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The Main Karoo Basin in South Africa is a typical example of an expanding arid region dependent on groundwater resources. Dolerite dikes in the region, analogous to dolerite dikes worldwide, are known to influence subsurface groundwater flow and spatially relate to high-yielding boreholes. Here, the effect of dolerite dikes on groundwater flow is remotely assessed using the Modified Soil Adjusted Vegetation Index derived from high-resolution multi-spectral satellite imagery. From imagery collected during the wet and dry seasons of 2018 and 2021, two aquifer models relating to 505 dikes were identified; (1) barrier-controlled aquifers are induced by ~ 56% of dikes, (2) fractured aquifers are induced by ~ 35% of dikes. Surficial areas overlying aquifers are also shown to sustain vegetation growth through dry seasons. This research demonstrates the efficacy of vegetation indices to rapidly characterise dike-related aquifer models and their seasonal sustainability, critical for effective groundwater exploration and management. [ABSTRACT FROM AUTHOR]

The Tarim Craton is an ancient Precambrian continental block, and detailed knowledge of its thermo‐tectonic history is crucial for understanding the early history of continental evolution. Abundant layered mafic rocks, which have commonly been regarded as basalts, occur within the Ediacaran Sugetbrak Formation (Fm.) in the Aksu region of the northwestern Tarim Craton. Clear intrusive features have now been discovered, including mafic rocks truncating Ediacaran sedimentary layers, exhibiting an intrusion‐baked margin where they interact with both the overlying and bottom wall rocks, and displaying a fine‐grained transition zone from their interior to their margins. The new findings demonstrate that these mafic rocks within the Aksu Ediacaran strata were not erupted basalts but instead are intrusive diabase dykes. Therefore, these mafic rocks cannot be used to constrain the timing of the Sugetbrak Fm. in the Aksu area, nor as marker layers for regional stratigraphic correlation. Furthermore, the Ediacaran thermo‐tectonic evolution in this region, deduced from the assumption that the mafic rocks are lavas, needs to be revised. [ABSTRACT FROM AUTHOR]

Identifying volcanic reservoir types and their distribution patterns in volcanic edifices is important for accurate prediction and exploration of hydrocarbon reservoirs. Herein, we analyzed the distribution patterns of different reservoir levels in volcanic edifices, discussed controlling factors, and reclassified reservoir types. This was done using core observations, whole-rock geochemistry, and reservoir physical property analysis, combined with logging, drilling, seismic, and oil-gas test data. Reservoirs can be divided into three classes based on their physical properties. The Mesozoic intermediate and basic rocks formed Class I reservoirs, most lithologies formed Class II reservoirs, and diabase intrusions and tight volcanic rocks formed Class III reservoirs. Reservoirs form in different lithologies in the Huanghua depression due to weathering. Tectonic faults deepen the influence of weathering leading to the formation of reservoirs in tight. Additionally, volcanic rhythms and fractures control the vertical distribution of Cenozoic basaltic reservoirs. Volcanic reservoirs are classified into five types based on the main controlling factors and distribution patterns in volcanic edifices: tectonic-alteration, vesicle-fracture, weathered-effusive, weathered-eruptive, and weathered-tectonic types. Among these, the weathered-eruptive type can easily form Class I reservoirs, making it the best target for exploration. Whereas the weathered-tectonic and vesicle-fracture types tend to develop Class II reservoirs and can be potential targets. The new classification takes into account the relationship between reservoir levels and their distribution in volcanic edifices, it is more conducive to igneous reservoir prediction in the Huanghua depression. This study provides a novel idea for the classification and comparative study of igneous reservoirs in petroliferous basins. [ABSTRACT FROM AUTHOR]

Dolerite dikes were studied in the western part of the Aldan terrane, in the middle reaches of the Tokko River. These dolerite dikes form a swarm of submeridional trend about 1 km wide. The dolerites of the thickest dike preserve their primary textural and structural features and mineral composition: plagioclase + pigeonite + augite + titanomagnetite. Dolerite in the chilled margins and central parts of the dike are homogeneous in composition, corresponds to low-Mg tholeiites, has low contents of Ti and other HFSE, with weak enrichment in light REE and small negative Nb anomalies. Sm–Nd isotope data on magmatic minerals of dolerite from the central part of the dike yield a good linear regression in an isochron diagram that gives to an age of 2510 ± 64 Ma, which probably corresponds to the crystallization age of the basalt. Metadolerites in a thin dike retain plagioclase porphyritic structures, but the pyroxenes are completely replaced by amphibole and chlorite. The metadolerites are contrastingly different in low contents of MgO, Cr, and Ni and in higher contents of TiO2, Fe2O3, P2O5, Nb, and all REE. The differences in the composition of the dikes may be explained by the longterm (about 65%) crystallization differentiation of the initial melt and the emplacement of the residual melt from a shallow intermediate magma chamber via opening cracks. Such conditions probably may have existed in tectonically stable intraplate settings. The age of the dolerites of the dike swarm is comparable to that of the anorogenic granites of the Nelyuki complex (~2.4–2.5 Ga), which are widespread in the western part of Aldan granulite–gneiss terrane. Our data bridge some gaps in characteristics of intraplate anorogenic magmatism that occurred in the western Aldan Shield in the Late Archean and marked the final consolidation of a large block of Archean crust in the Chara–Olekma granite–greenstone area. [ABSTRACT FROM AUTHOR]

Knowledge of the closure of the archipelago-type southern Paleo-Asian Ocean has been limited by uncertainty regarding whether the Alxa tectonic belt was isolated from the North China craton by an ocean around the Helanshan tectonic belt. Newly released seismic reflection profiles across the Alxa-Ordos border showed that the Alxa tectonic belt and Ordos Basin were located in a paleogeographically linked basin throughout the Paleozoic, indicating that the Tianshan and Solonker sutures were contiguous. The ca. 320–285 Ma successions in the Helanshan tectonic belt and surroundings, fed by a northeasterly Inner Mongolia continental arc source, display a retrogradational stacking pattern along with diabase sill emplacement. This inferred retroarc extensional setting was coeval with asthenospheric upwelling and thinning of the continental arc driven by retreating subduction of the Paleo-Asian Ocean. The subsequent ca. 280–260 Ma sedimentary hiatus coincided with magmatic flare-up, crustal thickening, and retroarc foreland formation in the Inner Mongolia continental arc, indicating a geodynamic transition from retroarc extension to compression in the mid-Permian. Then craton-scale drainage reorganization occurred during the Early Triassic (ca. 250– 230 Ma), manifested by the discharge of the Middle Triassic fluvial system southeastward to the central Ordos Basin; this was steered by southeastward expansion of the Alxa tectonic belt during the final termination of the Paleo-Asian Ocean. Postcollision lithospheric adjustment since ca. 230 Ma resulted in vigorous alkaline magmatism and supracrustal stretching in the Inner Mongolia continental arc as well as mafic magmatism and rifting in the study area. Hence, Carboniferous to Triassic polyphase tectonic transitions in the western North China craton were retroarc basin expressions related to complicated subduction-closure processes in the southern Paleo-Asian Ocean. [ABSTRACT FROM AUTHOR]

Heat flow data obtained in connection with geothermal resource exploration suggests anomalous upper crustal structure and processes in parts of central east Tasmania. The regional scale crustal geology of the Midlands of Tasmania is, however, mostly obscured at the surface by the Permo-Triassic sedimentary sequences of the Tasmania Basin together with extensive exposures of Jurassic dolerite. We investigate controls on undercover crustal processes in this region by combining long period and broadband magnetotelluric (MT) datasets in 3D inversions for the geoelectric structure; followed by an interpretation that is informed by aspects of the pre-existing 3D regional geological and geophysical model. The new 3D model allows improved resolution of low resistivity anomalies together with a qualitative appraisal of spatially variable model sensitivity. The most robust features ( $ \lt 1\,\Omega {\rm m} $ < 1 Ω m ) in the 2–3 km depth interval occur where N–S and E–W faults intersect with a high point in the topography of the upper surface of a deep seated granite body. Enhancement of conductivity in this zone by clay, graphite or mineralisation, or a combination thereof, is likely. Other low resistivity features suggest that conductive pathways exist where major or multiple faults are present. These interpretations provide support for continued exploration in the Midlands of Tasmania for a variety of resources related to crustal fluids and fracturing. [ABSTRACT FROM AUTHOR]

Purpose: To investigate diabetic retinopathy (DR) as a potential marker of cardiovascular disease (CVD) in adults with type 1 diabetes attending the Danish DR‐screening programme and non‐diabetes adults. Methods: In this registry‐based matched case–cohort study, we identified 16 547 adults with type 1 diabetes, who were registered in the Danish Registry of Diabetic Retinopathy (DiaBase). Each case was age‐ and sex‐matched by five non‐diabetes individuals (n = 82 399), and odds ratios (ORs) and hazard ratios (HRs) were estimated for incident and upcoming CVD in multivariable models. Results: Adults with type 1 diabetes (median age 44.5 years, 57.6% male) were more likely to have prevalent CVD (OR 1.29; 95% CI, 1.20–1.38) and to develop CVD within 5 years (HR 1.19; 95% CI, 1.08–1.30) as compared to non‐diabetes control. However, adults without DR were less likely to develop CVD (HR 0.84; 95% CI, 0.72–0.97) compared to the reference population. For adults with type 1 diabetes, there was an increasing risk for incident CVD for increasing levels of DR (HR 1.33, 1.95, 1.71 and 2.39 for DR‐levels 1–4, respectively). Patients with CVD at the time of the first screening had a higher risk to develop DR during follow‐up (HR 1.23; 95% CI, 1.02–1.49). Conclusion: In a nationwide matched case–cohort study adjusted for potential confounders, DR was identified as an independent marker of prevalent and incident CVD in type 1 diabetes with increasing risk demonstrated for higher levels of DR. Likewise, CVD also independently predicted the risk of incident DR. [ABSTRACT FROM AUTHOR]

