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Based on comparison of morphotectonic analysis results with the SL index analysis, airborne geophysical measurements and field geological and structural data, possible Miocene to Holocene development of the landscape relief of Novohradské Mts. (southern Moldanubian Zone; Bohemian Massif) with a significant contribution of active faulting is interpreted. We suppose a polyphase reactivation of pre-existing faults under (a) the Miocene-Pliocene stress-field (regional ∼ NNW–SSE extension) as (oblique) normal faults trending ∼ SW–NE to ∼NW–SE were responsible for the subsidence of the Třeboň Basin and Kaplice Furrow and (b) the Pliocene to Holocene stress-field (Shmax = 146°) when horizontal in the ∼NNW–SSE direction with possible activity of the prevailing ∼ NNE-SSW trending faults as a sinistral strike-slips or weak reverse oblique-slip movement. The second set of subvertical ∼ WNW–ESE faults was predominantly reactivated in a dextral strike-slip regime or as gentle reverse oblique-slip faults. These Miocene to Holocene events reflect the coupling between the East-Alpine–Carpathian segment and its northern foreland, mainly due to northward motion of the African and the Arabian lithospheric plates. The core of the Novohradské hory Mts. experienced a significant uplift compared to the neighboring areas of the Kaplice Furrow and the Třeboň Basin. The most significant uplift has been found near Rychnov nad Malší, and on the tectonic border between the Kaplice Furrow and the Bukovský hřbet Ridge. This uplift took place during the late Pliocene and Pleistocene, after the sedimentation of lacustrine sediments in the Kaplice Furrow. Although the combination of GIS, morphotectonic and geophysical analyses with validation by field structural data does not provide the final proof of young tectonic activity, we conclude that there is strong indication of Neogene-Quaternary reactivation of several faults in the Novohradské Hory Mts. Based on similar morphological features, it can be supposed that many areas in the Alpine Foreland and Bohemian Massif underwent similar tectonic evolution during the Miocene to Holocene era. [ABSTRACT FROM AUTHOR]

Borborema Province is an orogenic belt of Neoproterozoic age part of the Brasiliano/Pan African Orogeny (600 Ma) in the northeast corner of the Brazilian shield. With an area of approximately 380,000 square kilometers, it is composed of fold and thrust belts, progressively stretched on continental scale transcurrent faults, and coeval plutonism. Its north and east flanks are limited by the Atlantic Ocean from a Mesozoic rift, and include passive margins basins and oceanic crust. Southwards, it is adjacent to the São Francisco Craton, while the west limit is overlain by the Paleozoic Parnaíba intracratonic basin. Besides the extensive metasedimentary and magmatic Neoproterozoic crust, it also involves Archean and Paleoproterozoic units. However, those units are obliterated by Brasiliano/Pan African Orogeny that segregates and disperses over the tectonic belts, hampering the interpretation of the architecture of the collisions of paleoplates during the Neoproterozoic. Magnetotelluric geophysical survey acquisitions have been conducted over the last decade by initiative of several Brazilian researchers and have been integrated to other geophysical methods in geotectonics in order to study the deepest parts of the lithosphere. We conducted the integration of twenty resistivity magnetotelluric sections and their interpretations, downplaying the electric response of the upper lithosphere (<100 km deep), aiming to emphasize and map differences in the lithospheric mantle. The resulting map shows high to moderate resistivity cores in the upper mantle, which are interpreted as continental lithospheric relicts, among high conductivity belts, associated to the Brasiliano paleosutures. These results are corroborated by gravimetric and magnetometric data. We propose that the southern limit of the Borborema Province with the São Francisco Craton is located under the Pernambuco lineament region, and that the western boundary with the Parnaíba lithospheric block is located under the Orós-Jaguaribe – Ceará Central Domain. [Display omitted] • Over 20 resistivity sections have been interpreted, using long wavelength data from Magsat and Gravsat as constrains. • Deep geophysics reveal persistent anomalies for lithosphere interpretation. • Neoproterozoic sutures and Archean-Paleoproterozoic blocks mapped. • Extensional regimes of lithospheric significance delimited. [ABSTRACT FROM AUTHOR]

Faults are thought to act as barriers or conduits for intraformational hydrocarbon migration within unconventional low-permeability hydrocarbon accumulations. However, well-documented studies substantiating this phenomenon at the regional-scale are scarce. Here, we use an extensive molecular and isotopic dataset for produced-gas samples (n = 562) from the Montney unconventional hydrocarbon accumulation of northeast British Columbia to show that regional-scale secondary migration of methane-rich gas was significantly influenced by the distribution and orientation of faults. Cross-plots using iC 4 /nC 4 , δ13C ethane and δ13C propane exhibit single coherent distributions, suggesting that the C 2+ components of most of these gases share interrelated histories of generation, maturation and primary migration. Conversely, cross-plots using gas dryness and δ13C methane against other selected gas parameters demonstrate geographic differentiation, with samples from the southeastern part of the study area generally exhibiting elevated molecular concentration and isotopic enrichment of methane compared to the samples from the northwestern part of the study area. The compositional and isotopic enrichment of methane in the southeastern samples signify significant late-stage secondary migration of highly mature methane-rich gas from deeper zones to shallower zones, and mixing with in-situ hydrocarbon fluids of lower thermal maturity. Previous structural mapping documents the presence of numerous subsurface thrust-faults related to the Cordilleran orogeny in the northwestern area, while these features are entirely absent in the southeastern area. Consequently, we conclude that thrust-faults, with accompanying clay-rich gouges, formed effective en-echelon barriers to the late-stage secondary migration of methane-rich gas in the northwestern area and prevented substantial mixing of hydrocarbon fluids. [Display omitted] • Montney Formation underwent secondary migration of highly mature dry gas during basin uplift. • Gas migration was influenced by faults acting as barriers, baffles and conduits. • En-echelon thrusts with clay-rich gouges formed effective barriers to gas migration. • Areas with thrusts had notably less dry gas migration than areas without thrusts. • Mature gas migration led to isotopically enriched methane in areas lacking thrusts. [ABSTRACT FROM AUTHOR]

The Shijiutuo Uplift within the Bohai Bay Basin(BBB)has experienced a complex evolutionary history since the Cenozoic. Studies of the Cenozoic evolution of the Shijiutuo Uplift are important for basin tectonics and petroleum geology. The formation of uplifts in rift basins is generally controlled by regional tectonic event and fault-block tilting. In this study, apatite fission track (AFT) data from fourteen samples and seismic data analysis were used to study the processes of regional uplift and fault-block tilting. We further investigated the Cenozoic evolution and formation mechanism of the Shijiutuo Uplift. The results indicated that the Shijiutuo Uplift experienced a two-phase differential tectonic uplift and erosion history (1) Widespread rapid uplift and erosion during the early Cenozoic (65–55 Ma) (2) Widespread uplift and erosion from 40 Ma to 16 Ma. The uplift and erosion substages of 40–38 Ma and 26–16 Ma were mainly caused by regional uplift, whereas those of 38–26 Ma resulted from fault-block tilting. Since the end of the third member from the Eocene Shahejie Formation, the Shijiutuo Uplift began to rise, causing the greater Bozhong Depression to be separated into the independent Qinnan and Bozhong Sags. These tectonic uplift and erosion events have a wide range of responses and regional dynamics in eastern China. The findings of this study will lead to a better understanding of the evolution and formation of uplifts within the BBB. [Display omitted] • The Shijiutuo Uplift underwent two stages of tectonic uplift and erosion events in the Cenozoic. • Formation of the Shijiutuo Uplift was associated with regional uplift and fault-block tilting. • The Shijiutuo Uplift did not exist before the end of the third member from the Eocene Shahejie Formation. • The tectonic uplift and erosion events had a wide response in eastern China. [ABSTRACT FROM AUTHOR]

This paper presents a geostatistical study of structural lineaments acquired from satellite data processing (L8: Landsat 8 OLI and AD: ASTER DEM) of the Zat area (High Atlas, Morocco). The lineaments are identified by their metric parameters, by defining three relationships (R1: length-spacing, R2: number-spacing, and R3: number-length) measured with linear regression analysis. The relations R1, R2, and R3 of the L8 set have respective relational weights of β1 (−0.079), β2 (−0.045), and β3 (0.083), giving a relational cascade with a mediating effect (Number → Length → Spacing). According to this model, the number and length grow proportionately, whereas the spacing varies inversely. However, the relations R′1, R′2, and R′3 of the AD set manifested the respective relational weights of β′1 (−0.043), β′2 (0.11), and β′3 (0.037) by materialising a different relational cascade (Number → Spacing → Length). This model shows that the number and spacing vary proportionately, while the length changes inversely. We illustrated that the L8 model matches the tectonic logic of the studied area better than the AD model. As a result, L8 data outperform AD data in structural mapping using remote sensing. • The application of statistics in the study of structural geology remains traditional to this day. • Lineaments are distinguished by their metric parameters (length, number, and spacing). • We propose a new statistical sense dedicated to the analysis of relationships between metric parameters. • The integration of digital mapping with appropriate statistical analysis has generated a comprehensive fracturing map. [ABSTRACT FROM AUTHOR]

