Alteration Minerals Research Articles

Mapping Geothermal Indicator Minerals Using Fusion of Target Detection Algorithms

Mineral mapping from satellite images provides valuable insights into subsurface mineral alteration for geothermal exploration. In previous studies, eight fundamental algorithms were used for mineral mapping utilizing USGS spectra, a collection of reflectance spectra containing samples of minerals, rocks, and soils created by the USGS. We used an ASD FieldSpec 4 Hi-RES NG portable spectrometer to collect spectra for analyzing ASTER images of the Coso Geothermal Field. Then, we established the ground-truth information and the spectral library by analyzing 97 samples. Samples collected from the field were analyzed using the CSIRO TSG (The Spectral Geologist of the Commonwealth Scientific and Industrial Research Organization). Based on the mineralogy study, multiple high-purity spectra of geothermal alteration minerals were selected from collected data, including alunite, chalcedony, hematite, kaolinite, and opal. Eight mineral spectral target detection algorithms were applied to the preprocessed satellite data with a proposed local spectral library. We measured the highest overall accuracy of 87% for alunite, 95% for opal, 83% for chalcedony, 60% for hematite, and 96% for kaolinite out of these eight algorithms. Three, four, five, and eight algorithms were fused to extract mineral alteration with the obtained target detection results. The results prove that the fusion of algorithms gives better results than using individual ones. In conclusion, this paper discusses the significance of evaluating different mapping algorithms. It proposes a robust fusion approach to extract mineral maps as an indicator for geothermal exploration.

Integrated stratigraphical, hydrogeochemical, and geophysical studies to characterize the shallow groundwater aquifers in Wadi Araba area, western Gulf of Suez, Egypt

The construction of the New Galala City besides great mining (e.g., konoozmisr) and Seawater Reverse Osmosis Desalination Plant projects in the semiarid Gulf of Suez region of Egypt increases the demand for groundwater resources. So, the current research provides integrated stratigraphical, hydrogeochemical, and geophysical studies to investigate the shallow groundwater aquifers in Wadi Araba area on the western side of the Gulf of Suez. The stratigraphic column starts with pre-Cambrian basement rocks which are non-conformably overlain by sedimentary succession of Phanerozoic Erathem. A detailed land magnetic profile has been conducted and processed to estimate the aquifer’s geometrical parameters. This includes the subsurface spatial extension and thickness to delineate the prevailed subsurface structures in the study area. Lithostratigraphically, these aquifers are represented by the Paleozoic- lower Cretaceous siliciclastic-dominated sediments of the Nubia Group and fractured carbonate-dominated facies of the upper Cretaceous Galala Formation. Lithological characters, sedimentary facies (fluvial to shallow and open marine), microfacies types, and diagenesis processes (e.g., compaction, cementation, dissolution, and fracturing) are the main factors that affect the quality of the shallow aquifers in the study area. The main microfacies of the studied aquifers are quartz arenite, subarkose, sublitharenite, mudstone/wackestone, and packstone/grainstone. These facies are characterized by different primary and secondary porosities. According to the water sampling standard methods, nineteen groundwater samples were collected from the available hand-dug wells and springs from the Nubian sandstone aquifer and the Upper Cretaceous aquifer, respectively. Inductively coupled plasma–mass spectrometry (ICP–MS), titration, spectrophotometer and a flame photometer were used to obtain a complete chemical analysis. The results of hydrochemical analyses indicated that total dissolved solids (TDS) and concentrations of major ions as well in the lower Cretaceous aquifer increase toward the Gulf of Suez and in general higher than that of springs of the Upper Cretaceous Aquifer. The predominant factors influencing groundwater chemistry include seawater intrusion, evaporation, mineral alteration, dissolution of fossils, and ion exchange. Groundwater in the study area is unsuitable for drinking except in one sample and moderately suitable for irrigation with caution for higher salinity in samples located near the Gulf of Suez.

