Quartz Grains Research Articles

Exploration of the X-ray Dark-Field Signal in Mineral Building Materials.

Mineral building materials suffer from weathering processes such as salt efflorescence, freeze–thaw cycling, and microbial colonization. All of these processes are linked to water (liquid and vapor) in the pore space. The degree of damage following these processes is heavily influenced by pore space properties such as porosity, pore size distribution, and pore connectivity. X-ray computed micro-tomography (µCT) has proven to be a valuable tool to non-destructively investigate the pore space of stone samples in 3D. However, a trade-off between the resolution and field-of-view often impedes reliable conclusions on the material’s properties. X-ray dark-field imaging (DFI) is based on the scattering of X-rays by sub-voxel-sized features, and as such, provides information on the sample complementary to that obtained using conventional µCT. In this manuscript, we apply X-ray dark-field tomography for the first time on four mineral building materials (quartzite, fired clay brick, fired clay roof tile, and carbonated mineral building material), and investigate which information the dark-field signal entails on the sub-resolution space of the sample. Dark-field tomography at multiple length scale sensitivities was performed at the TOMCAT beamline of the Swiss Light Source (Villigen, Switzerland) using a Talbot grating interferometer. The complementary information of the dark-field modality is most clear in the fired clay brick and roof tile; quartz grains that are almost indistinguishable in the conventional µCT scan are clearly visible in the dark-field owing to their low dark-field signal (homogenous sub-voxel structure), whereas the microporous bulk mass has a high dark-field signal. Large (resolved) pores on the other hand, which are clearly visible in the absorption dataset, are almost invisible in the dark-field modality because they are overprinted with dark-field signal originating from the bulk mass. The experiments also showed how the dark-field signal from a feature depends on the length scale sensitivity, which is set by moving the sample with respect to the grating interferometer.

Garnet: The archive of prograde metamorphic records of granulite-facies terranes

<p indent="0mm">Whether granulite terranes can preserve prograde metamorphic records is a perturbing topic in metamorphic petrology, and related research is rare. This is mainly because the metamorphic records of the granulite terranes have information asymmetry. Generally, the mineral assemblages and compositions of granulite-facies rocks are considered to reflect peak and retrograde metamorphism, rather than prograde metamorphism. However, this assumption must be made with caution. Case studies of granulites from the junction area of Shanxi and Hebei province in the North China Craton suggest that garnet could serve as “temperature and pressure resistant containers” under granulite-facies conditions, and retain the evidence of pre-peak metamorphism. For pelitic granulites, their protoliths are supracrustal rocks, and must have undergone prograde metamorphic processes from the Earth’s surface to the deep crust. Therefore, a confirmatory study seeking prograde metamorphic records for pelitic granulites from the Huai’an-Datong area was conducted. In the studied pelitic granulites, inclusions in garnet display well-preserved microstructural zoning, with radical zonal distribution patterns: Crowded quartz grains in the core, a few K-feldspar-kyanite-bearing assemblages in the mantle, and some sillimanite flakes in the rim. The major element zoning (here, major endmember proportions X_Sps, X_Alm, X_Pyr, and X_Grs are used) of garnet is relatively homogeneous. However, the high rare earth elements (HREEs) exhibit bell-shaped profiles decreasing from the core to the rim. This suggests that even if the major elements of garnet are homogenous due to high-temperature diffusion, microstructural zoning and some trace elements with slow diffusion rates could be protected from peak- and retro-grade high-temperature modification. For garnet mafic granulites, their protoliths are considered as gabbro dykes, and there is no robust evidence of prograde metamorphism from the upper to lower crust; therefore, their tectonic significance is unclear. Here, an exploratory study of prograde metamorphism for garnet mafic granulites from the Huai’an-Hengshan area was conducted based on the study experience of pelitic garnet. In the investigated mafic granulites, garnet also displays a zoned distribution of various mineral assemblages from its center to rim, including quartz- and titanite/ilmenite-bearing assemblages in the core, rutile-bearing assemblages in the outer mantle to the inner rim, and a resorbed rim. Fortunately, garnet of the mafic granulites displays well-preserved compositional growth zoning patterns, with bell-shaped X_Sps, increasing X_Pyr from core to mantle, and a resorbed rim (X_Sps). The HREEs (for example, Yb) show bell-shaped patterns similar to those of the X_Sps. Both textural and compositional zoning patterns in the studied mafic granulites documented multiple generations of garnet growth history from the prograde to peak metamorphic stages. These findings provide robust metamorphic evidence for the Paleoproterozoic subduction and assembly of the Jin-Yu Mobile Belt in the North China Craton. The above two case studies suggest that high-temperature granulite-facies metamorphism may not completely reset the multi-generation growth information retained in the garnet. In contrast, minerals in the matrix only record the history of intensive re-equilibration at the peak or rehydration retrogression metamorphism. Thus, garnet is an important archive of prograde metamorphic information. This study further suggests that caution should be exercised when determining the peak<italic> P-T</italic> conditions of granulites using garnet core compositions.

