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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]

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]

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 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]

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]

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]

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]

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]

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]

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]

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]

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]

This study investigated the possibility of using basalt, diabase, and andesite natural stones instead of virgin fine aggregates. Substitution percentages varied between 10% and 40% according to the sand mass. The effect of basalt, diabase, and andesite addition on concrete performance was evaluated using strength and durability tests performed on the samples at the end of 7, 28, and 60 days. In addition, petrographic-mineralogical, X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses of basalt, diabase, and andesite stones were evaluated. The 60-day compressive strengths of the samples were 39% higher in samples with basalt additives, 35% higher in samples with diabase additives, and 37% higher in samples with andesite additives than in the control sample. At the end of 28 days, the water absorption rates of the samples with additives were 113.83%–55.81% less that of the control sample, on average, and the samples suffered 26%–52% less wear loss than the control sample. In addition, at the end of the freeze–thaw cycles, the compressive strengths of the samples with basalt, diabase, and andesite added were 67%, 63%, and 64% higher than that of the reference sample, respectively. The compressive strength values of samples exposed to the effect of sulfate for 180 days were examined, and samples with basalt, diabase, and andesite added had compressive strength values an average of 33.35%, 32.52%, and 32.80% higher than that of the reference sample, respectively. This study proves the usability of basalt, diabase, and andesite natural stones and their wastes as fine aggregate. [ABSTRACT FROM AUTHOR]

Melt inclusions in the minerals from a dolerite dike of the Vilyui–Markha dike swarm, located on the northwestern shoulder of the Vilyui paleorift, have been studied. Data on the composition of homogeneous glasses of melt inclusions in minerals made it possible to establish the PT parameters of mantle sources of primary deep melts responsible for the formation of gabbro-dolerites of the Vilyui paleorift. Two levels of generation of the initial melts have been established for dolerites: in the intervals of 95–65 km at 1480–1400°C and 55–45 km at 1360–1320°C. The presence of two intermediate chambers in the crust, where melts crystallized, was identified at depths of about 12 and 9–4 km with a decrease in temperature to 1175–1125°С. The two-level arrangement of centers of magma generation, as well as the heterogeneity of the chemical composition of the minerals studied, makes it possible to explain the presence of two pulses of Devonian basic magmatism. [ABSTRACT FROM AUTHOR]

Mafic dikes are developed in the Shangsu region of Jiangxi, including Nanyuan Mountain and Mianhuaao. These dikes intrude into the Upper Triassic Anyuan Formation and are primarily composed of pyroxene, plagioclase, and opaque minerals, exhibiting a dolerite texture. The mafic dikes were found to have an SiO2 content ranging from 48.38% to 50.53% and the (K2O + Na2O) content ranging from 2.88% to 4.16%. The Na2O/K2O ratio was found to be between 2.56 and 3.99. The Eu anomaly was absent (δEu = 0.91–0.95), suggesting no influence of plagioclase fractionation during the rock formation process. The Ce anomaly was found to be absent (δCe = 1.04–1.08). The Mg# was found to range from approximately 40.06 to 45.06, indicating minimal crystal fractionation within the magma. The mafic dikes are enriched in light rare earth elements and large ion lithophile elements (LILE) and Th, while they showed significant depletion of high field strength elements (Nb, Ta, Ti). The Ti depletion may be related to the separation and crystallization of Ti-bearing minerals such as amphibole and ilmenite. Zr and Hf anomalies were evident, likely due to the contamination of zircon minerals in the samples. The mafic dikes were most likely products of the Middle–Late Yanshanian magmatic intrusion, formed in an extensional setting within the intracontinental rift environment caused by the collision of the Pacific Plate and the Eurasian Plate. The lithospheric mantle source was influenced by subduction zone fluid, and the magma source region exhibited mixed crustal materials. [ABSTRACT FROM AUTHOR]

