Major Mineral Phases Research Articles

Were South India and North China Craton attached during the Paleoproterozoic (Orosirian) Nuna Assembly? Novel geochemical and isotopic investigations of A2-type granites from the Khammam Schist Belt, Eastern Dharwar Craton, India

The paper presents novel geochemical and geochronological data from granites in Khammam, Eastern Dharwar Craton (EDC), India. The studied granites contain major mineral phases like quartz, alkali-feldspar, plagioclase, biotite, and muscovite in decreasing order of abundance. The accessory phases are epidote, titanite, and zircon. The samples comprise 70 ‐–77 wt% SiO2 and 12–15 wt% Al2O3. The K2O and Na2O concentrations range from 2.57 to 5.65 wt% and 1.17 to 2.69 wt%, respectively. They are enriched in Rb, Th, and Pb and depleted in Nb, Ta, and Ti. On a chondrite-normalized plot, the samples exhibit a rightward trend with a negative Eu anomaly. Zircon saturation in silicate melts yields a temperature (TZr) of 859 ‐ 978 °C. The microstructure and U - Pb isotopic analysis of zircon grains (n = 79) reveals the presence of magmatic and polymetamorphic grains with 207Pb/206Pb age clusters at 1844 Ma (number of analyses, n = 7) - 1858 Ma (n = 8), 1737 Ma (n = 5) -1768 Ma (n = 4), 1619 Ma (n = 7) - 1634 Ma (n = 6), and 1554 Ma (n = 5), respectively. The magmatic zircons exhibit ε(Hf) values between 3 and 18.9 with a two-stage model age of 2.03 Ga. In contrast, the metamorphic zircons exhibit ε(Hf) values between −5.6 and 18, yielding a two-stage model age of 1.97 Ga. The geochemical and geochronological studies indicate that the rocks are A2-type granite emplaced during the accretion of the eastern block of the North China Craton (NCC) and EDC between 1844 Ma and 1858 Ma. The zircons from 1737–1768 Ma and 1620 Ma show the time of metamorphic growth during Antarctica-Nellore Schist Belt (EDC) accretion. Finally, the U-Pb zircon ages from 1554 Ma represent Nuna's final amalgamation. The results of this study posit an association between EDC and NCC during Nuna assembly.

Expanded Insights into Martian Mineralogy: Updated Analysis of Gale Crater’s Mineral Composition via CheMin Crystal Chemical Investigations

This study presents mineral composition estimates of rock and sediment samples analyzed with the CheMin X-ray diffraction instrument on board the NASA Mars Science Laboratory rover, Curiosity, in Gale crater, Mars. Mineral composition is estimated using crystal-chemically derived algorithms applied to X-ray diffraction data, specifically unit-cell parameters. The mineral groups characterized include those found in major abundance by the CheMin instrument (i.e., feldspar, olivine, pyroxene, and spinel oxide). In addition to estimating the composition of the major mineral phases observed in Gale crater, we place their compositions in a stratigraphic context and provide a comparison to that of martian meteorites. This work provides expanded insights into the mineralogy and chemistry of the martian surface.

Gold recovery from roasted refractory gold concentrate through cyclic extraction using MnO2-assisted thiocyanate leaching and cementation with zinc powder

Cyanidation has long served as the industrial standard in the gold industry, necessitating heightened attention to cyanide management owing to its inherent toxicity. This study developed a novel MnO2-assisted thiocyanate leaching system as an alternative to cyanide. The sample was generated from a refractory gold concentrate processed by roasting, containing 54.4 g/t gold with iron oxide and quartz as the major mineral phases. Within the framework of the novel system, gold recovery was investigated in terms of gold association, recovery behavior, thermodynamics, and optimization using cyclic extraction protocols. The most suitable leaching conditions were determined as 1.20 mol/L NaSCN, 4.00 mmol/L MnO2, pH at 1.00, liquid-to-solid ratio of 4 mL/g, and leaching duration of 24 h, resulting in a maximum gold extraction of 94.8%. Subsequent zinc precipitation facilitated a gold recovery of 99.4% from the leachate. Furthermore, the implementation of a cyclic extraction scheme, coupled with reagent addition to offset consumption, yielded a significant thiocyanate dosage reduction by 75% while maintaining gold recovery. This acidic leaching system yields satisfactory gold recovery with minimized reagent consumption, particularly suited for refractory gold ore that has undergone acidic pretreatment.