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The Nellie Tonalite forms a discontinuous 20 km elongate northwest-trending felsic intrusion at the far-western end of the Western Zone of the Lamboo Province, in the Wunaamin Miliwundi Orogen, Western Australia. This intrusion is poorly understood with previous interpretations assigning it to the ca 1860 Ma Paperbark Supersuite. We present the first geochronological results for the Nellie Tonalite, which have a weighted mean laser ablation, inductively coupled plasma, mass spectrometry (LA-ICP-MS) U–Pb zircon age of 1794 ± 4 Ma. This date is coincident with the age for felsic granophyres of the Hart Dolerite, which have previously been described from the Kimberley Basin overlying the Halls Creek Orogen and central parts of the Wunaamin Miliwundi Orogen. Other similarities of the Nellie Tonalite with the felsic Hart Dolerite are micrographic and granophyric intergrowths of quartz and K-feldspar, and a distinct geochemical depletion of V. This V depletion is interpreted to be the result of closed-system, in situ fractional crystallisation of titanomagnetite from a basaltic composition. The fractional residue from this process can be found at several locations across the Halls Creek Orogen and Wunaamin Miliwundi Orogen and at Speewah Dome in the east Kimberley where magnetite gabbros within the Hart Dolerite also host a large Ti–V mineral resource. It is proposed that the Nellie Tonalite is a western correlate of the felsic Hart Dolerite. This demonstrates that the magmatic processes required for Speewah-style Ti–V mineralisation are extensive across the entire Lamboo Province. Additionally, the scale, constancy of the composition, texture and age of the felsic Hart Dolerite encompassing the entire inland margin of the Kimberley Region, and the rapid emplacement time of <3 m.y., support the interpretation of a mantle plume model for the emplacement of the Hart Dolerite. KEY POINTS: The Nellie Tonalite is redefined as a granophyric granite, has been dated to 1794 ± 4 Ma and is coeval with the ca 1800 Ma Hart Dolerite. Petrographic, geochemical and geochronological evidence suggests that the Nellie Tonalite is a product of in situ fractional crystallisation of the Hart Dolerite (felsic Hart Dolerite). Plots of Ti/Nb vs V/Sc are ideal in identifying the distinctive V-depletion associated with the felsic Hart Dolerite, which marks a valuable stratigraphic horizon for identifying potential Speewah-style Ti–V mineralisation. [ABSTRACT FROM AUTHOR]

The energy budget and the interplay between stable friction evolution and dynamic stick‐slips are tested here under continuous slip along rough faults. We conducted 34 direct‐shear experiments coupled with precise roughness measurements on diabase and limestone fault samples. The faults broad roughness ranges from highly rough and interlocked fractured interfaces to smooth polished surfaces. The analysis focuses on two slip phases: (a) the evolution of the shear strength of rough sample under stable, cumulative displacement; and (b) the dynamic of unstable stick‐slip sliding. We found that the breakdown work during frictional strength evolution increases with roughness increase across multiple scales. The diabase samples are more sensitive to roughness increase than limestone samples in terms of the breakdown work implied by frictional evolution. We attribute this increased diabase sensitivity with fault roughness to its higher bulk elasticity and not to the fault shear stiffness. The diabase faults displayed multiple periodic system‐size stick‐slips, and the measured stored energy during the preparatory stage were surprisingly independent of the fault roughness. This finding suggests that during the preparatory stage a balance between the intracycle fault stiffness and stress drop govern the stored energy magnitude. Further, this energy balance suggests that some interface conditioning occurs before the spontaneous slip overcomes a sticking barrier. Plain Language Summary: The breakdown energy dissipated as work during friction evolution along laboratory faults can be determined by integration of the shear stress versus shear displacement. In this study, we quantitatively analyze the relationship between the roughness of laboratory faults and the dissipated energy during sliding. The experiments with rough diabase and limestone faults show an increase of breakdown work implied by the frictional strength with increasing fault roughness, and breakdown work increase with increasing host rock rigidity. We also find that the energy dissipated during frictional evolution of rough faults is four orders of magnitude larger than the energy dissipated during system size stick‐slip cycles in the same experimental setting. We attribute this observed discrepancy to the difference in contact area between interlocked, and sheared, surfaces. Surprisingly, our examination of breakdown work during stick‐slip cycles reveals a roughness‐independent behavior. We ultimately show that the energy components of both stick‐slip and friction evolution follow the same power law relationship when scaled to the sliding displacement. Key Points: The breakdown work implied by the evolution of frictional strength scales with roughness (RMS) height and elasticity of intact rockThe stored energy within stick‐slip cycles is four orders of magnitude lower than the energy accommodated during friction evolutionThe stored energy at the onset of breakdown during stick‐slip cycles is generally independent of fault roughness [ABSTRACT FROM AUTHOR]

Petrological, geochronological, and geochemical analyses of mafic rocks in northern Liaoning were conducted to constrain the formation age of the Proterozoic strata, and to further study the source characteristics, genesis, and tectonic setting. The mafic rocks in northern Liaoning primarily consist of basalt, diabase, gabbro, and amphibolite. Results of zircon U-Pb chronology reveal four stages of mafic magma activities in northern Liaoning: the first stage of basalt (2209 ± 12 Ma), the second stage of diabase (2154 ± 15 Ma), the third stage of gabbro (2063 ± 7 Ma), and the fourth stage of magmatic protolith of amphibolite (2018 ± 13 Ma). Combined with the unconformity overlying Neoproterozoic granite, the formation age of the Proterozoic strata in northern Liaoning was found to be Paleoproterozoic rather than Middle Neoproterozoic by the geochronology of these mafic rocks. A chronological framework of mafic magmatic activities in the eastern segment of the North China Craton (NCC) is proposed. The mafic rocks in northern Liaoning exhibit compositional ranges of 46.39–50.33 wt% for SiO2, 2.95–5.08 wt% for total alkalis (K2O + Na2O), 6.17–7.50 wt% for MgO, and 43.32–52.02 for the Mg number. TiO2 contents lie between 1.61 and 2.39 wt%, and those of MnO between 0.17 and 0.21 wt%. The first basalt and the fourth amphibolite show low total rare earth element contents. Normalized against primitive mantle, they are enriched in large ion lithophile elements (Rb, Ba, K), depleted in high field strength elements (Th, U, Nb, Ta, Zr, Ti), and exhibit negative anomalies in Sr and P, as well as slight positive anomalies in Zr and Hf. The second diabase and the third gabbro have similar average total rare earth element contents. The diabase shows slight negative Eu anomalies (Eu/Eu* = 0.72–0.88), enrichment in large ion lithophile elements (Ba), depletion in Rb, and slight positive anomalies in high field strength elements (Th, U, Nb, Ta, Zr, Hf, Ti), with negative anomalies in K, Sr, and P. The gabbro is enriched in large ion lithophile elements (Rb, Ba, K), depleted in high field strength elements (Th, U, Nb, Ta, Zr, Hf), and exhibits positive anomalies in Eu (Eu/Eu* = 1.31–1.37). The contents of Cr, Co, and Ni of these four stages of mafic rocks are higher than those of N-MORB. The characteristics of trace element ratios indicate that the mafic rocks belong to the calc-alkaline series and originate from the transitional mantle. During the process of magma ascent and emplacement, it is contaminated by continental crustal materials. There are residual hornblende and spinel in the magma source of the first basalt. The other three magma sources contain residual garnet and spinel. The third gabbro was formed in an island arc environment, and the other three stages of mafic rocks originated from the Dupal OIB and were formed in an oceanic island environment. The discovery of mafic rocks in northern Liaoning suggests that the Longgang Block underwent oceanic subduction and extinction in both the north and south in the Paleoproterozoic, indicating the possibility of being in two different tectonic domains. [ABSTRACT FROM AUTHOR]

The Jurassic igneous rocks on Sumatra Island are important for investigating the Mesotethyan evolution and regional correlation in Southeast Asia. This paper presents new laser ablation-multicollector-inductively coupled plasma-mass spectrometry zircon U-Pb-Hf geochronological and isotopic, whole-rock elemental, and Sr-Nd isotopic data for the newly identified Glebruk dolerite and andesite in North Sumatra. New zircon dating results suggest that these mafic-intermediate volcanic rocks, with ages of 150-146 Ma, were formed during the Late Jurassic. The Glebruk dolerite and andesite belong to the calc-alkaline series, are enriched in the light rare earth elements, and exhibit depletion in Nb, Ta, and Ti. Thus, they resemble arc-like volcanic rocks. They have low (87Sr/86Sr)i ratios of 0.7038-0.7048 and strong positive eNd(t) and eHf(t) values of +6.4 to +7.5 and +4.8 to +18.6, respectively. Their geochemical signatures suggest that these Late Jurassic volcanic rocks were derived from a depleted mantle wedge that was metasomatized by the slab-derived melts. The Glebruk volcanic rocks were formed in a continental arc setting in response to the Late Jurassic northward subduction of the Woyla Ocean beneath West Sumatra. Our results and regional geological observations suggest that the Mesotethyan subduction-related igneous rocks could extend from South Qiangtang through West Yunnan to North Sumatra. The Woyla Ocean could represent the southern extension of the Mesotethyan Ocean. [ABSTRACT FROM AUTHOR]

