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ABSTRACT Comprehending pre‐suture geological setting and post‐suture intricate tectono‐thermal chronicle in a crustal‐scale orogeny and discerning the temporal connections among different tectonic domains within an orogen yields valuable insights into worldwide tectonic phenomena leading to the reconstruction of paleogeographic configurations of fragmented crustal components within erstwhile supercontinents. Since the tectonic evolution of the Indian subcontinent during the Proterozoic remains a topic of discussion due to multiple controversial views, the Central Indian Tectonic Zone (CITZ) offers a great archive for the protracted geological history of subduction, collision, and suturing of northern Indian cratonic blocks (NIC; composed of Bundelkhand and Aravalli cratons) and southern Indian cratonic blocks (SIC; composed of Bastar, Singhbhum, and Dharwar cratons). Events belonging to two Supercontinents namely, Columbia (ca. 2100 to 1800 Ma) and Rodinia (ca. 1200 to 900 Ma) are embedded within the geological history of CITZ, as it records multiple events that occurred between the Paleoproterozoic and Neoproterozoic. In this backdrop, the present contribution attempts (i) the deconvolution of pre‐suture (pre‐CITZ formation) plate margin basin depositional history including tracking of detrital provenance, and (ii) a review of different stages of collision and suturing as the plate margin evolved in the form of an orogen subsequent to the closure of the basin. A back‐arc basin setup in a subduction margin is recommended for the Mahakoshal Basin which witnessed several tectonic pulses resulting in the formation of alluvial fans/fan deltas along the basin shoreline. It is suggested that the basin was open, at places, even after ca. 1700 Ma, and received sediments. [ABSTRACT FROM AUTHOR]

The North Sea Basin is the most important oil and gas producing area in Europe and the birthplace of many classic petroleum geological theories. From the perspective of multi-spheric interactions in the Earth, this study investigated the rift-foreland-rift evolution process of the North Sea Basin, which was controlled by the deep dynamic driving forces of the continental collision orogeny, mantle plume uplift, and intraplate deformation. The North Sea Basin was found to have drifted northward since the Carboniferous and passed through the low-latitude Hadley and the mid-latitude Ferrel cells. Two sets of main hydrocarbon source rocks have formed, the coals and coal measures of the Upper Carboniferous Westphalian and the marine shale of the Upper Jurassic Kimmeridge Clay Formation. We propose that the deep processes, tectonic activity, and transgression-climate evolution jointly controlled the types and horizons of the source rocks, reservoirs, and seals in different regions of the North Sea Basin. In the southern North Sea Basin, a Carboniferous-Lower Triassic gas-rich petroleum system was formed, which is characterized by transitional coal measure source rocks, desert aeolian sandstone reservoirs, and evaporite cap rocks. In the northern North Sea Basin, an Upper Triassic-Paleogene oil-rich petroleum system was formed, which is characterized by marine graben-type source rocks, deltaic sandstone and marine limestone reservoirs, and marine tight marl and shale cap rocks. The late tectonic burial and uplift in the North Sea Basin further controlled the processes of oil and gas generation and accumulation, ultimately leading to a differential distribution pattern which is oil rich in the northern part and gas rich in the southern part of the basin. In the future, there is an urgent need to re-examine the mechanisms for the petroleum generation and accumulation in large mature exploration areas (e.g., super basins such as the North Sea) and low exploration areas (e.g., the Okhotsk Sea and Arctic regions) from the perspective of multi-spheric interactions in the Earth in order to provide new theoretical support for increasing the identification of oil and gas reserves globally. The development of artificial intelligence in the petroleum industry should focus on the massive amount of exploration and geological data collected in the North Sea Basin. Through digital geological innovation, carbon neutral comprehensive utilization of oil, gas, and associated resources (e.g., helium and hydrogen) can be achieved, providing a new paradigm for global oil and gas exploration and development. [ABSTRACT FROM AUTHOR]

The horizontal propagation of slab detachment (slab tearing) is known to control lateral migration of the mountain uplift along the collisional belt. However, along‐strike differential collision due to an oblique passive margin geometry can make the topography response more complex. In this study, we employ 3D thermomechanical modeling to distinguish between the lateral migration of the mountain topography driven by slab tearing and oblique continental collision itself. In our models, slab breakoff is triggered by the transition from oceanic to continental subduction, occurring earlier on one side of the passive margin than on the other due to the initial oblique configuration. However, once slab breakoff has begun, it spreads horizontally in the form of tearing at high velocity (∼38–118 cm yr−1), and associated topographic uplift also propagates with the same velocity. In contrast, the along‐strike migration of subsequent continental collision and related topographic uplift propagation is typically much slower (∼2–34 cm yr−1). Similarly, the vertical magnitude of surface uplift caused by slab tearing is higher (up to 10 mm yr−1) than the following collision phase (<4 mm yr−1). The parametric analysis reveals that slab tearing velocity and the associated horizontal propagation of mountain uplift depends on obliquity angle and slab age, whereas the migration of collision‐induced topographic growth is controlled by the convergence velocity and obliquity angle. Finally, we show that presence of microcontinental block detached from the passive margin leads to spatial and temporal transition from horizontal to vertical slab tearing and more intense syn‐collisional mountain building. Plain Language Summary: Continental collision begins after the complete subduction of the oceanic domain, initially located between the colliding continents. As the oceanic slab has negative buoyancy, it detaches from the positively buoyant continental plate shortly after the start of continental collision. Slab detachment leads to a rapid uplift of the surface topography and usually moves sideways, a process known as slab tearing. Slab tearing in turn results in a lateral propagation of the topographic uplift along the continental margin. However, if the colliding plate margins are initially at an angle to each other, an oblique continental collision occurs, which can also lead to along‐strike migration of the mountain uplift. To differentiate between the topography response to slab tearing and oblique continental collision, we have carried out 3D numerical modeling. Our parametric analysis reveals that the rate of slab tearing and the associated horizontal propagation of mountain uplift primarily depend on the angle of collisional obliquity and the age of the subducting oceanic slab, whereas the velocity of plate convergence controls the migration of collision‐induced topographic growth. Our findings also indicate that the surface uplift associated with slab tearing is more pronounced and spreads laterally much faster than during following oblique continental collision. Key Points: We explored numerically in 3D the topography response to horizontal slab tearing during retreating oblique continental collisionHorizontal slab tearing can initiate before collision due to the transition from oceanic to continental subduction below fore‐ and back‐arc domainSurface uplift associated with slab tearing is more pronounced and spreads laterally much faster than in the subsequent collision phase [ABSTRACT FROM AUTHOR]

Sixteen morphometric relief parameters have been identified whose positive anomalies correspond with seismic areas in the Greater Caucasus. An analysis of four parameters which were considered to provide the most information using the γ-operator in fuzzy logic has enabled us to develop a scheme for an index of neotectonic activity that was used along with the results of computerized geodynamic simulation to identify zones of possible earthquake sources. The new approach does not require detailed information on present-day and paleo seismicity, hence can be used to deal with an analogous problem for territories whose seismotectonics is poorly known. We have demonstrated an interrelationship between recent deformations and regional seismicity, and the possibilities offered by the method of lineament analysis due to Yu.V. Nechaev (2010) for identification of active faults. [ABSTRACT FROM AUTHOR]

Ceratophryid frogs inhabit the lowlands of South America and exhibit greater diversity in the semiarid Gran Chaco. The presence of Ceratophryidae dates back to the late Miocene on the eastern slopes of the Andes in Argentina. Herein, we describe the remains of Ceratophrys from late Miocene of Palo Pintado Formation (Salta, Argentina). Fragmentary bones were recovered from the base of the unit in beds dated between 8 and 7.7 million years ago. The specimen IBIGEO-P141 exhibits the fusion of dentary and mentomeckelian bones forming a fang, a sharp-edged lower jaw, and sculptured bones as Ceratophryidae. The granular pattern of sculpturation, differences between pars facialis and pars dentalis of maxillary, and the shape of lower jaw, support its assignment to the genus Ceratophrys. Combined bioclimatic data and geographic distribution of living Ceratophrys indicate a strong influence of precipitation variables in the distribution of these frogs with adaptations to survive long dry periods. These facts suggest a seasonal rainfall with a well-defined dry season during the deposition of lower levels of Palo Pintado Formation. The palaeoclimatic conditions resemble those occurring in the actual semiarid Chaco, and reveal that the historical geographic distribution of Ceratophryidae was retracted eastward due to the Andean uplift. [ABSTRACT FROM AUTHOR]

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ABSTRACT The western Black Sea region is a key area for the study of the Neo‐Tethys orogenic belt, as it contains records of the evolutionary history of the entire Alpine orogeny from subduction to oceanic closure and collision. The Izmir‐Ankara and the Intra‐Pontide suture zones represent the final closure of the Neo‐Tethys oceans. However, when the final closure took place is still disputed. In this study, we investigate syn‐collisional faulting events in the western Black Sea region near Istanbul. We performed kinematic analyses of faulting and U–Pb dating of syntectonic calcite precipitates on the fault planes to constrain the timing of Neo‐Tethys Ocean closure and post‐collisional contractional tectonics. Syntectonic calcite precipitates associated with regional N‐S compressional tectonics provide precise U–Pb ages between 48 and 57 Ma, constraining the early Eocene age of reverse faulting and associated closure of the Intra‐Pontide Ocean. [ABSTRACT FROM AUTHOR]

