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Deep sea cold seeps are sites where hydrogen sulfide, methane, and other hydrocarbon-rich fluids vent from the ocean floor. They are an important component of Earth's carbon cycle in which subsurface hydrocarbons form the energy source for highly diverse benthic micro-and macro-fauna in what is otherwise vast and spartan sea scape. Passive continental margin cold seeps are typically attributed to the migration of hydrocarbons generated from deeply buried source rocks. Many of these seeps occur over salt tectonic provinces, where the movement of salt generates complex fault systems that can enable fluid migration or create seals and traps associated with reservoir formation. The elevated advective heat transport of the salt also produces a chimney effect directly over these structures. Here, we provide geophysical and geochemical evidence that the salt chimney effect in conjunction with diapiric faulting drives a subsurface groundwater circulation system that brings dissolved inorganic carbon, nutrient-rich deep basinal fluids, and potentially overlying seawater onto the crests of deeply buried salt diapirs. The mobilized fluids fuel methanogenic archaea locally enhancing the deep biosphere. The resulting elevated biogenic methane production, alongside the upward heat-driven fluid transport, represents a previously unrecognized mechanism of cold seep formation and regulation. [ABSTRACT FROM AUTHOR]

Polygonal fault systems (PFS) are developed in many sedimentary basins, and their formation, growth, and ultimate geometry have been widely studied. The geometry and growth of PFS forming under the influence of regionally anisotropic stresses, however, are poorly understood, despite the fact these structures may serve as key paleo‐stress indicators that can help reconstruct the tectonic and stress history of their host basins. We here use high‐quality 3D seismic reflection data and quantitative fault analysis to determine the geometry and evolution of a PFS in the Qiongdongnan Basin (NW South China Sea), and its possible relationship with the geological and stress history of the basin. The PFS is dominated by two intersecting NNW‐to‐N‐ and E‐striking fault sets, which initiated in the Early Miocene. The dominant fault strike at the structural level at which the faults nucleated and where strain is greatest (i.e., Lower Miocene) is close to NW–SE. However, at the top and bottom of the PFS tier faults strike NNW–SSE, thereby defining a very slight vertical, clockwise rotation of strike. Based on the observation that the host rock is flat‐lying, it is unlikely that basin‐tilting perturbed (i.e., δ2 ≠ δ3) the otherwise radially isotropic stress field that typically characterize PFS. Likewise, diapirs that punctuate the host rock and that are spatially related to the PFS appear not to control fault geometry. We instead infer that the PFS geometry reflects a combination of local isotropic and regional, extension‐related tectonics stress affecting the Qiongdongnan Basin during the Early Oligocene to Middle Miocene. Regional studies suggest that during this time, extensional stresses in eastern Qiongdongnan Basin rotated clockwise from roughly NNW to N; we noticed the rotation of strike of the PFS, within which the vertical change in fault strike being relatively minor. Our study determines the timing of polygonal fault growth within the Qiongdongnan Basin and the associated geometry, highlighting the key role played by regional and local stresses.The polygonal faults are dominated by two intersecting NNW‐to‐N‐ and E‐trending fault sets of the Qiongdongnan Basin, NW South China Sea, which initiated in the Early Miocene. The geometry of the polygonal faults was mainly influenced by isotropic stresses in the Qiongdongnan Basin during the Early Oligocene to Middle Miocene. [ABSTRACT FROM AUTHOR]

A fossil salt sheet emplaced in the Jurassic in submarine conditions is described in the Eastern Alps of Austria, providing unique insights into the emplacement of similar submarine structures and their potential control on depositional systems. The salt sheet is a plug‐fed extrusion emplaced due to squeezing of a salt diapir under compression. The preserved mylonitic shear fabric in the evaporites indicates radial, south‐directed emplacement of the salt sheet. Tectono‐sedimentary relationships record the evolution of the salt structure, from initial diapiric growth, to salt sheet extrusion and posterior collapse. Syn‐extrusion sediments record the variable bathymetry of the extruding salt sheet, with reefal carbonates building up on the crestal bulge while their deeper water equivalents accumulated on the extruding salt lobe. This is the first description of a salt allochthon still linked to its source diapir in the Eastern Alps. [ABSTRACT FROM AUTHOR]