The post-collisional evolution of the Tibetan lithosphere is of paramount significance to our understanding of collisional orogeny. It is generally postulated that the Lhasa lithospheric mantle was horizontally shortened and thickened coherently with the overlying crust to form a physical barrier, preventing Indian subduction beneath Tibet until the thickened mantle root was foundered during the Miocene. This study first identifies post-collisional oceanic-island basalt (OIB)-type magmatism in the Lhasa Block (LB), as attested by zircon U-Pb age (ca. 58 Ma) and geochemistry--positive Nb-Ta anomalies, high La/Yb, and depleted bulkrock Sr-Nd and zircon Hf isotopes, of diabase in the northern (inboard relative to Indus Suture) part of this block. Coupled with extensive early Paleogene arc-type magmatism in the southern-central LB and thermodynamic modeling, we suggest that these diabases were formed by partially molten upwelling asthenosphere near the base of continental crust, where much of the underlying lithospheric mantle had been removed due to Neo-Tethyan slab rollback and lithospheric delamination. Compared to OIB-type magmatism worldwide, the diabases investigated here were emplaced peculiarly in a region where the continental crust was under horizontal compression and shortening by coeval thrusting. Our study thus implies a decoupled deformation between the crust and mantle of the LB during the early Indian-Asian collision. [ABSTRACT FROM AUTHOR]

The Newark Basin comprises Late Triassic and Early Jurassic fluvio-lacustrine rocks (Stockton, Lockatong, Passaic, Feltville, Towaco, and Boonton Formations) and Early Jurassic diabase intrusions and basalt lava flows. Boron concentrations in private well water samples range up to 18,000 μg/L, exceeding the U.S. Environmental Protection Agency Health Advisory of 2000 μg/L for children and 5000 μg/L for adults. Boron was analyzed in minerals, rocks, and water samples using FUS-ICPMS, LA-ICP-MS, and MC ICP-MS, respectively. Boron concentrations reach up to 121 ppm in sandstone of the Passaic Formation, 42 ppm in black shale of the Lockatong Formation, 31.2 ppm in sandstone of the Stockton Formation, and 36 ppm in diabase. The δ11B isotopic values of groundwater range from 16.7 to 32.7‰, which fall within those of the diabase intrusion (25 to 31‰). Geostatistical analysis using Principal Component Analysis (PCA) reveals that boron is associated with clay minerals in black shales and with Na-bearing minerals (possibly feldspar and evaporite minerals) in sandstones. The PCA also shows that boron is not associated with any major phases in diabase intrusion, and is likely remobilized from the surrounding rocks by the intrusion-related late hydrothermal fluids and subsequently incorporated into diabase. Calcite veins found within the Triassic rock formations exhibit relatively elevated concentrations ranging from 6.3 to 97.3 ppm and may contain micro-inclusions rich in boron. Based on the available data, it is suggested that the primary sources of boron contaminating groundwater in the area are clay minerals in black shales, Na-bearing minerals in sandstone, diabase intrusion-related hydrothermal fluids, and a contribution from calcite veins. [ABSTRACT FROM AUTHOR]

New evidence of the Early Silurian sublithospheric magmatic activity in the eastern part of the Altai–Sayan orogen has been obtained. This activity occurred between large-scale mantle-derived magmatic episodes of the Middle–Late Ordovician and Devonian. It involved high-Mg (15–22 wt % MgO) picritic dolerite dikes of the Naryn complex in the western part of the Tuva–Mongolian Superterrane. The dike complex consists of simple picrodolerite dikes and those combined with a central picrodolerite zone and granitoids at contacts with mingling relationships between contrasting rocks. The picrodolerite geochemical signature is similar to enriched basalts of the mid-ocean ridges or intraplate regions and is indicative of a sublithospheric mantle source. Initial picrodolerite melts were formed at a depth of about 120–140 km, a temperature of 1600–1640°C, and a melting degree of up to 20% at a dry peridotite source. These values are consistent with the conditions of the hot spot magmas origin. Granitoids from the combined dikes had a crustal geochemical signature and were formed due to the anatexis of the Tuva–Mongolian Superterrane host rocks initiated by the picrodolerite intrusion. The U–Pb zircon age (SHRIMP-II) of leucogranite from the combined dike is 439 ± 3 Ma interpreted as the age of the Naryn dike complex. The Early Silurian mantle-derived magmatic activity of the Southeastern Tuva most likely caused the migration of the Siberian paleocontinent over the African mantle hot field. [ABSTRACT FROM AUTHOR]

Mesoproterozoic (ca. 1.3 Ga) magmatism in the North China Craton (NCC) was dominated by mafic intrusions (dolerite sills) with lesser amounts of granitic magmatism, but our lack of knowledge of this magmatism hinders our understanding of the evolution of the NCC during this period. This study investigated porphyritic granites from the Huade–Kangbao area on the northern margin of the NCC. Zircon dating indicates the porphyritic granites were intruded during the Mesoproterozoic between 1285.4 ± 2.6 and 1278.6 ± 6.1 Ma. The granites have high silica contents (SiO2 = 63.10–73.73 wt.%), exhibit alkali enrichment (total alkalis = 7.71–8.79 wt.%), are peraluminous, and can be classified as weakly peraluminous A2-type granites. The granites have negative Eu anomalies (δEu = 0.14–0.44), enrichments in large-ion lithophile elements (LILEs; e.g., K, Rb, Th, and U), and depletions in high-field-strength elements (HFSEs; e.g., Nb, Ta, and Ti). εHf(t) values range from –6.43 to +2.41, with tDM2 ages of 1905–2462 Ma, suggesting the magmas were derived by partial melting of ancient crustal material. The geochronological and geochemical data, and regional geological features, indicate the Mesoproterozoic porphyritic granites from the northern margin of the NCC formed in an intraplate tectonic setting during continental extension and rifting, which represents the response of the NCC to the break-up of the Columbia supercontinent. [ABSTRACT FROM AUTHOR]

It is well established that Cretaceous magmatism in the South China Block (SCB) is related to the Paleo‐Pacific subduction. However, the starting time and the associated deep crust‐mantle processes are still debatable. Mafic dike swarms carry important information on the deep earth (including mantle) geodynamics and geochemical evolution. In the Jiangnan Orogen (South China), there is no information on whether the Mesozoic magmatic activities in this region are also directly related to the Pacific subduction or not. In this study, we present detailed zircon U‐Pb geochronological, whole‐rock element and Sr‐Nd isotope data for Early Cretaceous Tuanshanbei dolerite dikes, and provide new constraints on the condition of the lithospheric mantle and mantle dynamics of the SCB during that time. LA‐ICP‐MS zircon U‐Pb dating suggests that this dolerite erupted in the Early Cretaceous (∼145 Ma). All samples have alkaline geochemical affinities with K2O + Na2O = 3.11–4.04 wt%, K2O/Na2O = 0.50–0.72, and Mg# = 62.24–65.13. They are enriched in LILE but depleted in HFSE with higher initial 87Sr/86Sr ratio (0.706896–0.714743) and lower εNd(t) (–2.61 to –1.67). They have high Nb/U, Nb/La, La/Sm and Rb/Sr, and low La/Nb, La/Ta, Ce/Pb, Ba/Rb, Tb/Yb and Gd/Yb ratios. Such geochemical signatures suggest that the fractional crystallization is obvious but crustal contamination play a negligible role during magmatic evolution. Tuanshanbei dolerite were most likely derived from low‐degree (2%–5%) partial melting of a phlogopite‐bearing mantle material consisted of ∼85% spinel peridotite and ∼15% garnet peridotite previously metasomatized by asthenosphere‐derived fluids/melts with minor subduction‐derived fluids/melts. Slab‐rollback generally lead to the upwelling of the hot asthenosphere. The upwelling of asthenosphere consuming the lithospheric mantle by thermo‐mechanical‐chemical erosion. The lithospheric mantle may have partially melted due to the heating by the upwelling asthenosphere and lithospheric extension. It is inferred that the Tuanshanbei dolerite might be associated with the initial slab rollback and corresponding lithospheric extension occurred potentially at ca. 145 Ma. [ABSTRACT FROM AUTHOR]

Background. Production of basalt fiber materials for thermal insulation materials, based on igneous rocks, meets the requirements of world standards. Purpose. Comparative analysis of chemical and mineralogical compositions and structures of igneous rocks for obtaining basalt fibers. Methodology. The studies were carried out using modern physicochemical methods adopted in the technology of mineral (basalt) fibers and thermal insulation materials. Originality. Chemical and mineralogical compositions and structures of various igneous rocks from different deposits were determined to establish their suitability for obtaining basalt fibers. Findings. The content of the main rock-forming components of igneous rocks was determined, their structure and properties were studied. [ABSTRACT FROM AUTHOR]

The stability of roadway sidewalls is crucial to ensuring people's safety and production efficiency in coal mining. This paper investigated the deformation and failure of deep roadway sidewalls, particularly the effects of height-width ratios and lateral pressure coefficients. Our research results indicate that brittle failure occurred in the diabase sidewall rock of the Datai coal mine, and a V-shaped pit was formed as a result of shear damage caused by high stress. When the height-width ratio of a roadway increases from 0.25 to 2.00, the tensile and shear plastic failure area of the sidewall increases, and vertical stress is transferred to a deep part of the roadway sidewall. There are two stress concentration zones and two stress peak points in the sidewall of a roadway. When the lateral pressure coefficient increases from 0.10 to 1.00, the tensile plastic zone of rock mass in the sidewall first decreases and gradually reaches stability. On the other hand, the shear failure area increases and then decreases. Similarly, the sidewall horizontal displacement decreases and then increases. Additionally, the vertical stress concentration position is located near the roadway sidewall. [ABSTRACT FROM AUTHOR]