[Display omitted] • Digital ore deposit models enhance conventional models by integrating clearer prospecting indicators based on metallogenic theories. They vividly depict 3D geological, geochemical, and geophysical models, improving the understanding of underground ore distribution. • This study introduces convolutional neural networks (CNNs) as an efficient method within comprehensive mineral prediction models. Leveraging deep learning, it identifies potential mineral-rich regions through spatial data analysis. • Achieving three-dimensional mineral resource predictions requires precise data integration and understanding of ore-forming principles. Comprehensive models incorporating multi-source data greatly enhance prediction accuracy. • At the Zaozigou Gold Deposit in Gansu Province, combining digital ore deposit models with CNN-based three-dimensional predictions delineated two promising prospecting areas. This approach augments prediction accuracy and offers novel insights for mineral exploration. With the depletion of surface mineral deposits, attention has shifted to deep mineral exploration prospecting. The emergence of three-dimensional digital ore deposit models, facilitated by the advancement of computer technology, has transformed traditional two-dimensional geological models into computer-recognizable numerical-symbolic digital models. This transformation allows qualitative geological concepts, originally expressed in natural language, to be quantitatively expressed, thereby enhancing the accuracy of deep mineral exploration. This paper first outlines the development from traditional ore deposit models to digital ore deposit models, asserting that digital ore deposit models can encompass a more comprehensive array of multidisciplinary geological information, including mineralogy, ore deposit types, structural geology, geochemistry, and geophysics. Building upon digital ore deposit models, a three-dimensional geological model is constructed, combining regional metallogenic regularities, identifying ore-forming favorable information, and conducting quantitative extraction. Subsequently, a comprehensive prospecting model is established, followed by the integration of deep learning methods for deep-seated mineral exploration, forming a unified system of quantitative prospecting methodology for hidden mineral deposits under the framework of geological prospecting models, three-dimensional geological modeling, and three-dimensional quantitative prospecting. Finally, using the Zaozigou gold deposit in Gansu Province as a case study, this approach is applied to mineral exploration prospecting, delineating prospective target areas and providing valuable reference for future exploration efforts. [ABSTRACT FROM AUTHOR]

Outcrop gamma-ray logging is crucial for understanding subsurface reservoirs, but it is rarely used on outcrops, especially for correlating gamma-ray data from borehole profiles. This case study focuses on a mature onshore reservoir in the Sergipe-Alagoas Basin, Brazil, which is currently discarded by the oil industry. The study used an ideal outcrop (M-17) to gather stratigraphic, sedimentological, and gamma-ray data to better understand the lateral heterogeneity and distribution of reservoirs thought to have formed in offshore environments in the Sergipe-Alagoas Basin. Seismic and paleontological data were used to reduce uncertainty in outcrop data. The results showed a paleoenvironment compatible with marine sedimentary deposits on the continental shelf, supported by evidence from Thalassinoides and Ophiomorpha ichnogenera. The model suggests sand was continuously deposited following cycles of accommodation generation, resulting in a single succession of rocks organized into three system tracts: lowstand, transgressive, and highstand. The gamma-ray response identified and correlated the Cidade de Aracaju Oilfield using a pseudo-well and a well in the Cidade de Aracaju Oilfield. The methodological approach was seen as useful as a correlation tool, revealing previously unknown exploratory potential in the surrounding areas of the overexploited Cidade de Aracaju Oilfield. This approach is both unprecedented and pivotal, revealing previously unknown exploratory potential in the surrounding areas of the overexploited Cidade de Aracaju Oilfield. • Facies association, gamma ray, seismic profiles, and structural geology are essential tools in reservoir characterization. • Thalassinoides sp. and Ophiomorpha nodosa ichnogenus support storm and wave dominate paleoenvironments. • Outcrop pseudo-well logs data (K, U & Th) enabled a reliable correlation with old wells in a mature oil field. • Offshore and Shoreface sandstone ridges are the main reservoirs of the Campanian interval of the Sergipe-Alagoas Basin. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Amgififa deposit in Sudan has high concentrations of Ag, Cu, Zn, and Pb. • The deformation phases of our study area resemble those in the Ariab mining region. • The deposit shows characteristics of bimodal mafic volcanogenic massive sulfides. • Four deformation stages in the deposit area are linked to ANS evolution. • Fault-bounded breccia in the region could be promising prospects for base metals. The knowledge about the Amgififa deposit in the Haya Terrane of the Arabian-Nubian Shield (ANS) in Sudan is limited due to the geological and structural features of this deposit are hidden beneath Quaternary deposits. This study reveals the characteristics of this deposit through systematic mapping (from trenches, drill holes, and artisanal mining pits), structural analysis, whole-rock geochemistry, and SHRIMP U-Pb zircon age dating. The results suggest that the deposit originated during the Neoproterozoic, with compelling evidence of bimodal–mafic volcanogenic massive sulfides (VMS) that evolved in a local extensional setting. Structural developments were associated with the NW-SE collisions between the Haya and Gebeit terranes, which occurred during the amalgamation of the ANS. A comparison between our study area and the Ariab mining area revealed several similarities, suggesting a regional correlation. In this study, we present a four-stage deformation model to provide insights into the geological history of the Amgififa deposit, which is affected by the tectonic evolution of the ANS. This study not only enhances our understanding of the tectonic chronology of the ANS in the study area, but also offers valuable insights into the mechanisms of regional mineralization. Notably, our study can strengthen the overall understanding of the Amgififa deposit in the ANS context and be used as a foundation for improving future mineral-exploration techniques in the region. [ABSTRACT FROM AUTHOR]

Calcite veins hosted by extension fractures and faults are common in the outcrop belt of the Austin Chalk – Eagle Ford – Buda stratigraphic section across south-central and west Texas, and contain aqueous and liquid hydrocarbon fluid inclusions. The hydrocarbon fluid inclusions in these thermally immature rocks indicate long-distance migration of oils from mature source rock down-dip and possibly from deeper units along faults. The widespread spatial distribution and extensive variety of oil types indicated by the fluid inclusion fluorescence suggest a protracted series of migration events – possibly from multiple source areas – rather than a single event. Oil inclusions in fault and fracture hosted calcite veins provide evidence of both strata-bound and cross-stratal oil migration along fault and fracture networks that are pervasive in the Austin Chalk, Eagle Ford, and Buda, as well as stratigraphically deeper units, in the subsurface and outcrop belt. Aqueous fluid inclusion microthermometry of the calcite veins provides evidence for significant exhumation of rocks in the Austin Chalk – Eagle Ford – Buda outcrop belt. Approximately 1.25–1.79 km of overburden was removed along the Balcones fault zone outcrop belt of south-central Texas, while in outcrop belt of the Devils River Uplift as much as 2.44–3.50 km of overburden was removed. In the productive region of the deeper basin down-dip from the outcrop belt, fluid inclusions in a deep core indicate that fluids were trapped during burial, but do not record maximum burial conditions. • Faults and fractures in immature Cretaceous strata of Texas host calcite veins. • Oil inclusion fluorescence in calcite veins records variety of trapped oils. • Protracted migration from distant and/or multiple source areas is indicated. • Migration from deep basin and/or deeper units along fault and fracture networks. • Exhumation across outcrop belt ranges from 1.25 to 3.50 km. [ABSTRACT FROM AUTHOR]

Structural control is one of the most important factors in developing the karstic system since the fractures facilitate the infiltration and circulation of groundwater. This accelerates the mineral dissolution processes responsible for the formation of endo and exokarstic geomorphological features, such as sinkholes and underground cavities, among other landforms that characterize this environment. This study provides information on the structural geology of the El Peñón karstic system, considered one of the most significant and extensive karstic regions in Colombia. The karst is tectonically controlled by joints with a preferential NW-SE orientation and cleavage planes with an NE-SW trend, guiding the development of drainage systems, closed depressions, and underground cavities. The stress tensor obtained with a NW-SE direction (127°) explains the deformation in the area and its influence on the development of the karstic system. It was also established that the potential groundwater flow occurs through open fractures with a direction of 120°–130° (parallel to the stress tensor) and along the cleavage planes (40°–50°). The fracture patterns are characterized by intermediate intensity values, predominantly low fracture density, minimal lengths, and good connectivity between fracture planes. • The exokarstic system is mainly controlled by cleavage and Mode I structures. • Gentle folds defining the Los Yariguíes Anticlinorium at a regional level. • The calculated stress tensor for the zone has an Shmax of 127°. • The mechanical coherence of the structures is explained by the same stress field. • Two potential fluid transit directions are proposed: 110°–140° and 40°–50°. [ABSTRACT FROM AUTHOR]

In Northeastern Brazil, the semi-arid region is known for its periodic natural drought phenomenon and the predominant fissured aquifer system, which is recognized for its low cost/benefit ratio concerning the construction of tubular wells for using groundwater. This work, therefore, aims at improving prospecting efficacy when exploring these natural resources using the available historical geological and structural data on the existing wells, integrated geophysical methods (resistivity and electromagnetic), and drone imaging. The proposed methodology was applied in a controlled environment in Cedro, Ceará/CE, using electromagnetism as a preliminary method followed by electroresistivity as a detailing technique. The analysis allowed us to recommend minimum values for the studied parameters in the research area. The dipole-dipole and Wenner-Schlumberger arrays with an electrode spacing of 10 m were the best suited for the study conditions. These results integrated with the structural geology can explain the failing wells observed in several areas as well as the successful wells associated with brittle structures found in the area. Thus, the proposed methodology allowed us to evaluate different responses and, consequently, define a set of basic steps to improve the accuracy of the studied procedures. • The dry season in the Northeast Region of Brazil is severe, leading to significant water supply problems that can persist for many years. • Groundwater serves as a viable source of water for sustaining the population and general use during prolonged dry seasons or to supplement regular water supplies. • Integrated resistivity and electromagnetic methods are highly effective in reducing errors in groundwater exploration, particularly in mapping structures that are favorable for groundwater accumulation. [ABSTRACT FROM AUTHOR]

The physical, mechanical and fracture properties at Stromboli volcano have been integrated at multiple scales to understand whether the interplay between a presumed NE/SW rift zone and the Sciara del Fuoco (SDF) depression has resulted in a zone of weakness able to promote fracturing prone to flank instability. Multiscale fracture quantification by imaging via FracPaQ toolbox both fractures and sample scale fractures has been integrated with rock physics and rock mechanics experiments on cm-scale samples belonging to the Paleostromboli, Vancori, Neostromboli, Pizzo and Present Deposit volcanic cycles that have been taken from within and outside the rift zone. The structural changes to the edifice have been quantitively assessed by mapping at different scale fracture properties such density and orientation within and outside the rift zone allowing to identify the potential damaged zones that could reduce the edifice strength. Results indicate that basalt textures, microfracture density, porosity, chemical zoning and preferential alignments, despite lithologically dependent, can be related to the NE/SW zone of weakness at the regional scale and to collapsed volumes that have been subject to continuous intrusive activity. Numerical inversion models have been performed to cross correlate fracture density in the basalts at multiple scales. A link between microfracture density and seismic velocities has been also established via numerical modelling, allowing to interpret in terms of degree of fracturing the results of seismic tomographies at the field scale, providing a novel method to image crack damage evolution within the inner structure of the volcano edifice. • NE/SW rift has influenced the distribution and orientation of fractures at Stromboli. • Fractures clustering around intrusions and the Sciara del Fuoco collapse. • Lithological dependency on the physical and mechanical properties of Stromboli basalts. • Numerical inversions of micromechanical data can be used to assess fracture damage from geophysical inversion. [ABSTRACT FROM AUTHOR]