The Qilian orogenic belt (QOB) located in the northeast margin of the Tibetan Plateau is featured by remarkable crustal thrusting and shortening, providing a key natural example to understand the lithospheric deformation of the Tibetan Plateau. Two types of continental collision are observed in the QOB: lithosphere subduction beneath Southern Qilian and crust underthrusting of Alxa terrain along the North Border Thrust (NBT). Deep seismic reflection profiles reveal complex stress field evolution, including compressional deformation in the lower crust, extensional deformation in the upper crust, and detachment deformation in the middle crust. In this study, we use 2D numerical modeling to investigate the dynamics of these two different collision types and the evolution of Qilian uplift. Model results suggest three patterns of continental collision, i.e., crust underthrusting follows lithosphere subduction, lithosphere subduction and the failed underthrusting/subduction. The key factors that may influence model evolution, including crustal rheology, convergence direction and rate, are systematically investigated. Our model results are further compared to observations, suggesting that lower convergence rate and crust underthrusting along NBT likely control the uplift and crust stress stratification of the QOB. [ABSTRACT FROM AUTHOR]

Although subduction is a continuous process, arc system behavior is non-steady-state, leading to uncertainty surrounding the composite spatial and temporal evolution of transcrustal arc magma plumbing systems. This study integrates field, geochronologic, and geochemical data sets from the central Sierra Nevada arc section to investigate the extent to which spatial inheritance is recorded in arc geochemical compositions, and how these signals may be modified by dynamic arc behaviors through time, from arc-wide flare-ups, migration, and crustal thickening to regional magma focusing. Geochemical patterns across Mesozoic arc rocks characterize persistent spatial signals of inheritance, whereas geochemical trends during Cretaceous arc activity provide the temporal component of simultaneous dynamic processes. Distinct bulk-rock isotopic signals define each of the three Mesozoic magmatic flare-ups, which, during Cretaceous arc magmatism, is coupled with eastward arc migration. Additionally, Cretaceous magmatic and tectonic thickening doubled the thickness of arc crust, and magmatism was focused toward a central zone, culminating in the formation of the ∼1100 km² Tuolumne Intrusive Complex. During magma focusing, temporal signals of magma mixing outweighed the previously pervasive signal of spatial inheritance. Distinct dynamic behaviors effectively primed the arc by the Late Cretaceous, generating transcrustal hot zones of increased magma mixing, recycling, long-term storage, and homogenization. Non-steady-state behavior in the Sierra Nevada resulted in mountain building and voluminous continental crust formation by transforming the physical, thermal, and chemical properties of the lithosphere over tens of millions of years. [ABSTRACT FROM AUTHOR]

West Tasmania has a complex geological history, including a Cambrian tectonic collision and related orogenesis, which formed ore deposits in a volcanic hosted massive sulfide (VHMS) setting. While the topography and dense vegetation covering the area presents challenges for on-ground investigations, the area is relatively well-studied such that 3D geological models are available. This contribution presents results of a broadband magnetotelluric (MT) 2D transect across the area (∼30 stations over a $ \sim 80\,{\rm km} $ ∼ 80 km line, deployed in early 2016) that enables a combined interpretation of regional-scale geoelectric and geological structures. After accounting for noise, distortion and geoelectric strike; we produce 2D resistivity models using OCCAM2D inversion. We infer low resistivity anomalies in the shallow ( $ \lt 3\,{\rm km} $ < 3 km ), mid (3–8 km) and deeper crust. Along this MT transect the shallow and mid crust low resistivity zones correspond to major crustal faults. Deep low resistivity features in the east of the transect suggest fluid pathways associated with metamorphism along the western boundary of the Tyennan block during the Cambrian Tyennan Orogeny, while others potentially represent the metasomatism of lower crustal rocks and fluid pathways converging into the mid crust. [ABSTRACT FROM AUTHOR]

The North American craton interior preserves a >1 Ga history of near surface processes that inform ongoing debates regarding timing and drivers of continental‐scale deformation and erosion associated with far‐field orogenesis. We tested various models of structural inversion on a major segment of the Midcontinent Rift along the Douglas Fault (DF) in northern Wisconsin, which accommodated ≳10 km of total vertical displacement. U‐Pb detrital zircon and vein calcite Δ47/U‐Pb thermochronometry from the hanging wall constrain the majority of uplift (≳8.5 km) and deformation to 1052–1036 Ma during the Ottawan phase of the Grenvillian orogeny. Combined U‐Pb zircon dates, Δ47/U‐Pb calcite thermochronometry, and field data that document syn‐ to early post‐depositional deformation in the footwall constrain a second stage of uplift (1–1.5 km) ca. 995–980 Ma during the Rigolet phase of the Grenvillian orogeny. A minor phase of Appalachian far‐field orogenesis is associated with minimal thrust reactivation. Our combined analyses identified the 995–980 Ma Bayfield Group as a Grenvillian foreland basin with an original thickness 0.5–2 km greater than currently preserved. By quantifying flexural loading and other subsidence mechanisms along the Douglas Fault, we identify dynamic subsidence as a mechanism that could be consistent with the development of late‐Grenvillian transcontinental fluvial systems. Minimal post‐Grenvillian erosion (0.5–2 km) in this part of the craton interior has preserved the Bayfield Group and equivalent successions, limiting the magnitude of regional erosion that can be attributed to Neoproterozoic glaciation. Plain Language Summary: Around 1.1 billion years ago, volcanic rocks and sediments began accumulating in a large rift basin around the present‐day Lake Superior region of North America. Continent‐continent collision on the edge of North America caused rifting to cease and major uplift to occur on thrust faults in the rift. The timing of the tectonic shift and the amount of crustal uplift and the number of uplift episodes are all poorly constrained. Our new geochronology precisely identifies the age of two major uplift episodes, ∼1.05 and ∼0.98 billion years ago. Mineral veins that formed during uplift record the age and temperature of formation, which enables reconstruction of an uplift history. We conclude that the collisional event ∼1.05 billion years ago resulted in ≳8.5 km of uplift followed by 1.0–1.5 km of uplift ∼0.98 billion years ago. A sedimentary basin associated with collision ∼1.0 billion years ago may have been part of a vast transcontinental river system. The surface underlying the Great Unconformity, a surface representing missing time, regionally did not undergo much erosion following uplift, suggesting long‐term stability of the North American craton interior over the last ∼0.98 billion years. Key Points: U‐Pb zircon and calcite dates constrain two‐stage Grenvillian inversion of the Midcontinent Rift on the Douglas Fault (DF) in northern WisconsinΔ47/U‐Pb thermochronometry constrains vertical displacement of ≳8.5 and ∼1.5 km in the Ottawan and Rigolet Grenvillian phases, respectivelyBasin analysis and clay mineralogy constrain original thickness, subsidence drivers, and erosion of a ca. 1010–980 Ma Grenvillian foreland [ABSTRACT FROM AUTHOR]

The eastern Iranian range, known as the Sistan suture zone in the past, has recently been identified as the Sistan orogen. This Paleogene orogeny is located between the Lut and Afghan microcontinents. The structural analysis shows that most of the thrusts dip towards the NW so that the Permo-Triassic sediments and Jurassic micro-diorites of the Lut Block overthrusted over the younger rocks. Structural studies show that the tectonic vergence was from the NW to the SE of the Sechengi area in the NW part of Sistan orogen. We recognized three deformation phases in eastern Iran. The first N-S deformation event (D1) resulted in the formation of tight E-W folds (F1) and associated cleavages (S1). The second E-W deformation event (D2), which occurred in the late Paleogene led to the bending of older structures, including the axial plane of the first-generation folds giving them a new northwest direction (F2). Additionally, the ramp of the first-phase thrusts (striking E-W) was reactivated, acquiring a new NNW orientation and exhibiting SSE tectonic vergence. The third deformation event (D3) resulted in the formation of NNE and WNW conjugate faults in eastern Iran. Such consecutive deformation events perpendicular to each other are inconsistent with the models of simple linear orogen presented for eastern Iran (i.e. rifting of eastern Iran continental crust and subsequence linear collision) and seem more consistent with the buckling orogeny (Orocline). [ABSTRACT FROM AUTHOR]

The Taiwan orogeny, an example of arc-continental collision, exhibits complex geological structures and rapid exhumation. Many models have tried and failed to fully capture the dynamics of these processes. We developed a comprehensive thermomechanical model that considers the transition from brittle to ductile behavior with depth, lithology-dependent erosion and observed decollement and backstop geometries. This model successfully reproduces the intricate structures observed within the Taiwan orogeny, aligns with structural complexities, metamorphic temperature profiles, thermochronological records, strain distributions, and the rates of exhumation and cooling and elucidates the roles of ductile deformation and ramp structures in forming the Hsuehshan Range and the Western fold and thrust belt. The insights from this model offer potential applicability to other orogenic wedges worldwide. [ABSTRACT FROM AUTHOR]

Structural, metamorphic, and geochronological study of the Delhi Supergroup rocks near the western margin of the Aravalli-Delhi Mobile Belt (ADMB) elucidate the Neoproterozoic tectonics of the South Delhi Fold Belt (SDFB) and its implication for the evolution of the Greater Indian Landmass (GIL). In this study, we establish three deformational events in the SDFB. While the D1 event produced isoclinal, reclined F1 folds synchronous with prograde amphibolite facies metamorphism (~5 kbar, 650°C), D2 formed outcrop to map-scale upright F2 folds. D3 comprised ‘partitioned transpression’ along two subvertical shear zones. Oblique dextral-reverse movement (D3a) along one shear zone formed an outcrop-scale positive flower structure, while sinistral-reverse movement along the other rotated and steepened the hinges of the F2 folds (D3b). U-Pb zircon dating of post-tectonic (post-D2, but pre-D3) and syntectonic (syn-D3) granite intrusives suggests >844 Ma age for D2 and ca. 820 Ma for D3. An older magmatic event (ca. 990 Ma) is recorded from sheared pink granites (pre- to syn-D1 intrusion). We suggest that the amalgamation of the ADMB and the Marwar Craton was initiated by the Grenville-age (ca. 1000 Ma) subduction-collision, while the younger events (ca. 844 Ma and 820 Ma) mark the final stitching of the ADMB – Marwar Craton along the Phulad-Ranakpur palaeo-suture zone to form the GIL. The distribution of early (ca. 1000–900 Ma) and late (ca. 800–700 Ma) Tonian magmatic and metamorphic ages in the SDFB suggest that the final growth of the GIL took place through multiple stages of oblique collision in a pulsating orogenesis through the Early Neoproterozoic. [ABSTRACT FROM AUTHOR]