Evidence for Low‐Pressure Crustal Anatexis During the Northeast Atlantic Break‐Up

AbstractWhile basaltic volcanism is dominant during rifting and continental breakup, felsic magmatism may be a significant component of some rift margins. During International Ocean Discovery Program (IODP) Expedition 396 on the continental margin of Norway, a graphite‐garnet‐cordierite bearing dacitic unit (the Mimir dacite) was recovered in two holes within early Eocene sediments on Mimir High (Site U1570), a marginal high on the Vøring Transform Margin. Here, we present a comprehensive textural, petrological, and geochemical study of the Mimir dacite in order to assess its origin and discuss the geodynamic implications. The major mineral phases (garnet, cordierite, quartz, plagioclase, alkali feldspar) are hosted in a fresh rhyolitic, vesicular, glassy matrix that is locally mingled with sediments. The major element chemistry of garnet and cordierite, the presence of zircon inclusions with inherited cores, and thermobarometric calculations all support an upper crustal metapelitic origin. While most magma‐rich margin models favor crustal anatexis in the lower crust, thermobarometric calculations performed here show that the Mimir dacite was produced at upper‐crustal depths (<5 kbar, 18 km depth) and high temperature (750–800°C) with up to 3 wt% water content. In situ U‐Pb analyses on zircon inclusions give a magmatic crystallization age of 54.6 ± 1.1 Ma, consistent with emplacement that post‐dates the Paleocene‐Eocene Thermal Maximum. Our results suggest that the opening of the Northeast Atlantic was associated with a phase of low‐pressure, high‐temperature crustal anatexis preceding the main phase of magmatism.

Study of mineralogy and distribution of rare earth elements in coal block of Eastern Coalfield, India

ABSTRACT Coal by-products are continuing to be explored as secondary resources for extraction of rare earth elements (REEs). Nevertheless, the knowledge of their geological abundance is still scarce compared to the high global demand. The present investigation aims to study the distribution of REEs in coal samples acquired from Eastern coalfield, India. A total of 27 samples collected from two boreholes (RGCF-1and RGCF-2) were thoroughly analyzed. The average REE concentration in RGCF-1 was 724 ppm, while for RGCF-2, it was 658 ppm with a distribution pattern of Ce>La>Nd>Y>Pr>Sc>Sm>Gd>Dy>Yb>Er>Eu>Ho>Tb>Tm>Lu. Quartz, feldspar, sanidine, magnetite, hematite, anatase/titanate and illite were deduced to be the major mineral phases in these coal ash samples prepared at 815°C. In RGCF-1, REEs were associated with magnetite, whereas in RGCF-2, they were primarily with aluminosilicate and titanate minerals. The overall concentration of critical REEs varied from 122.5 to 387.8 ppm with an outlook co-efficient (C outl) of 0.58–1.26, indicative of the suitability of the chosen coal block for future exploration. Such an exploration-based investigation on abundance of REEs in the Indian subcontinent coupled with the knowledge of their mineralogical association is beneficial in not only understanding their enrichment but also coining a suitable extraction strategy for these valuables.

An insight into the characteristics of some oxidized low-grade coals of Indian origin

