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Rhombic structures have been observed in the Qom-Zefreh-Nayin-Dehsheir-Baft region, specifically along the direction of the dextral faults, which have caused significant changes in strike length. This study investigates the geological features and fault interactions in the region through the examination of aerial images, fault-lithology correlations, petrology, crustal thickness, and seismic studies. The analysis of aerial photos and geological correlations revealed the presence of ophiolites and pluto-volcanics associated with faults and rhombic structures. By conducting field geology and combining various geological studies, a pull-apart basin was identified in the area, contributing to the formation of three rhombic structures. This basin played a crucial role in the genesis of the region's ophiolites and pluto-volcanics. The research suggests that the initial tensional stress leading to the pull-apart basin was caused by the right step of a dextral fault within the Urumieh-Dokhtar magmatic arc. This fault formation occurred due to the oblique Arabian subduction towards the Iranian plateau. During the Zagros orogeny, the stretched area persisted, leading to the formation of oceanic crust in this location. The subduction angle changes from subduction to super-subduction, resulting in the classification of the region into two types: C and E genes. Different types of magma, including alkaline, subalkaline, shoshonite, calcalkaline, and adakitic, were identified in this region. The study highlights the significance of tholeiitic arcs, abyssal features, crust thickness, and seismicity in understanding oblique diagonal subduction models and tensional pull-apart basins, which are crucial in the transition from subduction to super-subduction. This research offers valuable insights into the geological complexities of the region and opens up opportunities for further exploration of similar models. [ABSTRACT FROM AUTHOR]

Field observations and laboratory data collected from the Taurus Mountains Range, Turkey during the last two decades provided evidence for the link between the evolution of hypogene karst and the geodynamic history. Major evidence includes; carbonate-hosted secondary ore deposits that are converted from primarily hypogene minerals by epigene, oxygenrich groundwater circulating at local to intermediate depths. Another piece of evidence of hypogene karst in the Tauride is the Kırkgöz Springs’ huge submerged cave/conduit system, which formed the Antalya Travertine Plateau, which is the world’s largest deposit precipitated by cool karst groundwater. The obruks in central Tauride are giant collapse dolines formed by ascending hypogene fluids in the upper continental crust, rich in volcanogenic carbondioxide. The groundwater’s noble gas and carbon isotope data are helpful in determining the existing but asymptomatic hypogene activity in the upper crust. Hypogene karst development seems common in parts of the world with current or past geodynamic activity. However, a hydrogeological overview of the geodynamic history is essential to assess the hypogene processes and their reflections on the land surface. [ABSTRACT FROM AUTHOR]

Rhombic structures have been observed in the Qom-Zefreh-Nayin-Dehsheir-Baft region, specifically along the direction of the dextral faults, which have caused significant changes in strike length. This study investigates the geological features and fault interactions in the region through the examination of aerial images, fault-lithology correlations, petrology, crustal thickness, and seismic studies. The analysis of aerial photos and geological correlations revealed the presence of ophiolites and pluto-volcanics associated with faults and rhombic structures. By conducting field geology and combining various geological studies, a pull-apart basin was identified in the area, contributing to the formation of three rhombic structures. This basin played a crucial role in the genesis of the region’s ophiolites and pluto-volcanics. The research suggests that the initial tensional stress leading to the pull-apart basin was caused by the right step of a dextral fault within the Urumieh-Dokhtar magmatic arc. This fault formation occurred due to the oblique Arabian subduction towards the Iranian plateau. During the Zagros orogeny, the stretched area persisted, leading to the formation of oceanic crust in this location. The subduction angle changes from subduction to super-subduction, resulting in the classification of the region into two types: C and E genes. Different types of magma, including alkaline, subalkaline, shoshonite, calcalkaline, and adakitic, were identified in this region. The study highlights the significance of tholeiitic arcs, abyssal features, crust thickness, and seismicity in understanding oblique diagonal subduction models and tensional pull-apart basins, which are crucial in the transition from subduction to super-subduction. This research offers valuable insights into the geological complexities of the region and opens up opportunities for further exploration of similar models.

Abstract The East China Sea, situated at the intersection of the Eurasian, Philippine Sea, and Pacific plates, is characterized by complex geology influenced by tectonic phenomena such as plate movements, volcanism, faults, and uplifts. Crustal density structure inversion provides a thorough understanding of the region's geological history as well as Earth's dynamical evolution, providing critical insights into seismic disaster mitigation, resource exploration, marine environmental protection, and maritime safety. The inversion process, on the other hand, presents challenges in data quality, quantity, model complexity, uncertainty, and computational resources. With the advancement of next-generation satellite gravity measurements and developing inversion techniques, the inversion of marine crustal density structures promises to be more precise and comprehensive. We explored the density distribution in the East China Sea and surrounding areas using an innovative wavenumber domain three-dimensional density imaging method along with high-precision global satellite gravity data. By overcoming data quality and computing resource constraints, wavenumber domain three-dimensional density imaging has transformed the discipline of marine geophysics, successfully delivering accurate density distributions in the study area. We were able to get a more precise and comprehensive characterization of the crustal density structure by combining high-precision satellite gravity data and cutting-edge imaging methods. Our investigation has unveiled previously unknown details about density distribution in the East China Sea and its environs. The East China Sea shelf displays smooth low-density perturbations at 18 km depth, whereas the trench–arc–basin region exhibits increasing density perturbations. Notably, the Okinawa Trough, which is surrounded by the Tokara Volcanic Ridge and the Ryukyu Trench, displays strong positive anomalies with a north–northeastern to northeastern orientation. In contrast, the Ryukyu Ridge and the Philippine Sea Basin exhibit smaller negative values and substantial northwestward positive density trends, respectively. These findings indicate diverse material distribution, which provides important insights into the area’s geological evolution and tectonic processes. This study adds new insights into density distribution in the East China Sea and adjacent regions, offering information on the geological complexity of the region. The research lays the groundwork for future research on crustal dynamics and enhances the field of marine geophysics and related disciplines. Graphical abstract

The Late Triassic igneous rocks associated with post-collision are widely distributed in the East Kunlun Orogenic Belt (EKOB), but their specific dynamic mechanism and evolutional process are still controversial. To address these key issues, we investigated the geochronology and geochemistry of intermediate–felsic igneous rocks from the EKOB, including trachyandesite, rhyolite, porphyritic monzogranite, syenogranite, granite porphyry and crystalline tuff. Zircon U–Pb isotopes of these rocks indicate that they were formed between 231.1 and 215.8 Ma (i.e. Late Triassic). These igneous rocks have moderate to high SiO2 (60.29–79.56 wt%) and low mantle compatible element contents (e.g. Co: 0.37–12.62 ppm; Ni: 1.55–15.59 ppm), suggesting that continental crustal-derived material played an important role in their formation. Porphyritic monzogranite (231.1 Ma), syenogranite (228.1 Ma), trachyandesite (227.4 Ma) and rhyolite (215.8 Ma) have Nb/U (1.41–4.71) and Ce/Pb (1.48–6.19) ratios like that of the crust, with εHf(t) values (–1.31 to 2.26) and old two-stage model (TDM2) ages of 1340–1119 Ma, suggesting that they originated from the partial melting of a Mesoproterozoic crust with minor mantle material involved in their source. Crystalline tuff (224.6 Ma) and granite porphyry (222.3 Ma) have Nb/U (1.93–3.81) and Ce/Pb (0.30–3.18) ratios, negative εHf(t) values (–7.04 to −5.12) and old TDM2 ages (1703–1581 Ma) closer to those of crust, suggesting that they were derived from the partial melting of a Paleo–Mesoproterozoic continental crust without addition of mantle material. Based on our new data and published data, the Late Triassic igneous rocks from the EKOB can be divided into three stages, 236–227, 226–218 and 216–208 Ma, corresponding to slab break-off, lithospheric mantle delamination and thickened lower crust delamination, respectively. The intermediate–felsic igneous rocks from the East Kunlun Orogenic Belt are dated from 231.1 to 215.8 Ma (i.e. Late Triassic). These igneous rocks were derived from the partial melting of ancient continental crust. The Late Triassic igneous rocks from the East Kunlun Orogenic Belt can be divided into three stages, including slab break-off, lithospheric mantle delamination and thickened lower crust delamination. [ABSTRACT FROM AUTHOR]