The West Qinling Orogen (WQO) is located in the western part of the Qinling Orogen and in the transition zone of Qilian Orogen, Songpan-Garze Orogen and Yangtze Block, and also the key position of Triassic collision orogenic event. The study of the Early Triassic strata in the WQO is contributed to analyze the closure process of the paleo-Tethys. We conducted LA-ICP-MS U-Pb dating studies on detrital zircons to determine the provenance, depositional age, and tectonic setting of the Early Triassic Longwuhe Formation in the Lintan area of the WQO. The results show that the majority of the detrital zircons in the Longwuhe Formation are mainly magmatic origin and have characteristic of crust source zircon. The lowest limit of sedimentation of the Longwuhe Formation is constrained to the Early Triassic, with the youngest detrital zircon age of 253 ± 3 Ma. The ages can be divided into five age groups: 3 346–1 636 Ma, with two peak ages of ca. 2 495 and ca. 1 885 Ma; 1 585–1 010 Ma, with a peak age at ca. 1 084 Ma; 992–554 Ma, with a peak age at ca. 939 Ma; 521–421 Ma, with a peak age at ca. 445 Ma; 418–253 Ma, with a peak age at ca. 280 Ma. Apparently, the sources of the Longwuhe Formation include the northern margin of the WQO, the Qilian Orogen (QLO) and the basement of the southern margin of the North China Block (NCB), of which the ancient basement of the southern margin of the NCB is the main source area of the Longwuhe Formation. Combined with previous studies, we propose that the Longwuhe Formation was formed in a fore-arc basin, which is related to the closure of the A'nyemaqen-Mianlüe Ocean from the Early Permian to Early–Middle Triassic due to the northward subduction-collision of the Yangtze Block (YZB). This also indicates that the A'nyemaqen-Mianlüe Ocean has flat subduction characteristics. [ABSTRACT FROM AUTHOR]

The Mesoproterozoic Belt Basin of the northwestern United States and southwestern Canada contains a 5-20-km-thick metasedimentary succession deposited during an important transition in the Precambrian development of North America. Key unresolved issues for the Belt Basin include the chronology of deposition, sources of siliciclastic sediment, and regional paleogeography during Laurentian orogenesis. To address these topics, we acquired detrital zircon U-Pb geochronologic data for eastern exposures of the Belt-Purcell Supergroup in the Lewis thrust salient along the USA-Canada border. To define an integrated chronostratigraphic and provenance framework for the Belt Basin, we calculated maximum depositional ages and qualitatively and quantitatively compared our geochronologic data set to a compilation of Laurentian igneous and metamorphic zircon U-Pb ages using multidimensional scaling and an inverse Monte Carlo model. The results suggest a stratigraphic age range of ca. 1495-1380 Ma, constituting a depositional duration of ~115 m.y. with an average sediment accumulation rate of ~40 m/m.y. for the studied locality (extrapolated to ~155 m/m.y. for the basin depocenter). Variations in sediment provenance are expressed by three distinct intervals within the Belt-Purcell Supergroup. The lower Belt Supergroup succession (Waterton to lower Helena Formations; ca. 1495-1440 Ma) is dominated by Paleoproterozoic and Archean grains derived from the northeastern Canadian Shield. The middle Belt Supergroup succession (upper Helena to Sheppard Formations; ca. 1440-1420 Ma) displays mixed early Mesoproterozoic, late Paleoproterozoic, and Archean zircon age groups. The upper Belt Supergroup succession (Gateway to Roosville Formations; ca. 1420-1380 Ma) contains almost entirely late Paleoproterozoic zircons sourced from the south (Yavapai-Mazatzal and Mojave crustal provinces). We interpret sediment provenance to reflect a continental-scale, fluvial drainage reorganization during middle Belt Supergroup deposition that can be linked to the recently recognized Picuris orogeny. [ABSTRACT FROM AUTHOR]

In the Alpine Corsica (France), the Santa Lucia Nappe represents a peculiar unit preserving the unique relicts of Paleozoic lower to medium continental crust. It consists of composite basement affected by Permian granulite facies metamorphic conditions unconformably covered by a Late Cretaceous clastic sequence (Tomboni Conglomerate and Tralonca Flysch) affected by polyphase deformation and low‐grade‐metamorphism. In this work, we present a new reconstruction of the deformation events registered by the Tralonca Flysch during the Alpine orogeny. The D1 phase was testified by rare isoclinal folds. The D2 phase produced a continuous foliation and a map‐scale sheath‐fold with a top‐to‐W sense of shear. The D3 phase produced E‐verging non‐cylindrical folds and S3 crenulation cleavage that is not associated to metamorphic blastesis. We present the first temperature‐pressure‐deformation (P‐T‐d) path for the Tralonca Flysch, demonstrating that the Santa Lucia Nappe underwent accretion and then first stage exhumation in the Alpine wedge during the D1 phase with pressure and temperature peaks both occurred under blueschist metamorphic conditions. The D2 phase occurred at lower pressure‐temperature conditions during a second stage exhumation. This pressure‐temperature‐deformation path is comparable with those of the Lower Units (i.e., the subducted continental units of Alpine Corsica) suggesting a common geodynamic history. [ABSTRACT FROM AUTHOR]

The Pan‐African mobile zone, situated at the margin of the Congo Craton in Cameroon, is characterized by a geological setting with polyphased tectonics, which can be summarised as the alternation of compression and extension events. The present study, conducted in a portion of the aforementioned zone, is aimed at investigating crustal structures using aeromagnetic data. To achieve this, a variety of advanced analysis and interpretation techniques were applied to reduce aeromagnetic data at the equator, including total horizontal derivative (THD), Centre for Exploration Targeting (CET), 3D Euler deconvolution (ED), spectral analysis, and 2D3/4 modeling. The results indicate that the study area can be divided into four magnetic units based on the magnetic properties (magnetic susceptibility, geometry, and depth) of the underlying rocks. The THD method reveals the presence of pseudocircular and linear structures, which are associated with mafic intrusions and faults, respectively. The structural trends of the lineament generated semiautomatically using the CET method suggest that the structures are oriented in order of priority: E‐W, WNW‐ESE, ENE‐WSW, and NE‐SW. These directions are probably related to the Pan‐African orogeny. According to the ED, the depths of these lineaments extend beyond 1250 m. A spectral analysis conducted on a profile intersecting some of the significant anomalies on the reduction to the equator (RTE) map indicates that the average depths of superficial and deep magnetic sources along this profile are approximately 0.5 and 6.5 km, respectively. The geological model obtained along this profile by direct 2D3/4 modeling indicates the presence of an ancient granitic basement, which is overlain by younger formations belonging to the Pan‐African. [ABSTRACT FROM AUTHOR]

Radiogenic isotopes of igneous and detrital minerals from various clastic rocks of mountain belts are used to reveal tectonic and sedimentary processes, which are otherwise difficult to detect. Here, we discuss the results of U–Pb and Lu–Hf zircon systems, and 40Ar/39Ar on detrital white mica in Eastern Alps. Zircon and white mica are chemically and mechanically stable and occur in magmatic, metamorphic and sedimentary rocks. During subsequent metamorphism, zircon is resistant against high temperature, >650 °C (U–Pb) and 900 °C (Lu–Hf). The Lu–Hf zircon system is used as a tracer of initial magma separation from the mantle, and the U–Pb zircon system records magmatic crystallization. The 40Ar/39Ar white mica system is stable up to 400–450 °C dating either formation or cooling after high-grade metamorphism. Detrital U–Pb zircon ages on two major rivers draining the Eastern Alps do not record any sign of Alpine orogeny or metamorphism. Consequently, U–Pb zircon studies can entirely miss the record of collisional orogeny in cool, magma-poor collision orogens. In contrast, 40Ar/39Ar white mica ages record Early and Late Alpine metamorphism but are limited to revealing the pre-orogenic history. U–Pb zircon and 40Ar/39Ar white mica yield different information in provenance studies. In the Eastern Alps, U–Pb zircon dating of magmatic and clastic rocks indicates intense formation of magmatic rocks between 630 and 230 Ma. Felsic rocks dominate the older age groups, and increasingly young mafic rocks were dated, specifically between 265 and 230 Ma. Hf isotopes record increasing juvenile input since ∼630 Ma. Two different groups with respect to Mesoproterozoic depleted mantle ages are shown: (1) one group with a Mesoproterozoic age gap typical for Gondwana-derived units, and (2) a rare group with Mesoproterozoic ages recording a new tectonic element in the Austroalpine basement in Alps. [ABSTRACT FROM AUTHOR]

Metamorphic investigations were conducted using mineral chemistry, phase equilibria modelling and conventional thermobarometry on four metamorphic country rock samples from the Nova-Bollinger Ni–Cu deposit, Western Australia. New P–T constraints obtained from phase equilibria modelling of garnet-bearing granulites and cordierite–sillimanite-bearing metasedimentary rocks indicate that the Nova-Bollinger deposit formed at mid-crustal depths (0.75–0.76 GPa and 880–920 °C), along high thermal gradients around 1200 °C/GPa. Peak metamorphic conditions are consistent with those obtained from the Nova-Bollinger intrusive rocks, and with metagabbros from the southern Fraser Zone, but are slightly elevated relative to metapelites examined in the southern Fraser Zone. The peak metamorphic conditions at Nova-Bollinger reflect the combined effects of regional-scale high-T conditions during orogenesis superimposed by contact metamorphism in a thermal aureole adjacent to the Nova-Bollinger mafic–ultramafic magmas. Thermal metamorphism may have been further enhanced by local heat transfer from intruding sulfide liquid, which pervasively infiltrated country rocks on scales of tens to hundreds of metres beneath the orebodies. This additional heat source may be locally significant, despite being volumetrically limited. Retrograde P–T conditions were determined by garnet–biotite conventional thermobarometry of garnet-core–matrix biotite pairs (0.29–0.45 GPa and 550–640 °C). These P–T conditions suggest that the Nova-Bollinger country rocks cooled along a near-isobaric cooling path and reflect the effects of thermal decay following emplacement of voluminous magmas into the Fraser Zone during Stage I Albany–Fraser Orogeny. We present the first quantitative P–T constraints for host rocks of the intrusion-hosted Nova-Bollinger Ni–Cu deposit in the Fraser Zone, Western Australia. Peak metamorphism at Nova-Bollinger occurred at 0.75–0.76 GPa and 880–920 °C (1200 °C/GPa). GBAQ-GB thermobarometry records re-equilibration conditions at 0.29–0.45 GPa and 550–640 °C, indicating near-isobaric retrograde cooling. Infiltration of sulfide liquids into host country rocks may provide a volumetrically low but significant contribution of heat to high-T metamorphism during formation of orthomagmatic deposits in mid-crustal terranes. [ABSTRACT FROM AUTHOR]