Based on a multi-scale and hydrostructural approach, this study presents the most relevant methodology to be applied to a karst hydrosystem in order to get a full understanding of underground water flow. It implies a complete structural analysis, from the hydrosystem scale to the outcrop scale, including the intermediate scale of the major geological structures. We illustrate the method in the Arcier hydrosystem, in the northwestern border of the Jura fold-and-thrust belt (Eastern France). Field mapping and structural analysis allow to update the geological vision of the hydrosystem with two kink-type fault propagation folds, including a trishear kinematic model, on either side of a plateau presenting a hollow-and-dome configuration. Fracturing analysis reveals a fault-fracture network that we infer governs the entire hydrosystem. A Riedel pattern is highlighted, characterized by a N–S-striking (N355° ± 5), sinistral strike-slip, regional shear zone. Then, two 3D geological models, at different scales, constructed with MOVE and Visual Karsys softwares are combined with water levels and artificial tracer tests. It reveals a multilayer aquifer and a redefinition of groundwater circulations for the Arcier hydrosystem. The results demonstrate a strong geological control of karstic hydrosystems on groundwater circulations, proving that classical hydrogeological methods, such as natural and/or artificial tracers, must be combined with rigorous geological analysis. Moreover, the multi-scale approach provides an explanation of groundwater circulation based on the intersection between 3D geometry of impervious layers delimiting the aquifers and their base water level, instead of the 2D view (section or map) requiring systematic recourse to inferred vertical faults to cross permeability barriers vertically or laterally. This study also brings a new vision to the local protection of the water resource. • Karst aquifers supply 25% of the world's population in fresh water. • Complex hydrogeological object due to high degree of heterogeneity and anisotropy. • Innovative multi-scale and multi-disciplinary hydrostructural approach is proposed. • Modeling of geological structures and fracturation, combining water level analyse. • Arcier hydrosystem defined as multi-layer aquifer with a new circulation model. [ABSTRACT FROM AUTHOR]

The hard rock aquifer systems of Crystalline Aquifer System II (CBASII) and Crystalline Aquifer System III (CBASIII) in Rio Grande do Sul (RS) State, Brazil, were characterized qualitatively and quantitatively through remote sensing, gis-analysis, aeromagnetometry and structural geology analysis. The methods were applied to understand the relationship between the structures and the well capacities in both aquifer systems. Analysis of 139 structures provided a basis for a conceptual model for municipality of São Lourenço do Sul, in Rio Grande do Sul Coastal Plain, scaling systematic and a connection to preexisting structures. Python programming language script are used for statistical analysis can be download to reproduce statistical analysis of this paper with structural data bank. São Lourenço do Sul, is underlain by Pelotas Batholith, a geological complex affected by deformational events related to the Dom Feliciano orogeny. The models provided NW-SE extensions fractures with higher densities in depth for CBASII and CBASIII. Nevertheless, only CBASII is productive due to interconnectivity with preexisting structures WNW-ESE and generated by D 1 and D 2 deformational events of the Pelotas Batholith. CBASIII decreases its permeability as it was affected by the youngest brittle D 3 event an extensional/strike-slip tectonic regime. The regional structures mapping with remote sensing and aeromagnetic ENE-WSE are mostly present in CBASIII. Structures mapping in remote are the same but vary in density. The relationship between oriented magnetic gradients and productive wells suggests fault zones with low hydraulic conductivity in areas with higher anomalies values. Fault damage zones are identified around these anomalies and characterized as the best areas for drilling. [ABSTRACT FROM AUTHOR]

Despite their proximity, the Búzios and Itapu oil fields in the Santos Basin have different structural configurations. The study of the deformation pattern of the area and the relationship of the observed structures with the tectonic evolution of the basement is important to understand the geologic setting and evolution of the studied oil fields. In this work, a 3D PSDM seismic volume calibrated with well data was used to characterize the different types of structures, the distinct structural domains that occur in the Pre-Salt of the Búzios and Itapu fields, and the relationship between the basement trends and the structures in the sedimentary section. The Búzios field is formed by a series of half-grabens and horsts elongated in the NE-SW and NW-SE trends. Over the structural highs, a wide carbonate platform was developed. The Itapu field is a structural high related to a single elongated half-graben with a N-S main trend. The main structural pattern in the area is defined by normal faults that indicate an extensional process, typical of rift evolution. However, there are several structures that show indication of oblique-like deformation with strike-slip displacements, throughout the studied area. A very important issue is the discussion of the hierarchy of the observed structures, both rift extensional structures, and the oblique-like ones. • Seismic interpretation of structural geology of Búzios and Itapu fields. • The framework and relative ages of rift faults were interpreted and defined. • Búzios and Itapu basement structures, structural style, and domains were defined. [ABSTRACT FROM AUTHOR]

The kinematic analysis of magmatic structures is key evidence for the tectonic settings and deformation mechanisms related to the emplacement of intrusive bodies. The Dom Feliciano Belt (DFB), southernmost Brazil, registers voluminous post-collisional magmatism during the Neoproterozoic and the Arroio do Silva Pluton (ASP) is a diorite-monzonite-syenite body emplaced in this tectonic setting. The ASP structural investigation and magnetic fabric analysis showed the coexistence of flat-lying and steeply-dipping planar structures in most rock types. Heterogeneous shearing along the steeply-dipping planes led to heterogeneities in the fabric, providing individual analyses of zones affected and unaffected by shearing. The magnetic fabric analysis corroborated the interpretation of dextral kinematics based on field structural data. Complementary gravimetric modelling of the ASP demonstrates its continuity in the subsurface along an NNE-SSW axis. The integration of structural and magnetic fabric analyses combined with gravimetric modelling indicates that the older ASP rock types register a syntectonic emplacement within a transtensional setting, whereas younger magmatic activity in the pluton occurred under extensional conditions. The integrative approach allowed a comprehensive characterisation of the magmatic structures developed under different tectonic stresses and their association with emplacement conditions for the pluton. • Magmatic composite S–C fabrics as a result of shearing. • Coeval transcurrence and extension shown by structural and magnetic fabrics. • Structural and geophysical methods demonstrate transtensional emplacement condition. • Successful magmatic pulses and tectonic settings correlated through magnetic fabrics. • Regional stresses resolved into coeval transpressional and transtensional tectonics. [ABSTRACT FROM AUTHOR]

The Himalayan orogen is an archetype of collisional orogens built by the continental collision between India and Asia in the Cenozoic, and it has been a natural laboratory for studying the tectonic evolution of continental collision zones. Various tectonic models have been proposed to interpret the formation and evolution of the Himalayan orogen. However, these models were primarily based on local observations of structural geology and petrology, and some of these models even contradict to each other. The widespread exposure of metamorphic rocks and their metamorphic features are crucial aspects for reconstructing the tectonic evolution of the collisional orogen, as it provides robust records of metamorphic pressure (P) and temperature (T) at different ages. In this study, we present a systematic review on the metamorphic features of crustal rocks from the Western through the Central to the Eastern Himalayas. In doing so, we outline the spatial and temporal changes of metamorphic features (including P – T paths and T/P ratios) at first and then discuss their tectonic implications. In general, the metamorphic evolution of the Himalayan orogen can be categorized into three periods: (1) pre-collisional period from the Early Jurassic to Paleocene, which is represented by low T/P Alpine type metamorphism forming high-pressure (HP) blueschists in the Western to Central Himalayas; (2) syn -collisional period from the Paleocene to Eocene, which is divided into two stages. The early stage from the Paleocene to early Eocene is characterized by continental deep subduction at low T/P ratios to form Alpine type HP to ultrahigh-pressure (UHP) eclogites in the Western Himalaya, whereas the late stage from the early to late Eocene is characterized by continental hard collision at medium T/P ratios to form Barrovian type medium-pressure (MP) amphibolite and HP granulite in the Central to Eastern Himalayas; (3) post-collisional period from the Oligocene through Miocene to Pliocene, which is also divided into two stages. The early stage during the Oligocene is represented by continuous metamorphism at medium T/P ratios. Tectonic reactivation for the transition from the moderate to high T/P metamorphism would occur locally in the early stage, but became extensive in the late stage when metamorphic T/P ratios were high enough to cause intensive anatexis in the Miocene, giving rise to Buchan type HT to UHT metamorphic rocks in the Central to Eastern Himalayas. The inspection of different metamorphic facies series throughout the entire Himalayan orogen indicates that the Indian continental crust was collisionally thickened at first and then underwent large-scale reworking through intracontinental extension in the post-collisional period. The deep subduction of oceanic and continental crust is characterized by Alpine type metamorphism at low T/P ratios, the continental hard collision is represented by Barrovian type metamorphism at medium T/P ratios, and the post-collisional reworking is indicated by Buchan type metamorphism at high T/P ratios. The difference in metamorphic T/P ratios is spatiotemporally distinguishable in the Himalayan orogen, documenting the tectonic transition from oceanic subduction through continental subduction and collision to post-collisional rifting along the convergent plate margin. Therefore, the secular change of metamorphic T/P ratios can be used to retrieve the change of geothermal gradients and dynamic regimes from syn -collisional compression to post-collisional extension in the lifetime of the convergent continental margin. As such, the orogenic wedge is a holistic model for the spatiotemporal occurrence of Himalayan sequences cross the collisional orogen, and the failed continental rifting is a viable mechanism for high T/P metamorphism and granitic magmatism in the intracontinental orogen. • Secular change of metamorphic thermobaric ratios during the Cenozoic is evident in the Himalayan orogen. • The Indian continental crust was deeply subducted to mantle depths in the Western Himalaya. • The Indian continental crust was significantly thickened during collisional compression in the Central and Eastern Himalayas. • The collisional orogen became an intracontinental orogen through active rifting in the post-collisional period. • The orogenic wedge is a holistic model for the formation and evolution of the Himalayan orogen. [ABSTRACT FROM AUTHOR]