For the Jiawula lead–zinc deposit, as easily accessible resources become depleted, mines are becoming deeper to replenish ore reserves. Identifying large, continuous, and high-grade ore bodies in deep areas has become a daunting problem. Moreover, separating lead–zinc-bearing complex ore bodies from waste material and extracting them from associated minerals are also difficult. Thus, pioneering exploratory strategies and technological methodologies are required to make breakthroughs in mineral discovery. Based on extensive-scale structural lithofacies mapping, this paper uses short-wave infrared (SWIR) spectroscopy technology to investigate hydrothermal alteration minerals in the mining area. It has identified a total of 16 hydroxyl-bearing alteration minerals, including chlorite, muscovite, illite, calcite, ankerite, kaolinite, and smectite. These minerals establish zoning characteristics around the ore bodies and on their flanks. They comprise a segmented assemblage that follows the pattern of comb-textured quartz–illite–chlorite–carbonate → muscovite–illite–chlorite–ankerite → illite–smectite–chlorite → chlorite–kaolinite–calcite. Deep-zone illitization with a lower Al–OH absorbance peak wavelength (<2206 nm) and higher crystallinity indices (>1.1) and chloritization with higher Fe–OH absorbance peak wavelengths (>2254) and higher crystallinity indices (>3.0) are indicators of potential hydrothermal centers in the deeper regions. By finding hydrothermal centers and connecting their spatial distribution with existing ore bodies, a pertinent relationship between diabase + andesite, Fe-chlorite + illite, and high-grade mineralization has been established. They correspond well with the lithology-alteration mineralization. This research provides a basis for predicting the positioning of concealed ore bodies deep inside a mine or at the periphery. [ABSTRACT FROM AUTHOR]

The dynamics and magma transport at the boundary between the upper and lower oceanic crusts (i.e., the dike–gabbro transition) are crucial for understanding the crustal accretion beneath mid-ocean ridges, which however have been studied at quite a few sites such as the East Pacific Rise and ophiolites like Troodos and Oman. Here we present detailed geological, petrological, and geochemical data for the dike–gabbro transition and associated basalts in the Yunzhug ophiolite, central Tibet, to constrain the complex magmatic processes in this specific horizon. The Yunzhug ophiolite contains a large (~ 20 km2) well-exposed sheeted dike complex, which is rooted in a dike–gabbro transition that consists of diverse lithologies, including diabase, gabbro, and minor porphyritic diabase. Petrographically, the Yunzhug gabbros could be grouped into the dominant Plg (plagioclase)-euhedral gabbros (euhedral–subhedral plagioclases enclosed in clinopyroxene oikocrysts) and a small amount of Cpx (clinopyroxene)-euhedral gabbros (with abundant euhedral clinopyroxenes). Plagioclases and their equilibrated melts of the two types of gabbros are similar, whereas clinopyroxenes and their equilibrated melts of the Cpx-euhedral gabbros are more primary and depleted than those of the Plg-euhedral gabbros. These petrographic and geochemical features suggest an earlier crystallization of clinopyroxene for the Cpx-euhedral gabbros, which is best explained by occasional water input in the magmatic system. Nevertheless, the modeled equilibrated melts of the two types of gabbros have compositions indistinguishable from the whole rock compositions of diabases and basalts, indicating a direct genetic linkage between these rocks. The unusual porphyritic diabases, on the other hand, provide evidence supporting for plagioclase accumulation and aggregation during magma upward migration, thus may have served as a unique way for magma to transport from the lower to upper crust. Studies of the Yunzhug ophiolite thus provide some key constraints on the complex magmatic processes in the oceanic dike–gabbro transition, regarding its dynamic accretion and magmatic plumbing mechanisms. [ABSTRACT FROM AUTHOR]

Early Paleozoic magmatism in the West Kunlun Orogenic Belt (WKOB) preserves important information about the tectonic evolution of the Proto-Tethys Ocean. This paper reports whole-rock compositions, zircon and apatite U-Pb dating, and zircon Hf isotopes for the Qiaerlong Pluton (QEL) at the northwestern margin of WKOB, with the aim of elucidating the petrogenesis of the pluton and shedding insights into the subduction-collision process of this oceanic slab. The QEL is mainly composed of Ordovician quartz monzodiorite (479 ± 3 Ma), quartz monzonite (467–472 Ma), and syenogranite (463 ± 4 Ma), and is intruded by Middle Silurian peraluminous granite (429 ± 20 Ma) and diabase (421 ± 4 Ma). Zircon εHf(t) values reveal that quartz monzodiorites (+2.1 to +9.9) and quartz monzonites (+0.6 to +6.8) were derived from a mixed source of juvenile crust and older lower crust, and syenogranites (−5.6 to +4.5) and peraluminous granites (−2.9 to +2.0) were generated from a mixed source of lower crust and upper crust; diabases had zircon εHf(t) values ranging from −0.3 to +4.1, and contained 463 ± 5 Ma captured zircon and 1 048 ± 39 Ma inherited zircon, indicating they originated from enriched lithospheric mantle and were contaminated by crustal materials. The Ordovician granitoids are enriched in LILEs and light rare-earth elements, and depleted in HFSEs with negative Nb, Ta, P, and Ti anomalies, suggesting that they formed in a subduction environment. Middle Silurian peraluminous granites have the characteristics of leucogranites with high SiO2 contents (74.92 wt.%–75.88 wt.%) and distinctly negative Eu anomalies (δEu = 0.03–0.14), indicating that they belong to highly fractionated granite and were formed in a post-collision extension setting. Comparative analysis of these results with other Early Paleozoic magmas reveals that the Proto-Tethys ocean closed before the Middle Silurian and its southward subduction resulted in the formation of QEL. [ABSTRACT FROM AUTHOR]

The study of the volcano–sedimentary sequence in the lower part of the Zaonega formation in the Paleoproterozoic Onega structure (Karelian craton, Fennoscandian Shield) has shown that tuffaceous and high-silica rocks predominate in its composition. High-silica rocks (SiO2 up to 94 wt %) are depleted in all elements and probably represent chemogenic siliceous silts. Tuffaceous rocks vary broadly in composition and were formed during mixing of tuffogenous basalt material and high-silica chemogenic sediments. In terms of levels of contents and the distribution character of trace elements, tuffogenous rocks are close to N-MORB volcanic rocks. This rock association is typical of the early stages of continental rifting in the Phanerozoic and may indicate the formation of volcano–sedimentary complexes of the Zaonega formation in the environment of continental rifting. The tuffaceous rocks in the lower part of the Zaonega formation are geochemically identical to dolerite dikes and MORB-type volcanic rocks 2.10–2.14 Ga in age. Their formation was probably related to this episode of large-scale extension and thinning of the continental lithosphere of the Karelian craton in the Middle Paleoproterozoic. In this case, the age limit of the Zaonega and underlying Tulomozero formations should be somewhat older than the 2.06–2.10 Ga interval accepted in the modern regional stratigraphic schemes of the Paleoproterozoic Fennoscandian shield. [ABSTRACT FROM AUTHOR]

Inner fracture zones play a decisive role in the formation of high-quality reservoirs in buried hill reservoirs in covered metamorphic rock. Based on core, sidewall core, thin section, seismic, logging and reservoir physical property data, the fracture development characteristics of the Bozhong 13-2 block buried hill reservoir are described in detail and the controlling factors and the influence on reservoir quality are discussed. The results showed: (1) three groups of tectonic fractures developed in the study area—near-EW-striking, ENE-striking and nearly N–S-striking fractures—were controlled by the early Indosinian thrusting, the late Indosinian to early Yanshanian sinistral strike-slipping and the late Yanshanian late dextral strike-slipping in the Bohai Bay Basin, respectively. The ENE- and nearly-E-W-striking fractures are the most common, and the dip angles of the fractures are mostly between 35° and 75° and thus oblique. (2) The Indosinian-early Yanshanian was the main fracture-forming period, and the dextral strike-slip action in the late Yanshanian was the key to maintaining effective fractures. Imaging logging shows that 97.87% of the fractures are effective fractures. Based on thin section observation, 14.47% of the fractures are unmodified open fractures and 80.37% of the fractures are effective fractures due to reactivation. (3) The late Yanshanian strike-slip fault transformed the deformation adjustment zone formed by the early Indosinian thrust faulting and the core of the fold structure was more conducive to fracture development. The fracture density of a single well located within the deformation adjustment zone and at the core of the fold is between 0.93–1.49 m−1, the fracture density of a single well located only at the core of the fold is between 0.67–0.75 m−1 and that of a single well located at the wing of the fold is between 0.35–0.59 m−1. Diabase dike intrusions promoted the development of local fractures. (4) Fractures promote the migration and accumulation of oil and gas, and the fracture density in the oil layer is between 0.81–2.19 m−1. That in the nonoil layer is between 0.25–1.12 m−1. In addition, fractures not only provide storage space but also effectively improve the reservoir capacity of the inner fracture zones of buried hill reservoirs by concentrating dissolution. [ABSTRACT FROM AUTHOR]