The dominant structural fabric in the Eastern Goldfields is the steep north- to north-northwest-trending S2 foliation that is axial planar to upright F2 folds, developed during intense horizontal east–west shortening (D2–4 event). These structures consistently overprint D1 structures, which comprise layer-parallel S1 foliation, extensional shears, thrusts and recumbent F1 folds. The D1 event represents a separate and distinct episode of deformation with a markedly different stress regime (dominant vertical σ1), compared with the stress regime during the D2–4 events (horizontal east–west oriented σ1). There is little evidence for pre-2670 Ma ductile deformation in the Eastern Goldfields, as: (1) the ca 2730–2670 Ma greenstone sequences are deposited conformably on the older ca 2800 Ma greenstone sequences, with the first significant angular unconformities observed at the base of the post greenstone late basins; (2) a lack of schist or gneiss clasts in the late basins suggests that the surrounding uplifted sequence was largely undeformed; (3) the layer-parallel S1 foliation is observed throughout the 2720–2670 Ma greenstone sequence; and (4) the dominant low north- and south-plunges of F2 folds suggest that the sequence was predominantly flat-lying prior to strong east–west shortening (D2–4 events). The ca 2670–2655 Ma D1 event represents a period of sagduction that occurred immediately after cessation of rifting as a result of gravitational instability from deposition of dense, cold, greenstone sequences onto thinned, light, hot felsic crust. Late basins represent depocentres on the sinking greenstones during sagduction. Marked contrasts in the structural style of gold deposits, metallogeny and fluid sources, typically attributed to progressive deformation during orogenesis, could instead reflect temporally distinct mineralising events during changing tectonic regimes. In the East Yilgarn, an early plumbing system dominated by north-northwest-trending basin-controlling structures was likely established during rifting and focused fluids during multiple hydrothermal circulation events. ca 2720–2670 Ma greenstone sequences in the Eastern Goldfields were deposited in intracratonic rift basins. Rifting triggered an episode of sagduction that formed the early dome-and-basin geometry of the Eastern Goldfields and the onset of orogenesis at ca 2650 Ma (D2–4 events) modified the existing dome-and-basin geometry. Late basins represent depocentres on sinking greenstone sequences during sagduction. Gold mineralisation occurred throughout the changing tectonic regimes. [ABSTRACT FROM AUTHOR]

The Sakarya Zone of northern Turkey contains a well-preserved Early-Middle Jurassic and Late Cretaceous submarine magmatic arc constructed over pre-Jurassic bedrocks that are considered to be the eastward extension of the Armorican Terrane Assemblage in Europe. In this study, we present U-Pb-Hf isotopic data from the detrital zircons of middle Permian and Lower Jurassic sandstones to reveal episodes of Paleozoic-early Mesozoic magmatic flare-ups. Detrital zircon ages, together with data from the literature, define three major age groups at 400-380 Ma, 326310 Ma, and 250-230 Ma, which indicates three distinct magmatic flare-ups. In addition, there are minor age clusters at 460-430 Ma and 215-195 Ma. Initial eHf values of the detrital zircons indicate significant juvenile input during the Triassic flare-up, the involvement of significantly reworked crustal material during the late Carboniferous magmatic flare-up, and both juvenile and reworked crustal material during the Middle Devonian magmatic flare-up. Within the pre-Jurassic continental basement rocks of the Sakarya Zone, the late Carboniferous igneous rocks are well documented and most voluminous, and the Middle Devonian rocks are known locally, while the Triassic igneous rocks--apart fromthose in Triassic accretionary complexes--are hardly known. Because the Sakarya Zone is a Gondwana-derived continental block that was later involved in the Variscan and Alpine orogenies, these magmatic flare-ups cannot be explained by subduction-related processes along a single subduction zone. We propose that the Sakarya Zone rifted from the northern margin of Gondwana during the Late Ordovician-Silurian, the Devonian magmatic flare-up (400-380 Ma) was related to the southward subduction of the Rheic Ocean beneath the Sakarya Zone during its northward drift, the late Carboniferous magmatic flare-up (326-310 Ma) occurred following the collision of the Sakarya Zone with Laurussia, and the Triassic flare-up (250-230 Ma) resulted from northward subduction of the Tethys Ocean beneath the Sakarya Zone. Comparison with data from the literature shows that the Triassic and late Carboniferous magmatic flare-ups are also characteristic features of neighboring Armorican domains, such as the Balkans and the Caucasus; however, the Middle Devonian flare-up appears to be restricted to the Sakarya Zone. Along with the late Carboniferous flare-up, the Late Ordovician-Silurian flare-up, which is locally recorded in the Sakarya Zone, is typical of the Armorican Terrane Assemblage as a whole. [ABSTRACT FROM AUTHOR]

[Display omitted] The Altai orogen is a typical intracontinental orogen in Central Asia that experienced far-field deformation associated with Indian-Eurasian plate convergence. This region is characterized by uplift comparable to that of the Tianshan Mountains but has a distinct strain rate. Half of the Indo-Asia strain is accommodated by the Tianshan Mountains, whereas the Altai Mountains accommodates only 10%. To elucidate how the Altai Mountains produced such a large amount of uplift with only one-fifth of the strain rate of the Tianshan Mountains, we constructed a detailed crustal image of the Altai Mountains based on a new 166.8-km deep seismic reflection profile. The prestack migration images reveal an antiform within the Erqis crust, an ∼10 km Moho offset between the Altai arc and the East Junggar area, and a major south-dipping (30° dip) thrust in the lower crust beneath the Altai Mountains, which is connected to the Moho offset. The south-dipping thrust not only records the southward subduction of the Ob-Zaisan Ocean in the Paleozoic but also controlled the Altai deformation pattern in the Cenozoic with the Erqis antiform. The Erqis antiform prevented the extension of deformation to the Junggar crust. The south-dipping thrust in the lower crust of the Altai area caused extrusion of the lower crust, generating uplift at the surface, thickening of the crust, and steep (∼10 km) Moho deepening in the Altai Mountains. This process significantly widened the deformation zone of the Altai Mountains. These findings provide a new geodynamic model for describing how inherited crustal structure controls intraplate deformation without strong horizontal stress. [ABSTRACT FROM AUTHOR]

The Klamath Mountains Province of Northern California and southern Oregon, USA, consists of generally east-dipping terranes assembled via Paleozoic to Mesozoic subduction along the western margin of North America. The Klamath Mountains Province more than doubled in mass from Middle Jurassic to Early Cretaceous time, due to alternating episodes of extension (e.g., rifting and formation of the Josephine ophiolite) and shortening (e.g., Siskiyou and Nevadan events). However, the tectonic mechanisms driving this profound Mesozoic growth of the Klamath Mountains Province are poorly understood. In this paper, we show that formation of the Condrey Mountain schist (CMS) of the central Klamath Mountains Province spanned this critical time period and use the archive contained within the CMS as a key to deciphering the Mesozoic tectonics of the Klamath Mountains Province. Igneous samples from the outer CMS subunit yield U-Pb zircon ages of ca. 175–170 Ma, which reflect volcanic protolith eruptive timing. One detrital sample from the same subunit contains abundant (~54% of zircon grains analyzed) Middle Jurassic ages with Paleozoic and Proterozoic grains comprising the remainder and yields a maximum depositional age (MDA) of ca. 170 Ma. These ages, in the context of lithologic and thermochronologic relations, suggest that outer CMS protoliths accumulated in an outboard rift basin and subsequently underthrust the Klamath Mountains Province during the Late Jurassic Nevadan orogeny. Five samples of the chiefly metasedimentary inner CMS yield MDAs ranging from 160 Ma to 130 Ma, with younger ages corresponding to deeper structural levels. Such inverted age zonation is common in subduction complexes and, considering existing K-Ar ages, suggests that the inner CMS was assembled by progressive underplating over a >10 m.y. timespan. Despite this age zonation, age spectra derived from structurally shallow and deep portions of the inner CMS closely overlap those derived from the oldest section of the Franciscan subduction complex (South Fork Mountain schist). These relations suggest that the inner CMS is a composite of South Fork Mountain schist slices that were sequentially underplated beneath the Klamath Mountains Province. The age, inboard position, and structural position (i.e., the CMS resides directly beneath Jurassic arc assemblages with no intervening mantle) of the CMS suggest that these rocks were emplaced during one or more previously unrecognized episodes of shallow-angle subduction restricted to the Klamath Mountains Province. Furthermore, emplacement of the deepest portions of the CMS corresponds with the ca. 136 Ma termination of magmatism in the Klamath Mountains Province, which we relate to the disruption of asthenospheric flow during slab shallowing. The timing of shallow-angle subduction shortly precedes that of the westward translation of the Klamath Mountains Province relative to correlative rocks in the northern Sierra Nevada Range, which suggests that subduction dynamics were responsible for relocating the Klamath Mountains Province from the arc to the forearc. In aggregate, the above relations require at least three distinct phases of extension and/or rifting, each followed by an episode of shallow-angle underthrusting. The dynamic upper-plate deformation envisioned here is best interpreted in the context of tectonic switching, whereby slab steepening and trench retreat alternate with slab shallowing due to recurrent subduction of buoyant oceanic features [ABSTRACT FROM AUTHOR]