Luminescence dating at Border Cave: attempts, questions, and new results

Border Cave hosts a rare Middle and Early Later Stone Age sequence of deposits that extends as far back as ca. 250 thousand years (ka). The site's chronology has been built mainly on Electron Spin Resonance (ESR) ages obtained from teeth, conducted at the end of the 1990s, and on radiocarbon dating for the more recent layers. In order to refine the sequence's chronology, several materials were selected for luminescence dating, including 34 siliceous lithic artefacts, and quartz and feldspar grains extracted from 10 sediment samples. Since the radioisotopic contents of the cave sediments are abundant in the volcaniclastic host rock (about 2% K, 10 ppm 232Th, 2 ppm 238U in the sediments) and the ages for the lower layers are over 40 ka, high (>150 Gy) equivalent doses (De) were expected for most samples. The saturated thermoluminescence (TL) signals of the lithic artefact samples suggested either that they had not been heated in the past, or that they were already too old to be dated. The presence in the sediments of 40–63 μm quartz grains dominated by the fast Optically Stimulated Luminescence (OSL) component and with apparent high D0 values (200–1000 Gy) suggested, a priori, that they could be appropriate for measuring high Des. However, a systematic drop of the De values for these high D0 grains was observed and could not be fully understood and corrected accordingly. The recently proposed pIT protocol, together with a global growth curve (GGC) approach, was applied to 63–80 μm feldspar grains extracted from the sediment samples. The data suggest that the IR225 signal was likely not fully bleached at the time of deposition. Nonetheless, two age estimates, assumed to bracket the target age, have been calculated for each sample. These estimates are consistent with the previous ESR ages and the ESR/C14-based Bayesian models. Further improvements can be considered in the future with the pIT - GGC method, which would allow both increased accuracy and precision.

Meteorite impact at Ramgarh, India: Petrographic and geochemical evidence, and new geochronological insights

The impact origin of Ramgarh crater in India has been a topic of debate for several decades due to its conspicuous morphology, with recent studies confirming the structure as a complex impact crater. In this work, we present the results from an integrated petrographic and geochemical study to evaluate the impact origin of the crater, in conjunction with introduction of a new geochronological data for the crater through zircon U Pb systematics. Petrographic studies of the target Vindhyan sedimentary rocks show the presence of shock fabrics such as planar fractures, decorated planar deformation features, brecciation, melted grain boundaries, diaplectic glass, and vitrified matrix. Geochemically, the lithounits have high concentrations of Cr, Ni, Cu, and the corresponding chondrite normalized values show notably elevated levels than crustal average. The elevated levels of Cr, Ni and Cu in the target rocks indicate its interaction with an extra-terrestrial object. The positive correlation between Ni and Co, higher concentration of Cr (9–623.35 ppm), and more importantly the average Ni/Cr (~0.006- ~ 1.3), Ni/Co (~1.8 to ~22) and Cr/Co (~57–~368) ratios in the target lithounits of Ramgarh, point to a differentiated achondrite being the possible impactor. The zircon U Pb geochronological data from two samples in this study do not show significant Pb-loss and U enrichment. However, the relatively younger age of 528–395 Ma, depicted by quartzite sample (AN-4), along with the discordance and distinguishable Pb-loss, might hint that the impact event at Ramgarh have occurred between this timeframe. This age is considerably closer to the Precambrian-Cambrian Boundary (543 Ma) and, it also encompasses the age corresponding to the mid-Ordovician Meteor Event (OME) (467.5 ± 0.28 Ma). As this study infers that the potential impactor at Ramgarh is a differentiated achondrite and not a L-chondrite, the OME age can be ignored, further narrowing the age of Ramgarh impact structure. Our study also confirms the Ramgarh structure as an impact crater, and constrains the possible timing of the impact. • Tracking the impact event at Ramgarh Crater, NW India • Shock features in quartz grains mainly includes decorated PDFs, and melting. • Whole rock, trace and REE geochemistry reveals impact event. • Zircon U Pb ages of 528 to 395 Ma, which is the first convincing age for this crater