Measurements of multiple cosmogenic nuclides in a single sample are valuable for various applications of cosmogenic nuclide exposure dating and allow for correcting exposure ages for surface weathering and erosion and establishing exposure-burial history. Here we provide advances in the measurement of cosmogenic 10Be in pyroxene and constraints on the production rate which provide new opportunities for measurements of multi-nuclide systems, such as 10Be/³He, in pyroxene-bearing samples. We extracted and measured cosmogenic 10Be in pyroxene from two sets of Ferrar Dolerite samples collected from the Transantarctic Mountains in Antarctica. One set of samples has 10Be concentrations close to saturation which allows for the production rate calibration of 10Be in pyroxene by assuming production-erosion equilibrium. The other set of samples, which has a more recent exposure history, is used to determine if a rapid fusion method can be successfully applied to samples with Holocene to Last-Glacial-Maximum exposure ages. From measured 10Be concentrations in the near-saturation sample set we find the production rate of 10Be in pyroxene to be 3.74 +/- 0.10 atoms g-1 yr-1 and is consistent with 10Be/³He paired nuclide ratios from samples assumed to have simple exposure. Given the high 10Be concentration measured in this sample set, a sample mass of ~0.5 g of pyroxene is sufficient for the extraction of cosmogenic 10Be from pyroxene using a rapid fusion method. However, for the set of samples having low 10Be concentrations, measured concentrations were higher than expected. We attribute spuriously high 10Be concentration to potential failure in removing all meteoric 10Be and/or a highly variable and poorly quantified measurement background. [ABSTRACT FROM AUTHOR]

Occupational safety risk assessment is always the basic stage of the systematic approach of reducing the impact of undesired events (work injuries and occupational illnesses), by decreasing both their likelihood of occurrence and the gravity/severity of the generated impact. Eighteen years ago, when, as a consequence of the regulatory changes induced by our country's accession into the European Union, the risk assessment became mandatory/compulsory. Since then some progress was factually realized in the spirit of applying different risk analysis techniques in all Romanian organizations. Even if there are many aspects that are requiring further improvement, an effectively validated and nationally accepted indigenous tool is nowadays available. This method was put in practice in this research paper, in order to analyse, evaluate and assess the safety risks related to several of the main activities/jobs in a diabase open pit mine exploiting construction stone in a certain province of the country. Based on the results obtained, it has become feasible to propose realistic measures aimed at preventing the identified and quantified risks located in the field of unacceptable risks and protecting exposed workers to their effects. The case study developed and synthesized in this article confirms the capability of the risk assessment process to facilitate the substantiation of the decisions regarding the allocation of resources towards the minimization of the risks encountered in the work processes by different categories of workers in the mining companies. [ABSTRACT FROM AUTHOR]

Several Jurassic, ophiolite-hosted Cu-Zn VMS deposits occur in Tuscany. They are hosted by tectonic units of oceanic affinity (Ligurian Units), such as the well-known deposits of nearby Liguria. Industrial production was small and definitively ceased in the 1960s. Locally, massive ore (chalcopyrite-bornite-chalcocite) with an exceptionally high grade was found. The Montecatini Val di Cecina mine exploited the largest "bonanza" and, for few decades in the 19th century, became one of the most profitable copper mines in Europe. This study provides an updated review of these deposits. Tuscan Cu-Zn VMSs mostly occur in proximity of the contact between the serpentinite-gabbro basement and the overlying basalts. Chalcopyrite-pyrite stockworks occur in serpentinite-gabbro cut by dolerite dykes, while the largest massive sulphide bodies are hosted by polymictic-monomictic breccias at the base of pillow basalts. Early chalcopyrite ores were mechanically–chemically reworked and upgraded to bornite-rich nodular ore embedded in a chlorite, calcic amphibole, Fe-rich serpentine, quartz, andradite, ilvaite, and xonotlite assemblage. This bornite-rich ore contains substantial amount of sphalerite and pyrite and ubiquitous grains of clausthalite, hessite, tellurium, and gold. They represent a prime example of the sub-seafloor portion of a hybrid mafic-ultramafic oceanic hydrothermal system formed in an OCC along the slow spreading ridge of the Jurassic Piedmont-Ligurian Ocean. The peculiar mineralogical–textural character of the bornite-rich ore was driven by an interface coupled dissolution–precipitation process mediated by fluids. [ABSTRACT FROM AUTHOR]

The tremolite nephrite deposit in Dahua county, Hechi City, Guangxi province, China is a new genetic type of nephrite deposit. It is hosed by Mg-poor limestone (~1.30 wt.% MgO) and intruded by diabase (~45 wt.% SiO2). The Mg and Si contents of these rocks are lower than those of the tremolite (58.18 wt.% SiO2, 13.18 wt.% CaO, 24.16 wt.% MgO), indicating an obviously insufficient source for the metallogenic material that generated the deposit. In particular, some tremolite nephrite ore bodies have no clear contact metamorphism between the host and intrusive rocks, which have the characteristics of stratified mineralization (stratified tremolite nephrite). The origin and mineralization of stratified tremolite nephrite remain poorly constrained. To address this shortcoming, the mineralogy, geochemistry and Sr isotopic of host rock, altered marble, stratified tremolite nephrite and intrusive rock in the Dahua stratified tremolite nephrite deposit were studied. The results show: stratified tremolite nephrite mainly consists of aggregates of microcrystalline-cryptocrystalline tremolites with content exceeding 95%. The in situ rare earth elements (REEs) distribution pattern of hydrothermal calcite in the contact position between stratified tremolite nephrite and marble is similar to that of marine carbonate rock, showing obvious enrichment of HREE, which is different from calcite in limestone and marble. 87Sr/86Sr of stratified tremolite nephrite is relatively uniform, with an average value of 0.7070, within the range of Permian seawater. The mean value of Y/Ho in the hydrothermal calcite is 51.24, indicating that the marine fluid has not been impregnated by terrigenous materials. In summary, the hydrothermal fluid rich in Ca and Si is formed after marine carbonate rocks are altered by marine fluids. Hydrothermal fluids alter diabase rocks formed by altered minerals like titanite, chamosite, zoisite, etc. This process leads to the formation of metallogenic hydrothermal fluids abundant in Si, Ca, Fe and Mg. The metallogenic hydrothermal fluids migrate in faults and fractures of marble and crystallize to form tremolite nephrite under suitable ore-forming conditions. [ABSTRACT FROM AUTHOR]

The Sanjiang Tethyan Orogen plays a pivotal role in elucidating the geodynamic processes related to the evolution of the Paleo-Tethys Ocean. Research on the Gicha Complex within this orogen is imperative for comprehending the intricate evolution of the region. This study presents new findings from zircon U‒Pb dating, Hf isotope analysis, and whole-rock elemental analyses of gabbro, olivine gabbro, and the recently discovered mylonitic rhyolite and diabase in the Gicha Complex. The zircon U‒Pb dating yields ages of 703 ± 3 Ma for the diabase, 296 ± 2 Ma for the gabbro, and 231 ± 1 and 228 ± 2 Ma for the mylonitic rhyolite, demonstrating that these rocks record the extended evolution from the breakup of Rodinia to the closure of the Paleo-Tethys Ocean. The Neoproterozoic diabase samples exhibit shoshonitic and arc-like geochemical properties, with positive zircon εHf(t) values ranging from 1.1 to 3.7 and high Th/Yb values ranging from 1.34 to 3.07, suggesting that they were generated by partial melting of enriched subduction-modified lithospheric mantle in an active continental margin. The early Permian gabbro samples are part of the tholeiitic series and exhibit low SiO2 and K2O contents; depletions in Nb, Ta and Ti; and enrichment in Pb, indicating derivation from a combination of depleted mantle peridotite and subduction-related components. The whole-rock geochemical features suggest that these rocks formed in a back-arc setting featuring a small, mature ocean basin. The mylonitic rhyolite samples exhibit weakly peraluminous characteristics (A/CNK = 0.98–1.12) with high-K calc-alkaline geochemical features. The samples are depleted in Ba, Nb, Ta, and Ti and enriched in Th, U, Pb, and LREEs and exhibit negative to positive zircon εHf(t) values ranging from − 0.5 to + 5.9, indicating that they originated from partial melting of Meso-Neoproterozoic juvenile lower crust. Geochronological, petrological, and geochemical analyses indicate that the subduction of oceanic crust occurred along the western margin of the Yangtze Block until the late Neoproterozoic (~ 703 Ma). [ABSTRACT FROM AUTHOR]

In this study, field descriptions of the dolerite dykes cross‐cutting the Pan‐African basement (DPB) and the dolerite and gabbroic dykes cross‐cutting the Cretaceous sedimentary basin (DGCSB) are used together with petrographic, bulk‐rock geochemistry, as well as Sr–Nd–Pb isotopic data to constrain the geodynamic setting and origin of these mafic (basanite, basalt and basaltic andesite in composition) rocks that outcrop in the Figuil–Léré area. The DPB dykes are alkaline with SiO2 of 46.63–49.03 wt% and MgO of 3.93–7.11 wt%. In contrast, the DGCSB dykes are subalkaline with SiO2 ranging between 50.24 and 53.16 wt% and MgO fluctuating between 5.22 and 7.90 wt%, comparable to dykes described in other regions of the Cameroon Line (CL). The rocks studied belong to the tholeiitic series and were emplaced in within‐plate basalts (WPB) and mid‐ocean ridge basalts (MORBs) setting. The variations in major and trace elements from the basanite to basaltic andesite compositions are dependable with fractional crystallization (FC) of different mineral phases such as opaque minerals, olivine, clinopyroxene, amphibole and alkali feldspar. Most samples exhibit negative Nb–Ta and positive Sr anomalies, which together with the negative correlation between MgO and 87Sr/86Sr, and isotopic ratio of 206Pb/204Pb <19.5 (18.27–19.49) suggests interactions of crustal components. Nevertheless, this contamination seems limited because there is a positive correlation between SiO2 and 143Nd/144Nd plot and low Ba contents (72–210 ppm) of the samples compared to the mid‐continental crust (259–628 ppm). Trace element modelling proposes a derivation of the Figuil–Léré dykes from parental melts generated by 4%–15% partial melting of a source containing garnet peridotite in the mixed lithospheric–asthenospheric mantle. The isotopic data of the dykes studied with hybrid magma composition are characterized by more radiogenic 87Sr/86Sr, 143Nd/144Nd and 206Pb/204Pb isotopic ratios with a dominant mixing of depleted MORB mantle (DMM)–enriched mantle 1 (EM1)–enriched mantle 2 (EM2), like those of other mafic dykes of the CL. [ABSTRACT FROM AUTHOR]