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ABSTRACTA detailed geological map of the Les Avellanes salt Diapir (South-Central Pyrenees, Spain) that includes both the diapir body and adjacent areas is presented to understand the diapir evolution and geometry. Structural, stratigraphical, and sedimentary data north and south of the diapir is used to infer the timing of its emplacement. The northern diapir boundary is characterized by a set of extensional faults oblique to the main Pyrenean trend, while the southern boundary is an extrusive salt sheet that overlays the late Eocene-early Oligocene sequence in three adjacent sub-basins. Salt extrusion occurred due to synorogenic folding. The topography created as salt extruded trapped the arrival of external sediments from the north, blocking the transport pathways southward. Low sedimentation rates southwards allowed for the lateral salt extrusion, advancing southwards from the feeder. The salt sheet emplacement was postdated by Oligocene conglomerates, indicating that the salt extrusion was a relatively quick event.

Active diapirs are commonly observed in sedimentary basins worldwide. Factors controlling overburden deformation processes and patterns during the active rise of active diapirs, such as sediment cohesion and overburden thickness, are not well understood. We have utilised the discrete element numerical simulation method to simulate active diapirism in models comprised of sediments with varying cohesions and roof thicknesses. We found that sediment cohesion can significantly affect overburden deformation with low‐cohesion sediments favouring the generation of a broad, smooth forced fold and a symmetric graben, while high‐cohesion sediments favour the formation of master reverse faults and preferentially uplifted and rotated fault blocks in their hangingwalls in the central crest, with an overall asymmetric structural geometry. Moreover, overburden thickness does not significantly affect structural styles in the overburden. Our results also suggest that the higher the sediment cohesion, the higher the amplitude (the lower the wavelength) of the forced fold above the rising diapir becomes. Our models produced a wide spectrum of deformation structures that resemble those in nature and reveal a strong link between structural styles and sediment diagenesis in the context of active diapir‐piercing sediments with varying degrees of lithification. [ABSTRACT FROM AUTHOR]

From the 1970s, the Dead Sea experienced severe halo-karstification and anthropogenic modifications. Progressively, but at an accelerating rate, subsidence, landslides, and sinkholes have increased in number and magnitude. The hazards' triggering factors are the terminal lake level lowering at more than one meter per year and the dynamic equilibrium of the hydrogeological system. Over the Lisan peninsula, archived satellite images revealed the extent of the damaged areas. On 22 March 2000, the destruction of dike 19 represented a loss of 38 M USD. This is the most important event recorded since the beginning of the Dead Sea recession some 50 years ago. In 2018, a rehabilitation project of that dike started. This research analyses the viability of the reinstatement works. The advanced space borne radar interferometry technique is applied to map ground deformations before and during the project. This article reveals that the ongoing rehabilitation and reinstatement works of dike 19 are threatened by ongoing halo-karstification processes. Field observations and subsidence/uplift dynamics support this statement. The past experiences are taken into consideration to adapt industrial expansion strategies. However, the permeability of the salt pan floor could trigger a fast development of a karst system able to destroy the rehabilitated dike 19. [ABSTRACT FROM AUTHOR]

Polygonal faults (PFs) generally have a classic polygonal geometry in map view. However, under the influence of tectonic faults, diapirs, channels, and slopes, the classic polygonal geometry of PFs is not preserved, demonstrating differences (different characters) in map-view 3D seismic data covering an area of 334 km2 of the Changchang (CC) sag, are used to document the map-view and cross-sectional characteristics of PFs. These data also help investigate the irregularly polygonal geometries of PFs due to the presence of influence factors, such as transtensional faults, submarine fans, channels, diapirs/gas chimneys, and the basal slope within the lower-middle Miocene strata. Results show that various irregularly polygonal geometries of PFs can be classified into en-echelon and arcuate PFs, channel-segmenting and -bounding PFs, radial PFs, and rectangular PFs in map-view. En-echelon and arcuate PFs are induced by transtensional faults and exhibit a unique 'flower' structure in NE- and SE-trending cross-sections in the NW area of the study area. This finding is documented for the first time. Channel-segmenting PFs occur in the (northwest) low-amplitude muddy channel and are inhibited in the (southeast) high-amplitude sandy channel in the SW area. Radial PFs are radially aligned around a gas chimney/diapir containing some high-amplitude anomalies (HAAs) in the middle area. The presence of intrusive sandstones with HAAs along the periphery of the diapirs restricts the occurrence of PFs. Two high-amplitude submarine fans act as a mechanical barrier to the propagation of PFs. Meanwhile, the (moderate) slope in the NE area induces rectangular PFs. Additionally, the geneses of the PFs in the current study are comprehensively discussed. This study adds to our understanding of the differences between PFs with irregularly polygonal geometries. [ABSTRACT FROM AUTHOR]