The basal contact of the Sudbury Igneous Complex (SIC) on the North Range is interpreted as the outer edge of a meteorite impact crater. Yet, the base of the SIC, and contacts within the SIC, and the overlying Onaping are not circular. Their outline is elliptical. This and other details of the geology of the North Range which have not been fully explained include variations in the width of the metamorphic contact aureole, lateral discontinuous variations in the thickness of the norite and granophyre units, paleomagnetic evidence that the North Range contact of the SIC originally had a dip of around 20°, and differing magnetic fabrics in the norite/gabbro versus the granophyre. Several metrics are used to determine how much of the current outline of the North Range is the result of post-impact deformation and how much is a primary feature related to a meteorite impact. Uplift, rotation, and translation experienced by different segments of the North Range of the SIC are established using dyke azimuth and petrographic analysis of Matachewan diabase dykes, and paleomagnetic and magnetic fabric data analysis. These analyses show (a) the elliptical form of the North Range is a primary feature associated with a near-circular impact crater, (b) some of the original crater wall must have been preserved, and (c) deformation of the North Range is limited to regional scale block rotation producing a southwest dip modified by minor block rotation tilting and vertical displacement associated with north–northwest-trending faults. [ABSTRACT FROM AUTHOR]

Atom probe tomography 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 constrain the average nuclear recoil distance of U-series daughter nuclei and thereby 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 recoil loss could be observed, but both surfaces showed no adjacent variations in Pb concentrations. However, the Great Dyke sample shows U zoning and the associated 206Pb zoning is affected by alpha recoil. A forward modelling approach was used where 206Pb redistribution functions were determined for a range of possible alpha recoil distances and synthetic 206Pb/238U profiles were determined from the convolution of the observed U profile with the redistribution functions. These can be compared to the observed 206Pb/238U profile. A complication is that the 400 nm range of sampling is lower than the range of possible alpha recoil redistribution effects. In order to get a realistic match to the observed 206Pb/238U profile, it was necessary to extrapolate the observed zoning as an oscillatory pattern. This gives a best estimate for the average alpha recoil distance of about 40 nm. [ABSTRACT FROM AUTHOR]

Studies on post-collisional magmatic rocks can provide key clues to researching the crust–mantle interactions and the tectonic evolution of collisional orogenic belts. This study investigated a suite of newly discovered mafic intrusions in the middle of the East Kunlun orogenic belt through integrated analysis of petrology, petrography, and zircon U–Pb dating. The data could offer new insights into the generation of the Proto-Tethyan tectonic evolution. The result shows that these mafic intrusions are mainly gabbro and diabase, formed in the Early Devonian, with zircon U–Pb ages of 408.9 ± 2.0 Ma for gabbro and 411.1 ± 3.1 Ma for diabase. It consists of plagioclase, pyroxene, and dark minerals, and a small number of calcite and chlorite. Diabase has a small amount of amygdale. Their Na2O + K2O contents range from 3.47 wt.% to 5.45 wt.%, with Na2O/K2O ratios from 1.39 to 3.09, suggesting that they are calc–alkaline rocks. These rocks have an Fe2O3ᵀ content of 7.68 wt.%–11.59 wt.% and Mg# of 50.58–59.48, belonging to the iron-rich and magnesium-poor type. The chondrite-normalized rare earth elements show similar patterns that are characterized by enrichment of light rare earth elements, with (La/Yb)N of 3.27–6.75 and no significant europium anomaly, indicating the rocks are homogenous. The studied rocks are characterized by low contents of compatible elements Cr and Ni, enrichment of large-ion lithophile elements such as Rb, U, Sr, and Nd, and high-field-strength elements such as Nb, Ta, Zr, Hf, and Th. The mafic magma originated from the partial melting of the enriched mantle and was assimilated and mixed with crust materials during the process of migration. Based on the regional tectonic evolution, we interpret that the Proto-Tethys Ocean had closed in the Early Devonian, and that the East Kunlun region was in a post-collisional extensional tectonic setting. [ABSTRACT FROM AUTHOR]