Natural hydrogen seeps called fairy circles have been identified in Mali, Brazil, Russia, and United-States. Natural hydrogen is produced from a field in Mali for 7 years. The natural hydrogen system is still poorly understood and needs to be studied in new geological contexts as to streamline hypotheses on the system dynamics and elements into concepts. In Australia, numerous circular surface features, commonly called salt lakes or swaps, are visible from the sky but no existing work shows nor quantifies any hydrogen content in those features. In this study, we reviewed the existing literature on fairy circles as to determine and directly test with soil-gas measurements if hydrogen surface-emitting features are present in Australia. We determined best candidates to test with a multi-disciplinary approach linking geology, multi-physical imaging, and seismic interpretation. Soil-gas measurements showed persistent hydrogen concentration localized in the external ring of circular depressions aligned along the Darling Fault, a major crustal boundary between the granitic, mafic and ultramafic rocks of the Yilgarn Craton from the sedimentary rocks of the Perth Basin. This work is the proof that fairy circles, in the meaning of H 2 emitting structures, are present in Australia and opens the door to new prospectivity pathways by evaluating original hypotheses on natural hydrogen generation, migration pathways and entrapment. This geological setting promotes deep serpentinization of ultramafic rocks as well as oxidation of iron-rich Archean rocks and mafic dikes as potential hydrogen sources that are both of massive potential economic value. This hydrogen can circulate and be entrapped as aqueous hydrogen in low-salinity aquifers or migrate in gaseous phase in fault zones up to intermediate structural reservoir or to the surface. • First discovery and field measurement of natural hydrogen seeps in Australia. • Original hypotheses on natural hydrogen generation, migration pathways and entrapment. • Link of the hydrogen seeps with the structural geological system. [ABSTRACT FROM AUTHOR]

Deformation across structural complexities such as along-strike fault bends may be accommodated by distributed faulting, with multiple fault splays working to transfer the deformation between two principal fault segments. In these contexts, an unsolved question is whether fault activity is equally distributed through time, with multiple fault splays recording the same earthquakes, or it is instead localized in time and space across the distributed faults, with earthquakes being clustered on specific fault splays. To answer this question, we studied the distributed deformation across a structural complexity of the Mt. Marine fault (Central Apennines, Italy), where multiple fault splays accommodate the deformation throughout the change in strike of the fault. Our multidisciplinary (remote sensing analysis, geomorphological-geological mapping, geophysical and paleoseismological surveys) study identified five principal synthetic and antithetic fault splays arranged over an across-strike distance of 500 m, all of which showing evidence of multiple surface-rupturing events during the Late Pleistocene-Holocene. The fault splays exhibit different and variable activity rates, suggesting that fault activity is localized on specific fault splays through space and time. Nonetheless, our results suggest that multiple fault splays can rupture simultaneously during large earthquakes. Our findings have strong implications on fault-based seismic hazard assessments, as they imply that data collected on one splay may not be representative of the behaviour of the entire fault. This can potentially bias seismic hazard calculations. • The change in strike across linkage zones can be is accommodated by multiple active fault splays. • Fault activity is localized in space and time on multiple splays within linkage zones. • Seismic hazard studies may be affected by clustering within distributed faults. [ABSTRACT FROM AUTHOR]

Structural control of volcanic activity is a topic of great significance around volcanic fields, mostly associated with risk management near cities. Structural geology provides valuable information for understanding the magmatic processes associated with the rise of magma and the presence of volcanoes. The Villamaría-Termales Monogenetic Volcanic Field (VTMVF) is a group of Quaternary monogenetic volcanoes settled in an active fault system, which allows us to propose the role that these faults play in the volcanic activity. The field is located near the city of Manizales (∼475.000 inhabitants), Colombia, on an active fault system at the western flank of the Cordillera Central in the northern Andes. The VTMVF is characterized by andesitic lava domes and flows, which individually reach volumes of up to 2.5 km3. This work uses 1) geometry and kinematics of the faults that affect the VTMVF to define the structural features associated with the emplacement of the volcanoes, and 2) new and published ages to evaluate periods of volcanic activity. Three trends of fault systems associated with the location of the volcanoes were identified: 1) NW-SE (Villamaría-Termales), 2) NE-SW (Sancancio, El Perrillo, Santa Rosa and Palestina), and 3) N-S to NNE-SSW (San Jerónimo and Samaná-sur). The fault kinematics are dominantly normal, with dextral (NE) and sinistral (NW) movements. Analysis of ages shows that the field has temporally evolved since 2 Ma in different time intervals (2.0–1.2 Ma, 0.18–0.045 Ma, and 0.045 Ma – Present). This supports the presence of different emplacement mechanisms related to both the movement in the strike of some faults and the intersection between faults. The pauses of volcanic activity could coincide with the absence of structural conditions (interseismic cycles for faults, where the sealing of the faults is generated) to facilitate the rise of magma; this is related to temporary compressive conditions. Despite the apparent structural controls, there is no clear spatial or temporal pattern of volcano distribution within the field. There is evidence of seismic activity in the area. Thus, the future formation of dilatating zones that allow the magma to rise and the emplacement of new monogenetic volcanoes is feasible not only in the area defined for the volcanic field but also in the continuation of the fault lines around it. • Fault interactions controlled the emplacement of evolved monogenetic volcanoes. • Based on distribution and emplacement ages, there is not a spatio- temporal eruption pattern. • A new monogenetic eruption in Colombia is likely to happen and therefore represents a hazard for the region. [ABSTRACT FROM AUTHOR]

• The Kopaonik Mt. of southern Serbia represents a highly complex segment of the Mesozoic Neotethyan suture. • The Kopaonik Mt. is an elevated productive core complex-related geothermal field (Jošanička spa and Slanište). • The investigated thermal aquifers of the Kopaonik Mt. are controlled by the complex extensional conduit–barrier faults systems. • Composite hydrogeological study yields a subsurface geothermal anomaly that is connecting the shallow and deeper fault-related thermal water reservoir network. A composite hydrogeothermal survey of the magmatic-metamorphic post-NeoTethyan late Paleogene - Neogene crustal core-complex of the Kopaonik Mt., southwestern Serbian highlands, provides new constraints on the subsurface hydraulic across- and along-fault flow fluid regimes and geothermal anomalies associated with the two shallow reservoirs. The study is involving synergistic approach by combining structural geology, exploratory drilling, temperature logging, hydrochemical and hydrodynamic constraints further illustrating a complex conduit–barrier fault-controlled spatial compartmentalization of the two thermal water reservoir(s). The thermal waters of the Kopaonik Mt. geothermal field are channeled by the major regional faults and associated fracture zones that are crosscutting the volcanics and the adjoining metamorphites. The results show that the subsurface compartmentalization of the active reservoirs, which are supplying the spa town of Jošanička banja, are controlled by a seismically active regional faults (including the fault that is crosscutting the Slanište locality, having N-S trending). Owing to the linear channeling of the fault-controlled reservoirs, in which the main quantitative water circulation takes place, it was possible to identify the thermal fluid flow paths and associated recharge zones (catchments). The Jošanička banja thermal waters reservoir is accommodated at ca. 400–500 m depth, whereas the Slanište aquifer maintains a shallower position. The new surface - subsurface constraints allowed the estimation of the subsurface reservoir elevations, pinpointing the origin of shallow crustal geothermal processes. Of particular importance is better understanding of the subsurface spatial distribution and the ultimate depth of the developing Kopaonik Mt. geothermal field. The new interpretation shows a qualitative agreement with the core-complex-related heat sourcing, as well as the fault-controlled reservoir compartments, impacting the efficient extraction of the thermal waters, in terms of quantity, quality and water temperature. [ABSTRACT FROM AUTHOR]

[Display omitted] • Surin-Mastgarh Anticline (SMA) is a Polyharmonic Anticlinorium with Flexural slip. • SMA has suffered both N-S and E-W compressional tectonic stress. • It is a Type-II superimposed folding as per Ramsay's classification. • A Blind Thrust is sandwiched between the SMA and Medlicott-Wadia Thrust. • Duplex-Thrust Complex lying on MHT are potential Hydrocarbon reservoir. The Surin-Mastgarh Anticline (SMA) at the frontal Siwalik range of the NW Himalaya possesses great interest for the evolutionary processes and hydrocarbon prospect. Most of the previous models have been proposed from geological data, which alone cannot picturise the SMA in the subsurface. This work aims to delineate subsurface characteristics, geometry of SMA, and stratigraphic divisions from seismic imaging along and across the eastern flank of SMA to shed light on inter-tectonics with the surrounding Main Himalayan Thrust (MHT) and Medlicott-Wadia Thrust (MWT), and evaluation of hydrocarbon resources. The seismic attributes including interval velocity have been computed, and seismic amplitudes have been traced for better comprehension of the objectives. It is inferred that the SMA is a polyharmonic anticlinorium with flexural slip consisting of stratigraphic layers: Lower Siwalik, Middle Siwalik and Upper Siwalik. It shows that during the formation of anticlinorium, flexural flow occurred within the upper and lower layers of the anticline. A blind thrust overran the Northern Limb of SMA, which was later overrun by the MWT. The MHT has no direct relation with the SMA, and is terminated in the south. It is also elucidated that this anticline experienced both major N-S compressional and minor E-W neo-tectonic stress regimes, which led to Type-II superimposed folding as per Ramsay's classification. The presence of Late Proterozoic Limestone and/or marine Pre-Siwalik Tertiary formations, which are organic-rich, below the MHT could generate hydrocarbons. This can be trapped by the overlying Duplex-Thrust Complex, and thus providing hydrocarbon prospects in this study area. [ABSTRACT FROM AUTHOR]