The application of PRISMA hyperspectral satellite imagery in the delineation of distinct hydrothermal alteration zones in the Chilean Andes: The Marimaca IOCG and the Río Blanco-Los Bronces Cu-Mo porphyry districts

This study provides an overview of the application of hyperspectral imagery acquired by the Italian satellite mission “PRecursore IperSpettrale della Missione Applicativa” (PRISMA), for mapping hydrothermal and supergene mineral alteration zones associated with different Cu deposits in the Chilean Andes. Study areas include the Marimaca Copper Project in the Naguayán district (Antofagasta Province), hosting Late Jurassic – Early Cretaceous iron oxide-copper–gold mineralizations and the Río Blanco-Los Bronces district (Santiago Region) known for its Late Miocene – Early Pliocene copper-molybdenum porphyry deposits. These mineral systems exhibit hydrothermal alteration haloes extending over several kilometers, with upward and outward mineral zonation.To characterize the surface-exposed alteration, the satellite imagery was processed using a multiple feature extraction workflow targeting the relative abundances and compositions of specific supergene and hydrothermal alteration minerals, including Fe-oxides and hydroxides (hematite-goethite), phyllosilicates (micas-kaolinite-chlorite), hydroxyl-bearing sulfates (alunite-natroalunite-jarosite) and epidote. The results reveal a zonation from proximal sulfates (natroalunite to alunite) and Al-rich white mica (ranging from 0.3 km-wide for the area identified to the east of the Marimaca deposit to 1 km-wide in correspondence of the Los Sulfatos deposit, respectively) to distal Al-poor white mica (0.2 to 0.5 km-wide, respectively) and an outer chlorite-epidote zone. In the Marimaca Project area, the structurally-controlled alteration evolves west to east from chlorite-rich to phengitic white mica (Al-poor). A NNE-SSW trending supergene leached cap covers a 6 km-long and up to 2 km-wide area from north to south. Our study documents how spaceborne hyperspectral imaging spectroscopy can support mineral exploration by enabling non-invasive reconnaissance mapping of the outcropping rocks, providing specific targeting information for follow-up field surveys and drilling campaigns.

Re-distribution and upgrade of metals induced by the superimposition of later magmatic fluids in the Archean Hongtoushan VMS deposit, NE China

The Hongtoushan copper-zinc deposit is a highly metamorphosed Archean volcanogenic massive sulfide deposit (VMS) in China. After metamorphism, the deposit underwent later fluid superimposition, which is of significance for the re-distribution of metals and upgrading ores. However, the hydrothermal modification mechanism and fluid source remain unclear due to the difficulties in accurately recognizing the mineral textures and assemblages formed by hydrothermal modification. In this study, the mineral texture was investigated to identify the modification mechanism of later fluid and in situ sulfur isotope and trace elements of chalcopyrite were tested to track the source of later fluid and metals. The dominant assemblage formed by superimposed fluid consisted of pyrite, chalcopyrite, sphalerite, minor galena, magnetite, calcite, anhydrite, and hydrothermal alteration minerals, i.e. sericite and chlorite. These minerals infilled the fractures in early pyrite porphyroblasts or precipitated along the grain boundary. Additionally, the pre-existing sulfides were corroded by these minerals. They exhibited replacement and porous textures, indicating that the superimposed fluids resulted in a dissolution-reprecipitation process and formed new sulfides. The hydrothermal metasomatism produced the sericitization of plagioclase and chlorization of biotite, which concurrently liberated silica to form silicification. These interactions suggested that the hydrothermal fluid is acid fluid. The chlorite geothermometer defined the formation temperature of 226–279°C, implying that the superimposed fluid has a moderate temperature. The chalcopyrite precipitated from superimposed fluid either coexisted with pyrite (Ccp 2a) or magnetite (Ccp 2b). The sulfur isotope of Ccp 2a defined a closing zero range (0.75–2.41‰), demonstrating the superimposed fluids were derived from magmatic fluids. In contrast, the Ccp 2b enriched heavy sulfur with a δ34S range of 4.10–8.63‰, which was attributed to the oxidation of fluids. Partial ferrous ions were oxidized to ferric iron, and ferrous and ferric iron precipitated as magnetite. The mineral assemblage changed from chalcopyrite + pyrite, followed by magnetite + chalcopyrite + pyrite, to magnetite + pyrrhotite, representing the local increase of the oxidation state of hydrothermal systems. During the oxidation process, the oxygen fugacity of the superimposed fluid decreased, whereas the pH increased. These results provide crucial evidence on the re-distribution pattern of metals and the post-hydrothermal modification process in the Hongtoushan Cu-Zn deposit.