Geological mapping of over 50 km2 area has been carried out in and around Obulapuram area, SE of Sandur Schist Belt. The Sandur Schist Belt (SSB), a part of Eastern Dharwar Craton (EDC) is a NW–SE trending lens-shaped late Archaean volcano-sedimentary belt. The litho-types exposed include peninsular gneiss of PGC, fuchsite quartzite, meta-basalt with intercalation of amphibolite, phyllite, metagabbro and quartzite, banded magnetite quartzite (BMQ), banded hematite quartzite (BHQ) belonging to the Donimalai Formation of Sandur Group. Granites, dolerite dykes, gabbro dykes and quartz veins are younger intrusives. Basement Peninsular Gneiss and intrusive granite are exposed towards the southern and eastern side of the study area. The area has undergone two phases of deformation, of which the earlier D1 deformation is quite pronounced producing the NW–SE trending S0∥S1 regional structures of the area. D1 deformation is responsible for the development of tight isoclinal and macroscopic (F1) folds. D2 deformation resulted in the development of open to close mesoscopic (F2) folds and broad warps with axial traces along ENE-WSW direction and crenulation cleavage (S2). The area is predominantly characterised by regional green schist facies of metamorphism, which increases to amphibolite facies near the contact of the schist belt with gneisses and intrusive granites. [ABSTRACT FROM AUTHOR]

Atom probe tomography (APT) of 238U and 206Pb has been applied to baddeleyite crystals from the Hart Dolerite (1791 ± 1 Ma) and the Great Dyke of Mauritania (2732 ± 2 Ma) in an effort to map U and Pb concentration at the nanometre scale. The purpose was to constrain the average nuclear recoil distance of 238U-series daughter nuclei in order to correct U-Pb ages determined on small baddeleyite crystals for alpha-recoil loss of Pb. Both crystals were thought to expose natural crystal surfaces providing a boundary where maximum effects of recoil loss could be observed. The Hart Dolerite sample showed no variations in Pb concentrations near the edge. The Great Dyke sample shows U zoning and the associated 206Pb zoning is affected by alpha recoil, apparently adjacent to a natural grain surface. The sample also shows 10 nm-scale apparently primary clusters of U atoms that contain about 40 % of the U. These are too small to constrain alpha recoil distance beyond a few nm but are apparently primary and their formation mechanism poses a dilemma. To constrain alpha recoil distance, a forward modelling approach is presented where 206Pb redistribution functions were determined for a range of possible distances and synthetic 206Pb/238U profiles were determined from the convolution of the observed U profile with the redistribution functions that were compared to the observed 206Pb/238U profile. A complication is the fact that the 40 by 400 nm size of the sample is lower than the range of possible alpha recoil redistribution effects so it was necessary to extrapolate the observed U zoning. An oscillatory pattern gives the best fit to the observed profile but any reasonable extrapolation constrains the average alpha recoil distance to be close to 80–90 nm, which is much larger than previous estimates using other methods. Either recoil distances can be highly anisotropic within small crystal samples or surface roughness was a factor that modified the recoiled Pb distribution. APT is a potentially useful approach to determining average alpha recoil distance but requires sampling of primary, smooth crystal faces. [ABSTRACT FROM AUTHOR]

The Kotuy intrusive complex was identified from the geological survey of the western slope of the Anabar Massif in the middle reaches of the Kotuy River. It is represented by dolerite–gabbrodolerite sills and dikes of Vendian age (556 ± 28 Ma). A number of sills are characterized by 30–80 m thickness, and dikes often have a length of a few dozen kilometers. The distribution area of the complex is a few hundred square kilometers. However, the geodynamic evidence for the formation of extensive intrusive bodies in the northern part of Siberia in the Vendian is not clear. We present new geochronological, geochemical, and paleomagnetic data indicating that at least part of the Kotuy magmatic complex intrusions in the middle reaches of the Kotuy River should be attributed to the ~1500 Ma Kengede magmatic complex (Kuonamka large igneous province). In this light, the very existence of Vendian intrusive magmatism on the western slope of the Anabar massif appears questionable. [ABSTRACT FROM AUTHOR]

The DL deposit is a typical tabular-shaped U deposit hosted in sandstones of the Upper Cretaceous Yaojia Formation in the southwestern Songliao Basin, northeast China. Owing to its recent discovery, the origin of the deposit remains unclear. In this study, mineralogical and geochemical data were used to constrain the genesis of the DL deposit. Two sources of U were recognized: (1) pre-ore U enrichment in the Yaojia Formation during diagenesis; and (2) the provenance of the Yaojia Formation, which comprises late Permian–Early Cretaceous granitic rocks from the southern Great Xing'an Range and northern margin of the North China Craton, rather than the oils and diabase dikes in the study area. Mineralogical and geochemical characteristics indicate that organic matter (OM) in the Yaojia Formation was derived mainly from plant debris and hydrocarbons. In situ S isotope data for pyrite from the ore-bearing sandstones show that most of the pyrite has similar δ34S values (−43.8‰ to −20.6‰) to those of pyrite associated with bacterial sulfate reduction (BSR). The pyrite is often typically replaced and/or overgrown by pitchblende, which has a high P2O5 content (0.07–1.64 wt.%), indicative of a genetic relationship between BSR and U mineralization. The geological, mineralogical, and geochemical features suggest that the U mineralization in the DL deposit was mainly associated with BSR. [ABSTRACT FROM AUTHOR]

The Atuba Complex occurs in the eastern region of Paraná State, located in the Southern Ribeira Belt. It is comprised of the Curitiba Terrane, northward of the Luís Alves Terrane, and southward of the Apiaí Terrane. This research was carried out by means of detailed petrography, microtectonics, and brittle and ductile structural analysis. The Atuba Complex is composed of migmatites, felsic granulites, granitoids, quartzites, phyllonites, schists, amphibolites, and cataclasites. The lithotypes are cut by diabase or gabbro dikes, lamprophyre dikes, pseudotachylites, and quartz, epidote, carbonate, or chlorite veins. The migmatites are characterized by two migmatization phases, the first composed of tonalitic leucosomes and the second formed by granitic leucosomes. The stromatic and mylonitized migmatites suggest dislocation creep mechanisms and dynamic recrystallization processes, mainly in quartz and feldspars. During the initial phase, melting reactions took place through dehydration, while in the subsequent phase, melting was facilitated by the presence of water-fluxed. The Atuba Complex comprises two foliations, Sn-1 (Dn-1 phase) and Sn (Dn phase). The Sn-1 surface (compositional banding) presents a ductile and anastomosed aspect with an N45W/55NE attitude, whereas the Sn mylonitic foliation is defined by the presence of mineral flattening or stretching and by the orientation of amphibole and biotite shapes, with a maximum plane of N45E/85NW. The observed faults and fractures strike in the NE-SW and NW-SE main directions. The paleostress study provided the recognition of a NE-SW sigma 1 associated with a NW-SE-striking sigma 3 for the left-lateral strike-slip faults and an E-W compressive SHMAX and an N-S distensive SHMIN for the right-lateral strike-slip faults. [ABSTRACT FROM AUTHOR]

There is a magmatic lull period in the East Kunlun orogen (EKO) during the Jurassic to the Cretaceous. However, due to the lack of records of magmatic activity restricts our understanding of the late Mesozoic magmatic-tectonic evolution of the EKO. Herein, an integrated study of geochronology, whole-rock geochemistry and Sr-Nd isotopes were conducted for the Cretaceous mafic dykes in the EKO, Northern Tibet Plateau, to reveal their petrogenesis and geodynamic implications. LA-ICP-MS Zircon U-Pb dating reveals that the studied mafic dykes comprising diabase and diabase porphyry emplaced at ca. 80.9 ± 0.8 Ma. The Cretaceous mafic dykes have low contents of SiO2 (46.36 wt.%~47.40 wt.%) but high contents of MgO (6.79 wt.%~7.38 wt.%), TiO2 (1.91 wt.%~2.13 wt.%), Nb (12.4~18.3 ppm) and Nb/U ratio (31~39), resembling Nb-enriched mafic dykes. They exhibit chondrite-normalized rare earth element (REE) and primitive mantle-normalized trace element patterns, remarkably similar but not identical to the oceanic island basalts (OIB). The moderate REE fractionation ((La/Yb)N = 3.55~5.37), weak negative Eu anomalies (δEu = 0.87~0.97) and relative enrichment of Rb, Ba, K, as well as high contents of Cr and Ni and slightly depleted Sr-Nd isotopes (εNd(t) = −0.18~1.33), suggest that the studied dykes originate from a partial melting of spinel lherzolite and a little of garnet which was previously modified by subducted sediments. Combined with other evidence, we propose that the studied Cretaceous Nb-enriched mafic dykes in the Northern Tibet Plateau were formed in the intraplate setting, which may be a partial melting of the enriched mantle in the lower lithosphere caused by the activity of the East Kunlun strike-slip fault. [ABSTRACT FROM AUTHOR]