The East China Sea, situated at the intersection of the Eurasian, Philippine Sea, and Pacific plates, is characterized by complex geology influenced by tectonic phenomena such as plate movements, volcanism, faults, and uplifts. Crustal density structure inversion provides a thorough understanding of the region's geological history as well as Earth's dynamical evolution, providing critical insights into seismic disaster mitigation, resource exploration, marine environmental protection, and maritime safety. The inversion process, on the other hand, presents challenges in data quality, quantity, model complexity, uncertainty, and computational resources. With the advancement of next-generation satellite gravity measurements and developing inversion techniques, the inversion of marine crustal density structures promises to be more precise and comprehensive. We explored the density distribution in the East China Sea and surrounding areas using an innovative wavenumber domain three-dimensional density imaging method along with high-precision global satellite gravity data. By overcoming data quality and computing resource constraints, wavenumber domain three-dimensional density imaging has transformed the discipline of marine geophysics, successfully delivering accurate density distributions in the study area. We were able to get a more precise and comprehensive characterization of the crustal density structure by combining high-precision satellite gravity data and cutting-edge imaging methods. Our investigation has unveiled previously unknown details about density distribution in the East China Sea and its environs. The East China Sea shelf displays smooth low-density perturbations at 18 km depth, whereas the trench–arc–basin region exhibits increasing density perturbations. Notably, the Okinawa Trough, which is surrounded by the Tokara Volcanic Ridge and the Ryukyu Trench, displays strong positive anomalies with a north–northeastern to northeastern orientation. In contrast, the Ryukyu Ridge and the Philippine Sea Basin exhibit smaller negative values and substantial northwestward positive density trends, respectively. These findings indicate diverse material distribution, which provides important insights into the area's geological evolution and tectonic processes. This study adds new insights into density distribution in the East China Sea and adjacent regions, offering information on the geological complexity of the region. The research lays the groundwork for future research on crustal dynamics and enhances the field of marine geophysics and related disciplines. [ABSTRACT FROM AUTHOR]

Modern ideas about the tectonics of the Eurasian continental margin are considered. Cratons, fold belts, platforms, and sedimentary basins are briefly characterized. A significant part of the Arctic continental margins is represented by folded structures of different ages. In the course of geological evolution, tectonic structures successively formed, modified and died off, on which the processes of rifting and ocean formation were superimposed. Multidirectional tectonic movements, both vertical and horizontal, which led to the formation of the contours of oceanic basins and the ridges separating them, also influenced the continental margin. The destruction of the continental crust of the outer part of the continental shelf resulted in the formation of graben-like and rift troughs. The history of the Arctic oceanic basin began with the opening of the straits that connected the once isolated basin, the waters of which were largely desalinated. The latest stage of development was characterized by processes in which the transgressions and regressions of the Arctic Basin, the development and degradation of terrestrial and underground glaciation, and other processes played a leading role. [ABSTRACT FROM AUTHOR]

The Proterozoic metasedimentary rocks of the Yaounde Group on the northern edge of the Congo Shield in Central Africa were investigated to understand their provenance and depositional environment. Petrography, geochemistry, and field evidence helped to subdivide the metasediments into paragneiss, mica schist, chlorite schist, and quartzite which were derived from greywacke, shale, quartz arenite, litharenite protoliths. They are immature with some mature samples, moderately weathered and reworked Neo- and Post-Archean metasediments. Rare earth element signatures (Chondrite Eu/Eu* ≤ 1), enrichment of light rare earth elements over the heavy ones, and the La/Sc ratio (> 0.7) are compatible with those of the intermediate and felsic sources from the upper continental crust. These metasediments were deposited in the continental arc setting and have evolved during Proterozoic times according to the Wilson cycle to form the West Gondwana including NE Brazil. [ABSTRACT FROM AUTHOR]

Bundelkhand Archaean–Proterozoic Granitoid Complex comprises of an amalgamation of older, deformed Palaeoarchaean Tonalite Trondjhemite Granodiorite (TTG) surrounded by the younger relatively undeformed Neoarchaean high-K calc-alkaline granites. These rocks commenced its evolution during the Palaeo-Archaean (3.3 Ga) and continued to Archaean–Proterozoic Transition (APT). Heterogeneity in granites from southwestern Bundelkhand Craton can be observed in their colour, textural feature and availability of mafic components, thereby dividing them into grey (mafic rich and intermediate variant) and pink granites, which further gets geochemically classified into Closepet-type granites (mafic-rich variant of grey granite: GG), Low Silica High Magnesium monzogranite (LSHM, an intermediate variant of grey granite: IG (for field classification purpose) and High Silica Low Magnesium monzogranite (HSLM, pink granite: PG) on the basis of their major elemental characteristics. The partial melting of the lithologically varied crust and the mantle/lithosphere took place approximately around the same time because of the incompatible element-enriched fluids and melts. This caused the generation of granitoids from Bundelkhand to be varied in nature, resulting in the crustal evolution and stabilisation of the craton around ~3.3 Ga followed by its steady reworking by ~2.57–2.54 Ga. The Closepet type granite resulted from crust-mantle interaction and the monzogranites from crustal melting. Understanding the granitic emplacement within such a short time will help to further decipher the geodynamic changes and the crustal evolutionary processes that were operative during the APT in SW Bundelkhand craton. Research highlights: The manuscript focuses on the geodynamic evolution of the varied granites from SW Bundelkhand Craton. The granites are categorised into grey (mafic-rich grey and intermediate grey) and pink granite on the basis of field geology and petrology. Geochemically they are divided into Closepet type granites (mafic-rich variant of GG) and monzogranites (low silica high magnesium: LSHM, intermediate variant of GG and high silica low magnesium: HSLM, pink granite variant). Their field expressions and the corresponding geochemical signatures can be attributed to a combination of partial melting and fractional crystallisation. The division of granites into a low-silica high-magnesium group indicates crust–mantle interactions (Closepet-granites), and a high-silica low-magnesium group points toward pure crustal melting (monzogranites). [ABSTRACT FROM AUTHOR]

[Display omitted] • First set of zircon ages (∼3.6 Ga to 100 Ma) for the Armenian metamorphic basement. • Major and trace element and Sr-Nd-Pb isotope geochemistry of Mesozoic sills and dykes. • 40Ar/39Ar and zircon U-Pb ages and palaeomagnetism of the Mesozoic magmatism. • Geodynamic evolution of the Gondwana-derived South Armenian Block since the Permian. The geodynamic evolution of the South Armenian Block (SAB) within the Tethyan realm during the Palaeozoic to present-day is poorly constrained. Much of the SAB is covered by Cenozoic sediments so that the relationships between the SAB and the neighbouring terranes of Central Iran, the Pontides and Taurides are unclear. Here we present new geochronological, palaeomagnetic, and geochemical constraints to shed light on the Gondwanan and Cimmerian provenance of the SAB, timing of its rifting, and geodynamic evolution since the Permian. We report new 40Ar/39Ar and zircon U-Pb ages and compositional data on magmatic sills and dykes in the Late Devonian sedimentary cover, as well as metamorphic rocks that constitute part of the SAB basement. Zircon age distributions, ranging from ∼3.6 Ga to 100 Ma, firmly establish a Gondwanan origin for the SAB. Trondhjemite intrusions into the basement at ∼263 Ma are consistent with a SW-dipping active continental margin. Mafic intraplate intrusions at ∼246 Ma (OIB) and ∼234 Ma (P-MORB) in the sedimentary cover likely represent the incipient stages of breakup of the NE Gondwanan margin and opening of the Neotethys. Andesitic dykes at ∼117 Ma testify to the melting of subduction-modified lithosphere. In contrast to current interpretations, we show that the SAB should be considered separate from the Taurides, and that the Armenian ophiolite complexes formed chiefly in the Eurasian forearc. Based on the new constraints, we provide a geodynamic reconstruction of the SAB since the Permian, in which it started rifting from Gondwana alongside the Pontides, likely reached the Iranian margin in Early Jurassic times, and was subject to episodes of intraplate (∼189 Ma) and NE-dipping subduction-related (∼117 Ma) magmatism. [ABSTRACT FROM AUTHOR]

Tracing coupled ocean closure and intra-continental orogenic processes using tectonomagmatic thermal events is important for performing plate reconstructions. In this study, we collected geochronological data obtained from Jurassic–Early Cretaceous volcanic sequences in the Great Xing apos; an Range (GXR) and compared and merged the data to obtain a better understanding of the timing of volcanism in the GXR. Jurassic–Early Cretaceous volcanism, which is mainly represented by the Tamulangou, Manketouebo, and Manitu formations, are ubiquitous in the GXR and do not contain a magmatic hiatus. Thus, 'diachronous' volcanism did not occur in the GXR. The volcanic sequences in these formations are also slightly ambiguous and therefore cannot be used to determine the timing of volcanism. However, absolute ages and rock assemblages can provide better constraints on this timing. Combined with data from Jurassic–Early Cretaceous tectonomagmatic thermal events in Mongolia, Siberia, and NE China, we re-evaluated the influences of the Jurassic–Early Cretaceous closure of the Mongol–Okhotsk Ocean (MOO), as well as the subduction and rollback of the Izanagi Plate, at different times in the GXR. The GXR likely underwent flat-slab subduction during the Late Jurassic–early Cretaceous as the MOO closed in an irregular 'scissor-like' fashion (i.e. not in a progressive west to east manner). Large-scale lithospheric delamination likely led to a large pulse of magmatism and mineralisation in the GXR during the late Early Cretaceous. [ABSTRACT FROM AUTHOR]

