Pyrite Minerals Research Articles

Geochemical and petrological studies of high sulfur coal and overburden from Makum coalfield (Northeast India) towards understanding and mitigation of acid mine drainage

Opencast coal mining produces trash of soil and rock containing various minerals, that are usually dumped nearby the abandoned sites which causes severe environmental concern including the production of acid mine drainage (AMD) through oxidation pyrite minerals. The current study entailed assessing the potential production of AMD from an opencast coal mining region in Northeast part of India. In order to have a comprehensive overview of the AMD problem in Makum coalfield, the physico-chemical, geochemical, and petrological characteristics of the coal and overburden (OB) samples collected from the Makum coalfield (Northeast India) were thoroughly investigated. The maceral compositions reveal that coal features all three groups of macerals (liptinite, vitrinite, and inertinite), with a high concentration of liptinite indicating the coal of perhydrous, thereby rendering it more reactive. Pyrite (FeS2) oxidation kinetics were studied by conducting the aqueous leaching experiments of coal and (OB) samples to interpret the chemical weathering under controlled laboratory conditions of various temperature and time periods, and to replicate the actual mine site leaching. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was operated to detect the disposal of some precarious elements from coal and OB samples to the leachates during our controlled leaching experiment. The Rare earth element (REE) enrichment in the samples shows the anthropogenic incorporation of the REE in the coal and OB. These experiments reveal the change in conductivity, acid producing tendency, total dissolved solid(TDS), total Iron(Fe) and dissolved Sulfate(SO42−) ions on progress of the leaching experiments. Moreover, the discharge of FeS2 via atmospheric oxidation in laboratory condition undergoes a significant growth with the rise of temperature of the reaction systems in the environment and follows pseudo first order kinetics. A bio-remediative strategies is also reported in this paper to mitigate AMD water by employing size-segregated powdered limestone and water hyacinth plant in an indigenously developed site-specific prototype station. Apart from neutralisation of AMD water, this eco-friendly AMD remediation strategy demonstrates a reduction in PHEs concentrations in the treated AMD water.

Diagenesis processes of the Gulneri Shale, Kometan, Mushorah formations within the upper Turonian - lower Campanian Supersequence from Bai Hassan area, North of Iraq

The upper Turonian - lower Campanian Supersequence is characterized with fine-grained, mixed siliciclastic-carbonate middle shelf to sub-basinal depositional system. The present study included the study of vertical and lateral changes of the diagenesis processes of the Gulneri shale, Kometan and Mushorah Formations within the sequences of the (upper Turonian-lower Campanian) cycle in two subsurface sections within the Dome of Daoud in the Bai Hassan field - northern Iraq. The first is represented by a section (BH-16) with a thickness of (213) m. In contrast, the second is represented by a section (BH-86) and a thickness of (233) m. The lithostratigraphy of the rock units of this study are consisting (206) slides were studied, (80) for well (BH-16) and (126) for well (BH-86).The study showed that the sequences of this cycle are unconformity with the lower Dokan Formation and upper contact with Hartha. The petrographic study showed that the rocks of the study were exposed to many diagenesis processes, like cementation, dolomitization, neomorphism, dissolution and compaction according to the degree of their prevalence with a large spread of locally authigenic minerals represented by the widespread pyrite mineral during the two sections of the study, in addition to a few presence of glauconite mineral. Depending on the petrographic description of the diagenesis processes, the vertical and lateral changes of the diagenesis processes were studied, and the diagenesis environments of the formations under study were deduced, where it was found that all the rocks of the two sections of the study were formed in the early stages of the diagenesis processes within the vadose environments as a result of exposure to tectonic processes that helped uplift their rocks to the surface and be affected by meteoric water.

The application of synthetic antibacterial minerals to combat topical infections: exploring a mouse model of MRSA infection

The development of new antibiotics has stalled, and novel strategies are needed as we enter the age of antibiotic resistance. Certain naturally occurring clays have been shown to be effective in killing antibiotic resistant bacteria. However, these natural clays are too variable to be used in clinical settings. Our study shows that synthetic antibacterial minerals exhibit potent antibacterial activity against topical MRSA infections and increase the rate of wound closure relative to controls. The antibacterial minerals maintain a redox cycle between Fe2+/Fe3+ and the surfaces of pyrite minerals, which act as a semiconductor and produce reactive oxygen species (ROS), while smectite minerals act as a cation exchange reservoir. Acidic conditions are maintained throughout the application of the hydrated minerals and can mitigate the alkaline pH conditions observed in chronic non-healing wounds. These results provide evidence for the strategy of ‘iron overload’ to combat antibiotic resistant infections through the maintained release of Fe2+ and generation of ROS via distinct geochemical reactions that can break the chronic wound damage cycle.