Thermal-Induced Microstructure Deterioration of Egyptian Granodiorite and Associated Physico-Mechanical Responses.

Mineral transformations often induce microstructural deteriorations during temperature variations. Hence, it is crucial to understand why and how this microstructure weakens due to mineral alteration with temperature and the correlated physical and mechanical responses. Therefore, in this study, physical, chemical, thermal, petrographic, and mechanical analyses were carried out to comprehend better the thermal behaviors of Egyptian granodiorite exposed to temperatures as high as 800 °C. The experimental results indicate that the examined attributes change in three distinct temperature phases. Strength zone (up to 200 °C): During this phase, the temperature only slightly impacts the granodiorite mass loss and porosity, and the P-wave velocity and E slightly decrease. However, the rock structure was densified, which resulted in a minor increase in strength. After that, the transition zone (200-400 °C) was distinguished by the stability of most studied parameters. For instance, mass and porosity did not significantly alter, and the uniaxial compressive strength steadily increased with an axial failure mode. When the temperature rises, transgranular cracks cause the P-wave velocity and elastic modulus to decrease moderately. The decay zone started after 400 °C and continued to 800 °C. This zone is characterized by complicated factors that worsen the granodiorite properties, lead to color shift, and produce a shear failure mode. The properties of granodiorite became worse because of chemical reactions, structural and crystal water evaporation, rising thermal expansion coefficient variation, and quartz inversion at 575 °C (α to β, according to the differential thermal analysis). Thermal damage greatly affected granodiorite's physical and mechanical properties and microstructure at 800 °C. As a result, UCS measurements were extremely small with a complex failure pattern, making Vp and E unattainable.

Stability analysis of a granite-based geopolymer sealant for CO2 geosequestration: In-situ permeability and mechanical behavior while exposed to brine

When considering the use of geopolymers (GPs), as potential alternatives for Portland cement, high durability during exposure to brine at encountered downhole is a key requirement. This study delves into the response of a granite-based GP system designed especially for CO2-geosequestration upon exposure to brines with different concentrations of NaCl. Exposure was carried out by imposed flow in a triaxial apparatus, at 90 °C and 13.8 MPa confining pressure. Mechanical properties were tested in the same apparatus once exposure was completed. A suite of micro-scale analytical techniques was then used to assess the GP's microstructure, mineralogical composition, and chemical bonding. The obtained results revealed increasing compressive strength with increasing brine salinity, suggesting greater resistance to deformation and potential cracking. Concurrently, decreasing Poisson's ratios and increasing Young's moduli could lead to an elevated risk of mechanical failure under strain. In addition, following a 3-week injection period, permeability of NaCl-flooded samples decreased by 20%–35% from initial values. Analysis of the effluents showed fluctuations in the pH and ion content with time, mainly attributed to complex chemical interactions including cation exchange, silicate dissolution and hydrolysis, precipitation of alkali-enriched gels, and mineral alterations. Micro-scale analyses revealed that the improved durability is linked with the formation of new minerals, especially zeolites in the presence of NaCl or portlandite when deionized water was introduced. In conclusion, this study presents new data on the durability of a rock-based GP system when exposed to brine and elevated pressure and temperature, offering insights for optimization to downhole environments.

Loss of maternal calcitriol reversibly alters early offspring growth and skeletal development in mice.