ABSTRACT The conversion of coal to a hydrophilic state presents a significant challenge for process engineers, especially when treating oxidized coals in flotation-based beneficiation plants. Flotation of oxidized coal often requires a substantial consumption of oily collectors, resulting in unacceptably low yields. To address this, several pre-processing methods have emerged for coal deoxidation, including mild grinding, surface activation, and ultrasonic or microwave treatment. However, their effective application depends on a thorough understanding of the degree of oxidation in the coals. Therefore, it is crucial to gain insights into the nature of oxidized coal before initiating the deoxidation process. This present study provides various characterization techniques such as XRD, SEM-EDS, FTIR Spectroscopy, Raman Spectroscopy, TGA, and Zeta Potential Analysis employed on oxidized low-grade coals. The study revealed that the proximate analysis of low-grade coals KC, DC, RC, and PC contains varying ash percentages of 32.65%, 44.47%, 25.44%, and 37.53%, respectively, with SiO2 and Al2O3 comprising over 80% of the total ash. XRD characterizations identified quartz and kaolinite as major mineral phases in all samples, while SEM-EDS confirmed rough coal surfaces with peeling, off-white aggregations, and surface pores. HGI value ranging from 80 to 91 was attributed to partial decomposition and surface cracking due to oxidation. FTIR spectra revealed pronounced oxidation behavior, with strong −OH peaks in the 3600–3700 cm−1 range. Zeta potential analysis affirmed the oxidized nature of the coals with a pH below 3.1 and an extremely negative zeta potential beyond 3.1. The findings mentioned above showcase the distinct characteristics of oxidized low-grade coals, which serve as crucial indicators for exploring coal beneficiation, especially through the flotation process.

Magma recharge in persistently active basaltic–andesite systems and its geohazards implications: the case of Villarrica volcano, Chile

We report whole-rock chemistry, mineral chemistry, and volatile content from Villarrica volcano’s major recent paroxysms and background activity. Composition of the volcanic products are basalt to basaltic andesite with whole-rock SiO2 content between 50 and 56 wt%, and a mineralogy dominated by olivine (Fo71-80), clinopyroxene (Mg# ~ 50) and plagioclase (An60–80). Volatile contents in melt inclusions are up to 1.5 wt% H2O, 500 ppm CO2, 1230 ppm sulfur and 580 ppm chlorine. Regardless of the type of activity, there are no substantial variations in whole-rock composition or the volatile content when the activity switches from background activity to a major paroxysm, strongly suggesting that this shift does not just depend on the arrival of new magma in the shallow magmatic system. Geothermobarometry constrains crystallization of the major mineral phases at various depths between 3 and 12.7 km, suggesting that degassing of a volatile-rich recharge magma occurs deeper than 12 km, producing efficient mixing throughout the whole system, and sustaining the lava lake activity in Villarrica’s summit crater. The occurrence of a permanent lava lake also suggests that the magma recharge must be close to continuous and therefore sudden changes between background and paroxysmal volcanic activity are likely controlled by relatively small changes in the rate of recharge and/or the volatile release rate in the magmatic system. This has important implications for the understanding of eruption triggers and the forecasting of volcanic eruptions.Graphical abstract

Comprehensive characterization of unscientifically disposed municipal solid waste (MSW) in Kashmir Region, India.

Unscientific dumping of municipal solid waste (MSW) is a common practice in Kashmir. To have an environmentally friendly and sustainable waste management system, MSW was collected from nine study locations of this region. They were air-dried, then oven-dried at 105°C for 24h, segregated, and characterized for various components. The overall average organic waste was > 55%, plastic waste about 17%, inert material about 10%, paper 9%, and cloth waste 7%. The calorific value of paper and plastic wastes exhibited was 4910kcal/kg, while organic waste had a calorific value of 1980kcal/kg. The proximate analysis showed that the moisture content ranged from 16 to 29%, volatile matter ranged from 49 to 72%, ash content ranged from 0.03 to 5%, and fixed carbon ranged from 5 to 20%. In S7, the volatile matter content recorded the lowest value at 49.15%, while in S5, the volatile matter content was notably higher at 71.84%, indicating easier ignition. Further, elemental analysis revealed that the major elements in MSW were carbon and oxygen, 53% and 37%, respectively, with small traces of heavy metals with an average of 0.02% cadmium (Cd) and 0.006% lead (Pb). Moreover, field emission scanning electron microscopy (FESEM) micrographs provided confirmation that the majority of components in the MSW exhibited either partial or complete degradation, resulting in a rough surface texture. In addition, the presence of silica and other silicate groups was also detected. Fourier transform infrared spectroscopy (FT-IR) analysis revealed that the main functional groups were alcohol. In the X-ray diffraction (XRD) analysis, all the major mineral phases were detected between 20 and 30° 2θ, except for the peaks at 50-60° 2θ in S3 and S9 where catalysts such as zeolite Y and zeolite X were detected. Overall, the MSW had low moisture content but higher calorific value, making it a viable feedstock.