Tianshan is one of the world's largest gold provinces; however, the relationship between gold mineralization and metasomatized subcontinental lithospheric mantle (SCLM) remains poorly understood. To improve our understanding, we present new bulk-rock geochemistry and platinum group element (PGE) concentrations of the SCLM-sourced Aksu Neoproterozoic diabase dykes in Chinese South Tianshan. These data, combined with in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of hydrothermal pyrite grains in the diabase dykes, are used to discuss the SCLM source characteristics in the region and their potential links to formation of gold deposits. The diabase dykes exhibit high Th/Yb (0.47–0.62) and low Nb/U (13.4–16.3) ratios, indicating that magma evolution involves subduction-related fluid metasomatism and limited contamination of the continental crust. This is consistent with little variation in whole-rock Pd/Zr, Cu/Zr, and Ni/MgO ratios, suggesting that no sulfide segregation was caused by crustal contamination and magma mixing. In addition, the diabase dykes show low PGE and Au contents, with high Cu/Pd (>105) and low Cu/Zr (<0.5) ratios, indicating that magmas were derived from low-degree partial melting of the SCLM under S-saturated conditions. Such source characteristics indicate residual sulfides and chalcophile elements (e.g., PGEs, Au, and Cu) were concentrated at the SCLM reservoir in South Tianshan. Hydrothermal pyrite in the studied dykes has similar Au/Ag ratios and trace element distribution patterns to gold-bearing pyrite of lode gold deposits in Chinese South Tianshan, indicating that metasomatized SCLM may have contributed ore metals during the formation of these gold deposits. Adding to the available data, our study highlights that the SCLM may be a potential metal source reservoir, and it may have contributed to formation of the lode gold deposits in Chinese South Tianshan. [ABSTRACT FROM AUTHOR]

To study the strain hardening and softening mechanism for hard brittle rocks, a strain hardening and softening constitutive model for hard brittle rocks is developed. First, the normalised hardening and softening factors are defined, which characterise the yield state of rock at the stages of pre-peak hardening and post-peak softening, respectively. Then, a unified strength parameter evolution model is established that can describe the nonlinear characteristics of cohesion and the internal friction angle under different confining pressures. Based on the Mohr–Coulomb criterion, a strain hardening and softening constitutive model is proposed. Finally, the proposed model was implemented in FLAC3D, and triaxial compression numerical tests of granite and diabase were conducted. The results show that the constitutive model can characterise the nonlinear mechanical behaviour of the pre-peak hardening stage and post-peak softening stage of hard brittle rock. The model was also able to satisfactorily capture the transition from brittle failure to plastic failure for hard brittle rock under high confining pressures. [ABSTRACT FROM AUTHOR]

This study presents petrography, geochemistry, mineral chemistry and geochronology of diabase dikes from Sidakan area, northeastern Iraq. The area consists of basalts and diabase dikes alternating with sedimentary rocks, hosted by Walash Metavolcanic Group (WMG) as part of the Zagros Fold-Thrust Zone (ZFTZ). These rocks are dark grey to pale brown in color, fine to medium in grain size, and have ophitic and porphyritic textures. They consist of plagioclase and clinopyroxene as essential minerals and minor olivine as well as their alteration and low-grade metamorphism products including amphibole, albite, epidote, chlorite, serpentine, calcite and sericite, with ilmenite as an accessory mineral. The diabase dikes consist (as average wt.%) of 51.41 SiO2, 15.82 Al2O3, 9.95 FeOt, 6.58 MgO, 9.63 CaO, 3.42 Na2O, 0.87 TiO2, 0.17 MnO, 0.35 K2O, 0.09 P2O5, and 1.92 LOI. The Harker diagrams indicate that the diabases were formed from fractional crystallization of tholeiitic parent magma. The classification diagram Nb/Y vs. Zr/TiO2 indicated that the studied diabases have affinities of subalkaline basalts, while the SiO2 vs. K2O diagram showed that they are divided between the low-K basalt and basaltic andesite. The tectonic discriminant diagrams show that the diabases are oceanic island-arc tholeiites with N-MORB geochemical affinities. The K − Ar age of the diabases is Late Eocene (Bartonian-Priabonian) ranging between 34.6 ± 0.84 to 39.2 ± 1.81 Ma representing their intrusion/crystallization age and possibly the age of the formation of Oceanic Island Arc and/or the initial collision stage between the Arabian-Iranian microplates.

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.