Stratigraphy, structure, and tectonics of the Turkish part of the intermontane Shirak Basin and the adjacent Susuz Basin were studied based on methods of structural geology, geological and geomorphological correlation, paleontology, paleomagnetism, and archaeology. For the first time, the Pliocene-Quaternary stratigraphy and tectonics of the western Turkish and eastern Armenian parts of the Shirak Basin were correlated. Sedimentary cover of the western part of the basin consists of four units: the Lower Akchagylian (Piacenzian) marine deposits, Karakhach, Ani, and Arapi lacustrine-alluvial units. The Upper Pliocene age of the former formation in the Demirkent section is evidenced by normal palaeomagnetic signature and dinocysts of the Akchagylian aspect with some forms known to have a highest stratigraphic datum near the Pliocene–Quaternary boundary. The age of the Karakhach unit is estimated at 1.9–1.7 Ma based on similar geomorphological position and composition with corresponding deposits in Armenia, normal polarity, and a record of the Early Palaeolithic artefact. The dating of the Ani unit to the Calabrian, and the Arapi unit to the lower Middle Pleistocene is evidenced by assemblages of molluscs and small mammals, Acheulian artefacts, palaeomagnetic data, and geomorphological position similar to the correlated sedimentary sequences in the Armenian part of the basin. The level of the Akchagylian brackish water basin at the Neogene–Quaternary boundary (2.58 Ma) was close to the recent oceanic level. The recent altitude of the top of the Lower Akchagylian deposits in the Demirkent section is 1565 m. This defines the average rate of the Quaternary uplift in this part of Lesser Caucasus at 0.6 mm/year. The Shirak Basin is bounded and ruptured by fault and flexure-fault zones. Because of offsets on the Çamuşlu and Akhuryan zones, the central part of the northern Shirak Basin is subsided relative to the Demirkent section at 130–165 m. The movements in the Çarçioğlu zone caused a 100–120 m rise of the Ani unit surface in the Susuz Basin relative to the adjacent part of the Shirak Basin. The north-western border of the Susuz Basin is uplifted on the Sarikamiş fault zone. Thus, the Quaternary uplift ranges near 0.6 ± 0.1 mm/year. To the north of the Shirak Basin, in the Upper Akhuryan and Lori Basins and the Debed River valley, the rate of uplift during 0.65–0.6 Ma is estimated at about 1 mm/year and the adjacent Bazum and Javakheti Ridges rose more intensively. Therefore, the uplift could accelerate during the time interval of 0.65–0.6 Ma. [ABSTRACT FROM AUTHOR]

The geology and long-term structural development of Imbabura volcano (Ecuador) have been discerned from field surveys, as well as petrographical and geochemical studies. The volcano is composed of an ancient edifice (Imbabura I), which has experienced one major volcanic landslide directed N 330–340°. After the emplacement of that debris-avalanche deposit, the petrographically and geochemically different edifices Imbabura II-1 and Imbabura II-2 developed on the N and NE flank of Imbabura I, as well as in its summit zone. Finally the smaller Imbabura II-3 edifice, a dome-complex locally known as Huarmi Imbabura, was emplaced in the SSW flank of Imbabura I. The relatively complex structure of the edifice (i.e. flank collapse direction and spatial distribution of the major stratigraphical units) cannot be explained solely by volcano-tectonic interactions with the regional left-lateral Río Ambi strike-slip fault, which traverses the edifice from NNE to SSW. Instead, the fact that the whole Imbabura edifice stands on a substratum dipping to the NW (i.e. the NW flank of the neighbor Cubilche volcano) is proposed to be the main factor influencing the departure of Imbabura structure from previously known models of volcanic edifices interacting with strike-slip faults. This hypothesis was tested with scaled experiments, during which the dip-direction of the substratum was systematically changed with respect to the strike of the fault. The structures developed by the experimental prototypes are highly coherent with those observed at Imbabura volcano. [ABSTRACT FROM AUTHOR]

The National Gas Hydrate Program Expedition 02 (NGHP-02) was designed to examine gas hydrate occurrences off the eastern margin of the Indian Peninsula. Twelve holes were logged with logging-while-drilling (LWD) tools and nine holes at five sites were cored in Area-B of NGHP-02. Five logging units were defined based on the characteristics in logging data responses. Distinctive Logging Units R1 and R2 characterized by high gamma ray log values and composed of quartz and biotite-rich medium sized sand grain units that act as gas hydrate resevoirs and correlated to strong seismic reflectors. Hydrate-bearing intervals can be identified by resistivity and sonic velocity logs and classified into pore-filling type, fracture-filling type, and a mixture of pore- and fracture-filling types based on borehole image characteristics. Pore-filling type gas hydrate is typically developed in the case where the depths of R1 and/or R2 is close to the seismic inferred bottom simulating reflector (BSR). Fracture-filling type hydrates associated the R1 section occur above the BSR associated with the anticline in Area-B. The occurrence of pore-filling and fracture-filling gas hydrate represent different processes of hydrate formation related to the regional geological structure. The stratigraphic layered pore-filling gas hydrate occurrences are generated along often dipping sand layers, which are also conduits for methane-bearing fluid migrating from below the BSR in many settings. Fracture-filling type gas hydrate is an alternative mechanism for the occurrence of gas hydrate in mudstone-rich sediments above the BSR and found associated with the anticline in Area-B. This structural constraint of the hydrate-bearing fractures in the Area-B anticline suggest that the fracture dominated reservoirs possibly formed by anticlinal flexure, and the upward flow of methane-bearing fluids along porous sedimentary layers and the subsequent formation of pore-filling gas hydrate occurrences account for the range of gas hydrate accumulations discovered during NGHP-02. • Logging units and gas hydrate zones of NGHP-02 Area-B in Krishna-Godavari Basin was established. • Gas hydrate occurrences in pore-filling, fracture-filling, and mixed fracture types were determined. • Gas hydrate occurrence is highly influenced by the anticlinal structure. [ABSTRACT FROM AUTHOR]

The Yakima Fold Province (YFP) is a series of asymmetric, north-verging anticlines in the Columbia River Flood Basalt Province of south-central Washington. Ridges represent anticlinal folds produced by tectonically active thrust faults, and their proximity to the Hanford nuclear facility has motivated many studies on the timing and extent of Quaternary deformation within the folds; however, multiple generations of faults and folds in the region have recorded a history of deformation spanning ~50 Ma. In this work, we utilize ~44 km of seismic profiles, structural orientation measurements collected in the field, USGS geologic maps, and stratigraphic information collected from 13 well logs to investigate the subsurface structure of the Saddle Mountains in the northern section of the YFP. We developed a three-dimensional structural model of the mountain range and estimated displacement and strain accommodated by faulting and folding. Our resulting model requires a multi-stage deformational sequence, and indicates that ~1800 m of uplift is generated by two parallel listric faults, soling into décollements at ~4 and ~8 km depth. Patterns of displacement and orientations of strain suggest that the deeper fault is older and that it may reflect a history of clockwise rotation, making the YFP the shortening counterpart to the extensional northern Basin and Range. The model presented has implications for understanding deformation in flood basalt provinces more broadly, and the methodology can be applied to interpret multi-stage deformation and reactivation histories of long-lived fault systems. • 3D model of fault and fold structures was used to calculate ridge deformation. • Two parallel listric thrust faults underlie Saddle Mountain. • One thrust fault extends to a 4 km deep décollement accommodating N–S shortening. • Another thrust fault extends to 8 km deep décollement accommodating NE–SW shortening. • The deeper fault may accommodate clockwise rotation within North American Plate. [ABSTRACT FROM AUTHOR]

Normal faulting earthquakes rarely rupture the entire extent of active normal faults, and can also jump between neighbouring faults. This confounds attempts to use segmentation models to define the likelihood of future rupture scenarios. We attempt to study this problem comparing the offsets produced in single earthquakes with those produced by multiple earthquakes over longer timescales, together with detailed studies of the structural geology. We study the active normal fault system that caused the Mw 6.3 2009 L'Aquila earthquake in central Italy, comparing the spatial distribution of coseismic offsets, cumulative offsets that have developed since 15 ± 3 ka, and the total offsets that have accumulated since the faults initiated at 2–3 Ma. Our findings suggest that: 1) faults within a segmented fault system behave as a single interacting fault segment over time periods including multiple earthquake cycles (e.g. 2–3 Ma or 15±3ka), with single earthquakes causing either partial or total ruptures of the entire system; 2) an along-strike bend causes throw and throw-rates enhancements within the bend throughout the seismic history of the fault system. We discuss the synchronised and geometrically controlled activity rates on these faults in terms of the propensity for floating earthquakes, multi-fault earthquakes, and seismic hazard. • Faults within a segmented fault system can behave as a single interacting fault segment over multiple seismic cycles. • Single earthquakes can float within the fault system, causing either partial and total ruptures of the system. • Along-strike fault bends in segmented fault systems cause throw enhancement within the bend. • Structural geology provides important information to assess the propensity of multi-fault earthquakes. [ABSTRACT FROM AUTHOR]

This article performs particle (/material point) tracking for ideal brittle faults with translational and rotational slip components. The fault planes are considered to be planar and step-like in separate cases. In the latter case the hangingwall block is considered to behave ductilely. For a specific choice of the three Cartesian co-ordinate axes, dip-slip fault will change two out of the three ordinates of any point in the faulted block that moves. A strike slip faulting can change one out of the three ordinates. On the other hand, whatever be the orientation of the orthogonal co-ordinate axes, an oblique slip fault of any dip amount and a purely rotational fault with dip ≠ 0, 90° alter all the three ordinates, except the pivot point in the latter case. As expected, oblique-slip faulting modifies the co-ordinates of the shifted material points depending on both (i) the pitch of stretching lineation, and (ii) the dip of the fault plane. • Particle tracking in faulted blocks using 3D coordinate geometry. • Translational, rotational and roto-translational faults explained with planar fault planes with and without steps. • Fault modeling in petroleum geosciences and in pure research. [ABSTRACT FROM AUTHOR]