Pre-concentration of REE values from nepheline syenite rocks of western Odisha, India

ABSTRACT The rare-earth elements (REEs) have gained enormous economic and scientific attention due to their distinct properties and new applications. Nepheline syenite rock is an important primary source of rare earth minerals. The nepheline syenite rocks from the Rairakhol area, western Odisha, have been characterized for their rare earth mineralogical and textural characteristics. Preliminary beneficiation studies of these rocks were carried out to upgrade the REE values using falcon gravity separation and floatation technique. Hornblende, biotite, K-feldspar, albite, and nepheline are the major mineral constituents of the nepheline syenite where REE-bearing minerals occur as accessory minerals. The REE mineral phases present are zircon, sphene, apatite, allanite, britholite, and REE phosphate, with grain sizes ranging from 10 to 50 microns. Allanite and britholite occupy the intergranular spaces of major mineral phases and occur as thin lines or veins whereas sphene and zircon occur as inclusions within major mineral phases. The flotation study shows that the total REE content of the froth product could be enriched to 1696 ppm, which is three times more than the total REE content (563 ppm) of the feed sample.

Synchrotron x‐ray diffraction for sealed Mars Sample Return sample tubes

AbstractThe joint NASA‐ESA Mars sample return campaign aims to return up to 31 sample tubes containing drilled sedimentary and igneous cores and regolith. The titanium alloy tubes will initially still be sealed when they are retrieved. Several types of measurement will be carried out on sealed samples in the pre‐basic characterization phase of scientific investigation. We show that powder x‐ray diffraction (XRD) analysis can be successfully carried out on sealed samples using an x‐ray source at the I12 beamline of Diamond Light Source synchrotron. Our experiment used an analog sample tube and a Martian regolith analog (Icelandic basaltic sand). The titanium walls of the tube analog give strong but few diffraction peaks, making identification of the major constituent mineral phases feasible. A more significant constraint on quantification of mineral phase abundances by this XRD technique is likely to be the grain size of the sample. This technique opens up the possibility of initial mineralogical analysis of samples returned from Jezero crater without opening the sample tubes and the potential changes to the sample that entails.

Characterization of the Angat Ophiolite: New insights from bulk major and trace element geochemistry and petrographic analysis

The Angat Ophiolitic Complex, located north-northeast of Manila, Luzon is perhaps one of Luzon’s most fundamental suspect terranes. The definite age of the ophiolite is not well-established, with various authors having different claims. Encarnacion et al. (1993) conducted a U-Pb age dating for the Angat wherein the Angat Ophiolite was found to have an Early Middle Eocene age (48 Ma), close to the ZOC age - leading to the assumption that the two ophiolites are related and underlie most of Central Luzon. Hence, this paper aims to collect samples from the Eocene and Cretaceous Angat Ophiolite for petrographic and geochemical analyses, identify the relationship between the separated basalt units from the basalts in the main ophiolite body, and compare the geochemistry of the Eocene and Cretaceous units of the Angat Ophiolite with the other well-known ophiolites from the literature. Field investigations were conducted in five important localities wherein 15 samples were obtained. The results highlighted that the major mineral phases in the samples collected are plagioclase and augite, with some samples having hornblende and olivine. All samples appear to have undergone low-grade greenschist facies metamorphism, which may be attributed to hydrothermal alteration. Chloritization of pyroxene minerals is also evident, along with the hydrothermal alteration products of plagioclase and pyroxenes. The relationship between the EAO, MOC, and separated basalt patch in Marilaque Highway is identified. The Coto Block of the Zambales Ophiolite and the Angat Ophiolite may be related and formed over a mantle initially enriched by a subduction component.