Ablation of Cyp27b1 eliminates calcitriol but does not disturb fetal mineral homeostasis or skeletal development. However, independent of fetal genotypes, maternal loss of Cyp27b1 altered fetal mineral and hormonal levels compared to offspring of WT dams. We hypothesized that these maternal influences would alter postnatal skeletal development. Cyp27b1 null and WT females were mated to bear only Cyp27b1+/- offspring. Forty-eight hours after birth, pups were cross-fostered to dams of the same or opposite genotype that bore them. Maternal and offspring samples were collected on days 21 (weaning) and 42. Offspring measurements included minerals and hormones, BMC by DXA, ash weight and mineral content, gene expression, 3-point bending tests, and microCT. Maternal lactational behavior was evaluated. Milk was analyzed for nutritional content. At day 21, offspring fostered by nulls, independent of birth dam, had ~20% lower weight, BMC, ash weight, and ash calcium than pups fostered by WT dams. Adjustment for body weight accounted for the lower BMC but not the lower ash weight and ash calcium. Hormones and serum/urine minerals did not differ across offspring groups. Offspring fostered by nulls had shorter femurs and lower cortical thickness, mean polar moment of inertia, cortical area, trabecular bone volume, and trabecular number. Dam lactational behaviors and milk nutritional content did not differ between groups. At day 42, body weight, ash weight, lengths, BMC, and tibial bone strength were no longer different between pups fostered by null vs WT dams. In summary, pups fostered by Cyp27b1 nulls, regardless of birth dam, have proportionately smaller skeletons at 21d, impaired microstructure, but normal mineral homeostasis. The skeletal effects are largely recovered by day 42 (3 wk after weaning). In conclusion, maternal loss of calcitriol impairs early postnatal cortical bone growth and trabecular bone mass, but affected offspring catch up after weaning.

Plasma levels and dietary intake of minerals in patients with type 2 diabetes and chronic kidney disease: A case-control study

Background and aimDiabetic kidney disease (DKD) is the primary cause of chronic kidney disease (CKD) worldwide. Altered mineral levels leading to adverse outcomes are widely reported in diabetes but limited in DKD, in the Indian scenario, hence this study was taken up to address this issue. MethodsA hospital-based case-control study was taken up with 54 healthy controls (C) and 140 subjects with type 2 diabetes wherein 74 subjects with diabetes and CKD formed the DKD group, and 66 subjects with diabetes but no CKD formed the diabetic no-chronic kidney disease (DNCKD) group. High-resolution inductively coupled plasma mass spectrometry was used to evaluate the blood levels of minerals (calcium (Ca), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), and selenium (Se)), and a raw food-based food frequency questionnaire for dietary intakes. Estimated glomerular filtration rate (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation (mL/min/1.73 m2) and albuminuria. Spearman’s rank correlation was used to evaluate the relationship between the categorical variables. ResultsThe median values of plasma Ca in the DKD group were significantly lower compared with the DNCKD and C groups (10.5 mg/dL vs. 11.0 mg/dL and 11.7 mg/dL, p<0.001). Furthermore, plasma Ca levels lowered with declining kidney function, as evidenced by the eGFR and albuminuria segregation. Dietary intake of minerals did not correlate with the corresponding plasma levels. However, in the DKD group, eGFR correlated positively with the plasma levels of Ca (r= 0.422, p=0.001), Cr (r= 0.351, p=0.008), Mn (r= 0.338, p=0.011), Fe (r= 0.403, p=0.002), Cu (r= 0.274, p=0.041) and negatively with Se (r= −0.486, p<0.001). ConclusionPlasma Ca levels are lower in the DKD group with a strong positive association with eGFR, indicating its role in predicting the onset and progression of kidney function decline.

Assessment of potential cobalt zones by modeling radiometric and ASTER data using the AHP method: A case of the Bou Azzer El Grara inlier, Central Anti-Atlas, Morocco

The Bou Azzer El Grara inlier belongs to the Central Anti-Atlas range, renowned for its mineral deposits. The study carried out on the inlier aims to identify potential areas of cobalt mineralization based on a multi-source methodology of radiometric and remote sensing data processing. The data used includes hydrothermal alteration minerals (argillic, phyllic, propylitic, iron oxides) mapped with Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery using band ratio and principal component analysis (PCA) techniques, potassium enrichment zones through K/eTh and K/eU ratios calculated from radiometric data, as well as geological data (serpentinite outcrops and geological faults). The analytic hierarchy process (AHP) was used to combine the various thematic layers. Validation was carried out through the field studies in several anomalous zones. The mineral prospectivity map generated highlights nine major zones that appear the most favorable for mineralization, some of which coincide with zones in production and others requiring further exploration.