Incorporating pH into DFT-D+U and microflotation recovery studies on heterocyclic collector-pyrite interactions

This study adopted both computational and experimental approaches to design by modification of 2-mercaptobenzothiazole (MBT), 2-mercaptobenzoxazole (MBO) and 2-mercaptobenzimidazole (MBI) heterocyclic collectors by introducing a carbon sulphide (–CS2) group and forming 2-trithiocarbonatebenzothiazole (TTCBT), 2-trithiocarbonatebenzoxazole (TTCBO) and 2-trithiocarbonatebenzomidazole (TTCBI) derivatives collectors. The adsorption behaviour of the heterocyclic collectors (and derivatives) on pyrite and subsequent hydrophobicity at different pH conditions were characterised using molecular modelling and microflotation approaches, respectively. The computational adsorptions were performed on dry and hydrated surfaces in their neutral thiolate and thione (acidic) form on the pyrite (100) surface. It was found that under dry and neutral conditions the TTCBONa and TTCBTNa were more exothermic, while under dry and acidic conditions the TTCBIH was more exothermic followed by MBIH and MBTH. Under hydrated and neutral conditions MBONa was predicted as the most exothermic, while for hydrated and acidic conditions MBTH, TTCBTH and TTCBIH were more exothermic. It was found that under acidic conditions, the heterocyclic collectors were more exothermic than for neutral condition on the hydrated surface. The microflotation at pH = 8 showed that MBO achieved higher recoveries, while at pH = 6 MBT, TTCBT and TTCBI achieved higher recoveries that could reach 90 %. The derivatives under acidic conditions were found to have good recovery performance, which showed that the introduction of a –CS2 group on the exocyclic sulphur atom improved the affinity and therefore hydrophobicity of the mercapto-heterocyclic collectors on the pyrite surface, and thus these derivatives can enhance the flotation of pyrite minerals. In addition, the computational predictions complimented by experimental recoveries are essential to a meaningful development of modelling as a tool in mineral processing reagent design.

The Boumaadine Fe–Mn–Pb–Cu (± Au) ore deposit (Jbel Skindis, eastern High Atlas, Morocco): New insights from geological, hydrothermal alteration and geochemical investigations

Petrographic, structural and geochemical analysis combined with SEM and XRD were performed on the Boumaadine Fe–Mn–Pb–Cu (±Au) mineralization of Jbel Skindis in the eastern High Atlas, (Morocco). The results indicate a polyphasic process of mineralization, which produced orebodies with distinct features and different chemical conditions formation. The earliest mineralization formed replacement and disseminated Fe–Mn–Pb orebodies under oxidizing conditions, with a mineral assemblage composed of coronadite, plumboferrite, cesarolite, specularite and calcite, in association with a large-scale hydrothermal alteration consisting essentially of Fe–Mn minerals, i.e., ferroan dolomite, hematite, jacobsite and limonite. The second event was formed under reducing conditions that generate some veins filled mainly by sulfides (galena, with minor pyrite and chalcopyrite), in addition of calcite and dolomite.The mineralization is hosted in Lower Liassic dolostones and is linked to the structural evolution of the study area. Fractures related to the displacement of the Boumaadine fault seem to control the disposition and the localization of the alteration and the mineralization: (i) the Fe–Mn–Pb oxides are related to a NE-SW conjugate fault system generated during the first phase of deformation, with a horizontal principal stress striking NNW-SSE, and (ii) the sulfide mineralization occurs mainly as filling conjugate fractures of two preferentially directions striking N80–90 and N150-165 with a slight dip (15–40°) to the NE. These latter were caused by a dextral movement along the Boumaadine fault, generated during the late phase of deformation with a NW-SE bearing horizontal principal stress.The deep-seated Boumaadine fault has acted as pathways for the rising fluids, and supports the origin of lead and other metals from the Paleozoic basement. The Triassic evaporitic sequence along the Boumaadine fault has also contributed to the chemical composition of the fluid, and represents the potential source of both the salinity and sulfur. The oxide-sulfide mineralogical assemblage and its associated alteration emphasize a polyphasic hydrothermal activity with distinct physicochemical conditions; an iron-manganese rich, and highly oxidizing brine is considered to be responsible for the Fe–Mn alteration and for the deposit of the oxide assemblage. Furthermore, a mixing of the oxidizing fluid with a meteoric reducing fluid could have resulted in the sulfide-rich ore.