Opposite Shear Sense from Quartz Shape and Crystallographic Preferred Orientation – a Dichotomy and Its Implications for Kinematic Analysis

ABSTRACT The present paper is written to bring to light a dichotomy that is noted in a naturally deformed rock, where the sense of shear inferred from quartz shape preferred orientation (SPO) is opposite to that deciphered from the crystallographic preferred orientation (CPO). Microstructural and quartz CPO data (obtained through SEM-EBSD analysis) from a quartz vein hosted in sinistrally sheared mylonitized granite of Gadwal region (Dharwar Craton) are presented. The vein thin section is prepared parallel to the kinematic reference frame (XZ section of the strain ellipsoid) using field-based information, which allows determination of sense of shear using microstructures. Three domains viz. Domain-I, II and III are identified in the rock thin section with grain size being 300-180 µm, 70-35 µm, and &amp;lt;20 µm, respectively. Of these, quartz grains of Domain-II show a well-defined quartz oblique grain shape fabric, which is indicative of dextral sense of shear. However, quartz CPO from the same Domain-II, as well as Domains-I and III, consistently shows a sinistral sense of shear; the latter complements the kinematics noted from the host rock mylonite. The dichotomy noted from Domain-II indicates that there maybe pitfalls in direct interpretation of kinematics based exclusively on quartz SPO analysis. Hence, caution must be exercised while extrapolating microscale kinematics based on quartz SPO to the regional scale.

Study of Light and Heavy Minerals and Their Effect on Oil Aggregation in the Zubair Formation for the Rumaila Oil Field in Southern Iraq

Zubair Formation is the most productive reservoir in southern Iraq, which is comprised of sandstones, interbedded with shale sequences and sometimes carbonate rock. It is an important formation in the lower Cretaceous cycle in Iraq. Rumaila oil field is the largest oil field in Iraq and the 6th in the world. Two wells were studied for three depths, one in the southern Rumaila and the other in the north. The study focused on light and heavy minerals in sand fractions and their relationship with hydrocarbon assemblages. For the survey to be complete, the sedimentological study of the cores was also conducted. This research aims to determine the effect of the amount of heavy and light minerals on the generation and production of oil in the reservoir layers. The sedimentological results were the prevalence of sand for all depths, especially in Southern Rumaila. The sand ratio ranged from 62% to 98%. The rate of heavy minerals in southern Rumaila was greater than in Northern on average at 1.17%. Light minerals were the most in Northern Rumaila up to 99.3% represented in quartz with a high percentage and a little part of feldspar represented in orthoclase. Heavy minerals were represented in Opaque (24%), zircon (27.6%), tourmaline (18%), rutile (11%), biotite (3%), chlorite (3.6%), muscovite (3.6%), staurolite (2%) and hornblende (3.6%). The proportion of quartz was the most in light minerals. The average of minerals is ultra-stable, and Opaque is the most dominant over the other minerals. Ultra-stable minerals in the sand that contain hydrocarbon assemblage are an index to mineralogical maturity for sandstone rocks. The SEM images showed deformations in quartz grains due to the high energy; on the other hand, the roundness and sphericity of the grains were evident, especially in Southern Rumaila sands.

Iron isotope evidence for siderite precursors to iron oxide concretions from the Navajo Sandstone, Utah (USA)