Timing and Mechanism of Ore Precipitation in Porphyry Cu Systems: Insight from LA-ICP-MS Analysis of Fluid Inclusions and In Situ Oxygen Isotope Analysis of Hydrothermal Quartz at Zhunuo Porphyry Cu Deposit, China

Abstract The timing and mechanism of ore precipitation in porphyry copper systems are hot topics and remain controversial. The large Miocene collision-related Zhunuo porphyry Cu deposit in the Gangdese belt of southern Tibet, China, was produced by multistage quartz veining and hydrothermal alteration, accompanied by Cu sulfide precipitation. In this study, we have combined cathodoluminescence (CL) petrography with in situ oxygen isotope analysis and fluid inclusion microthermometry and laser ablation-inductively coupled plasma-mass spectrometer microanalysis to constrain the growth history of individual quartz veins, the source and evolution of the hydrothermal fluids, and the timing and mechanism of ore precipitation at Zhunuo. Early quartz A veins associated with potassic alteration are composed of quartz, K-feldspar, biotite, Cu-Fe sulfides, and pyrite. Quartz B veins are composed of quartz, Cu-Fe sulfides, molybdenite, and pyrite. CL imaging shows that quartz grains in the A and B veins consist of abundant early generation of bright-luminescent quartz (QA and QB) with volumetrically minor later generation of dull-luminescent quartz (QA-crack and QB-crack) occurring in the voids or at the margins of the QA and QB veins with embayed contacts. Cu-Fe sulfides are generally in contact with the dull-luminescent quartz and locally in contact with the bright-luminescent quartz and K-feldspar in the A and B veins or occur as disseminations in the potassic-altered porphyries that have been overprinted by chlorite ± muscovite alteration. QA and QB contain single-phase intermediate-density inclusions and abundant brine and vapor-rich inclusions. A boiling assemblage in QA has a homogenization temperature of ~560°C and trapping pressure of ~530 bar. Two boiling assemblages in QB have homogenization temperatures of ~440°C with trapping pressures of ~230 and ~250 bar, indicating a transition from lithostatic to hydrostatic conditions at a paleodepth of ~2.0 to 2.5 km. QA-crack and QB-crack contain aqueous inclusions with lower homogenization temperatures of 340° to 400°C and salinities of 6 to 12 wt % NaCl equiv. In situ oxygen isotopes indicate that QA and QB have δ18O values of 7.6 to 11.4‰, whereas QA-crack and QB-crack have δ18O values of –7.2 to 6.7‰. Combined with fluid inclusion compositions, we propose that condensation of vapors into brines and mixing with 25 to 60% meteoric water can produce the salinity and oxygen isotopes of fluids that caused the dissolution of the early bright-luminescent quartz and the precipitation of the later dull-luminescent quartz. Zhunuo Cu-Fe sulfides are in contact with the bright-luminescent quartz and cut the growth bands. The dull-luminescent quartz in contact with the Cu-Fe sulfides has oscillatory growth banding. In addition, Cu-Fe sulfides in the A and B veins or in the potassic-altered rocks coexist with chlorite ± muscovite alteration minerals. These geologic observations, together with evidence that there is an abrupt drop in the Cu/(Na + K) ratio by more than one order of magnitude in the aqueous fluids within the dull-luminescent quartz compared to the brines within the bright-luminescent quartz, indicate that precipitation of Cu-Fe sulfides occurred after the potassic alteration stage and during the chlorite ± muscovite alteration stage. Ore precipitation was associated with mixing of magmatic fluids (brines + vapors) with meteoric water, accompanied by fluid cooling, salinity decrease, and retrograde quartz solubility as the rocks transitioned from lithostatic to hydrostatic conditions. During continued cooling in the latest stage, the hydrothermal fluids precipitated D veins that contain abundant pyrite with minor quartz. Quartz in the D veins (QD) contains aqueous inclusions with much lower temperatures and Cu/(Na + K) ratios, indicating that most of the Cu-Fe sulfides have been precipitated during this stage.