Partial melting of continental crust and granite genesis were investigated in the Camboriú region, south Brazil. Structural geology and geochemistry were used in order to characterize the link between the high Ba-Sr Itapema Granite (IG) and the syntectonic melting of orthogneisses and amphibolites of the Camboriú Complex (CC). The IG is a sheet-like intrusive body of biotite monzogranite to granodiorite with large amount of migmatitic amphibolite and gneiss xenoliths, and a well-developed magmatic foliation concordant with the main gneissic banding. Discordant, m-thick granitic dykes which crosscut the migmatitic sequence and transport magma and xenoliths to feed the IG main body mark the transition from the migmatitic to the magmatic system within the complex. Whole-rock geochemical data reveal important contamination and assimilation processes of xenoliths during IG magmatic flow which give rise to different facies and geochemical signatures. The generation of the IG is an example of a continuous exposure from source to sink formed through a continuous and efficient deformation-driven melting/extraction/transport system generated during coeval folding and anatexis of the CC metamorphic sequence. • Syntectonic anatexis produces melts to be extracted from the source and form granites. • Extraction dykes mark transition from migmatitic to magmatic dynamics of the system. • Granites develop compositional diversity due to xenoliths disaggregation/assimilation. [ABSTRACT FROM AUTHOR]

Felsic schist units in the Lone Star Ridge area of the northern Klondike Gold District, Yukon, Canada, host both locally gold-bearing orogenic quartz veins and much more extensive zones of disseminated gold mineralization that is stratabound within specific schist units and is interpreted to be syngenetic in origin. Scarcity of outcrop and the difficulty in distinguishing between subtly different schist units has hampered correlation between surface exposures and drill core, and production of a detailed geological map of the area. Lithogeochemistry offers an alternative, unbiased way to map and interpret the various subunits of the felsic schist package that host disseminated gold mineralization and gold-bearing veins in parts of the Klondike, and that can potentially form the basis for correlations between various drill holes, and between drill holes and surface exposures. A detailed investigation of 4590 multi-element geochemical analyses (by 4-acid digestion) from a set of 27 diamond drill holes in the vicinity of the Boulder Lode open cut (Lone Star gold occurrence) on Lone Star Ridge has revealed several lithogeochemical signatures that correlate closely with gold content and to some extent with lithological units distinguished during initial logging of the drill core. Research quality geochemical analyses for a suite of representative rock units selected from the 2005 drill holes have been used to verify the multi-element geochemical analyses, and to determine the petrochemical character of some of the individual rock units. Results of this study demonstrate that it is possible to construct a chemostratigraphic framework for the felsic schist units in the vicinity of the Boulder Lode. Distinctive rock units can be broken out that have very consistent geochemical signatures, and elevated gold values related to the presence of disseminated gold appear to be consistently associated with specific rock units. These chemostratigraphic marker units have been utilized to constrain the geology and structure of the immediate study area, and in particular to define the geometry of the schist units that contain disseminated gold. The same approach has also been applied to a very extensive set of geochemical data (comprising nearly 34,000 individual samples) from chip samples, diamond drill core, reverse circulation drill samples, and conventional soil samples obtained during other historical and more recent exploration programs, to better resolve the geological interpretation of entire Lone Star Ridge area. • Disseminated gold occurs within very specific schist rock units in Klondike, Yukon. • Limited exposure (<1%) hampers geological mapping and structural analysis. • Chemostratigraphic marker units have been identified from standard assay data. • Tracing marker units constrains geology and geometry of gold-bearing rock units. • ~34,000 geochemical analyses constrain the structural geology of the entire study area. [ABSTRACT FROM AUTHOR]

This paper sets the historical context for the Journal of Structural Geology when it was first published in 1979. The major advances in Structural Geology over the past 40 years are then highlighted. Finally, ten Grand Challenges for the next decade are nominated. • The history of Structural Geology up until the first issue of the Journal of Structural Geology in 1979 is highlighted. • Progress from 1979 to the present is summarised. • Some Grand Challenges for the future are outlined. [ABSTRACT FROM AUTHOR]

We present an orientation system for thin sections used for microanalysis, applicable to both billets and cores. The orientation system enables spatially referenced observations and consists of three parts. First, we establish a reference corner that is the uppermost corner of the sample on the thin section, in its original geographic orientation in the field or laboratory setting. This corner is tied to a right-hand coordinate system, in which all reference axes point downward. A geographic direction-based, rather than uppermost corner-based, convention for a reference corner can be substituted for projects that utilize sub-horizontally oriented thin sections. The reference corner - combined with orientation metadata - define a unique position of the thin section in geographic space. Second, we propose a system of small saw cuts (notches) that minimizes the number of notches required on the sample, to distinguish both the reference corner and the orientation of the thin section relative to fabric (e.g., foliation/lineation), if present. The utility of a notching standard is that it provides an inherent doublecheck on thin section orientation and facilitates sharing between users. Third, we develop a grid system in order to locate features of interest on the thin section, relative to the reference corner. Any of these systems – referencing, notching, and gridding – can be used independently. These systems are specifically designed to work with digital data systems, which are currently being developed, allowing researchers to share microstructural data with each other and facilitating new types of big data science in the field of structural geology. • Universal system for orienting thin section, cores, and billets that will provide a standard for digital databases. • Reference corner and orientation of l, m, and n-reference axes allows reorientation of thin sections to geographic space. • A notching system allows thin sections to be reoriented using metadata for foliation and lineation measurements. • A UTM-based gridding system is tied to the reference corner and allows precise location of objects within a thin section. [ABSTRACT FROM AUTHOR]

Minerals precipitated from fluids carry a chemical signature of fluid origin and transport history. We use this concept to test the hypothesis that a subset of veins precipitated in the Loma Blanca fault zone, Rio Grande rift, NM, USA, record fault-valve behavior. Previous studies of this site show syntectonic calcite veins formed in response to post-seismic fluid discharge following repeated ground-rupturing earthquakes. U-Th ages on veins constrain the timing of fault slip over a period of >400,000 years. The radiogenic isotope (Sr, Pb, and U) data we report here demonstrate that a cluster of earthquakes that occurred at ∼430 ka, when fault-slip frequency increased by nearly one order of magnitude, corresponds with a brief period of particularly large and rapid variations in post-seismic fluid chemistry. Isotopic variations are consistent with fluid input from the Socorro magma body, a large, active, mid-crustal basalt intrusion 19 km below the surface. The short duration of the earthquake cluster (<50,000 years) precludes a role of thermal weakening of the crust in increased extension. We suggest that volatile exsolution and heating of ambient fluids during magma crystallization increased fluid volume and thereby pore-fluid pressure at depth, weakening the fault and driving more frequent failure through fault-valve action. This conclusion could not have been reached using traditional approaches in structural geology, stable isotope geochemistry, or geochronology alone, illustrating the utility of integrated data sets including radiogenic isotope analyses in studies of fluid-fault interactions. • We studied co-seismic calcite veins that provide evidence of >400 ka of seismicity on a normal fault. • Radiogenic isotopic analyses of these veins give insight into post-seismic fluid flow pathways. • Veins recording "background" seismicity document formation from upper-crustal brines. • Veins recording more frequent earthquakes contain evidence of fluid input from a magma body. • We infer fluids exsolved from magma drove fault-valve behavior, increasing earthquake frequency. [ABSTRACT FROM AUTHOR]

The forty-year history of the Journal of Structural Geology has recorded an enormous increase in the description, interpretation and modelling of deformation structures. Amongst factors that control deformation and the resulting structures, mechanical anisotropy has proven difficult to tackle. Using a Fast Fourier Transform-based numerical solver for viscoplastic deformation of crystalline materials, we illustrate how mechanical anisotropy has a profound effect on developing structures, such as crenulation cleavages, porphyroclast geometry and the initiation of shear bands and shear zones. Image 1 • Mechanical anisotropy strongly enhances strain localisation. • VPFFT + ELLE simulations illustrate effect of mechanical anisotropy. • Axial planar crenulation cleavages can be simulated with the VPFFT + ELLE code. • Mechanical anisotropy reduces rotation of objects, forming σ instead of δ-clasts. • Even small amounts of anisotropic minerals lead to C/C′ shear bands in shear zones. [ABSTRACT FROM AUTHOR]

In this essay, we explore a central problem of structural geology today, and in the foreseeable future, which is the determination of constitutive laws governing rock deformation to produce geologic structures. Although laboratory experiments provide much needed data and insights about constitutive laws, these experiments cannot cover the range of conditions and compositions relevant to the formation of geologic structures. We advocate that structural geologists address this limitation by interpreting natural experiments, documented with field and microstructural data, using continuum mechanical models that enable the deduction of constitutive laws. To put this procedure into a historical context, we review the founding of structural geology by James Hutton in the late 18th century, and the seminal contributions to continuum mechanics from Newton to Cauchy that provide the tools to model geologic structures. The procedure is illustrated with two examples drawn from recent and on-going field investigations of crustal and mantle lithologies. We conclude by pointing to future research opportunities that will engage structural geologists in the pursuit of constitutive laws during the 21st century. • Natural structures provide bases for mechanical models to test constitutive laws. • Methodology is applicable in all lithologies throughout the lithosphere. • Granodiorite exhumed from mid-crust shows plastic yielding enhances fault slip. • Deformation observed in exhumed mantle conflicts with empirical constitutive laws. • Technological advances will propel this methodology throughout the 21st century. [ABSTRACT FROM AUTHOR]

Recent advances in statistical methods for structural geology make it possible to treat nearly all types of structural geology field data. These methods provide a way to objectively test hypotheses and to quantify uncertainty, and their adoption into standard practice is important for future quantitative analysis in structural geology. We outline an approach for structural geologists seeking to incorporate statistics into their workflow using examples of statistical analyses from two locations within the western Idaho shear zone. In the West Mountain location, we test the published interpretation that there is a bend in the shear zone at the kilometer scale. Directional statistics on foliations corroborate this interpretation, while orientation statistics on foliation-lineation pairs do not. This discrepancy leads us to reconsider an assumption made in the earlier work. In the Orofino location, we present results from a full statistical analysis of foliation-lineation pairs, including data visualization, regressions, and inference. These results agree with thermochronological evidence that suggests that the Orofino area comprises two distinct, subparallel shear zones. The R programming language scripts that were used for both statistical analyses can be downloaded to reproduce the statistical analyses of this paper. • Statistical analysis of foliation-lineation data from the western Idaho shear zone. • Analysis includes plotting, regressions of geographic trends, and inference. • Fully commented R language scripts accompany all statistical analyses. [ABSTRACT FROM AUTHOR]

