Hematite (U-Th)/He constraints on Plio-Pleistocene deformation and hydrothermalism in the eastern Island of Elba, northern Apennines (Italy)

<p>The northern Tyrrhenian Sea and the inner northern Apennines (NA) are classically regarded as a late Miocene–Pleistocene back-arc system characterized by crustal extension and acidic magmatism coeval with shortening farther east at the front of the belt. The orogenic prism of the NA, which is well exposed in the easternmost Island of Elba, formed by eastward thrusting, stacking and folding of oceanic and continental units from the Eocene down to the late Miocene. Eastern Elba hosts the historically and economically most important Fe district of Italy, which, in the study area, consists of sulphide- and Fe-rich veins and breccias, in addition to minor massive Fe ore bodies of hydrothermal origin emplaced in actively deforming upper crustal conditions (Mazzarini et al., JSG, 2019). The Zuccale fault (ZF) on Elba is generally interpreted as a major normal fault, which would have greatly facilitated regional E-W extension during the late Miocene. It is an east-dipping low angle fault that displaces the nappe pile by up to 6 km. The fault architecture is complex, although it can be approximated by an exclusively brittle, flat-lying component dated to < c. 5 Ma by K-Ar on illite from fault gouge that cuts through steeper, brittle-ductile and earlier top-to-the E thrust related fabrics (Viola et al., Tectonics, 2018).</p><p>Aiming at directly constraining the syn- to post Pliocene evolution of the ZF and the age of the hydrothermal Fe deposits of the historic mining district, we performed hematite (U-Th)/He dating of the low-angle, hematite-decorated principal slip surface of the ZF at the famous Terra Nera section. Hematite samples examined in this study comprise platelet-shaped crystals (specularite), fine aggregates coating fault slip surfaces, massive veins, the fine matrix of breccias, and euhedral millimetric crystals from low strain domains. Ages from the ZF striated fault plane span the ~4.2±0.4 to 3.6±0.4 Ma time interval, fully consistent with available fault gouge illite K-Ar dates. Later NNE-SSW strike-slip faulting, associated with centimetric specularite veins, is constrained to between 2.1±0.2 and 1.7±0.2 Ma, roughly coeval with transient and local reactivation of the ZF as indicated by 1.9±0.2-1.5±0.2 Ma old euhedral, millimetric hematite infilling dilational jogs within the foliated ZF fault zone. Farther north, in the Rio Albano area, mineralised hematite breccias genetically associated with top-to-the E spectacular extensional faults are dated to between 1.6±0.2 and 0.9±0.1 Ma and postdate older ~2.7-2.6 Ma quartz-hematite veins associated with a discrete phase of top-to-the W shearing.</p><p>All obtained dates fit our independently built structural model of the investigated area, where clear crosscutting relationships and structural/metamorphic considerations have permitted establishing a sequence of kinematically constrained deformation events. For the first time we have defined the exact timing of deformation in the study area, contributing to the unravelling of the local, long and complex tectonic and mineralization history and to a better constrained regional picture.</p>

Neighborhood relation diagrams for local comparison of carbon footprints in urban planning

The dreaded effects of climate change have led to a new research focus in many applications. In urban planning, the visualization of carbon footprints has become one of the most sought after aspects. Urban planning data of carbon footprints contains spatial (location) and abstract (statistical indicators) information. Although many techniques for the visualization of such partially spatial data have been successfully applied in the area of geovisualization, the core focus has been on a global depiction of non-spatial information. However, conducting local comparisons, as in the case of comparing neighborhood districts and households, is of particular importance in investigative tasks. Additionally, representing different carbon footprint indicators (multiple non-spatial parameters) and unstructured parameter values (resulting in scaling issues) in a static representation provides an interesting challenge for visualization. This paper describes a novel and generic solution to the above-mentioned issues: a neighborhood relation diagram for the local comparison of non-spatial information in partial spatial data. The technique is based on the geometric computation of Voronoi diagrams according to a weighted neighborhood metric. The shape of spatial regions (e.g. city districts) within this diagram is characterized by a directed and constrained deformation according to the non-spatial (i.e. carbon footprint) relations to neighboring regions. The effectiveness of our method is highlighted in a preliminary study of carbon footprint patterns in downtown Phoenix (Arizona, USA). In this study, neighborhood relation diagrams enable city planners to detect local effects on carbon emissions and their relation to planning projects.

Mechanics Model of Stress Compute on Contract Deformation of the Concrete’s Foundation Mat

It is a knotty problem in the actual project, that contraction deformation produce stretching stress on the concrete engineering. To counter deformation characteristic of the large-scale concrete foundation mat in construction temperature field,this paper has put a complete set of compute mechanics model of stress analysis and influence limits of constrained deformation on the basis of Saint-Venant’s principle. A number of computing formulas were inferred with theory of materil mechanics and structural mechanics,so that have obtained a set of analysis methods.By theory analysing and computing an actual project, it was that compute result accorded with structure law and the seat of compute crack was identical with cracking seat of the actual project.So, the achievement has the same values about the theory and the engineering application.