The majority of Neoproterozoic rocks exposed in southern Libya, are comprised of intrusive coarse-grained porphyritic, two-mica, and high K-calc alkaline granite. The Jabal Fezzan Granite (JFG) is located in southwestern Libya. In this study, trace elements and whole-rock geochemistry have been used to understand the origin and the process of petrogenesis of the studied granites. The JFG is high-Si, Rb, Y, Nb, and (ASI values greater than 1.1). Mineralogically, it is characterized by the presence of minor muscovite and biotite and a lack of hornblende, exhibiting features of S-type granites, and having a character that belongs to an alkali-calcic series. According to geochemical value, light REE-enriched, characterized by moderate enrichments in LREE (La/Sm), HREE, and weak negative Eu-anomalies. The geochemical modeling of the (JFG) reveals that the JFG derived from the melting of the crust and underwent high fractional crystallization (~50%) of plagioclase and K-feldspar at (H-P) conditions (750–980°C/1–4 GPa). The Jabal Fezzan (JFG) formed during Pan-African orogenic events during the destabilization of the interior Saharan metacraton due to compression stress and transpressive movements along pre-existing weakness and reactivation of shear zones inherited from Paleoproterozoic evolution. The Neoproterozoic basement forms the northernmost margin of the intracratonic Muruzq Basin, as evidenced by (greenschist facies) and intruded granitic rocks derived at the syn-collision stage (630–540 Ma). [ABSTRACT FROM AUTHOR]

Comprehensive U-Pb detrital zircon geochronology of Ediacaran sandstones from Oman indicates that they originated from Neoproterozoic basement with a peak magmatic age of ca. 850-780 Ma (Tonian), with lesser Paleoproterozoic and Ediacaran sources and renewed magmatic input starting at ca. 550 Ma. Comparison with detrital zircons from the Arabian-Nubian and NW Indian Shields supports an eastern Gondwana affinity for the Ediacaran succession of Oman. Tonian basement sediment sources are present in Oman. Sources for older Paleoproterozoic zircons (ca. 2500 and 1800 Ma) are not found in Oman but are known from the cratonic Indian Shield. The signal of the main magmatic events of the juvenile Arabian-Nubian Shield, peaking at ca. 640-620 Ma, is rare or absent in the Ediacaran rock succession of Oman. However, deformed Ediacaran clastic units with an Arabian-Nubian Shield affinity occur in western Oman. Influx of latest Ediacaran-early Cambrian zircons (550-525 Ma) is interpreted as due to final Cambrian Angudan/Malagasy orogeny-related magmatism. These results, together with new ages for volcano-sedimentary terranes in the subsurface of SW Oman and seismic observations, support the interpretation that the Ediacaran succession of Oman was deposited along the western, passive margin of the Greater Indian Shield, on the eastern (east and west in this paper refer to present-day coordinates) side of the Mozambique Ocean. Oman then collided with the Arabian-Nubian Shield in the early Cambrian, when the Angudan/Malagasy orogeny led to final consolidation of Gondwana. Our data support the inference that the youngest and final suture between the Indian and Arabian Shields lies in the subsurface of Oman along the early Cambrian western deformation front. [ABSTRACT FROM AUTHOR]

Although many collisional orogens form after subduction of oceanic lithosphere between two continents, some orogens result from strain localization within a continent via inversion of structures inherited from continental rifting. Intracontinental rift-inversion orogens exhibit a range of structural styles, but the underlying causes of such variability have not been extensively explored. We use numerical models of intracontinental rift inversion to investigate the impact of parameters including rift structure, rift duration, post-rift cooling, and convergence velocity on orogen structure. Our models reproduce the natural variability of rift-inversion orogens and can be categorized using three endmember styles: asymmetric underthrusting (AU), distributed thickening (DT), and localized polarity flip (PF). Inversion of narrow rifts tends to produce orogens with more localized deformation (styles AU and PF) than those resulting from wide rifts. However, multiple combinations of the parameters we investigated can produce the same structural style. Thus, our models indicate no unique relationship between orogenic structure and the conditions prior to and during inversion. Because the style of rift-inversion orogenesis is highly contingent upon the rift history prior to inversion, knowing the geologic history that preceded rift inversion is essential for translating orogenic structure into the processes that produced that structure. [ABSTRACT FROM AUTHOR]

The Sidi Bou Othmane (SBO) pegmatite district is situated in the Central Jebilet massif, Western Meseta domain, Morocco. The SBO district is hosted essentially in a volcano-sedimentary series composed of Late-Devonian Sarhlef shales. Pegmatite bodies crop out as dykes, which are oriented from N-S to E-W and are generally variably deformed with ductile and/or brittle structures with ante, syn- or post-kinematic criteria. Petrographic observations of pegmatite dykes show that feldspars (i.e., albite, microcline) are the most abundant mineral phases, followed by quartz and micas, with tourmaline and accessory minerals such as garnet, and zircon also featuring heavily, as well as secondary minerals such as clinochlore, sericite, and illite. The geochemical study of the SBO pegmatites indicates that they have mainly S-type granitic compositions, which are peraluminous granites with calc-alkalic affinities. The study of trace elements indicates that SBO pegmatites were formed in post-orogenic syn-collision context during the Variscan orogeny by the partial melting of argilliferous sediment. They can be ascribed to the muscovite-bearing pegmatite; moreover, they have good potential regarding ceramics. They also contain minerals, such as feldspar, which have been recently assessed as critical raw materials by the European Union. [ABSTRACT FROM AUTHOR]

The present‐day deformation style of the Eastern Cordillera in NW Argentina is strongly influenced by the inversion of pre‐existing Paleozoic and Mesozoic structures. In particular, the extensional faults and lithological contrasts resulting from the Cretaceous–Paleogene Salta Rift phase form heterogeneities that were preferentially reactivated during the Andean orogeny. Constraining the timing and characteristics of reactivation is a key to understanding the interplay between tectonics and inherited crustal anisotropies. In this study, we combine structural and sedimentological field data with a low‐temperature thermochronology data set from the area surrounding the fault‐bounded Cianzo basin. The southeastern boundary is formed by the inverted Hornocal fault, which was the basin‐bounding normal fault of the Lomas de Olmedo sub‐basin (Salta Rift basin). Lacustrine deposits of the Yacoraite Formation overspill on the footwall of this fault and mark tectonic quiescence during the post‐rift phase of the Salta Rift. Apatite (U‐Th‐Sm)/He and fission track ages in the Hornocal fault hanging wall show an onset of rapid cooling interpreted to be concomitant with fault inversion between the latest Oligocene and middle Miocene (∼24–15 Ma). Low‐temperature thermochronology data also constrain the timing of major folding in the eastern limb of the Cianzo syncline to pre‐10 Ma, whereas the western limb started tilting post‐10 Ma. Characterization of exhumation patterns related to fault activity surrounding the Cianzo basin emphasizes the influence of the pre‐existing structural framework on deformation in fold‐and‐thrust belts. Key Points: Pre‐existing structures in fold‐and‐thrust belts influence deformation and exhumation patternsLow‐temperature thermochronology data show that inversion of the Hornocal normal fault began in the latest Oligocene–middle MioceneOut‐of‐sequence activity along the Cianzo thrust, as well as eastward propagation of exhumation began in the middle Miocene–Pliocene [ABSTRACT FROM AUTHOR]

It is of great importance to evaluate simple methods to identify mineral occurrence for the future development of society. Applying a reconnaissance magnetic data analysis can help detect the main structural trends mounted to the occurrence of minerals. In this study, geological and geophysical data were analyzed to evaluate the main structural trends affecting mineralization in the area of Wadi El-Nakheel. Geomagnetic data were processed to remove the earth's magnetic field and reduce the magnetic pole. Some mathematical filters related to detecting and enhancing boundaries between rock units, depending on their magnetization affinity, were applied, including the first vertical derivative, the analytic signal, and 3D Euler deconvolution. After structural analysis of these data, we reached the following findings: The main structural trends from the surface and subsurface estimations were the northwest–southeast trend and the northeast–southwest trend. The orientation and origin of Wadi El-Nakheel are aligned with the main structural trend affecting the area that formed during the Red Sea Rift movement and the Pan-African orogeny. The depth of the deep-seated structure controlling the valley is 1500 m and all mineral occurrence is mainly structurally controlled in the studied area; phosphate ore outcrops are usually aligned with the northwest–southeast geological trend, and metallic ores are related to basement rock succession and the main dominant geological structures in the studied area. Finally, the magnetic method was demonstrated to be a reliable tool for detecting the subsurface boundary between geologic units. [ABSTRACT FROM AUTHOR]

The Eastern Kunlun Orogenic Belt (EKOB), located north of the Qinghai-Tibetan Plateau, recorded voluminous late Palaeozoic – early Mesozoic intermediate-acid volcanic rocks. The tectonic evolution of the Palaeo-Tethys Ocean from initial subduction and final closure and post-collision extension has been hotly debated. This study examines the petrogenesis of Palaeozoic to Early Mesozoic volcanic rocks at six locations: Xiahe, Elashankou, Jirimai, Harizha, Nagengkangqieer, and Yazigounan. The investigation involves detailed field observations, petrology, zircon U-Pb geochronology, Lu-Hf isotopes, and whole-rock geochemical analysis. The rocks analysed represent three episodic volcanic events. The ca. 257–245 Ma volcanic rocks were derived from magma mixing response to the subduction. The ca. 227–220 Ma highly fractionated I-type volcanics were derived from partial melting of the ancient lower crust, with varying contribution proportions of mantle materials. The ca. 216 Ma A-type volcanic rocks derived from partial melting of the juvenile crust. In this study, using existing regional geological data and spatiotemporal distribution of the magmatic region, combined with our new data, we attempt to propose more rational models to reveal the tectonic evolution of the Palaeo-Tethys Ocean, and we recognize three significant time nodes: (1) Ca. 240 Ma marks the final closure time of the Palaeo-Tethys Ocean. (2) Ca. 230 Ma indicates the vital tectonic regime transition from compression to extension response to slab break-off and continued lithospheric delamination. (3) Ca. 216 Ma mark the beginning of the final stage of orogeny in the EKOB, and mild magmatism lasts to ca. 200 Ma in response to the mountain collapse. [ABSTRACT FROM AUTHOR]