Geochemical and mineralogical evaluation of Libale iron- rich manganese deposit, North-central Nigeria

The iron-rich manganese deposits of Libale area is located within the basement complex of North-central Nigeria. Mineralogically, the major mineral phases are: goethite (Fe2O3.H2O), spessartine (Mn32+Al2(SiO4)3), hematite (Fe2O3), and quartz (SiO2), while minor mineral phases are orthoclase (Al2O3.K2O.6 SiO2), illite (KAl2Si3AlO10(OH)2), and manganite (Mn2O3.H2O) suggesting a trend of mineral assemblage attributed to the differential mineralization of the iron-manganese deposit that may have been caused by the geochemical tectonic activity during its formation. Geochemically, on average, the Fe2O3, SiO2, Al2O3, CaO, P2O5 content are 34.59 wt.%; 26.30 wt.%; 6.94 wt%, 2.60 wt%, 2.01 wt% correspondently while K2O and TiO2 are less than 1wt%. Suggesting oxide facies type for the deposit. The trace element composition of V (1040 ppm), Cr (100 ppm), Co (833.33 ppm), Cu (1740 ppm), Nb (1280 ppm), W (240 ppm), Ta (320 ppm) and Zr (302 ppm) were relatively high compared to Maro, Muro and Kakun BIFs in North-central Nigeria. Bivariate plot of Fe2O3 Vs. Al2O3, suggest enrichment of Fe2O3 but depleted in SiO2 and Al2O3, which possibly indicates replacement of precursor silica and kaolinite with goethite which are subsequently dehydrated to hematite. Al2O3-SiO2-Fe2O3 ternary diagram indicates Precambrian Banded Iron Formation (BIF) for the Libale iron- rich manganese deposits, this was confirmed by MnO Vs. FeO. Discriminative plots: FeO. SiO2 - (FeO + MnO) - Fe2O3 and Al2O3+ K2O + Na2O Vs. MnO + FeO confirmed mixed facies as the analyzed data plots between silicate facies and magnetic-silicate facies, this is linked to chemical association between Al2O3 and SiO2 for the iron-rich as it confirms a transitional grade of silicate facies to magnetite-silicate facies. SiO2 Vs. Al2O3 plot revealed hydrothermal and diagenetic processes for its deposition. The iron-rich manganese deposit is of low grade iron (Av. Fe=24.19%) characterized by ferruginous manganese (Av. MnO2=23.82%) based on the generalized percentages of element of major interest in assessing quality of iron and manganese ore, therefore, good for cast iron production.

Mechanical and creep properties of granitic minerals of albite, biotite, and quartz at elevated temperature

Fundamental mechanical and creep behavior of minerals at elevated temperatures is relevant to many subsurface exploration and resource recovery processes, yet remains largely elusive. This study uses instrumented indentation to measure microscale deformation and nanoscale creep of biotite, albite, and quartz, which are the major mineral phases of granitic rocks, at temperatures up to 400 °C. The results show that the elastic modulus of biotite is not only the lowest at room temperature but also decays the most at elevated temperature (i.e., by 25% reduction at 400 °C) compared to that of albite and quartz. The creep deformation within 20 s doubles when the temperature increases from 20 °C to 400 °C for albite, quartz, and biotite, and biotite showed at least three times the overall creep deformation compared to quartz and albite under the same temperature. The indentation creep deformation can be well characterized using a logarithmic time model, showing both transient and constant-rate creep deformation. The secondary creep rate for biotite is about three times that of albite and quartz at the same temperature, and as the temperature increases from 20 °C to 400 °C, the rate of secondary creep becomes approximately 10 times faster for the three tested minerals. Both transient creep deformation and the rate of secondary creep can be empirically correlated to the elastic moduli, which allows quick estimates of the temperature-dependent creep behavior of granitic minerals using their elastic properties, especially when those creep constants are not readily available at elevated temperatures. These results enhance the understanding of temperature-dependent creep deformation at small scales and provide insight into mineral-level damage in granitic rocks due to temperature and long-term deformation.