The discovery of spherical accumulations of iron oxide mineralization on Mars has prompted renewed interest in widespread but enigmatic accumulations of iron oxide on Earth. The rinded iron oxide concretions found in the Navajo Sandstone (Utah, USA) have been among the most extensively studied of these occurrences. At least four different models have been proposed for the formation of iron oxide concretions in the Navajo Sandstone. These include 1) mixing of reduced Fe(II)-bearing and oxygenated groundwaters, 2) neutralization of oxidized, acidic waters by calcite concretions, 3) neutralization of reduced, acidic waters by calcite concretions, and 4) oxidation of siderite by microbes during invasion of the Navajo aquifer by oxygenated groundwaters. We measured δ56Fe values of iron-bearing minerals from whole-rock Navajo Sandstone, concretionary iron oxide cements, iron oxide stains that are oriented in the direction of paleo-groundwater flow, iron oxide stains on the interior of rinded concretions, and ferroan carbonate cements. We have then combined these data with published measurements to evaluate each of the four published models. Whole rock Navajo Sandstone from the Kolob Plateau has been interpreted to be unaltered by bleaching fluids and has a δ56Fe value of 0.21‰. Iron in the Kolob Plateau sample comprises a mixture of hematite grain coatings (δ56Fe = 0.12‰) and a magnetic mineral fraction (interpreted to comprise largely detrital magnetite) that has a higher δ56Fe value (0.45‰). Iron oxide cements have δ56Fe values that are typically negative and as low as −0.74‰. In contrast, iron oxide-stained Navajo Sandstone in close proximity to a rinded iron oxide concretion has δ56Fe values that are 0.9 to 1‰ greater than the δ56Fe value of the associated iron oxide concretion. Finally, ferroan carbonates from the Navajo Sandstone yield δ56Fe values as low as −0.86‰. These values are in good agreement with measurements published previously for lithologies for which comparable measurements have been made. The presence of ferroan carbonates with negative δ56Fe values is evidence that aqueous Fe(II) was transported through the Navajo Sandstone aquifer and produced carbonate mineralization with negative δ56Fe values. The difference in δ56Fe values between the iron oxide concretions and associated iron oxide staining is more consistent with equilibrium fractionation between aqueous Fe(II) and Fe(II) adsorbed on quartz grains than it is with equilibrium fractionation between aqueous Fe(II) and any reduced or oxidized iron oxide mineral species. The negative δ56Fe values of the iron oxide concretions are best explained by oxidation of a reduced iron phase in a closed system from which no aqueous Fe(II) could escape. We interpret the iron isotope data as evidence that iron was stripped from Navajo sand grains by reducing fluids, reprecipitated in the Navajo aquifer as siderite, and oxidized by groundwaters under closed conditions during incision of the Colorado Plateau.

Temporal variation in sandstone composition of Miocene Jatiluhur Formation in the Bogor Trough, West Java, Indonesia

Bogor Trough in the West Java are typified by turbidity deposits with the source are mostly characterized by volcanoclastic materials from the southern area. The Trough actually receipt the sediment from both volcanoclastic materials from the south and continental source from the north. But, the discussions of sediments in term of composition and temporal variation are rare to be reported, especially the sediments from the north. This manuscript intends to discuss the temporal variation in detrital compositional and depositional facies of the Neogene sediments that delivered from the north (i.e., Sundaland) into the Bogor Trough, which is represented by Miocene Jatiluhur Formation.&#x0D; A total of 36 selected samples have been taken for identifying the minerals using a polarization microscope. Modal analysis of the Gazzi-Dickinson method was applied for this provenance study of sandstones samples, which are consisting largely of quartz and feldspar, then sedimentary rock and volcanic rock fragments, glaucony, mud chips and skeletal fragments.&#x0D; Sundaland, a continental block highland area in the north, is interpreted to have been the provenance of sediments of the Jatiluhur Formation, which is also considered to be the source area for the Paleogene sediments. Granitic igneous rocks are interpreted as the source of dominance of monocrystalline quartz grains, or the product of long-distance transport of polycrystalline quartz from metamorphic rocks&#x0D; But, however late Miocene samples (upper part of formation) represent that the size and amount of glauconite grains are increasing, and texturally mud supported. Volcanic rocks materials are also observed. The upper part of Jatiluhur Formation records the starvation of sediment discharge into the basin, which has been also promoted for development of carbonate reef Klapanunggal Formation in the self-margin setting, and suggesting that the basin have directly received or indirectly some contemporaneous volcanic provenances sediment from the southern area.

Spatiotemporal Mineral Phase Evolution and Arsenic Retention in Microfluidic Models of Zerovalent Iron-Based Water Treatment.

