Geological Samples Research Articles

Rapid method of arsenic estimation in geological samples by WD-XRF using a novel concept of As-Pb concentration equivalence.

The presence of arsenic in ground waters of many countries has been a subject of global concern due to its toxicity. Primary sources of arsenic are geogenic, i.e. weathering and erosion of rocks and soils containing arsenic. This paper presents a rapid method for determination of arsenic in solid geological samples by wavelength dispersive X-ray fluorescence spectrometer. To achieve the best LLD (lower limit of detection), the most intense X-ray fluorescence line Kα1,2 is preferably used for determination of elemental concentrations because it pertains to the most probable transition. But the greatest challenge in arsenic estimation is the serious line overlap of AsKα1,2 lines with the equi-energy PbLα1,2 lines. By using the conventional line overlap correction methods, uncertainty and detection limits in arsenic determination are degraded to an unacceptable degree in samples which contains high lead and low arsenic concentrations. The proposed method bypassesthe line overlap issue in employing a novel concept of arsenic-lead concentration equivalence factor for the cumulative peak of AsKα1,2 and PbLα1,2 fluorescence lines. The constancy of this factor for all geological matrices facilitates arsenic determination in samples universally irrespective of matrix elements. For the method validation, 22 international certified reference materials have been analysed and the results proved to be propitious wherein only one value out of 22 determinations showed relative error more than 20% of the certified values. This attests to the high accuracy of the proposed method which can effectively determine arsenic below 5mg/kg in the presence of high lead concentration up to 1000mg/kg.

Chemical and Mineralogical Analysis of Samples Using Combined LIBS, Raman Spectroscopy and µ-EDXRF

Energy-dispersive X-ray fluorescence (EDXRF) analysis is one of the standard techniques for the evaluation of mineral deposits. The advantage of EDXRF is the fast delivery of information about the bulk elemental composition as well as the elemental composition of each mineral class. With micro energy-dispersive X-ray fluorescence (µ-EDXRF) analysis, information can be obtained with a micrometer resolution. However, it has some limitations. With EDXRF, light elements (e.g., lithium) cannot be detected, and the count rates for carbon, fluorine and sodium are very low. This might lead to a misinterpretation of the mineral classes and the worth of the deposit. Furthermore, the identification of the alteration phases of primary minerals is ambiguous. Here, we will present an approach to overcome the limitations of µ-EDXRF by complementing it with combined laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy. In contrast to EDXRF, LIBS is able to detect all elements, including light elements. Raman spectroscopy can identify mineral phases and eventually provide additional information on their alterations and modifications. In the present paper, we show results for two different samples covering a certain chemical and mineralogical range that demonstrate the potential of the proposed combination of methods for the chemical and mineralogical analysis of geological samples.

Combined use of multiple external and internal standards in LA-ICP-MS analysis of bulk geological samples using lithium borate fused glass

We describe a method for laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) elemental analysis of geological materials using low-dilution Li-borate fused glass wavelength dispersive X-ray fluorescence (WDXRF) pellets, with samples, drift monitor and 18 reference materials (RMs) identically prepared. After analysis for 46 elements by WDXRF, LA-ICP-MS intensities from samples and RMs are collected, and background corrected with Iolite software. HALite , a new software application, was developed to derive the elemental compositions from the LA-ICP-MS net signals. In HALite , elements are drift-corrected using polynomial functions, and flux-fused RM element sensitivities are calculated from known mass fractions. Multiple internal standard (IS) elements are used to model each sample's laser response. Analyte mass fractions in unknowns are determined using the calibrated sensitivity correlation models for multiple IS elements. Either the WDXRF mass fractions or the initial round of calculated LA-ICP-MS mass fractions are used to calculate weighted mean sensitivities. Validation experiments with flux-fused RMs run as unknowns yield results with less than 5–10% total relative uncertainty for most analytes. We derive equations which allow calculation of the precision and total uncertainty as a function of mass fraction for each analyte element. Supplementary material : Table 1 - RMs used; Table 2 - Operating parameters; Table 3 - Model v. accepted mass fractions; Table 4 - NIST 610 v. multiple IS models; Table 5 - Fitting parameters; Appendix 1 - HALite description; Appendix A - Summary calibration graphs; Appendix B - Validation results; Appendix C - WDXRF comparisons; Appendix D - Repeatability uncertainties; Appendix E - RM uncertainties; and Appendix F - Total uncertainties for this article are available at https://doi.org/10.6084/m9.figshare.c.6639885