A detailed geological map of the Les Avellanes salt Diapir (South-Central Pyrenees, Spain) that includes both the diapir body and adjacent areas is presented to understand the diapir evolution and geometry. Structural, stratigraphical, and sedimentary data north and south of the diapir is used to infer the timing of its emplacement. The northern diapir boundary is characterized by a set of extensional faults oblique to the main Pyrenean trend, while the southern boundary is an extrusive salt sheet that overlays the late Eocene-early Oligocene sequence in three adjacent sub-basins. Salt extrusion occurred due to synorogenic folding. The topography created as salt extruded trapped the arrival of external sediments from the north, blocking the transport pathways southward. Low sedimentation rates southwards allowed for the lateral salt extrusion, advancing southwards from the feeder. The salt sheet emplacement was postdated by Oligocene conglomerates, indicating that the salt extrusion was a relatively quick event. [ABSTRACT FROM AUTHOR]

The Zagros Fold-and-Thrust Belt is one of the world's richest hydrocarbon regions, with Palaeozoic sediments being a key element in hydrocarbon plays. The main aim of this research is to provide a model for the formation and development of the sedimentary basin during the Palaeozoic Era in the Zagros and Persian Gulf regions. We utilize data from exploratory wells and surface outcrops of Palaeozoic sediments specifically in the northern parts of Iran's Zagros Mountains. The seismic profiles of the eastern region of the Persian Gulf provide more detailed information due to their distance from the Zagros hinterland. The investigation reveals that folds with wavelengths of several tens of km were formed on the Infra-Cambrian Hormuz Salt or its equivalent décollement.This study has identified halokinetic activities as the primary cause of Palaeozoic deformations in the Zagros region, with tectonic and orogenic factors playing a secondary role. The Palaeozoic sediments are divided into pre-kinematic, syn-kinematic and post-kinematic categories. Sedimentary sequences possibly including the Palaeozoic hydrocarbon source rock could be present throughout the study area. • The Palaeozoic sediments of the Zagros divided into pre-kinematic, syn-kinematic, and post-kinematic. • The construction of diapiric and non-diapiric structures within known unconformities is attributed to halokinetic activities. • The possibility of the existence of the Palaeozoic source rock in the lowlands of the region is described. [ABSTRACT FROM AUTHOR]

The South China Sea is one of the four major offshore oil and gas accumulation centers in the world. Many oil and gas fields and hydrate deposits have been found on the northern slope of the South China Sea. The amount of hydrate resources is huge. Relying on high-precision seismic exploration technology, the exploration of hydrate deposits in the South China Sea has progressed greatly in recent years, but the success rate of seismic detection technology needs to be improved. Scientific drillings have proved that there are multiple solutions to find hydrate only by identifying BSR in the stable zone, while the research on hydrate accumulation system is not deep enough, especially the migration, accumulation and dispersion system. Fractures are the main systems of hydrate accumulation and mineralization in the north of the South China Sea. In order to effectively characterize the fracture system of hydrate, this paper, combined with the successful experience of oil and gas reservoir migration and accumulation system research, applied the fracture identification technology used to study fracture channels to discover the diapir gas field to the BSR area of Qiongdongnan Basin, and successfully identified the hydrate fracture transport system. Based on the results, the migration efficiency was discussed. In the study of gas hydrate accumulation systems, the seismic characterization of fractures can be used as a means to study the transport system.