Arsenic (As) is a toxic element, and elevated levels of geogenic As in drinking water pose a threat to the health of several hundred million people worldwide. In this study, we used microfluidics in combination with optical microscopy and X-ray spectroscopy to investigate zerovalent iron (ZVI) corrosion, secondary iron (Fe) phase formation, and As retention processes at the pore scale in ZVI-based water treatment filters. Two 250 μm thick microchannels filled with single ZVI and quartz grain layers were operated intermittently (12 h flow/12 h no-flow) with synthetic groundwater (pH 7.5; 570 μg/L As(III)) over 13 and 49 days. Initially, lepidocrocite (Lp) and carbonate green rust (GRC) were the dominant secondary Fe-phases and underwent cyclic transformation. During no-flow, lepidocrocite partially transformed into GRC and small fractions of magnetite, kinetically limited by Fe(II) diffusion or by decreasing corrosion rates. When flow resumed, GRC rapidly and nearly completely transformed back into lepidocrocite. Longer filter operation combined with a prolonged no-flow period accelerated magnetite formation. Phosphate adsorption onto Fe-phases allowed for downstream calcium carbonate precipitation and, consequently, accelerated anoxic ZVI corrosion. Arsenic was retained on Fe-coated quartz grains and in zones of cyclic Lp-GRC transformation. Our results suggest that intermittent filter operation leads to denser secondary Fe-solids and thereby ensures prolonged filter performance.

Testing the use of continental standardized growth curves (SGCs) for De estimation on coarse quartz grains from Lake Woods, Northern Australia

Using continental SGCs built by Fu et al. (2020) can save significant machine time for constructing SGCs when compared to traditional SGC methods, which need significantly more time for building sample-specific or regional SGCs. In this study, the reliability of continental SGCs is tested using coarse quartz grains (180–212 µm) from Lake Woods in Northern Australia. De values obtained by continental SGCs are consistent with De values obtained by regional SGCs and by the SAR procedures.

Multi‐stage evolution of frost‐induced microtextures on the surface of quartz grains—An experimental study

AbstractCoarse sand‐sized (0.5–1.0 mm) grains of vein quartz were subjected to frost‐induced stress under controlled laboratory conditions. A total of 1,000 freeze–thaw (FT) cycles, simulated under different (low, high) water mineralization conditions in the temperature range from −5°C up to +10°C, were used to test effects on collected samples. Scanning electron microscopic (SEM) microtextural analysis of grain surfaces was performed at 0 (start) and after 50, 100, 300, 700, and 1,000 FT cycles. The results indicate that variable frost‐induced microtextural imprints encountered on quartz grain surfaces prior to and following analysis depend largely on the mineralization (dissolved solute content) of water involved in the weathering process. The higher the water mineralization, the greater the intensity of mechanical weathering. Two predominant outcomes in the course of these micro‐scale frost weathering tests have been identified: a physical (mechanical) aspect manifested by the occurrence of conchoidal fractures and breakage block microtextures dominating up to 300 FT cycles, and a chemical aspect resulting in the occurrence of precipitation crusts and obliteration of grain microrelief. Moreover, three additional stages of microtexture development may be distinguished with the evolution of frost‐induced microrelief on the surface of quartz grains: (i) initial cracks of large‐sized conchoidal fractures, (ii) increasing frost cycles yielding additional small‐sized conchoidal fractures, and (iii) advanced breakage blocks. Frost‐induced exposure of fresh, unweathered grain surfaces leads to refreshing of the grain surface.

Variation of luminescence sensitivity of quartz grains from loess in eastern Tibetan Plateau and its provenance significance

The loess deposits widely distributed in the eastern Tibetan Plateau (ETP) are important archives for reconstructing the paleoenvironmental changes and dust transportation history of the Tibetan Plateau. A lack of sufficient investigations on the source of the ETP loess has limited our understanding of dust transportation and paleoenvironmental implications. Quartz luminescence sensitivity holds great potential for tracing eolian dust sources. Numerous quartz luminescence sensitivity investigations have provided new insights into the dust sources and transportation of the Chinese loess. However, studies on luminescence sensitivity and its significance for the ETP loess provenance are scarce. In this work, we selected quartz grains in loess from different sites of the ETP to investigate the variation of luminescence sensitivity by testing the 110°C thermoluminescence (TL) peak and optically stimulated luminescence (OSL) sensitivities of quartz grains and discussed the provenance implications for the ETP loess based on quartz luminescence sensitivities. Our results show the quartz luminescence sensitivities of loess at different locations were significantly different in the ETP. The luminescence sensitivity values of the Machang (MC), Xiaojin (XJ), and Wenchuan (WCH) sections were much higher than those of the Xinshi (XS) and Zhouqu (ZQ) sections. The sensitivity values of the 110°C TL peaks and OSL in the paleosol and loess layers show distinct differences. The quartz luminescence sensitivities of the ETP loess are mainly influenced by the dust sources. Our results show that the luminescence sensitivities of quartz grains have great potential for identifying the loess sources in the ETP.