The East Kunlun Orogenic Belt (EKOB) is the most important Triassic polymetallic metallogenic belt in China. A study about the petrogenesis of the ore-related intrusions is of great significance to the geodynamic evolution of orogenic belts. In this study, analysis of U–Pb zircon dating, whole-rock major and trace element compositions, and zircon Hf isotopes for the granitoids hosting the Aikengdelesite Mo (–Cu) and Halongxiuma Mo deposits in the EKOB are studied to determine their chronology and petrogenesis. Zircon date results show that the Aikengdelesite granite porphyry and the Halongxiuma granodiorite porphyry formed at 244.2 ± 1.7 Ma and 230.0 ± 1.0 Ma respectively. All samples of the Aikengdelesite granite porphyry and the Halongxiuma granodiorite porphyry which have high SiO2 and K2O contents, and low MgO and Cr, belong to the high-K calc-alkaline series. The Aikengdelesite granite porphyry samples show I-type geochemical affinities, whereas the Halongxiuma granodiorite porphyry samples are A-type granitoids. They all show negative zircon εHf(t) values (−7.4 to −3.3 and −3.7 to −2.5). We suggest that the Aikengdelesite granite porphyry may have been derived from the lower continental crust. While the Halongxiuma granodiorite porphyry could have formed by partial melting of basic lower crustal materials. By combining the results of this study with previous data, two magmatic and mineralization peak periods (278–237 Ma and 230–210 Ma) were observed in the Paleo-Tethys of the EKOB. Porphyry–skarn deposits occurring in the first episode were formed in the setting of an active continental margin related to the Paleo-Tethys Ocean plate subduction (e.g., Aikengdelesite porphyry deposit), while deposits occurring in the second episode were formed in a post-collisional setting (e.g., Halongxiuma porphyry deposit). [ABSTRACT FROM AUTHOR]

Syenites are relatively rare within the Nigerian Basement Complex. As a result of their rarity, these rocks have been given less research attention over time and are consequently poorly understood. The syenitic rocks at Igarra were studied to ascertain their tectonic evolution using geochemistry. Sampling was carried out using the survey-type geological field mapping approach. A total of 10 samples of syenitic rocks were collected for laboratory analyses. Compositionally, the rocks are intermediate with regards to SiO2 content (58.02% - 60.58%), having Al2O3 and alkali (Na2O + K2O) compositional ranges of 15.34% - 15.52% and 8.99% - 9.7% respectively. The sampled rocks are similar and consistent in their trace and rare earth elements concentrations (the only exception being Zr with values ranging from 4 ppm to 79 ppm). The rocks are relatively enriched in Ba, K, TI, and Sr but depleted in Tc, Nb, U, Hf, Yb, Te and Ta. The syenites also show fairly high ratios of Rb/Nb and Rb/Sr with mean values of 488.627 and 0.171 respectively. As seen from the geochemical analyses, the syenites around Igarra are high-K calcalkaline, alkalic to alkalic-calcic. The rocks are peraluminous in character as shown by the bivariate plot of A/NK vs. A/CNK. Sedimentary protolith with continental crustal parent magma is inferred for these rocks. The similarity and consistency of the trends of major, trace and rare earth elements is indicative of cogenetic origin for the rocks. The geochemistry and discrimination plots for the rocks indicate geodynamic setting ranging from orogenic to post-orogenic. A volcanic arc geotectonic setting is interpreted for the Igarra syenites, with magma emplacement and evolution thought to have been initiated during the late stages of the Pan-African reactivation and continued into post-orogenic times. [ABSTRACT FROM AUTHOR]

The paper presents data on geology and composition of rocks from the Ustoyarvi region (the North-Western Arctic zone of Russian Federation). Their compositional analysis (including mathematical evaluation of the similarity/difference measure) provided much reliable conclusion that the rocks from this area, which are presumably attributed to the Ustoyarvi structure (Ustoyarvinsky Greenstone Belt) were similar to those from the Ura-Guba area in the Kolmozero-Voronya Belt and continued it. In addition, it has been shown that from west to east lithotectonic units in the adjacent (Suormussky) Block become gradually impregnated with tectonic wedges of rocks of the Ustoyarvi Greenstone Belt. It indicates increasing collisional interaction between rock associations with a varied genesis. P-T formation parameters have been specified for komatiites from greenstone belts, i. e. the Kolmozero-Voronya, Ura-Guba, Ustoyarvi and Western Litsa area. It has been defined that komatiites of the Ustoyarvi Greenstone Belt were formed under pressure of about 5 hPa, komatiites of the Ura-Guba area – about 4.5 hPa, komatiites of the Kolmozero-Voronya – about 2 hPa. Thus, komatiites of the Ustoyarvi Greenstone Belt are more high-pressure formations.

The changing nature of detrital signatures in clastic wedges of the Circum-Mediterranean orogenic systems reflect the provenance relations from different source rocks of evolving geo-puzzle terranes, including ophiolite bearing, uplifted continental crust (both shallow to deep crust terranes), volcanic and sedimentary source rocks. We selected here sandstone suites directly occurring over the Mesomediterranean Micropaleoplate during the final stages of closure of the western-southern Tethyan realm. They are unconformably over the internal domains of the Circum-Mediterranean thrust belts, and include Oligocene-to-lower Miocene siliciclastic formations of the Betic Cordillera (As, Bosque, Río Pliego, El Niño, Ciudad Granada, Fuente-Espejos, Alozaina and Viñuela fms), Rif Chain (Fnideq and Sidi Abdeslam fms), and Calabrian terranes (Paludi, Pignolo and Stilo Capo d'Orlando fms). All these sandstone suites range from quartzolitic to quartzofeldspathic detrital modes reflecting close relations with their Paleozoic metasedimentary and plutonic source rocks and their related Mesozoic sedimentary covers. Marked differences have been recognized from western (Betic-Rif) to eastern (Calabria) portions in terms of detritic suites. Detrital suites of the Betic-Rif portions reflect a transition between a craton, transitional and recycled orogenic provenance type. Contrarily, detrital suites of the Calabria portions reflect their transition from transitional continental to basement uplift orogenic provenance reflecting deposition in wedge-top basins during final subduction of the MFB below the MM and the opening of the Mediterranean basin as a backarc.

The Kopongo greenstone belt lies within the Paleoproterozoic Nyong Complex, which is categorized as the northwestern edge of the Archean Congo craton in southern Cameroon. These metamorphic terrains consist of gneissic iron formations (GIFs) with resource estimation of 82.9 Mt@32.1%Fe inferred, 46.4%SiO2, 3.7%Al2O3, 0.15%P and 0.48%S. These formations display elongated distorted bands with poor interlayering. The mineral assemblages of the GIFs and country rocks conform to a medium to high-grade metamorphism. Their lithopackage comprises of regolith, gneissic iron and gneissic country formations. The chemical composition shows > 98 wt% Fe2O3 and SiO2, suggesting that quartz and iron oxide are chemically precipitated sediments. Furthermore, the low concentrations of Al2O3, TiO2, K2O, Na2O, MgO and CaO, coupled with a strong positive correlation between MgO with CaO (r ˂ 1.0), are indicative of negligible terrigenous influx in a marine environment. These geochemical characteristics indicate that the Kopongo GIFs were the result of deep ocean hydrothermal activity mixed with sea water at an extensional geodynamic setting as Algoma-type and other greenstone belts within the Congo craton. Five main iron mineralization types were identified in the Kopongo: Detrital iron, Magnetite-quartz, Quartz-hematite breccia, Magnetite and Enriched magnetite mineralizations. The Kopongo structural evolution shows intense polyphase deformations defined by three major episodes of folding from Dn to Dn+2 disturbed by a series of brittle-ductile and brittle tectonics, similar to other Congo craton greenstone belts. Magnetite ore bodies are controlled by Fn+1 and Fn+2 folds, while enriched magnetite ores occur as anastomosing mesobands in Fn+2 folds. [ABSTRACT FROM AUTHOR]