Fe(III) Biomineralization in the Surface Microlayer of Acid Mine Waters Catalyzed by Neustonic Fe(II)-Oxidizing Microorganisms

The formation of thin mineral films or encrustations floating on the water surface of low-flow or stagnant zones of acid mine drainage (AMD)-affected streams is probably among the most exotic features that can be found in mining areas. However, most fundamental questions about their origin (biotic vs. abiotic), structure, mineralogy, physical stability and metal-retention capacity remain unanswered. This study aims to reveal the factors promoting their formation and to clarify their composition in detail. With this purpose, the major mineral phases were studied with XRD in surface film samples found in different mine sites of the Iberian Pyrite Belt mining district (SW Spain), and the major oxide and trace metal concentrations were measured with XRF and/or ICP-MS. Fe(III) minerals dominated these formations, with mineralogy controlled by the pH (jarosite at pH~2.0, schwertmannite at pH 2.5–3.5, ferrihydrite at pH > 6.0). Other minerals have also been identified in minor proportions, such as brushite or khademite. These mineral formations show an astounding capacity to concentrate, by orders of magnitude (×102 to ×105), many different trace metals present in the underlying aqueous solutions, either as anionic complexes (e.g., U, Th, As, Cr, V, Sb, P) or as divalent metal cations (e.g., Cu, Zn, Cd, Pb). These floating mineral films are usually formed in Fe(II)-rich acidic waters, so their formation necessarily implies the oxidation of Fe(II) to Fe(III) phases. The potential involvement of Fe(II)-oxidizing microorganisms was investigated through 16S rRNA gene amplicon sequencing of water underneath the Fe(III)-rich floating mineral films. The sequenced reads were dominated by Ferrovum (51.7 ± 0.3%), Acidithiobacillus (18.5 ± 0.9%) and Leptospirillum (3.3 ± 0.1%), three well-known Fe(II)-oxidizing genera. These microorganisms are major contributors to the formation of the ferric mineral films, although other genera most likely also play a role in aspects such as Fe(III) sequestration, nucleation or mineral growth. The floating mineral films found in stagnant acidic mine waters represent hotspots of biosphere/hydrosphere/atmosphere interactions of great value for the study of iron biogeochemistry in redox boundaries.

Molecular modelling of cementitious materials: current progress and benefits

Developing new sustainable concrete technology has become an urgent need, requiring faster and deeper insights into the fundamental mechanisms driving the cement hydration reactions. Molecular simulations have the potential to provide such understanding since the hydration reaction and the cement chemistry are particularly dominated by mechanisms at the atomic scale. In this letter, we review the application of two major approaches namely classical (including reactive) molecular dynamics simulations and density function theory calculations of cementitious materials. We give an overview of molecular simulations involving the major mineral and hydrate phases.

Characterization of a carbonatite-derived mining tailing for the assessment of rare earth potential

Depletion of high-grade deposits of rare earth elements (REEs) has led to increased interest in reprocessing mining tailing, particularly from carbonatite-related deposits. This is because most of the world’s REEs are produced from such deposits. The objective of this study was to physically, geochemically, and mineralogically characterize a carbonatite-related tailing from an Australian mine site to assess the REEs recovery potential. The tailing sample sourced from the mine site was analyzed by dry screening, laser particle size analysis, X-ray fluorescence (XRF), X-ray diffraction (XRD), Inductively Coupled Plasma Mass Spectrometry, and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). The results revealed that tailing consisted of mainly fine particles with 50 wt% below 61 µm. The geochemical results showed that the tailing consisted mainly of iron (Fe), and REE accounted for over 50% and 9% of the mass, respectively. The identification of major mineral phases by XRD followed by verification by SEM-EDS found monazite and florencite were the main REE-bearing minerals. The main gangue mineral is identified as goethite. The metallurgical balance showed that over 70% of the mass, REE, and Fe were concentrated in finer particle fractions below 63 µm. The SEM-EDS-based mineral liberation analysis found that REE-minerals were primarily associated with goethite and were locked within the latter in larger particle sizes over 100 µm. However, the smaller (<50 µm) REE-mineral grains were mostly liberated. The findings of this study suggest that light grinding of the particle fractions above 63 µm would potentially liberate the locked REE-minerals and subsequent separation by gravity, magnetic, and flotation processes can be tested to make REE concentrate. Because the sample is fine-grained, direct hydrometallurgical processing could potentially be effective to recover REE from this tailing.