Comparison of two gallium purification procedures for isotopic measurements by MC-ICP-MS in a set of silicate reference materials

Gallium is a moderately volatile, moderately siderophile element with two stable isotopes: 69Ga and 71Ga. A general interest in Ga isotopes arose over the last few years, as its moderately volatile behavior potentially marks it as a useful tracer of various processes such as condensation and evaporation. Nevertheless, there is a lack of agreement between laboratories for consistent δ71Ga values in geological reference materials. In this work, we have developed and evaluated two methods for purification protocols leading to precise analysis of gallium (Ga) isotopic composition in silicate rock materials. The first method is a three-step column chemistry using the resins AG1-X8, HDEHP, and AG50W-X12 whereas the second method uses only two columns, AG1-X8 and AG50W-X8. The two methods were applied to a range of both synthetic (multi-element) solutions and geological samples. Both methods show comparable results with no isotope fractionation occurring during purification chemistry, allowing us to define the δ71Ga of selected USGS reference materials (BHVO-2, BCR-2, RGM-2). Similar to previously reported results, we also observe no Ga fractionation between distinct igneous terrestrial materials.

Solvent Extraction, Sequential Separation and Trace Determination of La (III), Ce (III), Nd (III) and Gd (III) with 2, 14-bis[m-nitrophenyl]-Calix[4]Resorcinarene-8, 20-bis[N- phenylbenzo]-dihydroxamic Acid

ABSTRACT A novel reagent 2,14-bis[m-nitrophenyl]-calix[4]resorcinarene-8,20-bis[N-phenylbenzo]-dihydroxamic acid (NPC4RADHA) is reported for the liquid-liquid extraction, separation, and simultaneous trace determination of La(III), Ce(III), Nd(III), and Gd(III). The method involves optimizing various parameters such as the concentration of NPC4RADHA, pH, solvent, and extraction time to achieve maximum purity (99.98%) extraction of these rare earths. The stability constant, molar absorptivity, and Beer’s law have been studied. The extracted samples were directly analyzed by ICP-AES, which improves sensitivity with determination limits of 0.020 ng/mL, 0.028 ng/mL, 0.018 ng/mL and 0.025 ng/mL for La, Ce, Nd, and Gd, respectively. The method has been applied to the determination of these elements in monazite sand and standard geological samples. The separation and determination mixture of a Ce(III) and Ce(IV) has been reported.

A new methodology for kerogen maturity estimation based on Raman spectroscopy and chemometric analysis

Diverse criteria or parameters have been cited as tools to determine the maturity of carbonaceous matter (CM) found in geologic samples using Raman spectroscopy. However, these approaches involve the mathematical decomposition of Raman bands which can vary with the specific method, the software employed, or even the individual user. Data should be treated spectrum by spectrum and a similar spectroscopic pre-treatment should be applied to the whole dataset. All these factors affect the final result and can introduce a wide uncertainty and bias. We propose an alternative chemometric method that avoids these sources of uncertainty by considering the entire spectrum, not just certain regions, while allowing specific regions of interest to be defined. Moreover, spectra pre-treatment is not required. We employ principal component analysis (PCA) across the whole range of spectra. While the method does not provide an absolute maturity value, it allows comparison of different CM in terms of maturity or H:C ratio. In the analysis of coal standards, samples were grouped by maturity.