Measurement of Grain Bulk Modulus on Sandstone Samples From the Norwegian Continental Shelf

AbstractThe grain bulk modulus is a crucial property of a rock frame, determining poroelastic responses such as seismic velocity. Conventionally, the grain bulk modulus is estimated with bulk moduli of compositional minerals. A systematic measurement is still scarce in answering what factors control the grain bulk modulus. We test 38 sandstone samples with porosity ranging from 4% to 35% from three fields on the Norwegian continental shelf through unjacketed tests. The measured grain bulk moduli range from 18 to 61 GPa. The deposition and composition from thin sections and X‐ray diffraction data can interpret abnormally low or high grain bulk moduli of samples compared to quartz. Carbonate cement is a factor correlating the low porosity with the high grain bulk modulus in a range of 46–61 GPa for tight sandstones. Illite/chlorite coating on the quartz grains can enhance the result to 48 GPa; nevertheless, bearing clay at the grain‐to‐grain contact correlates with the low grain bulk modulus. The measured grain bulk modulus overall increases with decreasing porosity. Specifically, cementation and composition, such as calcite and clays, account for the correlation. Therefore, when people model the elastic properties of sandstones, direct usage of the quartz bulk modulus may cause significant errors. We suggest the unjacketed test as the most reliable way to determine grain bulk moduli of sandstones with different geological features.

Response of eolian quartz flux and grain size in the Parece Vela Basin sediment to the mid-Pleistocene transition

The most significant climate changes in the Quaternary occurred in the mid-Pleistocene transition (MPT). However, as the main component of eolian dust, it remains unknown how the fluxes and components of quartz responded to the MPT. We recovered a sediment core from the Parece Vela Basin (PVB), which dated back to 2.1 Ma, and quantitatively separated quartz from the sediments in order to track source area and transport mechanism. The grain size compositions, morphological characteristics, oxygen isotope compositions, and crystallinity indices of quartz showed that quartz minerals in the sediments were composed of fine-grained endmembers (EM1) with a mode grain size at 3.2 μm, and coarse-grained endmembers (EM2) with a mode grain size at 9.5 μm. The EM1 quartz mainly came from the Mongolian Gobi and Taklimakan Desert, and the EM2 quartz was predominantly derived from volcanic island arc. By fitting the grain size composition with the Weibull function, we were able to quantitatively separated EM1 and EM2 quartz fractions, and calculated the contents and mass accumulation rates (MARs) of eolian quartz. The mode grain sizes of eolian quartz increased at 1.2 Ma, but fluctuated during the mid-Pleistocene. The MARs of the eolian quartz have increased significantly since the mid-Pleistocene, most likely due to enhanced aridity in the Asia interior. Our study demonstrates that eolian quartz in the northwest Pacific can be used to trace the long-term paleoclimate change in the Asia continent.

The trace element chemistry of quartz in carbonatite-related REE deposits: Implication for REE exploration

Quartz is a common gangue mineral in many magmatic-hydrothermal ore deposits (e.g., porphyry, epithermal and skarn deposits) and its trace element composition was widely used to constrain ore genesis. Quartz is also a common phase in carbonatite-related rare earth element (REE) deposits, but its geochemical characteristics and significance for ore genesis have not previously been documented in this environment. In this contribution, we report in-situ LA-ICP-MS trace element compositions of quartz from seven carbonatite-related REE deposits, namely the Maoniuping, Lizhuang and Dalucao deposits in the Mianning-Dechang REE metallogenic belt, SW China and the Miaoya, Taipingzhen, Huangshuian and Huanglongpu deposits in the Qinling REE metallogenic belt, Central China. Rare earth element mineralization in these deposits is associated with well-developed hydrothermal systems in which the dominant REE minerals, bastnäsite, parisite, and monazite, are intergrown with aegirine-augite, arfvedsonite, calcite, fluorite, barite, and quartz. The results show that quartz grains from the carbonatite-related REE deposits are characterized by low budgets of trace elements, of which Al is generally less than 50 ppm whereas others are generally less than 10 ppm. In general, the trace element concentrations in quartz from different deposits are similar (the total concentration is commonly <50 ppm), and are distinguishable from those of quartz in other magmatic-hydrothermal systems. The low concentration of trace elements in carbonatite-related REE deposits is controlled by the unusual nature of carbonatitic magmas and their derived fluids, and thus can be used for defining the affinity of hydrothermal REE systems that are of unknown origin. Significantly, the trace element chemistry of quartz samples collected from a cross-section in the open pit of the Maoniuping REE deposit displays a systematic spatial variation such that the concentrations of Al, Ti, Na, and K decrease with increasing distance of the samples from carbonatites. This spatial variation correlates well with the variation of physio-chemical conditions during the evolution of ore-forming fluids. This implies that the geochemistry of quartz can be used as a vector detecting the concealed carbonatite intrusions in carbonatite-related REE deposits.