Continental lithosphere is deformed, destroyed, or otherwise modified in several ways. Processes that modify the lithosphere include subduction, terrane accretion, orogenesis, rifting, volcanism/magmatism, lithospheric loss or delamination, small-scale or edge-driven convection, and plume-lithosphere interaction. The eastern North American margin (ENAM) provides an exceptional locale to study this broad suite of processes, having undergone multiple complete Wilson cycles of supercontinent formation and dispersal, along with ∼200 Ma of postrift evolution. Moreover, recent data collection efforts associated with EarthScope, GeoPRISMS, and related projects have led to a wealth of new observations in eastern North America. Here I highlight recent advances in our understanding of the structure of the continental lithosphere beneath eastern North America and the processes that have modified it through geologic time, with a focus on recent geophysical imaging that has illuminated the lithosphere in unprecedented detail. Eastern North America experienced a range of processes that deform, destroy, or modify continental lithosphere, providing new insights into how lithosphere evolves through time. Subduction and terrane accretion, continental rifting, and postrift evolution have all played a role in shaping lithospheric structure beneath eastern North America. Relict structures from past tectonic events are well-preserved in ENAM lithosphere; however, lithospheric modification that postdates the breakup of Pangea has also been significant. [ABSTRACT FROM AUTHOR]

The Sulu orogenic belt, formed by the collision between Sino‐Korean and South China blocks, has important geological implications due to its unique tectonic setting. To understand the deep crustal structure of the extension of the Sulu orogenic belt in the Yellow Sea, we presented a 220‐km long active‐source ocean‐bottom seismometer wide‐angle reflection/refraction profile across the Yellow Sea. The obtained P‐wave velocity structure exhibits significant horizontal and vertical variations. The middle and upper crustal regions of the north beneath the survey line exhibit a higher velocity and larger thickness than those of the south, whereas the opposite is the case with the lower crust. The lower crustal high‐velocity zone in the Northern Depression of the South Yellow Sea Basin is a manifestation of the mantle material upwelling and accretion to the lower crust. Magmatic intrusions occurred along the faults and formed a high‐velocity zone in the middle and upper crusts. Due to undulating Moho interface and varying crustal velocities, the Qingdao–Rongcheng fault is identified as a fault in the Sulu orogenic belt without the significance of tectonic zoning. This study shows that the Sino‐Korean Block, Sulu orogenic belt and South China Block are bounded by the Jimo–Muping faults (an extension to the sea), Qianliyan fault and deep fault of the South Yellow Sea. Furthermore, the Sulu orogenic belt may have been formed by the northward subduction of the South China Block beneath the Sino‐Korean Block during the Indosinian orogeny to the east of the Shandong Peninsula. [ABSTRACT FROM AUTHOR]

A new tectonic model is presented to explain the tectono-stratigraphic evolution of the Paleoproterozoic Karrat Group in central West Greenland and the polyphase deformation, magmatism, and metamorphism of the Rinkian orogen. Sedimentation of the Karrat Group initiated after ca. 2000 Ma in an intracratonic rift basin with basal quartzites overlying Archean gneisses of the Rae craton. Rift-related alkaline volcanic rocks and synrift siliciclastic sediments were deposited in the north while an evaporite-carbonate platform developed in the south. The rift basin evolved to a back-arc basin, with associated subalkaline volcanic rocks, concomitant with the intrusion of arc-related granitoids of the Prøven igneous complex along the basal contact of the Karrat Group between 1900 Ma and 1850 Ma. The Karrat Group and magmatic arc rocks underwent metamorphism ca. 1830-1800 Ma during the collisional phase of the Rinkian orogeny. The metamorphic grade of the Karrat Group increases from greenschist facies in the south to granulite facies in the north, where it is marked by migmatization and emplacement of S-type leucogranites. Extensive east-southeastward thrust emplacement and fold vergence characterize the Rinkian orogen south of the Prøven igneous complex magmatic arc, where the arc-continent collision is established along a top-to-the-ESE shear zone postdating the Rinkian metamorphism. In summary, the Karrat Basin developed on the upper plate above eastward-dipping subduction and, together with the Rinkian orogen, represents the result of arc-continent collision that initiated the structuring of a backarc fold-and-thrust system antithetic to the subduction system. [ABSTRACT FROM AUTHOR]

Sardinia (Italy) represents one of the most comprehensive cross-sections of the Variscan orogen. The metamorphic and structural complexity characterizing its axial zone still presents many unresolved issues in the current state of knowledge. The data presented from the structural study of the entire axial zone of this area have allowed the authors to propose a subdivision into two new structural complexes. In particular, a younger complex is identified as the New Gneiss Complex, containing remnants of an older and higher-grade metamorphic complex defined as the Old Gneiss Complex. The structural and geometric relationships between the two complexes suggest the redefinition of the axial zone of Sardinia as part of the intracontinental East Variscan Shear Zone/medium-temperature Regional Mylonitic Complex. Comparable relationships are also highlighted in many other areas of the Variscan chain (e.g., Morocco, Corsica, Maures Massif, and Argentera Massif). Extending this new structural interpretation to other axial zones of the South European Variscan orogen could provide new hints for reconstructing the collision boundaries between Gondwana and Laurussia in the late Carboniferous to the early Permian periods. [ABSTRACT FROM AUTHOR]

The Eastern Cuban block has experienced a complex tectonic history characterized by plate interactions, resulting in a diverse array of geological features observable in the offshore sedimentary record. We investigate the tectonic evolution of offshore Eastern Cuba, specifically in the Old Bahamas Channel and its surrounding areas, by integrating multi‐channel seismic (MCS) reflection and published geological data. Our analysis employs stratigraphic frameworks and MCS data to assess deformation and key geological events in the region. We highlight the complex tectonic history of the Eastern Cuban block, marked by significant geodynamic events, such as rifting, the subduction of the oceanic Proto‐Caribbean plate, and syn‐orogenic and post‐orogenic phases. The seismic units observed in the majority of the study area reveal the early evolution of the Northern Proto‐Caribbean margin, subsequently impacted by the Cuban orogeny and the reactivation of the Cuban Transform Fault zone corresponding to a former plate boundary. We propose estimated ages for the seismic sequences, correlating them with available well data from neighboring regions. This study offers valuable insights into the tectonic history and geological evolution of offshore Eastern Cuba, contributing to a more comprehensive understanding of the region's geodynamic development. Key Points: The Old Bahamas Channel offers insights into the Caribbean's early tectonic history dating back to the Pangea breakupBahamian carbonate banks formed as reefs on top of tilted blocks following the Pangea rift and were later affected by fault reactivationThe Eocene northern Caribbean plate boundary aligns with the Cuban Transform Fault, reactivated in the Cuban orogenic and post‐orogenic phases [ABSTRACT FROM AUTHOR]

Observations over the last few decades from a number of orogenic systems have highlighted the possible importance of tectonic exhumation, i.e., ductile thinning and normal faulting, in exhuming rocks once buried in high-pressure conditions. Taiwan is one of the few active orogens in the world where rocks that once experienced high-pressure metamorphism (> 50 km) are exposed at the Earth's surface, providing a natural laboratory for advancing our understanding of exhumation processes. We integrate previously published studies of the Taiwan orogen with new structural, geochronological, and fluid inclusion microthermometry data to argue that tectonic extrusion and structural thinning played a critical role in exhuming the metamorphic core of the orogen until very recently, ca. 0.7 Ma. We propose a two-stage process for exhuming the high-pressure metamorphic rocks of the Yuli Belt: an initial stage where exhumation is driven primarily by pressure gradients in a subduction channel and a second stage that is initiated as an orogen-parallel regional-scale strike-slip zone, the Tailuko shear zone, is offset by an orogen-normal strike-slip zone. The offset generates an extensional bend that is filled with extruding high-pressure rocks as the upper crust is structurally thinned. Evidence for tectonic thinning comes primarily from a low-angle penetrative foliation that records significant vertical shortening and a suite of sub-vertical late-stage, mineral-filled veins. Isotopic dating indicates that the second stage started ca. 2.4–3.1 Ma and ended at ca. 0.7 Ma when the northern Backbone Range orocline started to form. We propose the low-angle foliation formed in the footwall of a regional-scale extensional shear zone that rooted to the east, beneath the forearc. Combined tectonic and erosional processes may have limited the topographic growth of the orogen from ~3.0 to < 1.0 Ma. [ABSTRACT FROM AUTHOR]