From the 1970s, the Dead Sea experienced severe halo-karstification and anthropogenic modifications. Progressively, but at an accelerating rate, subsidence, landslides, and sinkholes have increased in number and magnitude. The hazards’ triggering factors are the terminal lake level lowering at more than one meter per year and the dynamic equilibrium of the hydrogeological system. Over the Lisan peninsula, archived satellite images revealed the extent of the damaged areas. On 22 March 2000, the destruction of dike 19 represented a loss of 38 M USD. This is the most important event recorded since the beginning of the Dead Sea recession some 50 years ago. In 2018, a rehabilitation project of that dike started. This research analyses the viability of the reinstatement works. The advanced space borne radar interferometry technique is applied to map ground deformations before and during the project. This article reveals that the ongoing rehabilitation and reinstatement works of dike 19 are threatened by ongoing halo-karstification processes. Field observations and subsidence/uplift dynamics support this statement. The past experiences are taken into consideration to adapt industrial expansion strategies. However, the permeability of the salt pan floor could trigger a fast development of a karst system able to destroy the rehabilitated dike 19.

Geosites are essential elements of Geoparks, which can be used to transform geoheritage into sustainable economic, educational and social resources. One of the challenges we are generally facing today is in using these sites to their maximum potential, while ensuring their proper protection. In our experience, doing so successfully implies on one hand correctly evaluating their values, both from a quantitative point of view and from a qualitative, management perspective. On the other hand, it involves anchoring the management of the sites within the local communities, and that can be done by connecting them with as many local economic touchpoints as possible. An additional layer that ensures both the proper functioning of geosites as local resources, as well as their proper protection, is a holistic interpretation strategy that combines elements of geodiversity, biodiversity and cultural diversity, particularly the connection between people and places. Here, we illustrate this multifaceted approach using as examples five salt geosites from Buzău Land, in the Carpathian Mountains, Romania. We quantitatively evaluate the scientific, educational and touristic values, as well as the degradation risks of the geosites, and we qualitatively assess the tourist attractor potential of these sites and their interpretive value. Based on these analyses, we create a valuing framework in the guise of five geotrails, each with a distinct thematic that combines as many elements of local heritage as possible, as well as connecting them with local community members and businesses (i.e. economic touchpoints). [ABSTRACT FROM AUTHOR]

We have identified seven mechanisms by which mobile shales can pierce their roofs. The operative piercement mechanism depends on mobile‐shale viscosity, roof strength and stress state. For mobile shales at depths of several kilometres, three mechanisms are possible: fracture piercement, thrust piercement and ductile "piercement." However, injection up fractures and faults appears to be the dominant mechanism by which mobile shales rise towards the surface. In this process, mobile shales behave similar to magmas rising through the Earth's crust. Nearer the surface, a wider range of piercement mechanisms becomes possible: passive piercement, reactive piercement, active piercement and erosional piercement. These mechanisms all have salt‐tectonics analogues. Although shale tectonics and salt tectonics share common piercement mechanisms, in many cases the resulting structures are different. This is because near‐surface mobile shales can have much lower viscosities than salt. Mobile shales that reach the surface extrude very rapidly, in many cases leading to caldera collapse of the underlying shale chamber. This instability in the near‐surface means that long‐term, stable growth of passive shale diapirs is unlikely, in contrast with the behaviour of salt. A key question in seismic interpretation of mobile‐shale structures is whether large‐volume mobile‐shale diapirs exist. We show that both active piercement and ductile "piercement" can create such structures. Both of these mechanisms create steeply upturned beds on diapir flanks, which are diagnostic. However, active shale diapirs appear to be rare, and ductile "piercements" are not documented. We therefore suggest that large‐volume shale diapirs should be interpreted with caution on seismic data. [ABSTRACT FROM AUTHOR]

Deepwater oil and gas exploration has become a global hotspot in recent years and the study of the deep waters of marginal seas is an important frontier research area. The South China Sea (SCS) is a typical marginal sea that includes Paleo SCS and New SCS tectonic cycles. The latter includes continental marginal rifting, intercontinental oceanic expansion and oceanic shrinking, which controlled the evolution of basins, and the generation, migration and accumulation of hydrocarbons in the deepwater basins on the continental margin of the northern SCS. In the Paleogene, the basins rifted along the margin of the continent and were filled mainly with sediments in marine‐continental transitional environments. In the Neogene–Quaternary, due to thermal subsidence, neritic‐abyssal facies sediments from the passive continental margin of the SCS mainly filled the basins. The source rocks include mainly Oligocene coal‐bearing deltaic and marine mudstones, which were heated by multiple events with high geothermal temperature and terrestrial heat flow, resulting in the generation of gas and oil. The faults, diapirs and sandstones controlled the migration of hydrocarbons that accumulated principally in a large canyon channel, a continental deepwater fan, and a shelf‐margin delta. [ABSTRACT FROM AUTHOR]