Stibioclaudetite from the Zlatá Idka Ag-Au-Sb deposit, Spišsko-gemerské rudohorie Mts., Slovakia

A rare mineral, stibioclaudetite, ideally AsSbO3 was discovered at the dump of the Najvyšší Štefan adit at the Zlatá Idka Ag-Au-Sb deposit near Zlatá Idka, Spišsko-gemerské rudohorie Mts., Košice-okolie Co., Košice Region, Slovakia. It occurs as colourless prismatic crystals up 5 mm with perfect cleavage, developed on fractures of quartz gangue with abundant stibnite, arsenopyrite and minor pyrite. The unit-cell parameters of stibioclaudetite from the Zlatá Idka (for the monoclinic space group P21/n) refined from the PXRD data are: a 4.5715(17) Å, b 13.112(2) Å, c 5.4182(15) Å, β 94.97(3) and V 323.55(14) Å3. Its chemical composition corresponds to the average empirical formula As1.09Sb0.91O3.00. Raman spectrum of stibioclaudetite is also given. Stibioclaudetite was formed by the in-situ weathering of primary ore minerals at the base of the supergene zone under the relatively reducing conditions.

Minerageny of Jurassic deposits of the northeastern side of the Ulyanovsk-Saratov depression

The Jurassic terrigenous-clayey complex on the territory of the northeastern side of the Ulyanovsk-Saratov depression contains numerous groups of solid minerals. Some of them are at the stages of industrial development, some have not found application due to local distribution. Analysis of the composition and conditions of formation of solid mineral raw materials showed that the main factor influencing the formation of minerals was the marginal position of the territory in the Middle-Upper Jurassic time. The relatively high bioproductivity of the epicontinental Central Russian paleosea contributed to the accumulation of layers of calcareous marls, oil shale and phosphate raw materials. All these rocks were formed in the Mesozoic basin of sedimentation with the active participation of organic matter, the producers of which were zoo- and phytoplankton. The accumulation of coccolithophora in clayey silts led to the formation of calcareous marls, the accumulation of dying algae in bottom sediments led to the formation of oil shale. Nodular phosphorites are also biochemogenic raw materials. During periods of regressive development of the Central Russian paleosea along the coast, conditions were created for the accumulation of oolitic siderites together with leguminous goethite-hydrogethite aggregates of iron ores. Periodically, regional faults were activated on the northeastern edge of the Ulnovsko-Saratov depression. At this time, there was an upward migration of deep mineralized fluids through weakened zones. Unloading in the bottom part of the Central Russian paleosea, they contributed to the formation of fields of pyrite and barite mineralization in sedimentary rocks.

Geochemical aspects on formation processes of vein-hosted pyrite in the Carboniferous-Permian rocks of the Karavanke/Karawanken tunnel, northwestern Slovenia

Abstract The Carboniferous-Permian organic-rich shale in the Karavanke/Karawanken tunnel exhibits extensive pyrite mineralization in the form of veins and impregnations. Significant thermal alteration, induced by the overlying Mesozoic rock sequences, led to the decomposition of organic matter into methane, which subsequently acted as a sulfate-reducing agent. The primary source of sulfate were the evaporitic layers hosted within the Paleozoic strata. Reduced sulfur species necessary for pyrite formation were produced through methane-mediated thermochemical sulfate reduction, catalyzed by specific cations (Ni2+, Fe2+) and clay minerals (montmorillonite). The mineralizing fluids originated from the expulsion of interstitial water and possibly from dehydration reactions related to the gypsum-to-anhydrite phase transition. The geochemical data indicate that the metals originated from the surrounding sedimentary rocks. These mineralizing fluids were characterized by low temperatures (< 300–350 °C), moderate reducing conditions, and low chlorinity. The low permeability of Carboniferous-Permian rocks, combined with the low trace element content of the investigated pyrite, mitigates the potential risk of environmental pollution.