Experimental diagenesis using present-day submarine turbidite sands

Hydrothermal-reactor experiments were conducted to investigate the potential formation of chlorite and microquartz grain coatings on detrital quartz and feldspar grains, and to understand their role in inhibiting the formation of quartz and feldspar (albite) overgrowths. Modern-day proximal and distal unconsolidated sediment from the Bute Inlet (British Columbia, Canada) with known amounts of precursor clay content, were used as starting material. The samples were heated to 250°C at water vapour pressure in a hydrothermal reactor for 72 h. The experiments were performed with and without a silica supersaturated Na2CO3 (0.1 M) solution. Detailed microscopy and EDS mapping analysis identified that the main chlorite precursor, crucial for the formation of the synthesized grain coatings, was a Mg-rich chlorite. The experimental results showed that where the volume of precursor chlorite was low (i.e., 0.1%), notably in the proximal channel Bute samples, chlorite coatings were poorly developed, with a clay volume and maximum chlorite-coating coverage of 0.5% and 47%, respectively. In contrast, with an initial precursor chlorite volume of 14.5%, the distal lobe Bute sample has generated chlorite volume ranging from 42.9% to 56.3% post-experiment, with a maximum chlorite-coating coverage of 77%. The chlorite and microquartz coatings formed in the study are morphologically similar to those seen in natural sandstone reservoirs, and they have restricted the development of quartz and albite cementation in the reactor experiments. The findings provide quantitative data that can be utilised to describe diagenetic changes in mesodiagenetic environments.

Micromorphological Characteristics of Fallow, Pyrogenic, Arable Soils of Central Part of Yakutia

The assessment of the micromorphological characteristics of soils is a powerful tool for studying the transformation of soils under the influence of various weathering mechanisms (physical, biogenic). The central part of Yakutia is characterized by a large area of agricultural lands, some of which has become fallow land and is subject to cryogenic processes, fires and anthropogenic impact. Under the conditions of climate change, the fallow soils of Yakutia can be re-involved in the agricultural complex. To study their state, a method of micromorphological investigation of thin soil sections is proposed. Thin sections of soils were analyzed using a polarizing microscope Leica DM750P. As a result of the work, zonal, fallow, pyrogenic and agricultural soils of the central part of Yakutia were analyzed. The soils were found to be in a degraded state. Zonal soils were characterized by the presence of quartz grains, feldspar, and undecomposed plant tissue, as well as biogenically transformed humus. Fallow soils were characterized by a thick organo-mineral (A) horizon, quartz grains, feldspar, and silty-clay plasma. Pyrogenic soils have differences from natural and fallow soils; as a result of fires and active illuviation of organo-mineral substances. The Anthrosol soils were characterized by a large number of aggregates of various sizes. In their composition there were various minerals, such as quartz, feldspar and mica. The signs of soil cryogenesis were noted only in the underlying horizons (B), while the upper horizon (A) had no signs of cryogenic transformation.

Estimation of 'dose-depth' profile in the surface layers of a quartz-containing tile from the former Hiroshima University building indicates the possible presence of beta-irradiation from residual radioactivity after A-bombing.