This study is concentrated on distinguishing recently exposed seismically induced sediment structures from those created in non-seismic environments. Earthquake structures documented in Hamburg (NW Germany) primarily consist of compressional forms; less frequent are structures resulting from extensional or gravitational stress. The diverse styles of these seismic deformations can be attributed to different mechanisms, e.g. compression as a result of seismic shock or of sediment intrusion, liquefaction, fluidisation, loading, or shear stress, as well as volume loss and collapse following blowout activity. Originally described two-sided flames, sandwiched occurring interlocked flames, blossom-like seismites, specific diapirs and sediment intrusions (veils) are supposed to be indicative of a seismic genesis. [ABSTRACT FROM AUTHOR]

To suggest the impacts of diapir evolutions on the ore deposits genesis, combined mineralogical, Raman spectrometry and C-, O- and H- isotopes studies of fluid inclusions trapped by their minerals were studied. In diapir zone, the evolution of hydrothermal fluids has been distinguished: type I hot fluids (365 °C) had formation water origin (δD ≈ − 21‰) and moderate salinity (12–23% wt% eq. NaCl) which were trapped by minerals where Mg/Ca ≥ 1, in particular, magnesite and secondary by dolomite 1. later, type II fluids less hot which were divided into two members. The first was the N2-dominant fluids (≈ 250 °C) and more saline (23–43 wt% eq. NaCl and/or KCl) which were trapped in particular by some dolomite 1, dolomite 2 and quartz. The end member was CO2-rich fluids; their trapping temperatures varying from 150 to 270 °C and salinities > 35 wt% eq. NaCl and/or KCl were trapped by minerals where Mg/Ca < 1, in particular in dolomite 2. These type II fluids were of formation water origin (− 52 < δD < − 16‰) which came probably from the dehydration of Triassic materials (mainly gypsum). All CO2 could be previously provided by thermal decomposition of Triassic carbonate. But N2 was of deep origin. The major halokinetic stages that happened at lower Cretaceous period and during the end of Tethysian rifting (associated to basic magmatism) had generated type I and II fluids. the last hydrothermal fluids (type III) derived from organic matter (− 80 < δD < − 65‰). Their temperature and salinity ranges were from 50 to 160 °C and 18.4–23 wt% eq. NaCl, respectively. The last halokinetic stage occurred during the dominant compressive and transpressive pyrenean and Alpine collision period. The similarities observed between geochemistry characteristics of type III and ore-bearing fluids of some peridiapiric mineralizations implying that only the last hydrothermal events had contributed to the genesis of ore deposits in the diapir zone. [ABSTRACT FROM AUTHOR]

Comparative analysis of three randomly chosen salt structures (diapir A, diapir B and diapir C) of the Southern North Sea has been presented through the interpretation and reconstruction of the 2D seismic data set (SNSTI-NL-87 & SNST-NL-83). The study area lies in the Southern North Sea, Dutch offshore and it was tectonically active in the Permian or prior to that, as the basement was faulted at several locations before the deposition of salt in the Late Permian. The salt started to move in the Late Triassic to the Early Jurassic and the resulting salt structures developed until the Mid-Miocene. In most of the cases salt started to move due to the basement faults but buoyancy and differential loading are also main factors for the initiation of the salt movement. Two main time periods are believed to enhance the salt movement in the study area i.e. the Late Jurassic to the Early Cretaceous (extension), and the Late Cretaceous to the Early Tertiary (inversion). The results show thick Triassic and Jurassic sediments in the graben area. In contrast, due to the possible erosion, thin layers of sediments observed on the structural highs. The Late Cretaceous was reported as the compressional period resulting thickness variations of sediments in the area. [ABSTRACT FROM AUTHOR]