Pt(IV)-ion imprinted ordered mesoporous organosilica for platinum preconcentration prior to electrothermal atomic absorption spectrometry determination in geological samples

Pt(IV) ion-imprinted thiocyanato-functionalized SBA-15 material (Pt(IV)S1) was proposed for preconcentration of Pt(IV) ions from digested geological samples before its electrothermal atomic absorption spectrometry (ETAAS) determination. The ion-imprinted material exhibited very good adsorption affinity towards Pt(IV) ions. Under the optimal pH (pH = 3) the maximum static adsorption capacity for Pt(IV) was equal to 175 mg g−1. The use of Pt(IV)S1 as an adsorbent allowed for the quantitative adsorption of Pt(IV) ions from solutions with concentrations up to 25 mg L−1. The creation of ion imprinted adsorption centres resulted in an increase of the adsorption rate and selectivity towards Pt(IV) compared to the similar non-ion imprinted material. The analytical procedure was based on the adsorption of Pt(IV) ions and dissolution of the Pt-loaded sorbent in a small volume of hydrofluoric acid before its dilution with 5% hydrochloric acid and introduction into an electrothermal atomizer. The enrichment factor of the proposed procedure was 38, while the limit of quantification was 0.079 mg kg−1.

Thermal behavior of modern and archeological enamel and dentin by in situ temperature‐dependent Raman spectroscopy

AbstractTeeth and bones are important bioarchives, which can be altered because of diagenesis or burning (cooking, funerary cremations, and fires). Though heating and diagenesis are different processes, an experimental heating of modern bioapatite reproduces in a short time effects similar to diagenetic processes occurring over geological time. The thermal behavior of modern and archeological human enamel and dentin using the in situ thermo‐Raman spectroscopy at 83–873 K was investigated to assess the structural changes in organic and mineral components of a tooth and their interrelationship. The ν1(PO4) vibrational mode in apatite is the most anharmonic and responsible for the reaction of the structure to external influences. The γiP isobaric Grüneisen parameters for archeological (0.41) and modern (0.24) enamel are different from those for fluor‐ (0.17) and chlorapatite (0.17), which indicates a stronger reaction of PO bonds in bioapatite PO4 tetrahedra to temperature changes as compared with geologic samples. The anomalies of the thermal dependences of the ν1(PO4) peak position and (T) autocorrelation function are caused by the combined effect of different factors such as breaking of hydroxyl and hydrogen bonds, the loss of adsorbed and structural water, collagen denaturation, organic phase combustion, and removal and relocation of B‐ and A‐type carbonate ions. The thermal (273, 313, 341, and 363 K) and cold (~160 K) denaturation of collagen is reflected in the ν1(PO4) and (T) dependences. The (T) differences between modern and archeological dentin and enamel are contingent on bioapatite composition (proportions of adsorbed and structural water, hydroxyl and carbonate ions, and trace elements as well as different types of organic matter — low‐molecular noncollagen compounds and high‐molecular collagen). The results obtained contribute to the knowledge about the thermal transformations of the mineral and organic phases of modern and archeological tooth tissues and allow their structural alterations to be evaluated.

Chemical Oxidation and Characterization of Carbon Nanotubes of Different Types for Improving the Efficiency of REE Preconcentration for Their Subsequent Determination in Geological Samples

Chemical Oxidation and Characterization of Carbon Nanotubes of Different Types for Improving the Efficiency of REE Preconcentration for Their Subsequent Determination in Geological Samples

Chemical Oxidation and Characterization of Carbon Nanotubes of Different Types for Improving the Efficiency of REE Preconcentration for Their Subsequent Determination in Geological Samples

Various methods for the oxidation of different types of carbon nanotubes (CNTs) in nitric acid and a mixture of nitric and sulfuric acids at various temperatures and durations of exposure are studied. Oxidation conditions that provide the high sorption activity of sorbents with respect to REE are found. Oxidized CNTs are characterized by acid-base titration and scanning electron microscopy, and the electrokinetic (ζ) potential of nanotube suspensions is determined as a function of pH. The elemental composition of CNTs is determined by ICP MS/AES methods. The sorption capacity of the oxidized CNTs with respect to a wide range of elements is determined. Their unique selectivity with respect to REE is revealed. A possibility of using oxidized CNTs for the efficient sorption preconcentration of REE with the aim to determine their ultralow concentrations in rocks is proved.