Understanding the petrogenesis of alkaline syenites is important for constraining the mechanisms of rare earth element (REE) and rare-metal mineralization. Here we report a detailed petrological and geochemical study of early Permian syenitic rocks from the southwestern Tarim large igneous province (TLIP) in the Wajilitag area (China). We use these data to investigate the complex magmatic processes responsible for the enrichment of incompatible elements (e.g. REEs and rare metals) in these rocks. The Wajilitag syenitic rocks comprise early hornblende syenite (281 Ma) and later nepheline syenite (278 Ma), both of which are spatially and temporally associated with mafic intrusions (i.e. gabbro and diabase). These syenitic rocks show continuous variations in major elements with the mafic rocks. They also have similar Sr–Nd–Hf isotopic compositions with the nearby mafic rocks, denoting that the Wajilitag syenitic rocks should be derived from the melts represented by these mafic rocks. However, these syenitic rocks, particularly the nepheline syenites, are typically characterized by extreme enrichment of incompatible elements, which is hard to be accounted by simple fractional crystallization of mafic magmas. Some clinopyroxene phenocrysts in the Wajilitag nepheline syenites show oscillatory zoning with strikingly increasing and then gradually decreasing MgO contents, which recorded replenishment of mafic magma at the interval. Low-MgO clinopyroxene mantles and/or rims have much higher incompatible element contents (e.g. Nb, Ce, and Zr) and ratios (e.g. Ce/Y) than their cores, which could reflect melt injection controlled by reactive porous flow in a mush reservoir of a crustal magma chamber. Such processes may also cause the high Ce and/or Nb contents of the mantles and/or rims of zoned titanite and apatite phenocrysts. The injection of reactive porous flow melts is the key process that produces the extreme enrichment of incompatible elements in the alkaline syenites from the western TLIP, as well as other plume-related alkaline syenites that host world-class REE and rare-metal deposits. [ABSTRACT FROM AUTHOR]

This article presents, for the first time, the study of diabases from various ophiolite complexes from Greece and Cyprus to identify their performance as concrete aggregates. Within this scope, in the first step, diabase samples from four selected ophiolite complexes of Greece (Veria-Naousa, Edessa and Guevgueli) and Cyprus (Troodos) were collected in order to estimate their suitability as concrete aggregates by means of their petrographic and physicochemical characteristics. In the next step, concrete specimens were prepared and their mechanical strength was measured in order to investigate their mechanical performance. Additionally, their petrographic characteristics in relation to the mechanical strength of the created concretes were investigated for the first time. Concrete specimens prepared by employing diabases from the Veria-Naousa and Guevgueli complexes as aggregates were reckoned as the most durable ones in contrast to those derived from the Edesssa complex and even more so than those from Cyprus, with the latter containing the most altered diabases (rodingitised). The overall conclusion of this research is that the engineering properties of the aggregates were dependent on their petrographic characteristics and hence they influenced the final mechanical behaviour of each produced concrete. [ABSTRACT FROM AUTHOR]

The organic geochemistry of organic-rich facies including shales, marls, and carbonates (Assistência Member) of the Irati Formation, Paraná Basin, Brazil, were analyzed to evaluate the thermal effects of igneous intrusions upon the kerogen present in these facies. Total organic carbon (TOC) content and hydrocarbon source potential (S2) of the Irati source rocks range from 0.03 to 20.4% and 0.01 to 112.1 mg HC/g rock, respectively, indicating excellent potential as a source for hydrocarbon generation. Hydrogen index (HI) values reveal that the kerogen is predominantly type I (HI: up to 892.6 mg HC/g TOC) and, therefore, an oil source, except for samples having low TOC content due to severe maturation caused by the heat from diabase intrusions. The thickness of igneous intrusions in the 64 wells investigated in this study ranged from 2 to 231 m. They clearly had a major impact on TOC, HI, and S2 values, which decrease in the vicinity of intrusions, indicating a gradual increase in maturation toward the igneous body. In wells without the influence of igneous intrusions, Tmax values of Rock-Eval pyrolysis and %Ro indicate that the organic matter is immature for the generation of hydrocarbons. [ABSTRACT FROM AUTHOR]