The intrusive age ranges of Linglong, Guojialing, Weideshan, and Laoshan granites in the Jiaodong Peninsula are 155–154 Ma, 131–130 Ma, 118–111 Ma, and 116 Ma, respectively. Together with the Shidao granite (227–200 Ma), five phases of magmatism can be classified by the time, all of which have different degrees of gold and polymetallic mineralization. The type of granites evolved from A–, S–type to I–, A–type from the Late Triassic to the Early Cretaceous, thus reflects the evolution of geodynamics in the Mesozoic, indicating the switch from North China Craton (NCC)–Yangtze Craton (YC) collision to subduction of the Paleo–Pacific Plate (PPP), with crustal thickening switching to lithospheric thinning and a compressional tectonic setting changing to an extensional setting. It directly leads to a series of extensional structures evolving in the Jiaodong Peninsula and demonstrates affinity for the extensive mineralization in the Early Cretaceous. The key markers of Jiaodong gold and polymetallic mineralization are magmatism, fluid activity and extensional structure. Extensive magmatic uplift and extensional structures in the Early Cretaceous formed the extensional tectonic system. During the formation process, a large proportion of crust and mantle materials exchanged and mixed, and the fluid interaction was highly active, resulting in a magmatic fluid metallogenic system, which provided favorable metallogenic conditions for gold and nonferrous metal hydrothermal deposits. Thus, a large-scale explosive mineralization occurred in Jiaodong in the middle and late Early Cretaceous. [ABSTRACT FROM AUTHOR]

The initiation of continental rifting from the latest Early Triassic was reconstructed by correlation of sedimentary formations deposited in the western end of Neotethys (in the Dinaric–Alpine oceanic branch). The shallow-marine and basinal strata of the Silica Nappes and the Bódvarákó Series from the Torna Nappe (located in the southern part of the Inner Western Carpathians) were studied and compared to sedimentary successions described from the Alps, the Carpathians and the Dinarides. The depositional zonation, developed on the shelf during the Late Permian‒Early Triassic transgression, was dissected and rearranged from the latest Early Triassic. The facies pattern and the differential sedimentary evolution of the shelf domains suggest that the accelerated subsidence began in the latest Early Triassic, and was connected to the onset of continental rifting. Three stages are reconstructed in the studied time-frame. (1) Dark grey carbonates, very poor in fossils, were deposited in restricted and hypersaline intraplatform basins in many shelf domains. In the external domains, shallow-marine carbonates, depositional gaps and terrestrial deposits are typical (formations in the Southern Alps, the External Dinarides and the Serbian–Macedonian Massif). From the latest Early Triassic, this latter shelf segment formed a threshold that restricted water circulation from the intraplatform basins. (2) Shallowing-up carbonate successions mark the next stage that implies a period of tectonic quiescence on the shelf from the late Early Anisian to late Middle Anisian. A peculiar change in biota occurring in previously restricted domains was coeval in shallow-marine and deep-marine settings. The biotic change is revealed by observations that dark grey carbonates, which are very poor in fossils, are overlain by carbonate successions rich in fossils typical for normal-marine water. The biota and environmental changes indicate the opening of a passage which allowed the circulation of well-oxygenated and normal-salinity marine water towards the previously restricted depositional areas. The geodynamic setting switching from continental rifting to spreading in the southern sector of the Dinaric–Alpine oceanic branch (Hellenides and Albanides), triggered the opening of the gateway between the future continental margins, i.e., between the External Dinaridic domain (Adria) and Serbian–Macedonian Massif (Eurasia). (3) Following the biotic event in the northern sector of the shelf, subsidence accelerated and additional intraplatform basins opened from the latest Pelsonian. [ABSTRACT FROM AUTHOR]

[Display omitted] • Understand the role of crustal blocks in the final configuration of the Central African Fold Belt. • Clarify some of the elements of correlation between Central Africa and NE Brazil. • Present a model of two subductions for the Central African Fold Belt north of the Congo craton. The Central African Fold Belt (CAFB) is the least well-known of all major Pan African belts. Here, we present new geochronologic work carried out in several critical areas of western Central African Republic, the region standing between northern Cameroon and southwestern Chad, and southern Cameroon. Our results allow us to: (1) clarify the regional extension of the Congo Craton in SE Cameroon and in the SW Central African Republic; (2) demonstrate that the units thrust along the northern edge of the Congo Craton from Cameroon to the Central African Republic are comparable in nature and in age; (3) better constrain the limits and described better the role of the Adamawa-Yadé crustal block during the Pan-African pre-collisional and collisional events in relation to the Congo Craton and the Yaoundé-Yangana nappe units to the South, and to the Poli-Leré magmatic arc to the North and; (4) clarify some of the elements of correlation with NE Brazil. Overall, a model involving two subduction zones is proposed to explain the evolution of the Pan-African belt north of the Congo Craton. The main steps include; (1) break-up and basin development from the early Tonian to at least 620 Ma on the northern edge of the Congo Craton, and on both the southern and the northern edges of the Adamawa-Yadé Block, concomitantly with the development of the Poli-Leré arc in northern Cameroon and Chad; (2) pre-tectonic plutonism in all domains since c. 800 Ma with culmination between 650 and 620 Ma; (3) collisional events starting around 620 Ma with metamorphism reaching the granulite facies at c. 600 Ma in all the domains; (4) nappe tectonics with thrusting of the Yaoundé-Yangana units onto the Congo Craton, accretion of the Poli-Leré arc to Adamawa-Yadé Block, and widespread syntectonic magmatism (600–580 Ma) with emplacement partly controlled by transcurrent regional shear zones, and emplacement of post-tectonic granitoids (c. 550 Ma) in both Adamawa-Yadé block and Poli-Leré magmatic arc. Collisional and post-collisional (620–550 Ma) events were synchronous along the entire belt from Central Africa to Brazil. [ABSTRACT FROM AUTHOR]

The Qinglong uranium ore field, including the Gangou and Panlingtou uranium deposits, is situated on the northern margin of the North China Craton (NCC). The Haifanggou Formation is a major uranium-bearing horizon in the ore field. We conducted petrographic, geochemical, electron probe, and high-resolution scanning electron microscope studies aimed at analyzing granite conglomerate samples of the Shigaizi ore-bearing horizon, which is located in the western Qinglong uranium ore field. We determined the geodynamic evolution and mineralization of the region by comparing the Gangou and Panlingtou uranium deposits. Geochemically, the granite conglomerate has a high silica content (62.53 wt %–74.70% wt %) and is rich in alkalis (4.41–7.98 wt %) and Al2O3 (7.62–17.58 wt %) but poor in MgO (0.35–3.01 wt %) and CaO (0.17–1.80 wt %). It exhibits a weak negative Eu anomaly (0.81–1.12), is enriched in LREEs, Rb, Th, U, and K and severely depleted in Nb, Ta, Ti, and P, indicating that it is similar to I-type granite and has the characteristics of adakitic rocks. The main uranium mineral is pitchblende, which is associated with pyrite, organic matter (soot), and calcite. The Shigaizi ore-bearing horizon displays many similarities with the Gangou and Panlingtou uranium deposits. Common features include the whole-rock compositions and mineral chemistry. Based on these results and the evolution of the northern NCC, we suggest that the granite conglomerate formed in an active continental margin environment and have a great prospecting potential. The lack of deep prospecting may be the main reason why the concealed large and thick orebodies remain undiscovered. [ABSTRACT FROM AUTHOR]

The Keivy domain (the northeastern part of the Arctic zone of the Fennoscandian Shield) during the period of the maximum manifestation of the Late Archean collisional processes was overlapped by tectonic allochthons of adjacent microcontinents thrust over it, submerged relative to other blocks of the continental crust, and acquired the features of a classical middle massif. In the process of studies that allow a detailed description of the formation of the supracrustal complexes of the Keivy structure, it has been found that the formation processes of the Kola orogeny had a pronounced spatial and temporal zoning and impulsive character. The maximum degree of orogeny was experienced by the rock associations of the Murmansk domain, as a result of which terrigenous material transported from its mountain slopes prevailed in the metasedimentary complexes of the Keivy domain throughout the entire period of their formation. The substance removed from the Murmansk domain was more actively accumulated in the metasedimentary rocks of the Lebyazhinsky suite; then a regular attenuation was observed within all domains, but at the last stage of the formation of the section of the Keivy sedimentary strata, the structural-material complexes of the Murmansk domain again begin to degrade more actively. A detailed study of the compositional features of the supracrustal complexes of the Keivy structure refutes the currently emerging point of view on the coeval formation of alkaline granites and felsic metavolcanics of the Lebyazhinsky suite. It can be argued with a high degree of probability that the rocks used to draw this conclusion (for which the age of 2.678 ± 7 Ma) is not typical of the supracrustal section of the metavolcanics of the Lebyazhinsky suite and are metasomatites.