One aim of structural geology is to understand the processes that operate during deformation and metamorphism so that the conditions (P, T, strain-rates, stresses, rates of other processes such as grain-size reduction) that control these processes can be identified and quantified. In this paper we explore ways of quantifying the geometry of deformed metamorphic rocks in ways that are directly related to the processes that operated. We propose that structures we observe in nature are the result of coupling between nonlinear processes and hence deforming metamorphic systems behave as nonlinear dynamical systems. As such the descriptions of such systems should utilise the toolbox of methods that have been developed for dynamic systems over the past 50 years or so. These methods include the construction of attractors, multifractal analysis, recurrence plots, recurrence quantification analysis and dynamical network analysis. We illustrate the approach first using numerical models of fold systems, with linear and nonlinear constitutive relations and with and without initially imposed noise (imperfections). We then extend the illustrations to consider natural fold systems. Our conclusions are that the irregularity we see in natural fold systems is the result of nonlinear constitutive laws, not that of initial imperfections and that the number of processes operating to produce the observed fold shapes is relatively small. Image 1 • The irregularity we see in natural fold systems is the result of nonlinear constitutive laws, not of initial imperfections. • The number of processes interacting to produce the observed fold shapes is relatively small. • The nonlinear toolbox includes the construction of attractors, multifractal analysis and recurrence quantification analysis. [ABSTRACT FROM AUTHOR]

The mechanical behavior of materials is not affected by our choice of a coordinate system. Thus, the description of the behavior should not be affected by this choice. This is known as the principle of coordinate invariance, and is important not only for plasticity theory but for theoretical investigations in structural geology. The deviatoric stress-strain space, which fulfills the principle, is shown to be useful for the formulation of stress inversion. Problems in the inversion schemes of fault data are transformed into geometrical problems so that we can solve the problems using geometrical interpretations. In addition, the formulation gives the good basis for defining the classes of dissimilarities between reduced stress tensors that are the solutions of the inversion. We redefine the classes, here, from the standpoint of probability. It is demonstrated finally that the violation of the principle spoils the accuracy and resolution of the inversion. • Deviatoric stress-strain space is useful for paleostress analysis. • The space fulfills the principle of coordinate invariance. • Inversion schemes violating the principle have anisotropic accuracy and resolution. • Mathematical apparatus using the space are provided for the analysis. • Dissimilarity classes of reduced stress tensors are redefined based on the principle. [ABSTRACT FROM AUTHOR]

Structural geologists support their mind with tools, and these tools are increasingly computer based. The advent of Intelligent Systems will allow creation of research teams that combine the strengths of the human mind and computer processing to produce new research results. The efficacy of these approaches will require a solid grounding in cognitive science. Critical to this approach are databases, which are potentially transformative solely in their ability to allow access to data, in a primary form. Emerging more recently, however, is the concept of a dataguide, in which computer-aided analysis informs ongoing decisions about where and what data to collect. The creation of human and computer teams can expand the types of questions that can be addressed in structural geology and tectonics research, but it will take a community-based effort to understand the value of data to experts and how computers might aid an expert in the field. • Human-computer field research teams could combine the strengths of human minds and computer processing to transform research. • Databases can provide new types of data to experts in the field, to support new field workflows. • Dataguides can aid data collection decisions, but must combine geology, cognitive science, and computational science. [ABSTRACT FROM AUTHOR]

The incorporation of active faults in seismic hazard analyses may have a significant impact on the feasibility, design and cost of major engineering projects (e.g., nuclear facilities, dams), especially when located in the site vicinity. The regulatory definition of active versus inactive fault is generally based on whether the fault has ruptured or not after a specific chronological bound (i.e. fault recency). This work presents a methodology, mainly based on geomorphological mapping and trenching, for determining whether specific faults can be considered as active or inactive. The approach is illustrated through the analysis of several faults located in the Spanish Pyrenees (Loiti, Leyre, La Trinidad, Ruesta faults). The 29 km long Loiti Thrust was included in the Neotectonic Map of Spain as a probable neotectonic structure. Previous works, based on geomorphological investigations, incorporated the 28 km long Leyre Thrust as a significant seismic source in a probabilistic seismic hazard analysis, which challenged the seismic design of nearby large dams. The production of detailed geomorphological strip maps along the faults allowed the recognition of specific sites where the faults are covered by Quaternary deposits. The establishment of chronosequences (pediments-terrace sequences) and the available geochronological data helped identifying the most adequate morpho-stratigraphic units for satisfactorily evaluating fault activity vs. inactivity. The excavation of trenches at the selected sites provided unambiguous information on the presence or lack of deformation in the Quaternary cover overlying the fault, and the origin of scarps (tectonic versus erosional). Trenches were also useful for collecting samples and reliably measuring the relative height of terraces overlain by thick colluvium. The evidence gathered by these methods were complemented with the numerical dating of non-deformed slope deposits covering a fault, the analysis of the longitudinal profiles of old pediment surfaces located in the proximity of a fault, the examination of a cave situated next to a fault searching for speleoseismological evidence, and regional geodetic and seismotectonic data (GPS measurements, earthquake focal mechanisms). The integration of all the data, and especially the trenches dug in non-deformed old terrace deposits (>100 ka) truncating the faults, indicates that the analysed faults can be considered inactive and that previous neotectonic postulations were based on non-valid geomorphological interpretations. • Evaluation of fault activity vs. inactivity by geomorphic mapping and trenching • Limitations of soils, Quaternary deposits and numerical ages for determining fault activity • The importance of trenching for reducing epistemic uncertainty • Geomorphology plays a key role in the identification of seismogenic fault sources. • The impact of incorrect geomorphic interpretations on seismic hazard analyses [ABSTRACT FROM AUTHOR]

Due to the difficulty and inaccuracy of in-situ porosity measurement methods in fluvial deposits, knowledge about spatial variation of river bed porosity is limited. The objective of this study was to develop a new accurate method to improve and facilitate the in-situ porosity measurement of fluvial deposits. For this purpose, a Structure-from-Motion (SfM) photogrammetry-based method is applied to determine the in-situ total volume (V t) of the sampling pit. The total volume is then combined with the solid fraction volume (V s) measured by the water displacement method to calculate the porosity. Several sets of experiments were carried out to evaluate the systematic and stochastic uncertainties of this new method. Combination of V t and V s uncertainties using standard error propagation showed the absolute uncertainty of the porosity to be less than 0.01. Compared to the existing methods, this new SfM method increases the measurement accuracy significantly and strongly speeds up the porosity measurements, as it is independent from field calibration and initial sediment sample stabilization. • Accurate determination of the in-situ porosity of fluvial sand-gravel mixtures • A practical application of Structure-from-Motion photogrammetric technique • Statistical uncertainty analysis reveals an unprecedented low absolute uncertainty. • The absolute uncertainty of the porosity to be <0.01 • The new method facilitates and speeds up the porosity measurement for field studies. [ABSTRACT FROM AUTHOR]

A number of large landslides, which have strongly affected fluvial processes in the upstream catchment of the Minjiang River along the eastern margin of the Tibetan Plateau, Sichuan, were investigated with regard to both geological structure and topographic development. Topographic analysis suggested that there is a major knickpoint that formed not as a result of landslides but via tectonic activity and that the knickpoint propagated upstream, forming an inner gorge and undercutting and destabilizing nearby slopes. The effects of the knickpoint propagation and inner gorge formation on slope stability are dependent on the geometrical relationships between the river and geological structures. When the geological trend is normal or highly oblique to the river axis, landslides generally do not occur, but gigantic rockslides have occurred on one side of the Minjiang valley, which can be attributed to a wedge structure consisting of bedding planes and joints with intersections dipping valleyward and tight folds with hinges plunging valleyward. When the beds are planar, moderately dipping, and strike nearly parallel to the river, buckling deformation commonly occurs on cataclinal slopes, often transforming into catastrophic failure. Landslide dams form another type of knickpoint on the river channel that gradually disappear from the downstream to upstream as a result of river erosion. Our findings strongly suggest that the study of slope development by river incision must consider geological structures and that an understanding of geological structures and river incision history can provide a conceptual model for the prediction and mitigation of geohazards in tectonically active drainage basins. [ABSTRACT FROM AUTHOR]

Fracture geometry in folded strata is fundamental to stress and strain analysis and outcrop reservoir analogues. The well-exposed Tian'mu anticline, which consists of interlayered micrite limestone and cherty limestone, was studied in order to reveal interlayer slip mechanisms, and stress and strain impacts of derived fractures and minor folds by using Terrestrial Laser Scanning LiDAR data. The minor folds, occurring predominantly within flexible micrite limestone layers, are closely related to interlayer slip and are largely affected by the lithology. The secondary structures were probably formed at different times during past folding processes. It is necessary to separate different joint sets and secondary folds, and to then judge their ages separately. This results in implications for joint research. More importantly, it is necessary to consider the overall strain of the primary fold, or a larger area when researching the strain variations. • A typical use of TLS LiDAR point cloud in structural geology is explained. • A detailed analysis of paleo-stress direction (obtained from joints) is displayed. • A case of stress and strain analysis, based on minor folds is presented. [ABSTRACT FROM AUTHOR]

The study of microfractures is one of the keys to understand a variety of geological issues as diverse as seismic rupturing mechanisms, process zone characterization and evolution toward large-scale fracturing, characterization of reservoirs of geological fluids, or identification of microhabitats outside Earth. In earlier works, microcrack initiation and propagation in rocks has been observed at microscale. We test Atomic Force Microscopy (AFM) as a tool to retrieve nanoscale digital elevation models (nDTM) of rock surfaces. Basalt samples from two different geological environments are studied. In a basalt from Siberia, the topography of the granular material infilling of the crack can be accurately characterised, and the pristine crack shape retrieved, opening access to an estimate of the volume of the infilling material. In a basalt from Ethiopia, mixed-mode fracturing (opening-shear) is identified from nanofracture topography, as well as a textbook example of along-strike variations of fracture displacement. These observations demonstrate that fractures already initiate and propagate at nanoscale, and AFM is a powerful tool to conduct quantitative structural geology analyses with a resolution of ∼1 nm. • A method for AFM-SEM joint observation of rock surfaces is presented. • It makes possible to do structural analysis of microscopic fractures at nanoscale. • This is illustrated with nanostructural analysis of two basalt samples. • Implications in the field of fracture initiation and in other fields are suggested. [ABSTRACT FROM AUTHOR]