Coal facies of the Middle Permian Baruunnaran deposit, South Mongolia

The Baruunnaran coal deposit is located in the northeastern part of the South Gobi Basin, southern Mongolia, and hosted in the middle Permian Tavantolgoi Formation. In this paper we present indices of coal facies determined from 34 coal samples obtained from three seams in the lower and upper part of the formation (III, IXG and X), by studying their organic petrography and the geochemistry of the coal ash. The results of coal petrography revealed that seams III, IXG and X are composed of 46.9-80.9 vol.% vitrinite, 11.6-47.5 vol.% inertinite and 1.2-18.2 vol.% liptinite. In samples from seams III and X the average content of mineral matter is low at 11 and 13.4 vol.%, respectively, and 6.3 vol.% in seam IXG, and consists of clay, silica, pyrite, carbonate, and other minerals. The inorganic content mostly occurs as fillings of cell cavities, cracks, and fissures of vitrinite and inertinite macerals. The vitrinite random reflectance values range from 0.81-1.07%. The Gelification Index and Tissue Preservation Index suggest the peats accumulated in wet forest swamp environments with high tree density. The majority of the seams accumulated in mildly oxic to anoxic conditions with good tissue preservation. The peat mire water ranged from weakly to strongly acidic. Further, it was determined by Al2O3/TiO2 ratios that the clastic sediments were probably sourced from volcanic basement characterized by intermediate felsic composition.

Maceral composition, coal quality and depositional environments of the middle Permian Ukhaakhudag coal deposit, South Mongolia

The Ukhaakhudag coal deposit is located c. 560 km SSE of the city of Ulaanbaatar in the northeastern sector the South Gobi Basin. The coal-bearing strata is part of the middle Permian Tavantolgoi Formation. This study aims to determine the coal petrographic composition and depositional environments of five coal seams in the lower part of the deposit based on petrographic and chemical analyses of 106 composite samples. Vitrinite ranges from 12 to 64 vol.%, and inertinite varies between 9 and 68 vol.%. Liptinite ranges from 1 to 7 vol.%. Microlithotype analyses indicate that coals are primarily vitrinertite, few coals are classified as trimaceralic microlithotypes duroclarite and clarodurite. The inorganic fraction in the studied coals is mainly composed of clay, small amounts of silica, carbonate, and pyrite minerals. The vitrinite random reflectance values of the samples vary between 0.93-1.16 %. Volatile matter content varies from 26.10 to 41.48 wt.% (dry ash free basis). Ash, moisture, and sulfur contents vary between 11.20-44.76 wt.%, 1.63-6.03 wt.% and 0.49-1.67 wt.%, (air dried basis) respectively. Based on random vitrinite reflectance values and volatile matter content, the studied coals are classified as coking (Ch4), fat (Ch5), 1/3 coking (Ch6), gas fat (Ch7) based on the Mongolian system and medium to high volatile bituminous coal when using the ASTM system. The Gelification Index and Tissue Preservation Index of the studied samples suggest most seams accumulated in wet forest swamps with a high tree density. The Middle Permian peats from this location accumulated in mostly alternate oxic and anoxic mire conditions. The climate was drier during the peat accumulation of Seam 0, but it became warmer, and humidity increased starting from Seam 3 accumulation.

Recently-discovered Bahçecik Au±Ag mineralization in the Eastern Pontides, Gümüşhane-NE Türkiye: geological and geochemical implications on the intermediate sulfidation epithermal deposit