The East Kunlun Orogenic Belt (EKOB) is the most important Triassic polymetallic metallogenic belt in China. A study about the petrogenesis of the ore-related intrusions is of great significance to the geodynamic evolution of orogenic belts. In this study, analysis of U–Pb zircon dating, whole-rock major and trace element compositions, and zircon Hf isotopes for the granitoids hosting the Aikengdelesite Mo (–Cu) and Halongxiuma Mo deposits in the EKOB are studied to determine their chronology and petrogenesis. Zircon date results show that the Aikengdelesite granite porphyry and the Halongxiuma granodiorite porphyry formed at 244.2 ± 1.7 Ma and 230.0 ± 1.0 Ma respectively. All samples of the Aikengdelesite granite porphyry and the Halongxiuma granodiorite porphyry which have high SiO2 and K2O contents, and low MgO and Cr, belong to the high-K calc-alkaline series. The Aikengdelesite granite porphyry samples show I-type geochemical affinities, whereas the Halongxiuma granodiorite porphyry samples are A-type granitoids. They all show negative zircon εHf(t) values (−7.4 to −3.3 and −3.7 to −2.5). We suggest that the Aikengdelesite granite porphyry may have been derived from the lower continental crust. While the Halongxiuma granodiorite porphyry could have formed by partial melting of basic lower crustal materials. By combining the results of this study with previous data, two magmatic and mineralization peak periods (278–237 Ma and 230–210 Ma) were observed in the Paleo-Tethys of the EKOB. Porphyry–skarn deposits occurring in the first episode were formed in the setting of an active continental margin related to the Paleo-Tethys Ocean plate subduction (e.g., Aikengdelesite porphyry deposit), while deposits occurring in the second episode were formed in a post-collisional setting (e.g., Halongxiuma porphyry deposit).

Triassic magmatism in Northeast (NE) China was geodynamically controlled by the Mongol–Okhotsk Ocean (MOO), Palaeo-Asian Ocean (PAO), and Palaeo-Pacific Ocean (PPO) tectonic regimes. To define the mechanisms of crustal accretion and geodynamics, the magmatic processes generated by ocean closure and plate subduction must be determined. In the present study, we assembled geochronological, geochemical, Cu (Mo)-porphyry deposit, and zircon Hf isotopic data from magmatic rocks throughout NE China. Central-NE China harbours more reworking of juvenile continental crustal material than the NE China margin. The widespread Triassic felsic magmas in NE China are primarily due to the recycling of juvenile and ancient crustal components during the tectonic evolution of the PAO. During the Triassic, NE China was subjected to a syn- to post-collisional orogenic regime accompanied by scissor-like basin closure and bidirectional subduction of the eastern PAO, before transitioning to the PPO tectonic regime in the latest Triassic. Magmatism in the Erguna and the central–northern Xing'an blocks was more affected by the MOO tectonic regime. Magmatism in the central–southern Xing'an Block, the southwestern Songliao Basin, and northern Lesser Xing'an–Zhangguangcai Range was linked to the closure of the PAO. Triassic magmatic rocks along the eastern Songliao Basin are extensional and formed during the opening of the Mudanjiang Ocean. The NE margin of Eurasia was a passive continental margin in the Late Triassic. [ABSTRACT FROM AUTHOR]

This article presents an evolution of geodynamics and eustatic sea-level changes in the Meso-Cenozoic and relates global events to the formation of Iberia and the Lisbon Metropolitan Area (LMA). The distensive tectonic regime resulted in the breakup of Pangea, the separation between the North American and Eurasian plates and the individualization of the Iberian microplate in the Lower Cretaceous. Rift basins were developed until the formation of oceanic crust in the Atlantic. The Lusitanian Basin is linked to the genesis of the Meso-Cenozoic Western Portuguese Border, where a large part of the Northern LMA is included. The compressive regime from the end of Cretaceous gave rise to mountain ranges in the Iberian Peninsula and to the reactivation of late-hercinian faults responsible for the formation and subsidence of a tectonic depression (Cenozoic Basin of the Tagus-Sado), where most of the Southern LMA is included. It was in this tectonic framework that the subvolcanic massif of Sintra was formed at the end of the Upper Cretaceous or the Arrábida chain during the Miocene. The transition to the compressive regime marked the maximum sea-level in the Meso-Cenozoic (170 to 250m above the current level). The variations in sea-level explain the LMA's lithological diversity. The formations of the Northern LMA date mostly from Cretaceous (prevalence of limestones and marls), while more recent formations are prevailing in the Southern LMA (Pliocene and Pleistocene), which justifies its detrital character. [ABSTRACT FROM AUTHOR]

The presence of metamorphic rocks along the North Patagonian Andes is well known. All these metamorphic rocks are intruded by plutonic igneous rocks of Devonian, Carboniferous and Permian ages. The geographic localization of these rocks in the same geological province led to a first approach to grouping them under the same lithostratigraphic unit (Colohuincul Complex). Later studies, based on geological mapping and geochronological, structural and petrological data, gave an account of the differences among these rocks. The main distinction is that these metamorphic rocks were affected by two dissimilar Palaeozoic tectono-metamorphic events. The oldest one is related to a lower Palaeozoic orogenic event (Famatinian orogeny) and the other one to an upper Palaeozoic event (Gondwanan orogeny). For this reason, it is necessary to distinguish and group the metamorphic rocks from the North Patagonian Andes basement in two different tectonostratigraphic units: the Colohuincul Complex (Cambrian-Ordovician) and the Cushamen Complex (middle Silurian-early Carboniferous) in order to better understand the geodynamic evolution of the Gondwana southwestern margin during the Palaeozoic. [ABSTRACT FROM AUTHOR]

Geodynamic and petrogeochemical study of the Keivy domain in the Baltic Shield has shown that it was overlapped by surrounding microcontinents in the Archean. As a result, the Baltic Shield was subject to cratonization. Thus, the Keivy microcontinent can be considered as the most ancient known median massif of the continental crust. Specific features of its geodynamic evolution predetermined conditions for formation of unique in scale stratiform deposits of alumina raw materials on the surface of the microcontinent. The paper describes and justifies the mechanism of alumina formation by physical-chemical decomposition of Archean and early Proterozoic metamorphosed sedimentary complexes in the Kola region of the Baltic Shield. Besides, the study of metallogenic features of transformation processes in the Archean continental crust of the Keivy microcontinent and its rimming suggests that carbonaceous schists of the Keivy domain that formed in the sedimentary cover can be significantly rich in nanogold. It will allow considering the central part of the Kola region as a major gold-bearing province. The authors believe that the metallogenic forecast based on geodynamic reconstructions is promising for further research of early Precambrian complexes. This work continues a series of publications on structural-material study of the Keivy domain.

The evolutionary nature of the Neoarchean basement, concealed below 66 Ma Deccan Large Igneous Province, remains largely unknown. We present here detailed results of integrated geoscientific investigations, carried out on 43 basement cores that cover an entire 270 m thick column, penetrated by the KLR-1 deep scientific borehole, drilled in the epicentral zone of 1993 Killari earthquake (Maharashtra, India). They dominantly contain high velocity-high density, halogen-rich, retrogressed and metasomatized amphibolite to granulite facies mid-crustal rocks, with intercalations of TTG, which were subjected to temperatures between 540 and 860 °C and pressure 5–7 kb, equating to 15–21 km emplacement depth. The granitic-gneissic layer, typical of the upper crust, appears absent. Geochemically, these iron-rich rocks are characterized by wide variation in which SiO2, MgO and FeOT contents vary from 45.12 to 69.96 wt% (avg. 58.11 wt%), 0.18–11.95 wt% (avg. 4.22 wt%), and 0.34–22.92 wt% (avg. 9.01 wt%) respectively. Measured FeOT contents are even higher than the normal lower crust. The granulite rocks exhibit tholeiite affinity, while amphibolite (which dominate the lithology) and TTG rocks show calc-alkaline character. Further, chondrite and primitive mantle normalized plots, show consistent and complimentary REE patterns (except in HREE), with negative Eu anomalies and LILE enrichment, indicating source rock fractionation. Well-marked depletion in Nb–Ta, Zr–Hf, subordinate depletion in Sr and Ba, and their distinct calc-alkaline to tholeiite character, indicate their subduction zone/arc-related affinity. In addition, large-scale crust-mantle interaction and pervasive metasomatism, have led to considerable alteration to the basic fabric of the rock thereby making it weak and characterized by reduced velocities due to biotitization and substantial Fe-enrichment. Quite likely, earthquake nucleation in intraplate stable regions may have a close link with mantle metasomatism. [ABSTRACT FROM AUTHOR]

