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Geothermal systems in terrains affected by polyphase deformation have reservoirs with a 3D geometry that is always difficult to predict. In this paper we describe a fossil exhumed geothermal system exposed in eastern Elba Island that developed in a polyphase folded and faulted setting, which can help us to understand how geothermal fluids circulate in geological bodies with inherited structures. Geothermal circulation at Elba allowed the deposition of Fe-ore deposits (haematite/magnetite and pyrite) and altered rock volumes, which represent tracers of the palaeo-fluid flow. Normal and oblique-slip faults dissected a polyphase folded metasiliciclastic succession and produced a secondary permeability in the range of 5 × 10−13 to 5 × 10−16 m2. From the permeable fault zones acting as feeder conduits, geothermal fluids permeated the hydraulically connected metasiliciclastic rock bodies previously deformed by two generations of folds. Geothermal fluids followed the already defined geometry, thus giving rise to apparent folded mineralized levels. Fluid migration into the metasiliciclastic rocks was possible due to their chemical aggression, which favoured the dissolution and reprecipitation of quartz, and Fe-oxide and sulphide deposition. Renewed fluids maintained their chemical properties (pH value and temperature, mostly). This conclusion provides inputs for reconstructing geothermal conceptual models and evaluating the geothermal potentiality of exploitable areas developing in similar geological settings.

The North Huicheng Basin strike-slip fault system is on the northeastern frontier of the Tibetan Plateau and separates the West and East Qinling differential orogeny. However, the deformation mechanism of this strike-slip fault system and its exact tectonic significance are unclear. Here, we carried out systematic field structural analysis, physical analog modeling, and multiproxy geochronological dating to address these issues. The field structural analysis indicates that the North Huicheng Basin strike-slip fault system was induced from the plate-like movement of the West and East Qinling Orogens, which underwent multiple left-lateral strike-slip faulting and controlled salient and recessed structures. The scaled physical analog experiment results confirm this hypothesis and reveal the primary spatial-temporal deformational kinematic process. Combined with published works, multiproxy geochronological dating (zircon U-Pb age of 213 Ma, biotite 40Ar/39Ar age of 203 Ma, and apatite fission-track age of 56 Ma) outlines the main thermal history of the hanging wall. Based on the above facts, the integrated research suggests that multistage strike-slip faulting played a significant role in the main tectonic events, that is, Late Triassic magmatic emplacement, Jurassic/Cretaceous local pull-apart, and Cenozoic rapid exhumation driven by Tibetan Plateau growth.

The aim of the present study was to determine paleogeographic and paleogeodynamic features of sedimentogenesis of sandstone-siltstone associations of upper Paleoproterozoic of Kryvoy Rog iron ore basin based on lithochemical data. The main tasks were to investigate the lithochemical structure of the geological data, reconstruct the source mineral composition of metase-dimentary rock, and compare the results with non-metamorphosed analogs. Multivariate statistic methods for clustering the data were employed, including the principle of serial comparison with non-metamorphosed analogs by a number of lithochemical coefficients and diagrams. Metasedimentary formations of Gleevatsky suite of Kryvoy Rog iron ore basin were attributed to poorly differentiated sub-greywacke and greywacke sandstone-siltstone rock association, which is characterized by intermediate petrochemical parameters between humid and arid terrigenous Phanerozoic series. Sedimentation was formed due to erosion of protolytes of plagiogranitoids of Archean base and earlier sediments of Paleoproterozoic cover. Research contribute to improving lithochemical systematic of metasedimental rocks of Krivoy Rog iron ore basin.