ABSTRACT Intermediate sulfidation epithermal deposits represent significant reservoirs of precious metals, playing a crucial role in global mining operations. The Anatolian Peninsula, predominantly characterized by relatively young (Tertiary) lithologies, hosts numerous occurrences of epithermal base and precious metal mineralization. Within the realm of research in Northeastern Anatolia, several hydrothermal alteration zones have emerged as indicators of concealed epithermal mineralization, with the Bahçecik mineralization standing out as a recent focal point. The Bahçecik mineralization represents an intermediate sulfidation epithermal Au-Ag system, hosted by Late Cretaceous andesitic rocks, as well as Eocene dacitic lava and tuffs. Employing U-Pb LA-ICP-MS zircon dating of the dacitic host rocks, the mineralization is estimated to have occurred during the Lutetian epoch (43.61 ± 0.35 Ma) or later. The genesis of the Bahçecik deposit is believed to be linked to postcollisional regional extensional tectonics, primarily controlling its structural arrangement. Comprising pyrite, chalcopyrite, low-Fe sphalerite, galena, tetrahedrite/tennantite, enargite-luzonite, and gold-silver minerals, the deposit is accompanied by prominent gangue minerals such as Mn- and Ca-carbonates, quartz, and barite. Microprobe measurements have identified a majority of Au-Ag minerals (krennerite, buckhornite, and nagyagite) closely associated with sulphide minerals. Fluid inclusion data reveal that mineralization and fluid transportation occurred at temperatures ranging from 153 to 327°C, with solutions exhibiting salinity levels consistent with those of intermediate sulfidation deposits (1.7–7.3 wt.% NaCl). This study unequivocally classifies the Bahçecik mineralization as an intermediate sulfidation deposit, contrary to the conclusions drawn in previous research. Moreover, our investigation has unveiled the presence of a substantial ore resource, totalling 7.84 million tons, featuring 1.76 g/t Au and 2.24 g/t Ag. As an intermediate-type deposit, it shares characteristics with other subtypes within the epithermal class, bridging the realms of both high and low sulfidation systems.

Paleo-marine redox environment fluctuation during the early Cambrian: Insight from iron isotope in the Tarim Basin, China

The Ediacaran to Cambrian period is generally considered to be the vital transition in the history of marine redox environment and life evolution on earth. The ocean oxygenation levels during this transition period are still debated. Since iron is widely involved in biogeochemical cycles and undergoes redox cycling both in the seawater and sediments, it has become a significant proxy to reconstruct paleo-marine environment. In order to constrain the paleo-marine redox state in the early Cambrian, the iron isotope composition of bulk rock (δ56FeT) is interpreted combining with iron-speciation, redox sensitive elements and pyrite sulfur isotope (δ34Spy) of Yuertusi Formation in Tarim Block. The δ56FeT values varies from −0.39 ‰ to 0.48 ‰, with an average of 0.07 ‰, mainly controlled by pyrite mineral facies in this study. Based on the mechanism of pyrite generation in different redox condition, it is proposed that the marine environment of the lower Cambrian in the Tarim basin is dominated by anoxic with intermittent euxinic state. The dynamic evolution of redox environment can be divided into three intervals. The gradual decrease of δ56Fe in Interval I indicates the paleo-marine environment changed from anoxic ferruginous to euxinic, and the paleo-marine sulfate reservoir decreased to a limited level, which might be attributed to abundant burial of organic matter and pyrite. For Interval II, δ56Fe values first increase to evident positive because of partial oxidization then decreased to that of seawater (about 0 ‰) due to complete oxidization. In Interval III, the continuous decrease of δ56Fe values infers a sustaining oxidization. In summary, the paleo-marine environment of the lower Cambrian Yuertusi Formation evolved from anoxic ferruginous to euxinic and then oxidized continuous. Iron isotope statistics from geological historical periods indicate that seawater was relatively oxidized after the NOE event but did not reach the oxidation levels of present-day seawater.

Analysis of Acid Mine Drainage Formation Potential on Coal Stratification in Lamuru Area, Bone Regency, South Sulawesi Province

The open-pit mining system in coal mines causes the rocks at the mining site to be exposed to the surface so that water and air will react with rocks directly which will cause the formation of acid mine drainage, diverse morphological coditions with many springs and agricultural fields around the research area have an important role that must be maintained so as not to be polluted or damage agricultural land. The purpose of this study was to analyze the presence of sulfide minerals with sulfur content in coal stratification as the initial potential of acid mine drainage, in the lithology of the study area obtained seven lithological samples on coal stratification including overburden, S-01 (siltstone), S-02 (coal seam 1), S-03 (siltstone), S-04 (claystone), S-05 (coal seam 2), S-06 (sandstone) and S-07 (top soil). The results of the X-ray Diffraction (XRD) analysis detected the presence of pyrite minerals, with the results of the analysis of total sulfur ranging from 0.046 to 4.62%, and the results of the analysis of scanning electron microscope (SEM) obtained anhedral, subhedral and framboidal morphology This type of framboidal pyrite is a very fine crystal, very fast to react with air so that this pyrite is believed to be a trigger for the formation of acid mine drainage.