APATITE VOLATILE CONTENTS OF PORPHYRY Cu DEPOSITS CONTROLLED BY DEPTH-RELATED FLUID EXSOLUTION PROCESSES

Abstract Porphyry Cu deposits are formed by Cu- and volatile (e.g., Cl, S)-rich fluids exsolved from underlying magma reservoirs. Intuitively, higher magmatic Cl and S contents likely correspond to higher magma fertility. However, the Cl contents of syn-ore magmatic apatite, one of the major Cl-bearing mineral phases in magmas, are highly variable among deposits (from &amp;lt;0.1 to &amp;gt;2 wt %). These variations may be controlled by different timing of apatite crystallization relative to fluid saturation among deposits, but the causes of these different relative timings remain obscure. Here we compile existing chemical data of magmatic apatite and amphibole phenocrysts from 25 porphyry Cu deposits worldwide and use these data to calculate magmatic physical-chemical conditions, such as water contents and magma reservoir depths. We find that the porphyry Cu deposits associated with deeper magma reservoirs are characterized by systematically higher magmatic H2O contents and apatite Cl, but lower apatite F contents and F/Cl ratios compared to shallower deposits. These correlations are best explained by early fluid exsolution and Cl loss that predate apatite crystallization in shallower porphyry Cu systems, which leads to elevated apatite F/Cl ratios. This is supported by the common occurrence of primary fluid inclusions in apatite from shallower systems. Postsubduction porphyry Cu deposits are normally associated with lower apatite Cl contents and shallower magma reservoirs, which is attributed to their formation under relatively extensional tectonic regimes. Our results demonstrate that the magma reservoir depth exerts an important control on the timing of fluid exsolution and accompanying Cl loss. In contrast, relatively high and constant apatite S content among deposits is minimally affected by fluid exsolution, possibly due to buffering of early-saturated sulfate in oxidized and S-rich magmas, and therefore might be used as a better potential fertility indicator than Cl.

Formation Damage Caused by Wax Deposition Results in Shale Production Decline

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210414, “First Evidence for Shale Production Decline as a Result of Formation Damage Caused by C60+ Paraffin Wax Deposition: A Permian Case Study,” by Amir Mahmoudkhani, SPE, Locus Fermentation Solutions, and Jonathan Rogers and Martin Shumway, SPE, Locus Bio-Energy Solutions, et al. The paper has not been peer reviewed. _ Analysis of production decline curves revealed that three candidate wells in West Texas depleted faster than indicated by a type decline curve, indicating a potentially abnormal permeability-reduction mechanism. A biosurfactant-based squeeze program was recommended and applied in three horizontal wells. The biosurfactant treatment offers an alternative and economical method for remediation of formation damage caused by high‑molecular‑weight paraffin wax deposition in porous media that does not require costly intervention techniques to apply. Introduction The Bone Springs horizontal oil play in the Delaware Basin spans from southeast New Mexico into West Texas. Stacked, multipay reservoirs, each with diverse rock properties, possess upside but also complexity. The initial targets in the play were conventional sandstones. Wells then tapped into carbonate lenses and, ultimately, low-permeability sandstones. As a result of horizontal drilling technology combined with hydraulic fracturing, very thin sands and other facies are now being produced. Generally, reservoir quality of this unconventional hydrocarbon system is controlled by carbonate content, where increased carbonate content typically is associated with lower productivity. Experimental Methods All crude oils exhibited precipitation of organics at ambient laboratory temperatures. Even after storing crudes at the bottomhole temperature of 140°F, a small amount of wax remained insoluble in bulk liquid. Samples of formation drill cuttings were received for various depth intervals between 8,500 and 12,000 ft. X‑ray diffraction analyses of solids revealed quartz as the major mineral phase, with clays and carbonates account for remaining phases. Combined fractions with 160-micron size were used for microcolumn oil-recovery screening tests. Carbon distributions of oils and waxes were performed by high-temperature gas chromatography (HTGC). The Du Noüy ring method was used to measure static surface tensions of biosurfactant solutions at different concentrations and was applied to calculate critical micelle concentrations at ambient temperature. Interfacial tension (IFT) measurements were performed using a drop-shaped tensiometer using the pendant-drop method. Finally, the IFTs of oil in synthetic formation water and in biosurfactant solutions prepared in city tap water were determined. Contact-angle measurements also were performed. The wax-appearance temperature (WAT) of crude and wax samples was determined by the differential scanning calorimetry method. Spontaneous imbibition experiments were performed using the Amott-cell method at reservoir temperature. Berea sandstone core plugs (25×50 mm) with a permeability of 385 md and porosity of 18.4% were used. Core plugs were saturated with homogenized crude oil samples at 140°F for 7 days.