The Awulale Iron Metallogenic Belt (AIMB) located in Central Tianshan is a significant iron ore belt in China. The Beizhan area exhibits extensive volcanic and intrusive rocks that formed during or close to the iron mineralization period. The iron ores in Beizhan are found in Early Carboniferous rhyolite and dacite tuff. The rhyolite is enriched in LILEs and LREEs, depleted in HFSEs, and shows high positive εNd(t) values (+3.0–+4.0). Late Carboniferous intrusive rocks include a granite stock and diabase and diorite dykes. The zircon grains from the granite yield a weighted mean 206Pb/238U age of 311.8 ± 2.6 Ma. The geochemical features of the granite are similar to those of rhyolite, but with pronounced negative anomalies of Eu, Sr, P, and Ti and higher positive εNd(t) values (+4.9–+5.1). The zircons in the diorite dyke yield a weighted mean 206Pb/238U age of 299.2 ± 1.4 Ma. Both the diabase and diorite dykes show an enrichment of LREEs and depletion of HFSEs with high positive εNd(t) values (+3.3–+7.3 and +2.3–+2.6, respectively), although the Eu, Th, and Sr anomalies are more negative in the diorite compared to the diabase. The rhyolite displays high positive εNd(t) values and young Nd model ages (TDM2 = 760–838 Ma) and has Nb/Ta ratios (11.3–12.8) close to that of the continental crust, indicating that it originated from the partial melting of the juvenile lower crust. The granite has similar geochemical characteristics (TDM2 = 656–673 Ma and Nb/Ta ratio = 8.7–10.9) and is also believed to have originated mainly from the partial melting of the juvenile lower crust. The diabase and diorite dykes have low (Tb/Yb)N ratios (<2) and high Ba/Th (31.8–353.2 and 185.3–251.3, respectively) and Sr/Th (113.8–312.9 and 144.7–163.1) ratios, and exhibit a pronounced depletion of HREEs and Y and negative Th anomalies, suggesting that they originated from a spinel-garnet lherzolite mantle source. The Early Carboniferous rhyolite erupted in a continental arc setting, whereas the Late Carboniferous granites, diabase dykes, and diorite dykes formed in an extensional setting associated with the upwelling of the asthenosphere. Therefore, the magmatism and Fe mineralization in the AIMB are correlated with an extensional setting associated with oceanic slab breakoff. [ABSTRACT FROM AUTHOR]

The majority of total radiation dose received by the world population comes from background natural radiation. The distinguishing features of this radiation include relatively persistent exposure of a population at a specific place. The amount of background radiation that is generally present in the environment is greatly influenced by the inhalation of radon (Rn), thoron (Tn), and their offspring. In light of this, measurement of dose rate exposure due to granite flooring has been attempted in Bangalore. Fifteen different granite samples, used as flooring for construction in buildings, were examined for a period of three years. Solid state nuclear track detector-based dosimeters, can technique, and radiation survey meters have been used. All the experimental observations were made according to the standard protocols provided by the Bhabha Atomic Research Centre, Mumbai, India. The arithmetic mean dose rate varied between 1.39 ± 0.06 and 2.09 ± 0.10 mSv y-1. The values of dose rates were found to be higher in granite and lower in coarse-grained dolerite. All 15 types of granite samples have undergone a minimum of 30 measurements. The greater activity concentration of radionuclides found in granite samples leads to higher dose rates. [ABSTRACT FROM AUTHOR]

This study assessed the adsorptive uptake of Cr(VI) onto eco-friendly adsorbent fabricated via the surface coating of pristine dolerite (PD) using the extract ofAzadirachta indica stem bark. The materials were characterised using the XRD, FESEM, FTIR, EDX, BET and Raman analysis. Optimum adsorption of Cr(VI) onto AMD was achieved at pH = 2, contact time of 180 min and dosage of 0.03 g. The adsorption equilibrium data for PD and Azadirachta indica extract modified dolerite (AMD)fitted well with the Langmuir and Redlich-Peterson models respectively at 318 K.Also, a good correlation between the experimental data and the Elovich kinetic model was achieved. The diffusion mechanisms were both controlled by film diffusion and intraparticle diffusion.The uptake of Cr(VI) onto PD and AMD was feasible, endothermic (ΔH: PD = 14.14 kJ mol−1 and AMD = 37.67 kJ mol−1) and entropy-driven (ΔS: PD = 17.69 J K−1 mol−1 204.3 J K−1 mol−1). Besides, the recyclabilitypropensity of AMD afterseveral cycles projects AMD as a fibrousbasedmaterialwithsustainablepotential for the decontamination of Cr(VI) polluted water. [ABSTRACT FROM AUTHOR]

The assemblage of oceanic islands and seamounts, arising from the widespread presence of mature oceans, plays a crucial role in reconstructing the evolutionary history of the paleoocean. Oceanic islands or seamounts within the Longmuco-Shuanghu metamorphic complex, a remnant of the Paleo-Tethys Ocean in the central Tibetan Plateau, have seldom been reported due to their remoteness. This study has identified an oceanic island-seamount in the Maoershan area, situated to the west of the Longmuco-Shuanghu metamorphic complex, composed of basalt, diabase, limestone, and siliceous rocks. Based on field observations, petrology, zircon U-Pb dating, whole-rock geochemistry, and Sr-Nd isotopes analyses, we have identified a suite of mafic rocks with OIB affinity. The youngest zircon U-Pb age cluster was concentrated at ~243–241 Ma. The geochemical characteristics of the siliceous rocks indicate a mixture of terrigenous material, suggesting that they formed in a continental margin. In combination with regional geological data, we conclude that the Longmuco-Shuanghu Paleo-Tethys Ocean remained open during the Middle Triassic. Furthermore, a fraction of the oceanic island-seamounts underwent scraping and transformed into a metamorphic complex, while other segments experienced deep subduction, resulting in the formation of high-pressure metamorphic rocks. Collectively, these processes gave rise to the distinctive high-pressure metamorphic complex within the central Qiangtang terrane. [ABSTRACT FROM AUTHOR]

Here we present an analytical method for Zinc (Zn) isotopic measurements using "standard‐sample bracketing" on a Nu Sapphire multi‐collector inductively coupled plasma‐mass spectrometer. The effects of Zn mass fraction and HNO3 molarity mismatch between the standard and the sample, as well as the presence of matrix elements have been evaluated. Long‐term reproducibility of better than ±0.03‰ for δ66Zn (2s) was routinely obtained. Accurate measurements were achieved when CNi/CZn < 0.001, CTi/CZn < 0.03, CBa/CZn < 0.05, CNa/CZn and CAl/CZn < 0.5, CMg/CZn < 0.1, CFe/CZn < 5 and CCu/CZn as well as CCd/CZn < 10. High‐precision Zn isotopic determination were performed on twenty‐one widely available geological certified reference materials, with an overall range of ~ 0.62‰ (0.15 to 1.07‰), which is nearly twenty times the current analytical precision (0.03), and the results are in agreement with most previously published data within 2s. Among them, δ66ZnJMC 3‐0749L of eleven geological certified reference materials are reported for the first time: 0.22 ± 0.03‰ (dolerite, DR‐N), 0.23 ± 0.02‰ (gabbro, GSR‐10), 0.20 ± 0.04‰ (microgabbro, PM‐S), 0.15 ± 0.02‰ (andesite, GSR‐2), 0.22 ± 0.08‰ (diorite, GSR‐9), 0.19 ± 0.07‰ (syenite, GSR‐7), 0.30 ± 0.06‰ (granite, GSR‐1), 0.25 ± 0.00‰ (rhyolite, GSR‐11), 0.37 ± 0.01‰ (shale, GSR‐5), 0.21 ± 0.03‰ (limestone, GSR‐6) and 0.20 ± 0.03‰ (hornblendite, GSR‐15). The novel Zn isotopic data from these certified reference materials can be used for future interlaboratory comparisons. [ABSTRACT FROM AUTHOR]

The late Early Permian basaltic rocks in the West Junggar of northwest China provide a critical geological record for revealing the termination of the Late Palaeozoic final-stage subduction history of the southwestern Palaeo-Asian Ocean. With the aim of providing constraints on the late stage of the Late Palaeozoic geodynamic evolution of the southwestern Altaids, an integrated study of detailed field observation, geochronology and geochemistry has been carried out on the Early Permian basaltic rocks from the Hala'alate Mountain of the southern West Junggar. Zircon LA-ICP-MS U-Pb dating of four basaltic andesites suggests that they were erupted during the late Early Permian with ages of ca. 286–283 Ma, coeval with the neighbouring mafic diabase stock and gabbroic dyke swarms. The basaltic rocks have low SiO2 and moderate MgO contents, with low (87Sr/86Sr)i ratios (0.70397–0.70447) and high positive εNd(t) values (+5.94–+7.19), and also show remarkable enrichment in large ion lithophile elements (Ba, U, K, Pb, Sr) and prominent depletion in high field strength elements (Nb, Ta, Zr, Hf, Ti), indicating that they were originated from the partial melting of a garnet-dominant with minor spinel lherzolitic depleted mantle source previously metasomatized by slab-derived fluids and subducted sediments. These basaltic rocks were most likely formed in a fore-arc extensional setting in response to the slab retreat of the Junggar oceanic slab during the mid-late stage of Early Permian. Combined with previously published regional achievements, our new results support that the down-going of the remnant oceanic slab and the resultant arc magmatic activity of the southern West Junggar probably continued until the ca. 283 Ma, and the closure of the West Junggar branch of the Palaeo-Asian Ocean should be later than the late Early Permian. [ABSTRACT FROM AUTHOR]