Mineral exploration using trace element composition of pyrite grains from till: A case study from the Petäjäselkä Au occurrence, northern Finland

Geochemical anomalies and indicator mineral studies in glacial sediments are commonly used to define mineral exploration targets in glaciated areas. Trace element composition of sediment-hosted heavy minerals, such as pyrite and chalcopyrite, can be potentially used to fingerprint mineral deposits. This study presents results from trace element compositions of pyrite in the heavy mineral concentrates of till and mineralized bedrock samples from the orogenic gold ore occurrences in the Petäjäselkä area, Central Lapland belt, northern Finland.The trace element contents of pyrite grains were evaluated by using a robust compositional data analysis workflow, including symmetric pivot coordinates and robust principal component analysis (PCA). Four different pyrite textures (A-D) were identified from the gold ore occurrences. Compositional data analysis showed that the heavy mineral pyrite correlated with Pyrite D in the ore occurrence and confirmed the discrimination power of pyrite in the heavy mineral grains as a tool for source characterization of transported sedimentary material. The study also discusses the difficulties of finding suitable grains for the LA-ICP-MS, highlighting the importance of proper heavy mineral grain recovery procedures and the factors of oxidization and weathering processes influencing the geochemical compositions of the pyrite grains.

Geodynamic settings of Silurian - Early Devonian volcanism in the north of the Sakmara zone (the Southern Urals)

The work provides characteristics of the Karamolinsky and Blyavinsky volcanic complexes, which were identified by I.A. Smirnova, V.L. Cherkasov, V.T. Tishchenko, I.B. Seravkin in the Mednogorsk region in the rank of strata. Based on findings of graptolites in limestones and siliceous shales, intercalations among pillow basalts and massive basaltic flows, the sequence is dated as the Middle to Upper Llandoverian. Based on the presence of facies replacement of the Karamolinsky sequence with siliceous rocks of the Sakmara Formation, the age of the Karamolinsky sequence is assumed to be S–D1. The Karamolinsky sequence (according to A.D. Petrovsky, L.D. Chegodaev) is identified with the Blyavinsky formation. We propose that the basalts of the southern wall of the Blyavinsky quarry and their analogues containing interlayers of siliceous rocks with graptolites (S1) be included in the Karamolinsky sequence and Blyavinsky formation, and the ore-hosting section of the Blyavinsky and Komsomolsk deposits with low-titanium basalts and acidic polyfacial rocks, is classified as the Blyavinsky formation (S–D1). The geodynamic conditions for the formation of the Karamolinsky strata are discussed. Materials on the composition and age of the Karamalinsky formation of the Maksyutov complex and pyrite mineralization of the Yuluk group of deposits in the Uraltau zone are considered. It is concluded that it is possible to partially compare the strata of the Maksyutov complex and the Silurian-Early Devonian volcanic sulfide-bearing strata of the Mednogorsk ore region.

Jahnsite-(NaMnMn), a New Jahnsite-Group Mineral from the Wiperaminga Hill West Quarry, Boolcoomatta Reserve, South Australia, Australia