The geological situation in Abu-Jir Faults Zone, western Iraq: evidence from the radioactivity in Hit–Haditha area

Total radioactivity measurements (cps) in 59 sites were achieved in the Hit–Kubaiysa–Haditha area. Geological samples (soil and rock) from those sites were analyzed for Ra-226, U-238, Th-232, and K-40 using Gamma spectroscopy system based on high pure germanium. The study aims to assess the radioactivity in the study area and attempt to understand the relationship between radioactivity and the geological situation in the area. The results showed that many sites have relatively high total radioactivity exceeding the background radioactivity by many times. The radioactivity concentrated in areas around the springs spreading in the area caused by the high concentration of Ra-226 which being have disequilibrium with its parent U-238. Some areas also have a relatively high concentration of U-238 in depressions areas where the upper part of the Euphrates Formation is outcropped. Based on the pattern of the spread of total radioactivity in the study area, the extension of the Euphrates Fault Zone and the Abu Jir Fault Zone could be determined. These fault zones extend towards northwest–southeast, in addition to the delineation of some of the recent faults that intersect with these zones in an east–west direction, most of which follow the spreading pattern of the springs in the region.

Establishment of an experimental system for X-ray fluorescence analysis with excitation using 3H/Zr source: Evaluation and applications

The goal of this study is to establish and assess an experimental apparatus for X-ray fluorescence analysis with elemental excitation in materials using a 3H/Zr source. The limits of detection and quantification, as well as analytical sensitivity, were estimated using a linear curve methodology. Furthermore, accuracy and precision were assessed by quantitatively analyzing the components of the reference material. The limits of detection and quantification of elements such as S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Ta, and Pb were estimated to range from 3.7 mg kg−1 to 573 mg kg−1, depending on the analyte. Analytical sensitivities were found to be between 1.2 and 867 cps/%. The measured elemental concentrations in the reference sample were compared with the inductively coupled plasma mass spectrometry method, and all bias (%) values were found to be lower than 10%. This study also determined the levels of Ca, Ti, Mn, and Fe in cement and K, Ca, Cr, Mn, Fe, and Zn in tea leaves. The results showed that the 3H/Zr source could detect and quantify components at concentrations of a few mg kg−1 or higher. X-ray fluorescence spectrometry is suggested for the analysis of the concentration of various elements in environmental, geological, food, and other samples.

Determination of bromine, iodine, and other components in northern Hainan island soil

The emergence of the integrated wavelength-dispersive and energy-dispersive Zetium X-ray fluorescence spectrometer technique offered new chances to analyze elemental distribution with minimal sample preparation in complex matrix geological samples-northern Hainan island soils. Wavelength-dispersive X-ray fluorescence was applied for the measurement of bromine in the northern Hainan island soil. To reduce the fluctuations of the low-bromine-content measurement results, a two-channel measurement of bromine was designed, and the average value of the two-channel measurements was used as the final result. The soil samples in northern Hainan Island were rich in iodine, with a content range of a few µg/g to more than 100 µg/g, and these were particularly suitable to be analyzed by energy-dispersive X-ray fluorescence spectrometer. The geological samples in northern Hainan Island were brown, purple, and brown-red soil containing kaolinite, ilmenite, rutile, anatase, and goethite. These soil samples were rich in titanium, aluminum, and iron. The titanium concentration in the northern Hainan Island soil was anomalously high (up to 15.05%), far exceeding the content range of the calibration curve. Owing to the empirical coefficient matrix correction method, unreliable or even unreasonable results were obtained for some elements. By systematically mitigating matrix effects through the development of custom reference materials and building matrix-matched measurement and calibration routines, the quantification of Vanadium, Barium, and major components in northern Hainan Island soil samples was optimized. The efficacy of the X-ray fluorescence spectrometer method was confirmed by comparison with inductively coupled plasma–optical emission spectroscopy analysis. This work demonstrates the capability of the integrated wavelength-dispersive and energy-dispersive Zetium X-ray fluorescence spectrometer technique for reliable quantitative elemental analysis of complex matrix geological samples.