This contribution reports new findings on petrogenesis and possible geotectonic setting of rare subvolcanic Triassic(?) dolerite cropping out in External Dinarides with a goal to contribute to the debate on the geodynamic evolution of the continental margin of the Adriatic-Dinaridic platform(s) at the onset of the Mesozoic. Petrography of the studied rocks revealed the crystallization order: clinopyroxene → plagioclase → alkali-feldspar ± amphibole ± Fe-Ti oxides. The geochemistry of calc-alkaline dolerite suggested magma generation from a spinel-garnet bearing peridotite mantle source (60sp:40grt). Twomechanisms explaining the origin of dolerite are here suggested. The first one involves a low-grade partial melting of the altered lithospheric mantle and the subduction-modified oceanic lithosphere accompanied with subducted/recycled sediments. The second one proposes a melting of the subduction-altered heterogeneous lithospheric (subcontinental)mantle contaminated and/or metasomatized during an earlier Variscan subduction in the Late Paleozoic. Accordingly, two geodynamic interpretations are suggested: (i) Middle Triassic north-vergent active subduction of the Paleotethys beneath the Andean-type active Laurasian continental margin coupled by the formation of a pericontinental volcanic arc and subsequent extension and back-arc rifting, within the Adria Plate, which led to the formation of locally aborted rift systems and subsidence of the platform, and (ii) Middle Triassic extension, unaffected by contemporaneous active subduction, of the High Karst nappe unit of the Greater Adria as a result of an ephemeral syn-rift volcanic stage, which featured the formation of the Dinaridic aborted rift system followed by the platformsubsidence and emergence of local sedimentary basins. [ABSTRACT FROM AUTHOR]

Classical locality Vyskočilka in the Barrandian Basin displays a well-exposed section of black Silurian shales penetrated by a ca. 10-m thick diabase sill. We examined the petrographic character and mineral composition of the intrusive body and enclosing shales, as well as the hydrothermal veins cutting the rocks. The diabase is a rock with basic affinity (paleobasaltoid), which was strongly influenced by post-magmatic alterations including albitization and zeolitization of feldspars as well as chloritization of clinopyroxenes and Fe-Ti spinelides. Host sediments show variously intense thermal overprint at the contact with the sill. The predominating Silurian shales are rarely accompanied by laminites, formed by siliciclastic material, calcite, apatite and probably also a pyroclastic component. A minor component of all sediments are Ti-rich chromspinelides, which are classified as chromite, magnetite, and spinel. Chromspinelides form isolated euhedral single crystals reaching up to 50 µm in size, as well as their intergrowths and fragments, which all do not display marks of abrasion due to transport. We therefore presuppose that they represent relics of ultrabasic pyroclastic material (volcanic ash), which was deposited during sedimentation of Silurian sediments. There are known few sills of Silurian meimechites in the Prague Basin containing chromspinelides with comparable chemical composition, which can thus represent a likely source of chromspinelides. The vein hydrothermal mineralizations, present at the study site, probably originated during different geological processes. The calcite veins with minor quartz and hydrocarbons likely formed during Variscan tectono-thermal overprint of the area. By contrast, the vein mineralization containing calcite, quartz, titanite, anatase, and Zn-Fe-Ni-Cu sulphides was likely associated with contact-metamorphic processes related to intrusion of diabase. [ABSTRACT FROM AUTHOR]

The Courel Mountains Geopark is in Galicia, Northwest Spain. Its total area is 578.29 km² . Parallel valleys and ridges characterize its relief from North to South. Their maximum altitude reaches 1,641 m. Their lithology is dominated by slates, quartzites, and limestones, together with small diabase outcrops. Materials are intensely fractured due to the tectonic dynamics that started during the Cenozoic, and sedimentary formations accumulated in response to environmental changes during the Pleistocene are abundant. As a result, a wide variety of structural landforms are present, along with a wide range of landforms and deposits of alluvial, fluvial, glacial, and periglacial origin. All of them have been mapped to enable sustainable use and management aimed at improving the livelihood of the inhabitants of the geopark area, which has suffered depopulation in recent decades. [ABSTRACT FROM AUTHOR]