Interpretational analysis of new seismic data allowed us to reconstruct the geodynamic settings that led to the formation of an ensemble of tectonic structural elements in the conjugation zone of the Eurasian Basin, Lomonosov Ridge, and Eurasian continental margin (Laptev and East Siberian seas). The presence of the Khatanga–Lomonosov fracture zone (KhLFZ), adapted to the conjugation zone of the continental margin, structures of the Eurasian spreading basin, and the Lomonosov Ridge, is substantiated. The representation of the KhLFZ in anomalous geophysical fields and wave pattern in seismic sections is analyzed to reveal the nature of kinematic relationship between the KhLFZ and adjacent tectonic elements. Shear displacements along the KhLFZ ceased in the Early Cenozoic (~46 Ma ago) simultaneously with the transition to the ultraslow spreading phase of the Gakkel Ridge. Our analysis of the geological and geophysical data shows that in the southern segment of the Eurasian Basin, where regular narrow magnetic anomalies are absent, the base of the sedimentary cover is predominantly represented by highly stretched blocks of the continental basement. The formation of the Gakkel Ridge's axial spreading zone in this segment took place in three stages: (i) rifting in the Aptian–Albian, (ii) telescoped development in the Late Cretaceous–Paleocene–Eocene, and (iii) inherited formation of the rift valley during the late interval of the neotectonic stage. The evolution of the Severny Basin, located in the conjugation zone of the Lomonosov Ridge and continental margin, has a formation scenario similar to pull-apart basins; its formation was interrelated with the simultaneously opening of the adjacent southeasternmost segment of the Amundsen Basin (part of the Eurasian Basin). [ABSTRACT FROM AUTHOR]

Ophiolitic peridotites exposed in the Eastern Desert (ED) of Egypt record multiple stages of evolution, including different degrees of partial melting and melt extraction, serpentinization, carbonatization and metamorphism. The present study deals with metaperidotites at two selected localities in the central and southern ED, namely Wadi El‐Nabá and Wadi Ghadir, respectively. They represent residual mantle sections of a Neoproterozoic dismembered ophiolite that tectonically emplaced over a volcano‐sedimentary succession that represents island–arc assemblages. The studied metaperidotites are serpentinized, with the development of talc‐carbonate and quartz‐carbonate rocks, especially along shear and fault planes. Fresh relics of primary minerals (olivine, orthopyroxene and Cr‐spinel) are preserved in a few samples of partially‐serpentinized peridotite. Most of the Cr‐spinel crystals have fresh cores followed by outer zones of ferritchromite and Cr‐magnetite, which indicates that melt extraction from the mantle protolith took place under oxidizing conditions. The protoliths of the studied metaperidotites were dominated by harzburgites, which is supported by the abundance of mesh and bastite textures in addition to some evidence from mineral and whole‐rock chemical compositions. The high Cr# (0.62–0.69; Av. 0.66) and low TiO2 (<0.3 wt%) contents of the fresh Cr‐spinels, the higher Fo (89–92; Av. 91) and NiO (0.24–0.54 wt%, Av. 0.40) contents of the primary olivine relics, together with the high Mg# (0.91–0.93; Av. 91) and low CaO, Al2O3 and TiO2 of the orthopyroxene relics, are all comparable with depleted to highly depleted forearc harzburgite from a suprasubduction zone setting. The investigated peridotites have suffered subsequent phases of metasomatism, from ocean‐floor hydrothermal alteration (serpentinization) to magmatic hydrothermal alteration. The enrichment of the studied samples in light rare earth elements (LREEs) relative to the heavy ones (HREEs) is attributed to most probably be due to the contamination of their mantle source with granitic source hydrothermal fluids after the obduction of the ophiolite assemblage onto the continental crust. The examined rocks represent mantle residue that experienced different degrees of partial melting (∼10% to 25% for W. El‐Nabá rocks and ∼5% to 23% for W. Ghadir rocks). Variable degrees of partial melting among the two investigated areas suggest mantle heterogeneity beneath the Arabian‐Nubian Shield (ANS). [ABSTRACT FROM AUTHOR]

The southern Mariana margin is a tectonically distinctive and rapidly deforming region with the world deepest trench and unusual deformation and magmatism. However, its related deep structure and dynamics are still poorly understood. In this study, we determine robust 3-D P and S wave velocity models down to 130 km depth beneath the southern Mariana margin by using arrival-time data of local earthquakes recorded at 12 near-field seismic stations. Our tomographic results together with local seismicity and focal mechanisms reveal that the subducted Pacific slab is rapidly rolling back with a steep dip angle and narrowly but strongly coupled with the thin forearc block, which results in the deepest trench. An inferred eastward mantle flow transports the enhanced hydrous mantle melt beneath the southwest Mariana rift to the southern Mariana Trough, causing unusual deformation, magmatism and volcanism in the new oceanic crust. In addition, seismicity in the west Mariana ridge lithosphere may indicate active foundering of the arc lower crust. • Robust 3-D P and S wave velocity models of the southern Mariana margin are determined by body-wave tomography. • The subducted Pacific slab at the southern Mariana margin is rapidly rolling back with a steep dip angle. • Eastward mantle flow transports magma to the south Mariana trough, causing unusual deformation and magmatism there. [ABSTRACT FROM AUTHOR]

Bedrock geological mapping indicates that diverse granitoid intrusions occur closely in space and time in the Paleoproterozoic Lynn Lake greenstone belt of the Trans-Hudson Orogen, Manitoba, Canada. These intrusions display distinct geochemical characteristics of I-type, A-type and adakite-like granitoids as revealed by their respective alkalinity, alumina saturation state, and trace element concentrations and ratios. The ca. 1879 Ma I-type granitoid pluton intruded the 1892 to 1884 Ma supracrustal package of volcanic, volcaniclastic and minor sedimentary rocks that constitute the greenstone belt, which was cut by 1873 Ma A-type granite and then by 1854 Ma adakite-like quartz diorite intrusions. Why the geochemical affinities of these granitoids change so rapidly (within ∼25 Myr) in orogenic belts, however, is not as well understood. Here we propose using Sm Nd isotope data and trace element modeling that the compositional variety of the granitoid intrusions likely reflects the mineral assemblages of their source rocks rather than magmatic fractionation. They may have been formed by partial melting of the disparate sources at different depths to respond to the change in tectonic regimes. The timing of the granitoid intrusions tracks a rapid geodynamic transition from subduction to intra-arc extension and to slab break-off due to terrane accretion and collision. This records a crucial piece of history in geodynamic evolution of the Trans-Hudson Orogen, which to date has been overlooked largely in many other orogens. • I-type, A-type and adakite-like granitoids occur in the Lynn Lake greenstone belt. • The granitoids record a rapid transition in tectonic setting from arc, intra-arc extensional and slab break-off. • Their compositions are correlative to their source regions and geodynamic regimes. [ABSTRACT FROM AUTHOR]

Petrological and isotope geochemical studies of volcanic rocks of the Crimean paleoarc (in the ground part and the Black sea), including data from the Nd-Sr isotope together with the set of informative ratios TR, REE elements indicators of geotectonic positions allow us to consider products of arc volcanism, as relics of a different age of fragments of island arcs of the Paleo-Neo-Tethys, overlap during the Alpine orogeny, in particular, we identified examples of «back arc» volcanism of Paleo-Tethys in the composition of the volcanic rocks of the Karadag volcano group. The totality of the information received, including the ratio of TR, REE elements indicators of geotectonic positions allows to identify the basalts of the lower series of the first phase of Karadag volcanism as products «back arc» volcanism, or residual arc Paleo-Tethys (196¸4 Ma, K/Ar), characteristics of the source magma which is comparable to the source of MORB basalts in the Nb/Yb — 5, Ba/Yb — 12; 143Nd/144Nd — 0,5128; 87Sr/86Sr — 0,7039). The volcanic rocks of the later stages of the eruptions with a high probability are products of different depts and depletion magmatic sources at successive stages of the evolution of the island arc system of the Meso-Tethys with multiscale contribution of the subduction component (trachyliparites stage 2 — 150¸5 million (K/Ar), Nb/Yb — 0,8, Ba/Yb — 98; 143Nd/144Nd — 0,5126; 87Sr/86Sr — 0,7094; Kainotype dacites 3 phase (74¸16 Ma, K/Ar); Nb/Yb — 1,15; 143Nd/144Nd — 0,5127, 87Sr/86Sr — 0,7049, Ba/Yb — 60,9. Rocks of all stages of the volcanism mainly relate to tholeiite series of differentiation, andesite dacites, rhyolites final of the second stage to the limestone-alkaline series. Isotope mineralogical and geochemical characteristics of volcanic rocks of the central part of the arc (Muholatka — Iphigenia): TiO2 < 0,6 wt. %. MgO > 8 wt. %, Ba/Yb > 400 etc., confirm the assumption of a depleted magma source in the front arc of «fore arc».