Abstract Jahnsite-(NaMnMn), NaMn2+(Mn2+Fe3+)2Fe3+2(PO4)4(OH)2·8H2O, is a new mineral from the Wiperaminga Hill West Quarry, Boolcoomatta Reserve, Olary Province, South Australia, Australia. The mineral occurs in seams in a matrix comprising triplite, quartz, fluorapatite, and minor pyrite and formed as a result of hydrothermal alteration. Associated minerals are bermanite, phosphosiderite, strengite, and an unknown Mn-Fe phosphate. The mineral occurs as orange-yellow prismatic crystals, elongated parallel to [100], flattened on {001}, exhibiting the forms {001}, {100}, {011}, and {201} that are twinned on {001}. Crystals are up to 80 μm in length and 25 μm across. The Mohs hardness is about 4, the tenacity is brittle, the fracture is splintery, and there is one good cleavage on {001}. The calculated density is 2.774 g/cm3. Jahnsite-(NaMnMn) is biaxial (−) with α = 1.645(3), β = 1.671(3), and γ = 1.674(3) (white light). The measured 2V is 36(1)°. Dispersion could not be observed, and the optical orientation is Z = b. Pleochroism is X = pale yellow brown, Y and Z = light yellow brown; absorption X < Y ≈ Z. Electron probe microanalysis gave the empirical formula (Na0.61Ca0.38)Σ0.99Mn2+(Mn2+1.11Fe3+0.53Mg0.29Mn3+0.07)Σ2(Fe3+1.68Mn3+0.26Al0.06)Σ2(PO4)3.98(OH)2.03·8.05H2O based on 26 O atoms per formula unit. Jahnsite-(NaMnMn) is monoclinic, P2/a, a = 15.1359(10), b = 7.2035(3), c = 9.9876(6) Å, β = 110.361(5)°, V = 1020.92(11) Å3, and Z = 2. The crystal structure has been refined to R1 = 5.70% for 2406 observed reflections with I > 2σI. The new mineral is isostructural with other members of the jahnsite group.

Study of nuclear magnetic resonance response mechanism in shale oil and correction of petrophysical parameters

Shale oil reservoirs, characterized by a low porosity, complex mineral composition, and heterogeneity of organic matter distribution, are common unconventional oil and gas reservoirs. Nuclear magnetic resonance (NMR) methods have great potential for the evaluation of petrophysical parameters in porous rocks. However, it is challenging to characterize the petrophysical properties of shale oil due to the complex mineral composition and heterogeneity of organic matter distribution. In this paper, a new NMR relaxation theory for shale was proposed for the first time, and the frequency dependencies of transverse surface relaxivity and internal magnetic field gradient for pore fluids were presented. The accuracy was verified by the extraction experiments, gas chromatography experiments, and multi-frequency NMR experiments for the first time. These experiments were also utilized to determine the transverse surface relaxivity and the transverse bulk relaxation time. Subsequently, the effects of the pyrite and clay minerals on shale oil T2 distributions at different instrument frequencies were analyzed with random walk simulations based on digital core technology for the first time. The results show the echo spacing, instrument frequency, pyrite content, and clay minerals are important parameters affecting the NMR response. Compared with the oil in organic pore, these factors have a greater impact on the NMR response characteristics for water in inorganic pore. When the content of pyrite is 5.3 % and the echo spacing is 0.2 ms, the numerical simulation results show that the NMR porosity of water in inorganic pore is 65.3 %, 12.3 %, and 1.6 % of the real porosity at the instrument frequencies (IF) of 2 MHz, 21.36 MHz, and 200 MHz, respectively. When chlorite with high magnetic susceptibility exists near the formation pores, it can also affect the NMR response of shale oil. The results show the effects of these factors on porosity and T2ML are non-negligible. The cross-plots of petrophysical parameters correction from shale oil T2 distributions were established for the first time. This work provides a theoretical guide for the NMR-based shale oil evaluation, which may be helpful for petrophysical parameter conversion between downhole and laboratory NMR instruments.

Geobody estimation by Bhattacharyya method utilizing nonlinear inverse modeling of magnetic data in Baba-Ali iron deposit, NW Iran

One of the essential geophysical concerns is the estimation of the physical and geometrical parameters of the reserve (geobody), which is done by exploiting the nonlinear inverse modeling of magnetic data. The present study includes preparing and modeling magnetic data to suggest the Baba Ali Iron ore deposit's drilling locations in NW Iran. The area is covered with 1000 points of geomagnetic reading with an almost 5 × 10 m2 regularly spaces grid trending WE. The areal and depth extent of the iron ore geobody was unknown. The Bhattacharyya method by MATLAB software coding was employed to underestimate the misfit function and re-construct potential field data, providing the most suitable fitting with measured magnetic data. In this order, the residual calculated anomaly exhibited an excellent two-dimensional conformation with forward modeling. Furthermore, 3D modeling correctly reconstructs the anomalies' productive resources' properties. After preparing full magnetic maps, the magnetic lenses distinguished in four anomalies of surface depths, 20, 50, and deeper than 50 m for this zone. This magnetite lens for the first zone was estimated based on analytical signal filters applied on the entire magnetic map so that the lens's depth is trivial and almost zero. Due to specific gravity calculated as 4.77 t/m3, initial storage capacity is suggested to be about 95,400 tons of magnetite, pyrite, and hematite minerals at most in an area about 6 Km2. Finally, to complete the preliminary explorations of the specified area, exploratory drilling is suggested for three points by inverse modeling. Regarding this study as the first try in magnetic reconnaissance step of Iron mineral exploration in the study area, there is no geological constraints available based on drilling evidences. However, the model is well satisfies the surface anomalies considering residual magnetic property.