This paper aims to update our understanding of the carbon cycle in the Himalayas, the most intense collisional orogeny globally, by providing new insight into its impact on Cenozoic climate cooling through the use of isotopic variations in both organic and inorganic carbon and an isotopic mass balance model. Our results from 20 selected hot springs show that the relative contributions of dissolved carbon from the mantle, metamorphic decarbonization, aqueous dissolution, and soil organic matter are approximately 2%, 82%, 6%, and 10%, respectively. Approximately 87% ± 5% of CO2 generated in the deep crust precipitates as calcite, while approximately 5.5% ± 1% of this carbon is converted to biomass through microbial chemosynthesis at depths less than 2 km. Our random forests approach yielded a metamorphic carbon flux from the entire Himalayan orogenic belt of approximately 2.7 ∼ 4.5 × 1012 mol/yr. The minor CO2 released into the atmosphere (2.5 ∼ 4.2 × 1011 mol/yr) is comparable to the carbon consumption driven by Himalayan weathering. This paper provides new insights into deep carbon cycling, notably that approximately 93% of deeply sourced carbon is trapped in the shallow crust, rendering orogenic processes carbon neutral and possibly acting as one of the major triggers of long‐term climate cooling in the Cenozoic. Plain Language Summary: Large‐scale deep metamorphic decarbonization and CO2 release into the atmosphere during continental collision orogenesis worldwide have had significant impacts on Cenozoic global climate change. However, the carbon sources and sinks and the mechanisms underlying their impacts on climate change are not fully understood. This paper reports the chemistry of aqueous solutions, carbon isotopic compositions of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC), and helium and carbon isotopic compositions of free gases from hot springs in southern Tibet. The carbon isotope fractionation model between gas and aqueous solutions revealed that the carbon released from depth underwent six different stages. Based on the random forests machine learning algorithm, we estimated the metamorphic carbon flux across the Himalayan orogenic belt. Furthermore, only a small fraction (7%) of deep carbon is eventually released into the atmosphere, and this volume is the same magnitude as the amount of carbon absorbed by silicate weathering on the Tibetan Plateau. This paper emphasizes that the carbon sequestration process in the upper crust may have resulted in nearly carbon‐neutral geological bodies in the Himalayan orogenic belt, thus playing a critical role in Cenozoic climate cooling. Key Points: Approximately 87% of deeply sourced carbon precipitates as calcite, while approximately 5.5% is sequestered as biomass in the shallow crustThe carbon flux across the Himalayan orogenic belt was estimated by the random forests approachCrustal thickening has attenuated long‐term deep carbon emissions from the Himalayas [ABSTRACT FROM AUTHOR]

The Getang is a representative Carlin-type gold deposit in Southwest China. It has a proven reserve of about 30 tonnes at an average grade of 5.1 g/t Au. The orebodies occur as strat-abound lenses, and are structurally controlled by shallow NWW- and NE-trending fold-fault systems and the unconformity between the Upper and Middle Permian. In this study, the regional- and deposit-scale structural investigations, joints and finite strain measurements, and stress and dynamic analysis were conducted with an aim to reveal the structural process of the Getang gold deposit and clarify the relationship between the gold mineralization and structures. Three phases of deformation were identified in the deposit: (1) paleokarst was generated by a crustal uplift when the Youjiang Basin experienced extension at the end of the Middle Permian, laying the foundation for the unconformity; (2) the NW-trending structures were formed under a NNE-SSW compression during the Indochina-South China collision (Indosinian orogeny) in Triassic; (3) the NE-trending structures were generated or reactivated under a NW-SE-oriented compression during the Yanshanian intracontinental orogeny. The unconformity recorded two episodes of tectonic evolution in the NNE-SSW and NW-SE directions. Structural analyses and geochronology data suggest that the Getang gold deposit was formed as a result of tectonic transition from compression to extension during the Yanshanian intracontinental orogeny. [ABSTRACT FROM AUTHOR]

Arc-arc amalgamation occurs during the evolution of composite orogens at convergent plate margins and plays a critical role in controlling accretionary patterns and processes. The eastern Junggar terrane in the southern Central Asian Orogenic Belt underwent a long-lived subduction-accretion process in the Paleozoic, but whether and how the Yemaquan and Dananhu-Harlik arcs were amalgamated remain debatable. A systematic U-Pb-Hf-O isotopic study was conducted on zircons from Silurian granitic rocks in the Yemaquan arc. The U-Pb dating results suggest that these rocks were emplaced at 433-422 Ma and inherited abundant 536-435 Ma zircons representing a predominant magmatic episode in the Yemaquan arc. Their positive εHf(t) values and young Hf model ages indicate that the Yemaquan arc is dominated by juvenile basement with significant crustal growth during the Neoproterozoic to early Paleozoic. The variations in zircon Eu/Eu*, εHf(t), and δ18O values reveal that the Yemaquan arc experienced remarkable crustal thickening and remobilization at ca. 450 Ma, similar to the northern Dananhu-Harlik arc, and this was followed by extension that initiated at ca. 420 Ma. These features support the amalgamation of these two arcs occurring ca. 450-420 Ma. Integrated with regional data, we correlated this amalgamation event in the eastern Junggar terrane with the orogenic event in the Chinese Altai terrane, and we propose a middle Paleozoic tectonic evolution model in the eastern Junggar-Altai area from arc assembly to dispersal in association with a transition in accretionary mode. This scenario probably took place as a response to plate reorganization during the breakup of the northern margin of Gondwana. [ABSTRACT FROM AUTHOR]

The Western Gneiss Region (WGR) is a Precambrian basement domain in the Scandinavian Caledonides and one of the world's largest high‐ and ultrahigh‐pressure terranes. The south–central WGR underwent regional eclogite facies metamorphism 415–400 Ma ago when Baltica subducted beneath Laurentia, during the Scandian orogeny. Eclogites in the WGR group into two traditional types: (1) Precambrian mafic intrusions metamorphosed in situ during Scandian continental subduction and (2) eclogites, garnet peridotites and garnet pyroxenites within ultramafic complexes derived from the subcontinental mantle beneath Laurentia. We document, using field relations, petrography, whole‐rock geochemistry and secondary ion mass spectrometry (SIMS) zircon geochronology, a hitherto unrecognized third type of eclogite in the WGR that places new constraints on its tectonic architecture: an eclogitized fragment of oceanic crust from the Iapetus Ocean. The Kråkfjord eclogite complex is a km2‐sized body with an interior consisting of kyanite eclogite (meta‐troctolite) and subordinate layers and lenses of garnet peridotite, garnet websterite and kyanite–garnet leucotonalite. This interior is capped by Fe–Ti‐rich eclogite, which locally contains subordinate pockets of migmatitic aluminous gneiss. The elemental abundances and isotopic compositions of the Fe–Ti‐rich eclogites resemble those of mid‐ocean ridge basalt (MORB). In contrast, the interior kyanite eclogites, peridotites and pyroxenites have compositions similar to the gabbroic cumulates in the lower oceanic crust of slow‐spreading ridges. U–Pb SIMS dating of igneous zircon cores from a leucotonalite pod in the interior of the Kråkfjord complex yields Cambro‐Ordovician igneous ages of 500–440 Ma, with the ~500 Ma age interpreted as the isotopically undisturbed age. This age matches those of Iapetan oceanic rocks exposed elsewhere in the mountain belt. Metamorphic zircon from an Fe–Ti‐rich eclogite in the carapace of the Kråkfjord complex dates the eclogite facies metamorphism at 421.9 ± 2.2 Ma, synchronous with the continental collision. Zircon from a leucosome in Fe–Ti‐rich retro‐eclogite indicates an age of 408.5 ± 2 Ma for the crystallization of partial melt following the decompression. Detrital zircon core ages from a pocket of aluminous migmatitic gneiss in the carapace indicate derivation of sediment from the Baltic crust. Collectively, the data show that the eclogite complex (1) originated at an Iapetus spreading centre near the continent Baltica, (2) subducted to eclogite conditions during Scandian continental collision and (3) was tectonically intercalated with the Precambrian Baltica basement of the WGR. [ABSTRACT FROM AUTHOR]

The Arabia – Eurasia collision zone in the central part of the Alpine – Himalayan orogenic system has had a complex deformation history since the Palaeozoic. In Iran, the collision zone consists of the Alborz‐Talesh, Kopeh Dagh and Zagros foldbelts and the intervening Central Iran area. In this review paper, we summarize the structural architecture and tectonostratigraphic characteristics of these domains and attempt to correlate regional deformation events between them. The results show that six regional‐scale deformation phases can be recognized and correlated in Iran over a time interval extending from the Late Palaeozoic to the Late Cenozoic. Late Palaeozoic rifting in northern Gondwana and subsequent oceanic spreading resulted in the separation of the Central and North Iran blocks from the Arabian Platform. These blocks later converged and collided with the southern margin of Eurasia due to the subduction of the intervening PalaeoTethys lithosphere ("Cimmerian orogeny": Late Triassic). The convergent setting resulted in the initial development of the Alborz‐Talesh foldbelt in present‐day northern Iran, while extensional basins developed in the forebulge area in Central Iran. Continuing northward subduction of NeoTethyan oceanic lithosphere at the southern Eurasia margin produced Early Cretaceous back‐arc extension and associated volcanism in Central Iran and the Alborz‐Talesh area to the north. A phase of compressional deformation in the Late Cretaceous was related to the collision of a series of microcontinents derived from Northern Gondwana, including the Ercinjan and Bitlis massifs, with the Central Iran block, and is recorded in the Alborz‐Talesh foldbelt and in Central Iran. Further back‐arc extension in the late Paleocene – Eocene was accompanied by pervasive volcanism and volcaniclastic sedimentation throughout northern and Central Iran. The final closure of NeoTethys and convergence between the Arabian and Eurasian Plates evolved through phases of early Oligocene "soft" collision and middle Miocene "hard" collision. This was accompanied by thrusting in the internal parts of the Zagros foldbelt and by folding and subordinate thrusting in the more external parts, with related development of the flexural Mesopotamian Basin in the foreland to the SW. [ABSTRACT FROM AUTHOR]