The intrusive age ranges of Linglong, Guojialing, Weideshan, and Laoshan granites in the Jiaodong Peninsula are 155–154 Ma, 131–130 Ma, 118–111 Ma, and 116 Ma, respectively. Together with the Shidao granite (227–200 Ma), five phases of magmatism can be classified by the time, all of which have different degrees of gold and polymetallic mineralization. The type of granites evolved from A–, S–type to I–, A–type from the Late Triassic to the Early Cretaceous, thus reflects the evolution of geodynamics in the Mesozoic, indicating the switch from North China Craton (NCC)–Yangtze Craton (YC) collision to subduction of the Paleo–Pacific Plate (PPP), with crustal thickening switching to lithospheric thinning and a compressional tectonic setting changing to an extensional setting. It directly leads to a series of extensional structures evolving in the Jiaodong Peninsula and demonstrates affinity for the extensive mineralization in the Early Cretaceous. The key markers of Jiaodong gold and polymetallic mineralization are magmatism, fluid activity and extensional structure. Extensive magmatic uplift and extensional structures in the Early Cretaceous formed the extensional tectonic system. During the formation process, a large proportion of crust and mantle materials exchanged and mixed, and the fluid interaction was highly active, resulting in a magmatic fluid metallogenic system, which provided favorable metallogenic conditions for gold and nonferrous metal hydrothermal deposits. Thus, a large-scale explosive mineralization occurred in Jiaodong in the middle and late Early Cretaceous.

The lithosphere-asthenosphere system beneath the central and eastern parts of the Iranian Plateau is investigated using a two-plane wave surface-wave tomography. We analyzed 11,430 teleseismic Rayleigh waveforms collected from 59 seismic stations and generated phase velocity maps at nine periods ranging from 25 s to 111 s. By inverting the phase velocity dispersion data, we constructed a 3-D S-wave velocity (Vs) model from the surface down to a depth of 200 km. Our investigation reveals a low-velocity anomaly within the uppermost mantle beneath the Iranian Plateau, presenting a sharp contrast to a high-velocity lithospheric mantle beneath the Zagros suture. This low-velocity anomaly characterizes an asthenospheric channel beneath the Iranian Plateau, where velocity varies non-uniformly, with the lowest Vs values located beneath areas of sparse Pliocene-Quaternary post-collisional volcanic activity in the Iranian Plateau. These observations might support the hypothesis of small-scale convection initiated after the Arabia-Eurasia continental collision. Furthermore, we explore the effect of the observed velocity anomalies on the isostatic compensation. We show that the local variations in both crustal thickness and upper mantle density account for the isostatic compensation of the surface topography in the Iranian Plateau. These factors may have interacted to shape the Plateau evolution and deformation over time. • 3D model unveils asthenospheric channel beneath Iranian Plateau. • Heterogeneous feature supports small-scale post-collision convection. • Heterogeneous feature underpins high Plateau elevation topography. • Lowest shear velocity detected under Pliocene-Quaternary magmatism. [ABSTRACT FROM AUTHOR]

In the Tethyan realm, leucocratic rocks were recognized as dikes and layers outcropping in the ophiolitic rocks of the Western Alps, in Corsica, and in the Northern Apennines. Several authors have suggested that the origin of leucocratic rocks is associated with partial melting of cumulate gabbro. Major and trace elements composition and paragenesis provided information about the leucocratic rocks genetic processes. This research aims at disclosing, for the first time, the petrographical and geochemical features of Timpa delle Murge leucocratic rocks, Pollino Massif (southern Italy), in order to discuss their origin and geodynamic significance through a comparison with other Tethyan leucocratic rocks. These rocks are characterized by high amounts of silica with moderate alumina and iron-magnesium contents showing higher potassium contents than plagiogranites, due to plagioclase alteration to sericite. Plagioclase fractionation reflects negative Eu anomalies indicating its derivation from gabbroic crystal mushes. The chondrite normalized REEs patterns suggest the participation of partial melts derived from a metasomatized mantle in a subduction environment. The results reveal some similarities in composition with other Tethyan leucocratic rocks, especially those concerning Corsica and the Northern Alps. These new data provide further clues on the origin of these leucocratic rocks and the Tethyan area geodynamic evolution.

In this paper, we report on LA‐ICP‐MS zircon U–Pb dates of 14 Mesozoic volcanic rocks from the central Great Xing'an Range (CGXR). These data are integrated with the temporal and spatial distribution of local magmatism‐related Mesozoic mineralization, in an effort to develop an understanding of the geodynamic evolution of the region. Periodic magmatic events in the GXR date from ~1,703 through ~145 Ma. Mesozoic volcanism in the CGXR can be subdivided into three episodes: Triassic (250–205 Ma), Early–Middle Jurassic (182–165 Ma), and Late Jurassic–Early Cretaceous (155–115 Ma). A revision of the previously defined volcanic sequence is offered using a combination of our zircon U–Pb ages and published Mesozoic geological and geophysical evidence from northeast China. We propose that (a) Early–Middle Triassic volcanism in the CGXR resulted from subduction of the Paleo‐Asian oceanic plate; (b) Late Triassic volcanism was related to subduction of the Mongol–Okhotsk oceanic plate (especially near the Erguna Block) and subsequent extension after the closure of the Paleo‐Asian Ocean; (c) Early–Middle Jurassic volcanism was mainly controlled by the southward subduction of the Mongol–Okhotsk oceanic plate; (d) Late Jurassic–initial Early Cretaceous magmatism was initiated by closure of the Mongol–Okhotsk Ocean; and (e) late Early Cretaceous volcanism was induced following the final closure of the Mongol–Okhotsk Ocean and rollback of the Paleo‐Pacific oceanic plate. [ABSTRACT FROM AUTHOR]

The tectonic and geodynamic evolution of the Pelagian platform and of the Pantelleria Rift System, located in the foreland of the Apennine‐Sicilian‐Maghrebian Belt, from the Late Oligocene onward, is still debated. Here we present a new interpretation based on structural data collected in the Malta and Gozo islands. With a tectonic back‐stripping approach, we recognized two main extensional events separated by a period of tectonic quiescence: (D1) Early Miocene WNW‐ESE extension and (D2) Late Miocene to Pliocene N‐S extension that led to the opening of the Pantelleria Rift System. During both extensional events the Maltese Islands and the Pelagian Platform were located in the foreland of the Apennine‐Sicilian‐Maghrebian Belt (Western Mediterranean Arc), in a period of slab rollback. We suggest that both tectonic events are an evidence of the extensional regime imposed on the foreland area by the rollback of the subducting slab. The switch in the main extension axis between D1 and D2 (WNW‐ESE vs. N‐S) can be interpreted as a result of the varying orientation and distance of the trench due to the progressive development of the Western Mediterranean Arc and provides an independent tool to "monitor" the slab rollback. Results obtained in this study allowed, for the first time, to bind the tectonic evolution of the area with the geodynamic evolution of the Western and Central Mediterranean. Key Points: Two independent extensional tectonic events, separated by a quiescence stage, are reconstructed in the Maltese IslandsBoth events were caused by the stress regime imposed in the Pelagian Platform by the rollback of the subducting slabThe switch in main extension direction between the two events is a result of the varying orientation of the trench [ABSTRACT FROM AUTHOR]