A major unsolved problem of the Proterozoic is the genesis and tectonic evolution of the massif type anorthosites. The idea of large-scale floating of plagioclase crystals in a basaltic magma chamber eventually generating massif type anorthosite diapirs from the floatation cumulates is not supported by observations of the major layered basic complexes of Proterozoic to Eocene age. In this paper, we test and propose a new genetic process of anorthosite diapirism through Rayleigh-Taylor instability. We have carried out a numerical modeling study of parallel, horizontal, multiple layers of norite and anorthosite, in a model layered basic complex, behaving like Newtonian or non-Newtonian power law fluids in a jelly sandwich model of the continental lithosphere. We have shown that in this pressure-temperature-rheology configuration the model lithosphere generates Rayleigh-Taylor instability, which triggers diapirism of the anorthosite. In our model, the anorthosite diapirs buoyantly rise through stages of simple, symmetrical upwelling and pronounced bulbous growth to a full-blown mushroomlike form. This is the growth path of diapirs in nearly all analog and numerical previous studies on diapirism. Our anorthosite diapirs fully conform to this path. Furthermore, we demonstrate that the progressive diapirism brings in striking internal changes within the diapir itself. In the process, the lowermost anorthosite layer rises displacing the upper norite and anorthosite layers as progressively stretched and isolated segments driven to the margin of the rising diapir--a feature commonly seen in natural anorthosite massifs. We propose that a large plume-generated basaltic magma chamber may be ponded at the viscous lower crust or ductile-plastic upper mantle or further down in the weaker mantle of the jelly sandwich type continental lithosphere. The magma may cool and crystallize very slowly and resolve into a thick-layered basic complex with anorthosite layers. Rheologically behaving like Newtonian or non-Newtonian power law fluids, the layers of the basic complex with built-in density inversions would generate RT (Rayleigh-Taylor) instability. The RT instability would trigger a buoyant rise of the unstable anorthosite from the layered complex. The upward driven anorthosite, accumulated as anorthosite plutons, would gradually ascend across the lower and middle crust as anorthosite diapirs. [ABSTRACT FROM AUTHOR]

Multibeam echo‐sounding and seismic data were obtained during three geophysical surveys by Guangzhou Marine Geological Survey (GMGS) on the north‐eastern slope of the South China Sea (SCS). Nineteen seafloor domes and numerous elongated pockmarks were distinguished in the study area. The seafloor domes vary on number of summits, shape, and spatial interrelation, based on which they were classified into four types which are single‐summit, double‐summits, elongated, and connected. Bottom simulating reflectors and blanking zone underneath were observed in the seismic profiles, indicating the potential existence of gas hydrate and free gas. Multiple faults and diapirs exist beneath the seafloor domes and pockmarks, which were inferred to provide efficient pathways for fluid migrating from deep subsurface. The seafloor domes exhibits high backscatter feature, which is potentially associated with the seep‐related gas hydrate and authigenic carbonate in the shallow sediment. It is speculated that fault and diapir activity, fault sliding caused by region extension and the interaction between neighbour domes control and affect the activity and formation of the domes. However, further investigations, including geological sampling and seafloor observation, are still needed to confirm whether they are mud volcanoes. [ABSTRACT FROM AUTHOR]

The western Iberian margin underwent complex evolution during the Mesozoic and Cenozoic. It was subjected to successive extensional and compressional phases, where salt tectonics played a significant role in both. The role of onshore structures during basin formation and inversion is not fully understood, and different chronological relationships between structures have been proposed. To better understand the history of salt body emplacement, we present paleomagnetic and magnetic fabric data from Jurassic carbonates, comprising cover rocks of the diapiric system. Magnetic fabrics show two types of behavior. Type 1 fabrics show magnetic foliation parallel to bedding—the magnetic lineation, after bedding correction, is horizontal and parallel to the diapiric contacts. This fabric is a consequence of overpressure during salt migration, whose effect is limited to the area near the diapirs. Type 2 fabric is characterized by a magnetic lineation parallel to the strike of bedding and—the intermediate and minimum magnetic axes are dispersed on a vertical girdle parallel to the shortening direction. This is interpreted as a compressional fabric that developed during basin inversion. Paleomagnetic results reveal a stable paleomagnetic component carry by magnetite with characteristic unblocking temperatures (175–450 °C) and coercivities (30–100 mT). Twelve of the 14 calculated mean directions show homogeneous behavior in their magnetic properties and directions, with positive inclinations, northward directions, with synfolding to postfolding behavior. We calculated the remagnetization direction (Dec: 347.5°, Inc.: 51.3°) and compare it to the APWP. It was likely acquired during the Cretaceous Normal Superchron, following the extensional deformation phase and prior to basin inversion. The paleodips (i.e., the bedding at remagnetization times) indicate that tilting occurred mainly during the extensional stage, meaning that the diapirs had already been developed. This indicates a strong Mesozoic salt tectonic component in the present-day structuring of this sector of the Lusitanian basin. • Jurassic rocks of the Lusitanian basin record widespread Mesozoic remagnetization. • Paleomagnetic directions are mainly postfolding due to Mesozoic diapiric activity. • Magnetic fabrics of the host rock diapirs are related to salt migration. • Salt migration drove a change in the stress axes due to horizontal overpressure. [ABSTRACT FROM AUTHOR]