Hydrogen physisorption in earth-minerals: Insights for hydrogen subsurface storage

Physisorption can contribute to hydrogen subsurface storage. However, hydrogen physisorption at the surface of geological samples is mostly unknown. We are unaware of previous studies that investigate H2 Physisorption in wide range of pure inorganic and organic earth minerals. Knowledge about H2 Physisorption is required to evaluate the suitability of underground H2 storage. We thus evaluated H2 physisorption on common earth minerals, including illite, kaolinite, quartz, calcite, and kerogen via lab experiments and Grand Canonical Monte Carlo (GCMC) simulations at temperature ranging between 273 and 373 K and pressure ranging between 5 MPa to 40 MPa. The simulation results, including densities and H2 adsorption uptakes, are in agreement with experimental results. The quantity of adsorbed hydrogen ranked as: illite > kerogen > kaolinite > quartz > calcite; and Gibbs energy change, enthalpy change, and isosteric heat energy indicated that H2 adsorption spontaneity increases as illite > kerogen > kaolinite > calcite > quartz. We conclude that H2 adsorption is high on the high-surface-area materials (clays or kerogen), and that H2 adsorption on earth minerals could improve the effectiveness of subsurface H2 storage.

Evolution of the Pristane/Phytane Ratio with Maturity of Lacustrine Source Rocks: Implications of a Thermal Simulation Experiment

The pristane/phytane ratio (Pr/Ph) of source rocks has been extensively used for the identification of paleosedimentary environments and oil–source rock correlations. However, the influences of maturity on the Pr/Ph ratio are not fully understood, which largely limits the applicability of this parameter under geological conditions. Based on a thermal simulation experiment performed on typical lacustrine source rock samples and systematic research on geological source rock samples, the evolution of the Pr/Ph ratio with increasing maturity was investigated in this study. The results indicate that the Pr/Ph ratios of the two source rock extracts progressively decrease with increasing maturity, and the decrease in this parameter is more significant for shallow lacustrine samples than for deep lacustrine samples. The Pr/Ph ratios of the two types of source rocks are different at the oil generation stage with EasyRo less than 1.02% but are similar at the oil cracking stage with EasyRo larger than 1.02%. The Pr and Ph of source rocks are contributed by both biogenic and thermal origins, which are largely determined by the sedimentary environment and maturity, respectively, and the contributions of the two origins are diverse at different maturity stages. The Pr/Ph ratio is mainly controlled by the sedimentary environment at the diagenetic stage, by both sedimentary and thermal maturity at the oil generation stage, and by thermal maturity at the oil cracking stage. The Pr/Ph ratio of source rocks can be used to identify sedimentary environments and oil–source rock correlations at diagenetic and oil generation stages.

New Insights into the Seamount Structure of the Northern Part of the Ninetyeast Ridge (Indian Ocean) through the Integrated Analysis of Geophysical Data

The linear Ninetyeast Ridge (NER) is the longest oceanic intraplate volcanic edifice and main feature in the Eastern Indian Ocean. Many seamounts are located on the ridge, whose origin and age remain unclear due to the lack of samples of the bedrock of which they are composed. Carbonate sedimentary caps on these seamounts prevent their direct geological sampling by dredging, therefore indirect geophysical methods are an alternative. Such integrated geophysical studies (the main methods are multibeam bathymetry and magnetic surveys) were carried out in cruise #42 of the R/V Akademik Boris Petrov in 2017 on a large seamount at the base of the NER’s western slope near 0.5° S. The collected data also includes seismic reflection data that reveal morphology, fault tectonics, depth structure, and an assumed origin of this volcanic feature. The Ninetyeast Ridge was formed by the Kerguelen plume magmatism at 50° S in the giant N-S fault. The seamount studied in cruise #42 of the R/V Akademik Boris Petrov was formed mainly to the north as a result of two-stage magmatism in a transverse strike-slip fault. The first stage (47 Ma) formed the main western part of the seamount at 20° S. The second stage (23 Ma) formed its eastern part at 8° S. The time intervals between the formation of the main massif of the Ninetyeast Ridge and the stages of subsequent magmatism that formed the western and eastern parts of the seamount are approximately 31 and 55 Ma, respectively.

Rare-earth element comparative analysis in chosen geological samples using nuclear-related analytical techniques

In this study, four analytical techniques for the detection of Sc, La, Ce, Nd, Sm, Eu, Tb and Lu in volcanic rock specimens from Ghana have been compared. These rock samples were examined using inductively coupled plasma mass spectrometry, X-ray fluorescence spectrometry, and instrumental neutron activation analysis. The Am-241 excitation-based X-ray fluorescence accuracies were good for Y, La, Ce, Nd, Eu, and the results were comparable to inductively coupled plasma mass spectrometry and instrumental neutron activation analysis except Silver-anode X-ray tube X-ray fluorescence. This demonstrates the limitations of the tube-based X-ray fluorescence excitation system for rare earth elements analysis, primarily caused by interference between the K-series X-ray emission from the transition metals and the relatively low intensities of L-series lines of the rare earth elements. Data on the precision and accuracy of these methods were based on IAEA SOIL-7 reference material.