The problem of differentiating between primary irradiation and exposure due to residual radioactivity following A-bombing (including beta-exposure), is the subject of special attention and discussions in order to understand the health effects following the Hiroshima and Nagasaki A-bombings, especially among newcomers to cities soon after the detonations. In this work, the method of single quartz grain luminescence retrospective dosimetry was applied for a retrospective estimation of the ‘dose-depth’ profile in a quartz-containing tile extracted from the building of former Hiroshima University (HU), which was a ‘witness’ of the Hiroshima atomic bombing on the 6 August 1945. It has been shown that results of retrospective estimates of the ‘dose-depth’ profile using the method of optically stimulated luminescence (OSL) from inclusions of quartz grains in very thin layers of the sample, in combination with the calculations of the ‘dose-depth’ profile using the Monte Carlo method, indicates the possible presence of beta irradiation of thin layers of the sample located near the surface of the tile facing the air, where there is no electronic equilibrium from gamma radiation.

Quartz luminescence sensitivity from sediment versus bedrock in highly weathered soils of the Piedmont of North Carolina, south-eastern USA

Deeply weathered soils cover most of the Piedmont physiographic province of the south-eastern United States of America (USA). These soils have traditionally been inferred to derive from weathered bedrock, but recent work (e.g. Ferguson et al., 2019) suggests that deposited sediments are more prevalent than recognized. Distinguishing sediment from weathered bedrock is integral to understanding critical-zone processes and overall Quaternary landscape evolution, yet the well-developed, red, clay-dominated Ultisols of this temperate and humid region mask differences between transported from non-transported material. Our goal is to determine if optically stimulated luminescence (OSL) methods can distinguish quartz sand from allochthonous (e.g. transported sediment) versus autochthonous (e.g. in situ weathered bedrock) material in soil-profile and core samples from the Redlair Observatory in southwestern North Carolina, USA. Here, we turn to OSL sensitivity and linear-modulated OSL (LM-OSL) to observe the intensity or lack thereof of the fast-decay luminescence component (most light-sensitive signal) in quartz grains from soil horizons and crystalline bedrock-derived saprolite. We find that quartz grains sampled from in situ weathered bedrock as well as from saprolotized clasts of rock have weak luminescence properties and are not dominated by a fast-decay luminescence component. In contrast, quartz grains from transported sediment (e.g. mobile regolith; colluvium; alluvium) contain sensitive grains with more dominant fast components. These results suggest that quartz luminescence sensitivity can be a tool to differentiate between in situ weathered bedrock and similar looking mobile regolith and colluvium over-printed by soil development.

Testing the applicability of standardised growth curves (SGCs) for OSL signals of quartz grains from the Yangtze Delta, China

The standardised growth curve (SGC) technique has the potential to save instrument time for equivalent dose (D e ) determination when applying single-aliquot regenerative-dose (SAR) protocol during optically stimulated luminescence (OSL) measurements. In this study, we test the applicability of two commonly used SGC procedures for OSL signals of quartz grains from aqueous deposits of the Yangtze Delta in China, which have been reported for weak luminescence signals and suffering from partial bleaching. Multiple silt-sized and sand-sized fractions of quartz samples from eight cores are used to construct SGCs by test dose standardisation (TD-SGC) and least-squares normalisation (LS-SGC), respectively. Three strategies, i.e. region-specific (SGC R ), region with core-specific (SGC R + C ) and core-specific (SGC C ), are adopted to categorise these normalised data into different SGC datasets. The large variability of dose response signals is substantially reduced by the SGC procedures for most of these datasets. Hence, common SGCs for a variety of samples from the Yangtze Delta can be established, irrespective of their distinctive particle sizes and luminescence characteristics. The D e values are then estimated using both TD-SGC and LS-SGC procedures for samples from a specific core. Comparing to the full SAR protocol, the TD-SGC procedure roughly gives reproducible D e estimates lower than ∼100 Gy while the LS-SGC procedure derives generally consistent D e estimates of up to ∼230 Gy. Although LS-SGC C and LS-SGC R + C procedures replicate the most consistent D e values, the LS-SGC R procedure performs better in efficiency with a slightly less accuracy. In addition to careful comparison of LS-SGC and full SAR procedures, we suggest that a synchronous ratio derived by the chosen regenerative dose and its response signal for re-normalisation can be used to predict the LS-SGC D e reliability on samples from similar sedimentary environments. • Standardised growth curves (SGCs) are applied to quartz samples from the Yangtze Delta. • SGC procedures are compared using three strategies. • Least-squares (LS) SGC D e values are consistent with those obtained by full SAR. • LS-SGC D e reliability is predicted by the chosen regenerative dose and signal.