Application of hydroxyethylidene diphosphonic acid as a depressant for efficient pyrite separation from serpentine: a performance and mechanistic study

Hydroxyethylidene diphosphonic acid (HEDP) is an industrial environmental reagent, often used as a chemical raw material in industrial water treatment, household cleaning products and personal care products. In this work, the effort to use HEDP to the flotation of pyrite containing fine-grained serpentine was conducted, and the selective separation of serpentine and pyrite was accomplished. During the flotation process, the introduction of 30 mg/L HEDP resulted in a rapid increase and recovery of 89% pyrite recovery at pH 9 under deteriorated conditions. The results of the micro-flotation method showed how well HEDP was selectively inhibited in the pyrite-serpentine flotation separation process. On the basis of a number of measures, including ICP-OES tests, Zeta potential testing, Scanning electron microscopy (SEM) characterization, and X-ray photoelectron spectroscopy (XPS) analysis, it was discovered that a substantial amount of HEDP was selectively adsorbed on the serpentine surface by chemically chelating with the Mg active site. In contrast, the adsorption of HEDP on the surface of pyrite was almost negligible. HEDP prefers to adsorb on the positively charged serpentine surface in the form of H5C2P2O73- negative charge, while accelerating the release of Mg from the serpentine surface into the solution by forming Mg3[H5C2P2O7]2 hydrophilic chelate. Both of these effects remarkably contribute to the reversal of the serpentine surface potential to a negative potential. Due to electrostatic repulsion, the hetero-coagulation of negatively charged serpentine and negatively charged pyrite was broken, and the selective collecting capability of the PBX collector on the surface of pyrite was regained, allowing for the selective separation of pyrite and serpentine minerals. The application of HEDP in the actual ore (Peru copper ore BM1-type sample) sorting further demonstrated its good selective inhibition effect, and HEDP was able to enhance the grade and recovery of Cu and S in the concentrate while ensuring the reduction of Mg grade and recovery.

Identification Analysis of Fluid Type in the Low Resistivity Zone of Well Z-2 Field "Z", South Sumatera

Hydrocarbon reserves are one of the main points that are very important in the sustainability of the productivity of an oil and gas field. This important point is greatly influenced by several parameters that can be obtained by various measurements and analysis. One of the most influential parameters in the analyses of the amount of hydrocarbon reserves in a reservoir is the water saturation value. The water saturation parameter will also be greatly influenced by the electrical parameters of the fluid-containing rock in the reservoir. Sometimes the electrical parameters of this rock, in this case resistivity becomes one of the benchmark parameters, whether the zone or reservoir has potential or is interesting to be developed or produced. However, there are several reservoirs or zones that experience low resistivity effects which will give an initial indication that the zones or reservoirs are not attractive or have no effect on development. In this Z field, there is a zone that experiences low resistivity effects, making this zone unattractive for production. So to be able to make these zones attractive for production, an identification analysis was carried out on Zones A and B in this Z field to determine the type or type of fluid from the two zones. The initial analysis was carried out petrographically from rock sample incisions at certain depths in Zones A and B so that it is known that the cause of the low resistivity effect in the two zones is the presence of pyrite minerals and illite clay which are the main causes of the low resistivity effect. Furthermore, an analysis of the identification of fluid types was carried out using the double apparent resistivity method with the results obtained that in Zones A and B there are 2 types of fluids, namely hydrocarbons and water with a depth limit of 3650 ft in Zone A and 4558 ft in Zone B. By knowing the type of fluid, the hydrocarbons contained in these two zones should be able to increase interest in the production of these zones as a potential zone for production, but it is necessary to perforate at a depth range indicated by the hydrocarbon fluid and carry out initial production tests to prove the results of the analysis in this study.