Optimization of fluoride removal using calcined bauxite: Adsorption isotherms and kinetics

Geogenic contamination of groundwater due to elevated fluoride (F−) concentrations is a significant issue worldwide (including in Tanzania). The present study focussed to assess the adsorption capacity of thermally treated (calcined) bauxite to remove the F− from contaminated water. Characterization of bauxite by X-ray fluorescence spectroscopy (XRF) revealed Al2O3, Fe2O3, and SiO2 as the major oxides in both raw and calcined bauxite. The major mineral phase in the raw bauxite was gibbsite, which disappeared after calcination. The optimum calcination temperature, dosage and contact time for F− removal by calcined bauxite were 400 °C, 40 g/L and 8 min, respectively. The experimental data revealed Freundlich isotherm as the best model to fit the F− adsorption process with kF and 1/n being 0.1537 mg/g and 0.8607, respectively. The pseudo-second-order kinetic and intra-particle diffusion models explained well the F− adsorption process with the rate constants of 115.43 g/mg min and 0.0025 mg/g min0.5, respectively. The values of ΔG, ΔH and ΔS indicate the F− adsorption on bauxite surface indicated that the adsorption process was spontaneous, endothermic and structural changes occurred during the adsorption process. The F− adsorption under optimum conditions lowered the pH and F− concentration to WHO and Tanzania Bureau of Standards (TBS) standards.

Tholeiitic to calc-alkaline and alkaline volcanisms in an extensional arc setting of a Tethyan ophiolite: insights from small-scale compositional and temporal transitions from the Dali sector (Armenia)

• Dali's sector shows a transition from island-arc magmatism to more alkaline volcanism. • Alkaline lavas comprise E-MORB, transitional calc-alkaline basalts and atypical OIB. • The transition to alkaline lavas occurred in the Tithonian–Valanginian time interval. • The diversity of magmatic affinities suggests an extensional oceanic arc setting. New field and petrographic observations, combined with whole rock and mineral geochemical analyses are applied on volcanic rocks present in the Dali sector, east of Lake Sevan (Armenia). A small-scale sampling of the volcanic sequence allows us to identify, for the first time in Armenian ophiolites, two groups of lavas (groups B and C1) stratigraphically and geochemically intermediate between previously recognized arc tholeiite (group A) and OIB-like (group C2) basalts. Their age is constrained by two distinct intercalated radiolarite sequences, which were dated as Tithonian – Valanginian. Group B lavas are low-K tholeiitic basalts and basaltic andesites derived from an enriched mantle source (La N /Yb N 1.8–6.1; Sm N /Yb N 1.3–2.4; Nb/Yb 2.0–6.7). The composition of their clinopyroxenes ranges from Ti-poor augite to Ti-rich diopside augite in correlation with higher La/Yb and Nb/Yb ratios in bulk rocks. Group C1 lavas are basaltic andesites containing Ti and Na-rich amphiboles (kaersutites, hastingsites) as major mineral phases. Three analyzed diopside-amphibole-porphyritic samples are alkaline trachybasalts (La N /Yb N 20–21; Nb/Yb 16–18). Both the group B and C1 lavas exhibit variable, although moderate, enrichments in Th/Yb for given Nb/Yb ratios and Nb negative anomalies in normalized multi-elements patterns (Nb/La 0.53–1.02), which are not correlated with the degree of enrichment of their mantle sources. Our results suggest that transitional and OIB-like volcanic lavas were generated by low- (group B) and very low- (groups C1–C2) melting of a heterogeneous mantle source in an oceanic arc–back-arc system in extension, possibly in relation with slab break-off.