Val d'Agri is a seismically active intermontane basin in southern Italy known for hosting the largest on-shore hydrocarbon reservoir in western Europe. Despite extensive study of the basin, important questions remain regarding fluid circulation and the possible link between deep hydrocarbon reservoirs, faults, natural and induced seismicity, and gas migration towards the surface. To address some of these issues we performed near-surface gas geochemistry and structural geology surveys throughout the basin at both the regional and local scale. While carbon dioxide data are due to shallow, biological processes in the soil, anomalous results for other gas species are interpreted as being linked to structural discontinuities. Coincident methane and ethane anomalies, which imply a deep thermogenic origin, occur primarily in the northern part of the Val d'Agri basin. The most dominant alignment of these gases starts from a surface hydrocarbon seep and extends above a buried, NE-SW-striking fault that transects the valley. In contrast, radon anomalies are localized in the southern part of the basin along the western border, in correspondence with the Monti della Maddalena Fault System (MMFS) and a cluster of background natural seismicity. The origin and implications of the observed anomalies are discussed. • Gas geochemistry / structural surveys were performed at Val d'Agri, host of Europe's largest onshore hydrocarbon reservoir. • Coincident methane and ethane anomalies along known / inferred faults imply upward migration of reservoir hydrocarbons. • hydrocarbon gas alignment above buried fault shows possible link between exploited reservoirs on either side of the valley. • The correlation between radon anomalies and recent low-level seismicity implies fracture enhanced emanation. [ABSTRACT FROM AUTHOR]

• Novel approach designed to study groundwater-surface water interaction in mountains. • Multiscale geological mapping, geophysics and hydrological data are combined. • A geologically-controlled resurgence is identified in an Andes ungauged catchment. • The link between geological and hydrogeological structures is robustly established. Mountain water resources are considered to be the world's water towers. Still, despite their importance for downstream societies and ecosystems and their vulnerability to climate change, they remain poorly understood – It is the case in particular of mountain groundwater systems. Their complexity makes them difficult to conceptualize, while their remoteness makes them difficult to study, both observationally and instrumentally. Understanding mountain hydrogeological systems is mostly limited by the lack of characterization of the subsurface geologic framework and by the limited understanding of the role of geological structures on groundwater flow and on surface water-groundwater interaction. Removing methodological barriers is therefore a necessary step for improving the understanding of mountain hydrogeological systems. To tackle this problem, we develop a comprehensive multi-disciplinary approach to gain insights into the hydrogeological role of geological structures in ungauged mountain catchments. The methodology consists of several complementary methods: (1) geological mapping at multiple scales; (2) a geophysical study including on-ground Electrical Resistivity Tomography (ERT) and, gravimetry transects, and a UAV-based magnetic survey; (3) hydraulic data, including a 9 km long transect of streamflow measurements in the recession period, the long-term Normalized Difference Vegetation Index (NDVI), and varied hydric markers (e.g., a thermal spring and a puddle). The methodology is tested in the Parque Nacional del Río Clarillo, an ungauged catchment in the Andes Mountains (≈130 km2) that is illustrative of the complexity of mountain hydrosystems featuring fault zones, weathered zones, intrusive rocks, and volcano-sedimentary successions. An increase of approximately 50% in the streamflow is observed over a short distance of 1 km. Such a localized and significant increase in the baseflow is not related to any superficial supply and can only be explained by groundwater exfiltration. Based on the multiscale geological mapping and geophysical survey, a regional N-S fault and a secondary set of E-W local faults are identified in the vicinity of the resurgence area, which conjointly are likely to export groundwater from a neighbouring subcatchment up to the resurgence area. Downstream of the resurgence area, no significant change in the baseflow is observed, corresponding to the presence of an impermeable granitic pluton identified by the geological and geophysical mapping. Finally, a fractured zone in the Andean foothills is identified in the volcanic unit, which coincides with a perennial thermal spring, indicating upwelling flow and hydrogeological connectivity between the mountain block and the alluvial basin. The results strongly support the ability of the proposed methodology to identify geological structures that substantially impact the evolution of the baseflow through the catchment. The complementary multi-disciplinary methods are used innovatively to infer the link between geological and hydrogeological structures. The methodology does not aim to fully characterize the geological framework of the catchment but pragmatically focuses on hydrogeologically pertinent structures that may impact baseflow and consequently catchment management. [ABSTRACT FROM AUTHOR]

In comparison with ophiolite, ophiolitic mélange, especially its matrix, contains more information about the evolution of the relevant ocean. The evolution of the eastern Palaeo-Tethys recorded a whole Wilson cycle of numerous continental blocks such as the South China Block and Indochina Block, including rifting away from the Gondwana continent, subsequent northward migration and final collage with the Laurasia continent. Based on structural geology, detrital zircon, and related geochemical analyses, the Ailaoshan–Song Ma ophiolitic mélange can be divided into M1, M2, and M3 units with distinct detrital zircon age spectra and ε Hf (t) values suggesting for different provenances. These units are in faults-contact along the orogenic belt, indicating a strike–parallel heterogeneity of the ophiolitic mélange. To further understand the heterogeneity of these ophiolitic mélanges, five samples from the matrix of the Ailaoshan ophiolitic mélange were collected to be conducted detrital zircon U Pb dating and Lu Hf isotope analyses. All samples share the same zircon age spectrum, with two obvious age peaks at 430 and 960 Ma, which is comparable with the M1 unit. These results imply that the northwestern Ailaoshan ophiolitic mélange segment can be subdivided into M1 in the interior and M2 in the exterior rather than the previous division, indicating a strike–perpendicular heterogeneity. Based on their geometries (NE-dipping) and depositional ages (M1, 310–270 Ma; M2, 260–240 Ma), the elder M1 unit was thrusted upon the younger M2 unit, indicating a tectonic inversion. This inversion, which is associated with the whole geometry of the Ailaoshan belt, is ascribed to the transpressive deformation of the Cenozoic Red River Fault. These spatial heterogeneities well match the different evolutionary stages of the eastern Palaeo-Tethys. • Ailaoshan-Song Ma-Song Chay ophiolitic mélanges have strike-parallel heterogeneity. • NW segment of Ailaoshan ophiolitic mélange shows strike-perpendicular heterogeneity. • Geometry of ophiolitic mélanges zone due to RRF sinistral strike-slip deformation. [ABSTRACT FROM AUTHOR]

The deformation processes (e.g. accretionary or intraplate) occurring within the Borborema Province have been widely discussed, however the eastern part of the central subprovince lacks further investigation in such aspect. In this contribution, we present integrated airborne gamma ray and magnetometric geophysical data, as well as meso- and microstructural markers of the Archean-Paleoproterozoic Alto Moxotó and Neoproterozoic Rio Capibaribe terrains (central Borborema Province), providing evidence for hidden accretionary episodes in the region. Fourteen radiometric and ten magnetic domains were described and fitted with most of the geological units and mapped structures, suggesting geological contrasts between the studied terrains. For instance, the Alto Moxotó terrain presents high-to-medium eTh and eU radiometric signatures, spatially distributed along folded geometry, whereas the lithospheric record of the Rio Capibaribe terrain is characterized by K (%) enrichment and a dominant NE-SW sheared crust. In addition, the obtained Euler solutions show good correlations with the main structures and delineated shallow to intermediate sources of the Congo-Cruzeiro do Nordeste strike-slip shear zone system, the proposed structural boundary. This large set of shear zones are characterized by large mylonitic corridors with characteristic vertical foliation planes with moderately-plunging mineral lineations. Associated microstructures include bulging, subgrain rotation and recrystallization that, in association with the well-developed S–C fabrics and myrmekites indicate deformation at moderate temperature values (∼400–500 °C). Also, conspicuous fracture networks seen in plagioclase grains demonstrate that deformation also took place at the later developed brittle-ductile transition. Hence, the described contrasting rock ages and nature, geophysical signatures and deformational patterns is herein interpreted as the result of crustal agglutination during the Neoproterozoic, in which the Congo-Cruzeiro do Nordeste shear zone system would represent relics of a terrane boundary developed during the assembly of western Gondwana. • Airborne geophysical data constrain the Rio Capibaribe and Alto Moxotó terrains crustal boundary. • The Congo-Cruzeiro do Nordeste shear zone system operated at the ca. 500-400 °C temperature interval. • Accretion tectonics is the likely mechanism that operated in this portion of western Gondwana. [ABSTRACT FROM AUTHOR]

Abstract Measurement of structure orientations is a key part of structural geology. Digital outcrop methods provide a unique opportunity to collect such measurements in unprecedented numbers, and are becoming widely applied. However, orientation estimates produced by plane fitting can be highly uncertain, especially when observed data are approximately collinear or the structures of interest comprise differently oriented segments. Here we present a Bayesian approach to plane fitting that can use data extracted from digital outcrop models to constrain the orientation of structures and the associated uncertainty. We also describe a moving-window search algorithm that exploits this Bayesian formulation to estimate local structure orientations for segmented structures. These methods are validated on synthetic datasets for which both the structure orientation and associated uncertainty is known. Finally, we implement the method in the point cloud analysis package CloudCompare and use it to estimate the orientation and thickness of dykes exposed in cliffs on the island of La Palma (Spain). The results highlight the potential of this method to generate structural data at unprecedented spatial resolution, while simultaneously characterising the associated uncertainties. Highlights • A Bayesian method for constraining structure orientations is presented. • Uncertainty is quantified by evaluating or sampling from the posterior distribution. • A moving-window algorithm is used to estimate orientations of segmented structures. • Digital outcrop data of a dyke swarm is used to test and demonstrate these methods. [ABSTRACT FROM AUTHOR]