Evidence of the anthropogenic origin of the ‘Carmel sapphire’ with enigmatic super-reduced minerals

AbstractCorundum with inclusions of enigmatic super-reduced minerals was found in mineral separates received as a result of alluvial sediment exploration near Mt Carmel, Israel by the Shefa Yamim Company. This corundum, registered as ‘Carmel sapphireTM’, has been an object of numerous publications by W. Griffin's scientific team, in which they propose a questionable hypothesis of sapphire formation at the crust–mantle boundary with the participation of CH4+H2 fluids. Typically the Carmel sapphire is in small fragments of breccia with white cement, which in the opinion of Griffin et al. is a carbonate-cemented volcanic ash. Our investigation of the ‘white breccia’ showed that it consists of unsorted angular fragments of Carmel sapphire from ~1 μm to 7 mm in size cemented by aluminium hydroxides (bauxite) and is a waste product of the fused alumina process, i.e. it has an anthropogenic origin. Phases typical for slags of fused alumina production and metallurgical slags were identified in the ‘white breccia’. Carmel sapphire has numerous microscopic spherical inclusions of Si–Fe alloy indicating that the removal of Si and Fe from the corundum melt occurred at a temperature >2000°С. Osbornite, TiN, from Carmel sapphire has a chemical zonation characteristic of osbornite from fused alumina with enrichment of central zones in carbon. Comparison of the growth heterogeneity of Carmel sapphire and ‘electrocorundum’ indicates that the crystallisation of the corundum melt proceeded in a similar way. Unfortunately, in the case of Carmel sapphire from the Carmel locality, the contamination of geological samples with anthropogenic material has led to popularisation of biased views.

101 contact twins in gypsum experimentally obtained from calcium carbonate enriched solutions: mineralogical implications for natural gypsum deposits.

Gypsum twins are frequently observed in nature, triggered by a wide array of impurities that are present in their depositional environments and that may exert a critical role in the selection of different twin laws. Identifying the impurities able to promote the selection of specific twin laws has relevance for geological studies aimed at interpreting the gypsum depositional environments in ancient and modern deposits. Here, the effect of calcium carbonate (CaCO3) on gypsum (CaSO4·2H2O) growth morphology has been investigated by performing temperature-controlled laboratory experiments with and without the addition of carbonate ions. The precipitation of twinned gypsum crystals has been achieved experimentally (101 contact twin law) by adding carbonate to the solution, and the involvement of rapidcreekite (Ca2SO4CO3·4H2O) in selecting the 101 gypsum contact twin law was supported, suggesting an epitaxial mechanism. Moreover, the occurrence of 101 gypsum contact twins in nature has been suggested by comparing the natural gypsum twin morphologies observed in evaporitic environments with those obtained in experiments. Finally, both orientations of the primary fluid inclusions (of the negative crystal shape) with respect to the twin plane and the main elongation of sub-crystals that form the twin are proposed as a fast and useful method (especially in geological samples) to distinguish between the 100 and 101 twin laws. The results of this study provide new insights into the mineralogical implications of twinned gypsum crystals and their potential as a tool to better understand natural gypsum deposits.

Machine Learning in Geology: Challenges and Prospects

Machine Learning methods, along with high-performance computing, is creating chances for data intensive science in various domains such as Geology. Known for its precision and efficiency, Machine learning has renovated many fields of science thoroughly. However, when it comes to Geology, Machine Learning methods aren’t fully applied, lacking an overall frame to arrange those works with scattered aims and methods. This paper presents a comprehensive review of research focusing on application of Machine Learning methods in Geology studies. The works analyzed were categorized in three aspects of Geology studies: mineral prospecting and mapping, land-cover monitoring; geochemical anomalies detection; earthquake monitoring and geological sample identification. The selection and classification of the presented articles demonstrate how Geology benefits from Machine Learning methods.