Southern Iran hosts abundant salt karst phenomena in numerous salt diapirs. This paper provides a new insight into the relationships among climate, cap soil and salt karst hydrogeology. Cave systems were documented and mapped. Soil, drip, stream, and flood waters from different environments were studied at several diapirs. It was revealed that the soil water chemistry depends on both the climate and cap soil thickness. In semi-arid climates, a thick cap soil forms (>3 m) and water has very low TDS values (0.15 g/l). In arid climates, a shallow cap soil forms, and soil water is gypsum-saturated with low dissolved halite contents. In both environments, drip waters from salt caves and springs displayed high TDS values (255 to 347 g/l). This is explained by the dissolution of halite and minor anhydrite/gypsum, a K-Mg sulfate and sylvite. Spring water plots on a local meteoric water line, whereas drips in caves have an evaporative signature. The flash flood runoff is dominated by event rain water based on isotopic data, while springs are dominantly supplied by a base flow component. The mean residence time of water on the diapirs is controlled by the cap soil thickness. Water residence times may reach several hundreds of years on a thick cap soil based on an exponential model butsoil.

The structure of the southwestern branch of the Alpine orogen is affected by the extensive Late Triassic evaporites. These evaporites have been involved in polyphased salt tectonics since the early Liassic, coeval with the Tethyan rifting, and are the décollement level for thrusts in the external parts during Alpine orogeny. The role of salt tectonics in this branch of the Alpine arc is re-evaluated in order to determine the relative importance of early deformation related to salt motion with respect to deformation related to main Alpine compressional events. This paper focuses on one structure identified as diapiric since the 1930’s: the Astoin diapir (Goguel, 1939). Analysis of geological maps together with new field work have allowed to better define diapirism in the Upper Triassic evaporites outcrops around Astoin. Study of the diapir and the surrounding depocenters reveals a major involvement of salt in the structuration of the area, since the Liassic. Several salt ridges are linked to a main diapiric structure, explaining why we call it the “diapiric complex” of Astoin. Salt tectonics was initiated during the Liassic rifting, and a few locations show evidence of reactive diapirism whereas in others evidence of passive diapirism as early as the Liassic is seen. Passive diapirism continued during the post-rift stage of Alpine margin history in the Late Jurassic and Cretaceous when an allochthonous salt sheet was emplaced. Diapirism also occurred during the Oligocene while the Alpine foreland basin was developing in this part of the European margin of the Alps. Serial interpretative cross-sections have been drawn in order to illustrate the lateral variations of diapirism and structural style. Sequential evolutions for each cross-section are proposed to reconstruct the diapiric complex evolution through time. The Astoin diapir shows a complex structural framework with an important along-strike variation of diapiric activity. Most of the geometries are inherited from salt tectonics that occurred during extension, and in some places these early structures are overprinted by Alpine compressional structures.

