–42.5°) is found, while the quasi-stationary solar cycle modulation is well correlated with the 5303 intensity near the solar equator (0°–17.5°). The different time behaviour of the solar activity at different heliolatitudes causes the step-like modulation. 相似文献
Transtensional basins are sparsely described in the literature compared with other basin types. The oblique‐divergent plate boundary in the southern Gulf of California has many transtensional basins: we have studied those on San Jose island and two other transtensional basins in the region. One major type of transtensional basin common in the southern Gulf of California region is a fault‐termination basin formed where normal faults splay off of strike‐slip faults. These basins suggest a model for transtensional fault‐termination basins that includes traits that show a hybrid nature between classic rift and strike‐slip (pull‐apart) basins. The traits include combinations of oblique, strike‐slip and normal faults with common steps and bends, buttress unconformities between the fault steps and beyond the ends of faults, a common facies pattern of terrestrial strata changing upward and away from the faults into marine strata, small fault blocks within the basin that result in complex lateral facies relations, common Gilbert deltas, dramatic termination of the margin of the basin by means of fault reorganization and boundary faults dying and an overall short basin history (few million years). Similar transtensional fault‐termination basins are present in Death Valley and other parts of the Eastern California shear zone of the western United States, northern Aegean Sea and along ancient strike‐slip faults. 相似文献