Since the 1960s, a deep groundwater system in Wright Valley, Antarctica, has been the hypothesized source of brines to hypersaline Don Juan Pond and Lake Vanda, both of which are rich in calcium and chloride. Modeling studies do not support other possible mechanisms, such as evaporative processes, that could have led to the current suite of ions present in both waterbodies. In 2011 and 2018, an airborne electromagnetic survey was flown over Wright Valley to map subsurface resistivity (down to 600 m) in exploration of liquid water. The surveys revealed widespread unfrozen brine in the subsurface near Lake Vanda, Don Juan Pond, and the North Fork of Wright Valley. While our geophysical survey can neither confirm nor deny deep groundwater connectivity between Lake Vanda and Don Juan Pond, it does point to the potential for deep valley-wide brine, likely within the Ferrar Dolerite formation. [ABSTRACT FROM AUTHOR]

The Alborz-Azerbaijan magmatic zone in northern Iran is one of the important zones of magmatic activity in the Cenozoic. Lithologically, this complex consists of olivine gabbro, monzogabbro, dolerite, and gabbro with granular, intergranular, and porphyritic textures. The main phenocrysts of these rocks are clinopyroxene, plagioclase, and sometimes iddingsitized olivine. The rocks producing magma has potassic and shoshonitic nature. Enrichment in large-ion lithophile elements (LILEs), i.e., Ba, Rb, and Th, and depletion of high-field strength elements (HFSEs), i.e., Ti and Nb, in the spider diagrams are of the characteristics of subduction and active continental margin rocks. Also, these diagrams show enrichment in the light rare earth elements (LREEs) compared to heavy rare earth elements (HREEs). This feature also is representative of the rocks of subduction zones and active continental margins. The geochemical and petrogenetic studies indicate unique origin of the intrusive rocks in the study area and the role of fractional crystallization with simultaneous crustal assimilation (AFC) and magma contamination with crustal rocks in the evolution of the magma forming these rocks. This magma is obtained from the low-degree partial melting of an enriched mantle source beneath the continental lithosphere with garnet lherzolite composition at a depth of 100 to 110 km in a post-collision extensional basin. [ABSTRACT FROM AUTHOR]

The chemical composition of alkaline (Late Cretaceous basanite) and subalkaline (Permian–Triassic dolerite) basaltoids of different ages in the northern part of the Minusa Trough was studied by optical emission spectroscopy and mass spectrometry with inductively coupled plasma. The revealed differences of subvolcanic rocks in the nature of enrichment in HFS- and LIL-elements may indicate the generation of primary magmas at different depths and small degrees of melting of garnet and spinel mantle peridotite. The model of decompression partial melting of the subcontinental lithospheric mantle under the garnet stability conditions is applicable to the formation of basanite. It is assumed that the formation of dolerite magma was due to the interaction of the melt from shallower spinel peridotite with the "OIB component" of the sublithospheric mantle plume. [ABSTRACT FROM AUTHOR]

This study presents the development and experimental assessment of novel, high strength, cementless binders that incorporate alkali-activated local waste. A silica-rich diabase mud (DM), currently considered as waste, was previously investigated for geopolymerization, signifying that the DM lacked the necessary reactivity to provide a stable geopolymer binder alone. Moreover, even after incorporation of small amounts of cement and metakaolin, the DM mixtures still did not yield adequate mechanical properties. In this study, the local DM was instead combined with another industrial byproduct known as Ground Granulated Blast-furnace Slag (GGBS) in varying mixtures. The mixture design trials enabled the development of three high strength cementless geopolymer mixtures with 28-day compressive strengths ranging between 60 and 100 MPa, comparable to conventional concrete compressive strengths. The results indicate that the innovative geopolymer material is very promising for the manufacturing of pavement tiles and other precast construction products. Most importantly, this study presents the first successful development of a construction material of adequate compressive strength that can absorb large quantities of the abundant quarry waste, following a course of 10 years of unsuccessful attempts to valorize the local DM. Although difficulties were encountered due to a high reactivity rate, especially for the mix that included the highest GGBS content, prototype pavement tiles were manufactured and assessed experimentally. The results reveal a promising potential of valorizing the local DM in the development of precast geopolymer products, despite the effects of shrinkage cracking on the experimental evaluation of the material mechanical properties. [ABSTRACT FROM AUTHOR]