• Volcanic lithologies in the Qingyuan greenstone belt formed during 2.57–2.53 Ga. • A Neoarchean continental arc setting in the Qingyuan greenstone belt. • Volcanic assemblages recorded tectonic regime changing from compression to extension. • VMS mineralization is related to an arc rifting event where FII-type dacites formed. The Qingyuan greenstone belt (QGB) situated in the northeastern section of the North China Craton (NCC) is considered to be the unique metallogenic province in China that hosts both banded iron formations (BIFs) and volcanogenic massive sulfide (VMS) deposits. Traditionally, the QGB is divided into the Hunbei and Hunnan terranes separated by the Hunhe fault and grouped into the lower Shipengzi, middle Hongtoushan, and upper Nantianmen formations, which have undergone amphibolite- to granulite-facies metamorphism. Exposed supracrustal rocks are composed of plagioclase amphibolite and biotite plagioclase gneiss with minor amounts of BIF, marble, and schist. In this study, detailed field and petrographic observations, lithogeochemical, U-Pb geochronological, as well as whole-rock Sm-Nd isotope analyses were conducted on the metamorphosed mafic and felsic volcanic rocks (i.e. plagioclase amphibolite and biotite plagioclase gneiss, respectively) in the QGB in order to discuss implications for tectonic evolution and comitant VMS mineralization. The supracrustal rocks of both Hunbei and Hunnan regions were formed synchronously from 2.57 to 2.53 Ga and then had undergone 2.52–2.48 Ga regional metamorphism. Specifically, the lower section of the Shipengzi Formation is composed dominantly of transitional-tholeiitic basalts with negative Nb anomalies, suggesting that they were likely generated by partial melting of a mantle source that was previously altered by variable amounts of slab-derived fluids or melts. In contrast, the lithologic assemblages grade upward into interlayered bimodal volcanic rocks (i.e. N-MORB-type tholeiitic basalts and FI- to FII-type dacites of transitional to calc-alkalic affinities), representing a change in tectonic regime related to subduction from compression to extension. Among them all the basalts are characterized by consistently positive initial Nd compositions (ε Nd (t) = +2.7 to +3.4) further indicate a depleted mantle source; whereas those dacites possess negative to positive initial Nd values (ε Nd (t) = −4.6 to +3.0), suggesting they were formed by partial melting of depleted mafic source (likely lower mafic crust) and accompanied with variable addition of old crustal material. Significantly, VMS deposits are genetically linked to this extensional event and closely associated with the FII-type dacites that were generated by higher melting degree at high-temperature conditions and shallow crustal level (likely 10–15 km). In all, geochemical features (e.g., negative Nb anomalies and ε Nd value), together with contamination from continental crusts for tholeiitic mafic rocks and inherited zircons from these volcanic rocks, imply a continental arc setting where the QGB was evolved. [ABSTRACT FROM AUTHOR]

Abstract The comparison of subsidence curves obtained from deep wells in sedimentary basins represents a powerful tool to identify major changes in subsidence distribution, both in time and space. The construction of subsidence curves from 19 wells, covering a time interval from the Cretaceous to the present in the Gabes Basin (Pelagian Domain of the eastern Tunisian Platform), provided the opportunity to reconstruct the subsidence patterns across the basin. Changes in the subsidence rates in different wells allowed the identification of six time-intervals (stages). Stage boundaries are defined by major changes in subsidence trends in the 19 wells: each stage is characterized by changes in the subsidence pattern of groups of wells, likely reflecting episodes of re-organization of the distribution of domains with different trends (increase or decrease) of subsidence. Comparisons among the subsidence curves highlighted, for each stage, parts of the basins with higher or lower subsidence, permitting to identify highs and lows and to reconstruct their significance in the different stages identified. The basin-scale changes in the distribution of subsidence rates reflect regional events of basin re-organization, potentially controlled by syndepositional faults or, for some stages, by halokinesis, due to the presence of salt deposits in the southern part of the study area. The comparison of the subsidence curves permitted to identify domains characterized, in different time intervals, by different patterns of subsidence rates, providing important elements for the characterization of the different stages in the stratigraphic and tectonic evolution of the basin. Highlights • 19 subsidence curves have been produced from wells in the Gabes Basin (Tunisia). • Six evolutionary stages have been recognized comparing the subsidence curves. • Distribution of the subsidence rates across the basin is provided for each stage. • Changes in accommodation space reflect syndepositional tectonics in the Gabes Basin. • Subsidence patterns are controlled by extension, compression and halokinetic movements. [ABSTRACT FROM AUTHOR]

Abstract In the Italian regions the stratigraphic successions of the Verrucano s.l. consist essentially of continental alluvial plain to coastal-neritic siliciclastic redbeds, deposited at different times in the Alps (Mid? –Late Permian), the Northern Apennines (Mid?–Late Triassic p.p., locally in Southern Tuscany also followed by the Jurassic Pseudoverrucano Complex) and the 'Calabro-Peloritani Arc' (Mid?-Late Triassic, exceptionally reaching earliest Jurassic), whereas in Sardinia the recognition of the Verrucano succession is still a topic of discussion. The most typical metamorphic lithofacies, in the Pisan Mts. of Tuscany, is represented by the Verrucano s.s. conglomerates and breccias, including quartz clasts and minor metamorphic and volcanic lithics, grading laterally and vertically to quartzitic sandstones and pelites. In the Pisa Symposium the term 'Verrucano' was suggested only for those detrital deposits laid down, in the Alpine-Mediterranean areas, after the final act of the Variscan orogeny, and also to use local geographical names. Consequently, the typical terms 'Verrucano Toscano', the 'Verrucano Lombardo', the 'Verrucano Briançonnais' and other similar deposits, being linked to the Variscan belt, were generally accepted. The ages of these 'Verrucanos', since they are devoid of fossils, can only be interpreted indirectly. The Verrucano Lombardo of central Southern Alps was recently ascribed to a Mid? –Late Permian interval (Late Guadalupian?–Lopingian p.p.), taking into account that the connected Val Gardena Sandstones of the nearby Venetian region are interdigitated with the Late Permian Bellerophon Fm. The Verrucano Briançonnais of the Maritime Alps is again mostly related to Late Permian, being covered by the Lower Triassic alluvial-deltaic quartzites. In the easternmost Ligurian Apennines, near La Spezia, the Mesozoic section of Punta Bianca, which begins with a fluvial conglomerate, transgressive and unconformable on a metamorphosed Paleozoic Variscan Basement, is composed of two main cycles, of which the upper one correlates to the typical Pisan Verrucano s.s. and the overlying Mt. Serra Quartzites, the latter yielding Carnian pelecypods and vertebrate footprints. The Verrucano from the Mid-Tuscan Ridge to Mt. Leoni and in the Argentario promontory is delimited above by the Tocchi Formation and presumably developed from Middle (Late? Ladinian) up to Late Triassic (Carnian) times; in contrast, in Calabria (e.g. the Longobucco unit of Sila Grande) and in Sicily (e.g. the Taormina-Longi Unit of Peloritani Mts.) the so-called (Pseudo-) Verrucano deposits pertain to Mid? –Late Triassic and are capped by a basal Jurassic succession, determined by the discovery of an Early Hettangian palynoflora. All over their distribution areas, the above-mentioned Alpine Verrucanos rest, through an unconformity marked by a gap of varying and imprecise duration, on Late Paleozoic volcanic/sedimentary successions or directly on the underlying Variscan metamorphic basement. Schematically, the post-Variscan succession in Italy can be subdivided into three main tectono-sedimentary megacycles: the first generally ranges from the Late Carboniferous to, or slightly above the Early Permian, the second from Mid? –Late Permian to Middle Triassic , while the third cycle begins with the Mid?-Late Triassic p.p., attaining the Jurassic in some parts of Southern Tuscany and the 'Calabro-Peloritani Arc'. After the Late Carboniferous and Early Permian transtensional tectonics represented by many strike-slip continental basins (cycle I), widespread Middle Permian geodynamic reorganization ('Mid-Permian Episode' Auctt.) led to the development of a dominant extensional regime, and the birth of tectonic plates and oceans (Neotethys, Meliata-Maliak, etc.) between Africa and Europe. The erosion of the Variscan relief was followed by ingression from S-E sectors of shallow-marine branches of Neotethys (cycle II). The major rifting events that led to the Jurassic birth of the Ligurian-Piedmont Ocean started during the Middle–Late Triassic, and were related to the eastern opening of the Atlantic Ocean. These rifting events gave rise to the development of the Adria and Europe-Corsica-Sardinia conjugate passive margins, characterized by an asymmetric structural and sedimentary evolution. In this geological context, the Verrucano-like deposits of Italy can be interpreted as a discontinuous and asynchronous 'tectofacies' that marks the final dismantling of the SE border of the Variscan chain. [ABSTRACT FROM AUTHOR]

The role of tectonics in the Neogene-Quaternary evolution of the forearc basin, between the Serre and Aspromonte Massifs, located in the southern Calabria, is widely documented in the exposed sedimentary successions. The structuration of these different basins is due to the southeastward migration of the Calabrian Terranes, which led to the subduction of the Ionian lithosphere and the spreading of the Tyrrhenian back-arc basin. The area is dominantly displaced by two NW–SE and NE–SW oriented regional fault systems. These fault systems were active during the infilling of the Neogene-Quaternary basins, and represent complex tear fault systems that accommodated stress generated in the accretionary prism during the subduction of the Ionian lithosphere. Furthermore, these structures play a relevant role as part of recent seismotectonic processes, which controlled the Late Quaternary geodynamic evolution of the area. [ABSTRACT FROM AUTHOR]