Multiple studies have applied zoned garnet geochronology to place temporal constraints on the rates of metamorphism and deformation during orogenesis. We report new high-resolution isotope dilution-thermal ionization mass spectrometry Sm-Nd isochron ages on concentric growth zones from microstructurally and thermodynamically characterized garnets from the Betic Cordillera, southern Spain. Our ages for the garnet core (13.64 ± 0.31 Ma), mantle (13.41 ± 0.37 Ma), and rim (13.34 ± 0.45 Ma) indicate rapid garnet growth and are consistent with published garnet ages interpreted to reflect high-pressure metamorphism in the region. Thermodynamic analysis indicates garnets grew during subduction at ~1.5-2.0 GPa and 570-600 ℃. The core to rim duration of spiral garnet growth was just a few hundred thousand years. While other zoned garnet studies have shown similar rapid growth in subduction zone settings, this is the first documentation of such rapid growth of a spiral garnet. Combining this garnet growth duration with the magnitude of spiral inclusion trail curvature, we compute a strain rate of ~10-13 s-1, an order of magnitude faster than all previous spiral garnet studies. We interpret that these spiral garnets recorded a rapid pulse of deformation and strain during the final stages of subduction and incipient exhumation. [ABSTRACT FROM AUTHOR]

Decades of empirical research have revealed how the geological history of our planet shaped plant evolution by establishing well‐known patterns (e.g., how mountain uplift resulted in high rates of diversification and replicate radiations in montane plant taxa). This follows a traditional approach where botanical data are interpreted in light of geological events. In this synthesis, I instead describe how by integrating natural history, phylogenetics, and population genetics, botanical research can be applied alongside geology and paleontology to inform our understanding of past geological and climatic processes. This conceptual shift aligns with the goals of the emerging field of geogenomics. In the neotropics, plant geogenomics is a powerful tool for the reciprocal exploration of two long standing questions in biology and geology: how the dynamic landscape of the region came to be and how it shaped the evolution of the richest flora. Current challenges that are specific to analytical approaches for plant geogenomics are discussed. I describe the scale at which various geological questions can be addressed from biological data and what makes some groups of plants excellent model systems for geogenomics research. Although plant geogenomics is discussed with reference to the neotropics, the recommendations given here for approaches to plant geogenomics can and should be expanded to exploring long‐standing questions on how the earth evolved with the use of plant DNA. [ABSTRACT FROM AUTHOR]

Post‐collisional magmatism contains important clues for understanding the reworking and growth of continental crust, as well as lithospheric delamination and orogenic collapse. Early Devonian magmatism has been identified in the North Qilian Orogenic Belt (NQOB). This paper reports an integrated study of petrology, whole‐rock geochemistry, Sm‐Nd isotope and zircon U‐Pb dating, as well as Lu‐Hf isotopic data, for two Early Devonian intrusive plutons. The Yongchang and Chijin granites yield zircon U‐Pb ages of 394–407 Ma and 414 Ma, respectively. Both of them are characterized by weakly peraluminous to metaluminous without typical aluminium‐rich minerals, LREE‐enriched patterns with negative Eu anomalies and a negative correlation between P2O5 and SiO2 contents, consistent with geochemical features of I‐type granitoids. Zircons from the studied granites display negative to weak positive εHf(t) values (–5.7 to 2.1), which agree well with those of negative εNd(t) values (−6.4 to −2.9) for the whole‐rock samples, indicating that they were derived from the partial melting of Mesoproterozoic crust. Furthermore, low Sr/Y ratios (1.13–21.28) and high zircon saturation temperatures (745°C to 839°C, with the majority being >800°C) demonstrated a relatively shallow depth level below the garnet stability field and an additional heat source. Taken together, the Early Devonian granitic magmatism could have been produced by the partial melting of ancient crustal materials heated by mantle‐derived magmas at high‐temperature and low‐pressure conditions during post‐collisional extensional collapse. The data obtained in this study, when viewed in conjunction with previous studies, provides more information about the tectonic processes that followed the closure of the North Qilian Ocean. The tectonic transition from continental collision to post‐collisional delamination could be constrained to ∼430 Ma, which is provided by the sudden decrease of Sr/Y and La/Yb ratios and an increase in zircon εHf(t) values for granitoids. A two‐stage tectonic evolution model from continental collision to post‐collisional extensional collapse for the NQOB includes (a) continental collision and crustal thickening during ca. 455–430 Ma, characterized by granulite‐facies metamorphism and widespread low‐Mg adakitic magmatism; (b) post‐collisional delamination of thickened continental crust and extensional collapse of orogen during ca. 430–390 Ma, provided by coeval high‐Mg adakitic magmatism, A‐type granites and I‐type granitoids with low Sr‐Y ratios. [ABSTRACT FROM AUTHOR]

Whether tectonic strain from the early stage India‐Asia collision has synchronously affected the far‐field margin of the Tibetan Plateau is crucial for understanding plateau deformation and growth processes. However, direct evidence for early far‐field deformation remains scarce. Utilizing illite K‐Ar dating of three fault gouge samples, we established the faulting history of the Leibo fault zone (LFZ) at the southeastern margin of the Tibetan Plateau (SEMTP). Consistent authigenic illite ages of 52 ± 2, 54 ± 12 and 55 ± 6 Ma suggest the reactivated thrust faulting of the LFZ in the Early Cenozoic. Positioned ∼700 km east of the collisional boundary and at the intersection of three blocks with distinct lithospheric rheology in strength/viscosity, this event suggests a quasi‐synchronous far‐field tectonic response in the SEMTP to the India‐Asia collision. Plain Language Summary: Understanding how tectonic strain resulting from the collision between the Indian and Eurasian plates in the Early Cenozoic can spread to the edges of the Tibetan Plateau is crucial for comprehending the plateau's tectonic development. To investigate this question, we used fault gouge, which resulted from the sliding of brittle faults, to directly reveal faulting information. By conducting illite K‐Ar dating on three samples from the Leibo fault zone (LFZ) at the southeastern margin of the Tibetan Plateau (SEMTP), we found consistent ages of newly formed illite, 52 ± 2, 54 ± 12, and 55 ± 6 million years ago. Since this type of minerals form simultaneously with faulting, these ages reveal a reactivated thrust faulting event of the LFZ, suggesting a nearly simultaneous response of faulting in the SEMTP to the early stage of the India‐Asia collision. Key Points: Fault gouge illite K‐Ar dating is used to establish the faulting history of the Leibo fault zone, SE margin of the Tibetan PlateauThree consistent authigenic illite ages of ∼55, ∼54, and ∼52 Ma suggest a reactivated thrust faulting event of the Leibo fault zoneThis event indicates a quasi‐synchronous far‐field response of the SE margin of the Tibetan Plateau to the India‐Asia collision [ABSTRACT FROM AUTHOR]

Zircon is not a common accessory mineral of banded iron formation (BIF), but it occurs in all BIF samples from the Kostomuksha Greenstone Belt (KGB) in the Karelian Craton of the Fennoscandian Shield. The Kostomuksha BIF is of Algoma type and is part of three variably old rock associations: BIF-1 is part of a sedimentary sequence in Mesoarchean (2.87–2.84 Ga) basaltic komatiites with dacites, BIF-2 is located in Meso-Neoarchean (2.8–2.79 Ga) felsic volcanics, and BIF-3 is part of a Neoarchean (2.76–2.74 Ga) greywacke unit with felsic volcanics. Analysis of zircon has revealed grains with cores and several generations of rims. The U-Th-Pb systems of zircon indicate that its isotopic age varies considerably from 2.98 to 1.89 Ga, forming up to 4 age clusters in each sample. Most samples contain single inherited grains. The bulk of zircon in BIF is younger than the host rocks and is interpreted as metamorphic. Most of metamorphic zircons display an oscillatory zoning, and their Th/U ratio varies from 0.01 to 4.7, i.e. their origin is hard to interpret reliably, based on the above characteristics. Paleoproterozoic (1.89–1.85 Ga) zircons from BIF-1 and 3, occurring as rims and individual grains, are related to local tectono-thermal processes simultaneous with the formation of the Svecofennian orogen and were described for the central Karelian Craton for the first time. Thus, both inherited and metamorphic zircons have been revealed in Meso-Neoarchean BIF metamorphosed repeatedly in the Neoarchean-Paleoproterozoic under up to amphibolite-facies conditions. All metamorphic generations of zircons from BIF are correlated with the tectono-thermal events in the Karelian Craton, including the effect of the Svecofennian orogeny. [ABSTRACT FROM AUTHOR]

The Sveconorwegian orogen in Scandinavia and the Grenville orogen in Canada are both remnants of large and hot orogens that formed part of the supercontinent Rodinia around 1 billion years ago. Formerly deeply buried portions of crust in these orogens are exposed and offer insights into the tectonic dynamics of the basement within large orogens. The Eastern Segment of the Sveconorwegian Province hosts a ~ 30 000 km2 crustal portion that was buried to c. 40 km depth at a late stage of the orogeny, 980–960 Ma ago, and is bound towards the foreland in the east by a ~ 25 km wide zone of step anastomosing deformation, the Frontal wedge. This zone represents the outermost ductile deformation that developed within the crystalline basement in the orogen. We investigated a heterogeneously deformed and recrystallised syenodiorite with the aim to understand the character of the deformation-related metamorphism within the Frontal wedge. Field relations, microtextures, and mineral reactions show that the metamorphic recrystallisation was governed by hydrous fluid infiltration along the ductile deformation zones. Equilibrium was attained on a millimetre scale only and metamorphic recrystallisation was dependent on the introduction of hydrous fluid. The metamorphism reached high-pressure epidote-amphibolite-facies; geothermobarometric estimates suggest 540°C to 600°C and 9 to 12 kbar. Metamorphic zircon formed during the breakdown of Zr-bearing igneous phases, primarily baddeleyite. SIMS U–Pb analyses of igneous zircon and baddeleyite date the igneous crystallisation of the syenodiorite at 1230 ± 6 Ma. Metamorphic zircon grains are <20 μm and too small for precise dating, but yielded ages around 1 Ga. Collectively, the metamorphic data indicate that subvertical movements along steep planes within the Frontal wedge allowed for the regional-scale tectonic burial to ~40 km depth of the Eastern Segment to the west. Some of the same steep deformation structures were re-utilised as discrete movement planes during later exhumation. [ABSTRACT FROM AUTHOR]