Dolomites are well-known minerals; belonging to the Infra-Cambrian Hormuz Series lies within the salt domes of southern Iran. In this paper, the origin and alteration of dolomitic rocks of Paskhand and Deh-kuyeh salt diapirs in the area of Larestan (southern Iran) are investigated. Based on petrographic (size and fabric) studies, we recognize four dolomite types that consist of very fine-to-fine crystalline dolomite (D1), neomorphic dolomite (D2), fine-to-medium crystalline euhedral-to-subhedral dolomite (D3), and pore- and fracture-filling dolomite (D4). The dolomite samples with up to 26% iron can be called ferruginous dolomites. Some igneous rock patches to gehter with hydrothermal iron veins are observable in the salt domes of Larestan. Oxygen and carbon isotope values of black and white, and altered red dolomite of Paskhand and Deh-kuyeh salt domes, are equal to − 12.35 to − 18.78 for δ18OPDB and − 5.48 to − 8.49 for δ13CPDB; values enriched δ180 with low-temperature (~ 70 °C) conditions are related to D1 dolomites and values depleted δ180 with higher temperatures (~ 270 °C) are related to D3 and D4 dolomites. The most important source for secondary dolomites is deeper hydrothermal and catchment sources, which ascended through faults during the intrusion. Meteoric waters can be mentioned as less important sources for these types of dolomites. We reported sassolite B(OH)3 mineral in Deh-kuyeh salt diapir for the first time in this paper. This mineral is only observed in the areas which have famous riftings Fumarol. Therefore, in this paper, the existence of sassolite in the studied area could be considered one of the most important the origin of the composing elements of Hormuz rocks from fumarols which are formed in an extensional regime. [ABSTRACT FROM AUTHOR]

We present 77 new granite whole-rock analyses from the Qattar and Gharib areas, Eastern Desert, Egypt. Both areas include a "normal" granite and either a hypersolvus (Gharib) or an almost plagioclase-free granite (Qattar) enriched in fluorite. According to earlier results, F influences element distribution in granitic melts forming complexes with specific elements as Nb, Ta, Ga, Hf, Th, Zn, Sn, whereas F excludes Ba and Sr. We use principal component analyses to split the granite into chemical groups allowing an unbiased study of the inter-group element distribution. This adds the heavy REEs and Y to the earlier lists of elements with an affinity for F. The light REEs show a decreasing affinity with decreasing atomic mass; fluorine separates Sm from Nd, whereas Zr follows La. Opposite to some, but in accordance with other earlier results, the ratio Nb/Ta is higher in the fluorite-enriched than in the other granite. Weak tetrad effects are present. Zircon in the hypersolvus granite is high in common lead. We suggest F to be instrumental for separating Pb2+ from Pb4+. Two hypotheses may explain the occurrence of the two contrasting granites: they have either different sources, or they are co-magmatic, but the magma was split into two discrete types. We apply the second hypothesis as our working hypothesis. The liquidus has a gentler slope with pressure than the diapir requiring crystallisation to be most important in the lower part of the magma chamber. Our hypothesis suggests that globules of magma, enriched in volatile components, form during crystallisation due to slow diffusion rates in the crystallizing magma. Elements accompanying F are distributed into this magma batch, which has a lowered density and viscosity than the rest of the magma due to its increased contents of volatile components. A mushroom-formed diapir rises, forming the hypersolvus (or almost plagioclase-free) granite. Due to an edge effect, it is concentrated close to the wall of the magma chamber. The size and form of the outcropping granite depend on the intersection of the diapir with the erosion surface. Fluorine only makes it possible to follow the process. The model may be generalised to explain the diversification of non-F enriched granite, since the buoyancy of a magma batch several thousand m3 in size has a much larger impact on the system than the small negative buoyancy of crystals or small crystal aggregates. A-type granite classified merely from its trace element content may form from separated F-enriched magma batches. This may be the reason for their high frequency in the Eastern Desert. [ABSTRACT FROM AUTHOR]

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The diapir anticline microdepression of Ocna Şugatag underwent an accelerated transformation immediately after the end of salt mining (at the beginning of the 1960s). During this period of over 50 years of evolution, lake basins formed and disappeared, either naturally, in small sinkholes, or mostly due to the collapse of salt mine adits or chambers, which led to the creation of large-sized lake basins. There is an accelerated dynamics of these basins, as indicated by the sliding of part of the banks at a pace of 0.5-1.5 meters/year. The collapse of the mines is far from over, because the largest mines (Mihai and Dragoş) are partly affected and the pillars supporting the ceiling of the adits have a small diameter. Given the present conditions, when the underground brine is used for bathing and treatment purposes, in short time it is possible that new lakes emerge, even larger than the already existing ones. From the point of view of the lake potential, there are important differences, according to the degree of salinity of the water and the more or less accelerated dynamics of the lake basins. The latest two years witnessed an important development of the tourism infrastructure in the analysed area, as well as arrangements of the lakes, which determined a significant increase in the number of tourists searching for outdoor bathing, especially during week-ends.