The study is aimed at evaluating the groundwater accumulations present in Alice using magnetic and electrical resistivity measurements to examine the trends of structural elements and characterize the groundwater resource for borehole drilling. The magnetic maps show a low magnetic linear structure moving northwest to southeast direction, which may be caused by fractures. The linear high intensities were probably caused by dolerite dykes, while dolerite sills caused broader high-intensity areas. The depth slices show that the near-surface magnetic structures are visible to a depth of about 19 m, and the deep-seated structures are found at a depth of about 31 m, possibly deeper. Twenty-five vertical electrical soundings (VES) of the Schlumberger array were measured with AB/2 varying between 1.5 m and 250 m across the study area. The VES interpretation showed four geoelectric layers composed of HK and HA curve types. The geoelectric layer's thicknesses are (1) topsoil from 0.4 to 1.8 m, (2) weathered layer from 0.8 to 17.5 m, and (3) weathered/fractured layer from 9.9 to 143.9 m; the third layer could be the productive water-bearing zones, and (4) bedrock layer has an infinite thickness. The layers have resistivity values of 20-5752 Ωm, 3-51 Ωm, 136-352 Ωm, and 44-60428 Ωm, respectively. A correlation of the VES with the borehole log indicated a well-matched result. The magnetic and electrical resistivity surveys provided a detailed subsurface structure and helped identify possible fractures that could act as a passage for groundwater. [ABSTRACT FROM AUTHOR]

The results of U–Pb (ID-TIMS) and U–Th–Pb (LA-ICP-MS) geochronological studies of baddeleyite from dolerite dikes of the Sulumat Complex and detrital zircon from red arkose sandstones of the Kebekta Group of the Ugui graben, Aldan Shield, are presented. It has been established that the Kebekta Group has an age of 2.01–1.87 Ga. The provenance areas of the Kebekta Group deposits were the Archean (2.92–2.52 Ga) igneous and metamorphic complexes of the Chara–Olekma Geoblock and the zone of its junction with the Western Aldan Megablock of the Aldan Shield, as well as the Paleoproterozoic (approximately 2.01 Ga) complexes unidentified on the present erosion level. The obtained geochronological data do not contradict the correlation of terrigenous rocks of the Kebekta Group of the Ugui graben and the Kemen Group of the Kodar–Udokan trough. The deposition of arkose sandstones of the Kebekta Group correlates in age with the glaciations in Australia and Sweden (approximately 1.9–1.8 Ga) associated with the formation of the Columbia/Nuna supercontinent. It cannot be excluded either that the deposition of the rocks in the Ugui graben was related to the inflow of glacial material into the intracontinental extensional basin from the southern and/or western (in modern coordinates) framing of the Chara–Olekma Geoblock at the stage of collapse of the Paleoproterozoic orogen. [ABSTRACT FROM AUTHOR]

Numerous Late Carboniferous – Early Permian dykes are found in West Junggar and represent an important part of the Central Asian Orogenic Belt. In this contribution, we use these dykes to assess the tectonic regime and stress state in the Late Carboniferous – Early Permian. The West Junggar dykes are mainly diorite/dioritic porphyrite with minor diabase and were formed in 324–310 Ma. They have been divided into two groups based on their orientation, petrology and geochronology. Group 1 dykes mostly comprise WNW-striking dioritic porphyrite and NE-striking diorite with minor diabase and resemble the Karamay-Baogutu sanukitoid. They were probably formed from depleted mantle at a relatively high temperature and pressure with the addition of 1–2% sediment/sedimental partial melt and 0–5% trapped oceanic crust-derived melts. Group 2 dykes are ENE-striking and are similar to sanukite in the Setouchi Volcanic Belt. These dykes were also derived from depleted mantle at a shallow depth but high temperature with the addition of 2–3.5% sediment/sedimental partial melt. Magma banding and injection folds in dykes and host granitoids indicate magma flow. Paleostress analysis reveals that both groups of dykes were formed in a tensile stress field. Their emplacement is favoured by presence of pre-existing joints or fractures in the host granitoids and strata. We conclude that large-scale asthenosphere mantle upwelling induced by trapped oceanic slab-off can explain the magmatism and significant continental crustal growth of West Junggar during Late Carboniferous to Early Permian. [ABSTRACT FROM AUTHOR]

The end-Cretaceous (ca. 66 Ma) Phenaimata alkaline igneous complex, associated in space and time with the Deccan large igneous province (LIP) in Western India, consists of bimodal (tholeiitic to alkaline) differentiated plutonic to volcanic igneous rocks. Mineralogy and petrology of variably fractionated alkaline lamprophyre and dolerite dykes of the complex are the focus of this study. The two lamprophyre dykes (termed as camptonite-I and camptonite-II) which intrude the host basalt/olivine dolerites and gabbro, differ in their liquidus minerals and crystal size distribution. Their respective rare earth element (REE) and trace element patterns suggest the lamprophyres to be genetically related, with the camptonite-II being relatively more evolved than that of the camptonite-I. Binary mixing model involving trace elements as well as the Sr˗Nd isotopic data in case of the camptonite-I, brings out involvement of crustal contamination in the generation of the lamprophyres. The two dolerites mostly consist of the liquidus phases, with the exception of olivine antecrysts created during early stages of the host gabbro formation but subsequently inherited into their magma. In terms of their trace element composition, the dolerites of this study show a strong similarity with that of the alkali basalts of the complex. The normal compositional zoning of pyroxene and amphibole from the lamprophyres shows that their parental magma initially experienced a closed system fractionation to form a large crystal mush zone and subsequently developed a smaller magmatic chamber where biotites of the camptonite-II first crystallised. Reverse zoning, resorption of crystals, disparity in crystal size distribution and their composition also reveals that a newer batch of magma was introduced from the feeding zone into the initially developed crystal laden magmatic chamber. This replenishment led to the disaggregation of crystals from the mush zone and the resulting magma subsequently evolved to form camptonite-I. Later on, the successive lateral spreading of the newly generated magma increased its buoyancy to rise through the smaller crustal chamber (with biotites) to generate camptonite-II. Our study demonstrates not only the operation of diverse open and closed system processes such as fractionation, replenishment and mush capturing that have occurred within inter-connected plumbing magmatic chambers beneath the alkaline complexes associated with the flood basalt volcanism in large igneous provinces but also their significant role in influencing the ultimate composition of the associated diverse rocks. [ABSTRACT FROM AUTHOR]

This article presents the results of a study of a composite coating made of ultrahigh molecular weight polyethylene (UHMWPE) with a diabase filler obtained by flame spraying. Diabase of 10 wt.%, 20 wt.%, 30 wt.% and 40 wt.% was chosen as a filler. The polymer coating was applied to the St3 metal substrate using temperature control in a conventional flame spraying process. The coating was studied using scanning electron microscopy, X-ray phase analysis, infrared spectroscopy, abrasive wear resistance, microhardness testing and determination of the friction coefficient. It has been shown that diabases do not have a negative effect on the initial chemical structure of UHMWPE and it is not subjected to destruction during flame spraying. The introduction of diabase into the composition of UHMWPE with a content of 10–40% of the total mass does not adversely affect the crystalline structure of the coating. It has been established that with an increase in the volume of the diabase filler, the wear resistance of the composite coating based on UHMWPE increases. It has been determined that with the addition of diabase, the microhardness of the coatings increases. [ABSTRACT FROM AUTHOR]

The Fawakhir area consists of an ophiolite sequence surrounded by an ophiolitic mélange. In the mélange, serpentinized ultramafic rock, gabbro, gabbroic diorite, diabase, andesite, and basalt occur as tectonic blocks within the metasediments. The gabbro gives a zircon U–Pb age of ~816 Ma, and the trace element composition of the zircon suggests its generation under a continental-arc tectonic setting. The geochemistry of gabbro and other tectonic blocks in the ophiolitic mélange indicates their formation from a backarc basin in a continental island arc tectonic setting. The ophiolite sequence consists of serpentinized ultramafic rock, gabbro, and basaltic rocks and was intruded by felsic dikes. The gabbro from the ophiolite sequence and felsic dikes give zircon U–Pb ages of 742 Ma and 723 Ma, respectively. Trace elements composition of this zircon refers to their formation in a continental-arc tectonic setting. The geochemistry of rocks in the ophiolitic sequence indicates their formation in a forearc basin. Together with previous studies, this study suggests that the tectonic blocks in the mélange formed in a backarc during the early-stage northwards subduction event, which may have started at ~816 Ma or earlier. On the other hand, the rocks in the ophiolite sequence can be considered to have formed in a forearc by the later eastwards subduction event at ~742–723 Ma. [ABSTRACT FROM AUTHOR]

Large‐scale magmatic activity and associated mineralization in South China are linked to the subduction of the palaeo‐Pacific Plate, although specific processes have remained controversial including the timing of subduction initiation and lithospheric extension. We present new geochemical data and zircon U–Pb and Lu–Hf isotope measurements on volcanic rocks, granites and mafic dikes from coastal south‐eastern China along the Eurasian continental margin. The biotite monzogranites show I–type granitoid affinity and fractional crystallization with zircon εHf(t) values ranging from −10.15 to +0.50, suggesting magma derivation from the melting of lower crust with the addition of juvenile crustal or mantle components. The biotite granites are typical of highly fractionated A‐type granites with εHf(t) values ranging from −3.63 to +1.35, indicating magma hybridization between anatectic granitic and mantle‐derived mafic magmas. The diabase dikes have zircon εHf(t) values ranging from −2.99 to +1.71, with high La/Nb and La/Ta ratios. This suggests derivation from partial melting of a lithospheric mantle metasomatized by fluid from a subducting–slab, with contributions of depleted asthenospheric mantle components. Our data, combined with those from previous studies, suggest that the shallow subduction of the palaeo–Pacific Plate beneath the Eurasian continent had begun by ca. ~170 Ma at least and the subduction orientation changed to oblique with respect to the continental margin. Steepening of the subduction angle likely caused a slab rollback during the Early Cretaceous, resulting in a tectonic transition from compression to extension in South China at ca. 145 Ma. [ABSTRACT FROM AUTHOR]