Mineralogy and Sr Isotope Characteristics of Dahua Stratified Tremolite Nephrite and Host Rocks, Guangxi Province, China

The tremolite nephrite deposit in Dahua county, Hechi City, Guangxi province, China is a new genetic type of nephrite deposit. It is hosed by Mg-poor limestone (~1.30 wt.% MgO) and intruded by diabase (~45 wt.% SiO2). The Mg and Si contents of these rocks are lower than those of the tremolite (58.18 wt.% SiO2, 13.18 wt.% CaO, 24.16 wt.% MgO), indicating an obviously insufficient source for the metallogenic material that generated the deposit. In particular, some tremolite nephrite ore bodies have no clear contact metamorphism between the host and intrusive rocks, which have the characteristics of stratified mineralization (stratified tremolite nephrite). The origin and mineralization of stratified tremolite nephrite remain poorly constrained. To address this shortcoming, the mineralogy, geochemistry and Sr isotopic of host rock, altered marble, stratified tremolite nephrite and intrusive rock in the Dahua stratified tremolite nephrite deposit were studied. The results show: stratified tremolite nephrite mainly consists of aggregates of microcrystalline-cryptocrystalline tremolites with content exceeding 95%. The in situ rare earth elements (REEs) distribution pattern of hydrothermal calcite in the contact position between stratified tremolite nephrite and marble is similar to that of marine carbonate rock, showing obvious enrichment of HREE, which is different from calcite in limestone and marble. 87Sr/86Sr of stratified tremolite nephrite is relatively uniform, with an average value of 0.7070, within the range of Permian seawater. The mean value of Y/Ho in the hydrothermal calcite is 51.24, indicating that the marine fluid has not been impregnated by terrigenous materials. In summary, the hydrothermal fluid rich in Ca and Si is formed after marine carbonate rocks are altered by marine fluids. Hydrothermal fluids alter diabase rocks formed by altered minerals like titanite, chamosite, zoisite, etc. This process leads to the formation of metallogenic hydrothermal fluids abundant in Si, Ca, Fe and Mg. The metallogenic hydrothermal fluids migrate in faults and fractures of marble and crystallize to form tremolite nephrite under suitable ore-forming conditions.

Chemical Reactivity and Alteration of Pyrite Mineral in the Kubi Gold Concession in Ghana

Pyrite is the most common among the group of sulfide minerals in the Earth and abundant in most geological settings. This gangue mineral in association with garnet, hematite, magnetite, and other sulfide minerals acts as an indicator mineral in the Kubi concession of the Asante Gold corporation in Ghana. X-ray diffraction (XRD), air annealing in a furnace, energy-dispersive x-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) were applied to investigate the crystal structure, identify individual elements, permanence, transformation, and chemical/electronic properties of such pyrite. The study aims to identify individual elements and to gain an understanding of the surface reaction mechanisms, as well as the properties of precipitated pyrite particles observed during the hydrothermal formation of the ore deposit. XRD shows that pristine and annealed samples contain some hematite and quartz besides pyrite. Results from air annealing indicate that the relationship between pyrite and hematite-magnetite is controlled by temperature. EDX reveals that the sample has O and C as contaminants, while XPS in addition reveals Ba, Au, P, Al, and N. These elements are attributed to pyrite that bonds metallically or covalently to neighboring ligands/impurity minerals such as oxides, chalcogenide sulfides, as well as the gangue alteration minerals of magnetite and hematite in the pyrite sample.These findings suggest that during the hydrothermal flow regime, pyrite, pathfinder elements, and impurity minerals/metals were in contact with quartz minerals before undergoing hematite transformation, which thus becomes an indicator mineral in the Kubi gold concession.

Comparative lithology and alteration mineral chemistry of host rocks at the Seabee Gold Operation, northern Saskatchewan, Canada: Implications for a connected orogenic gold-mineralizing system

The Seabee Gold Operation, located in northern Saskatchewan, Canada, hosts the Santoy and Seabee gold deposits, as well as the Fisher property; the latter is an important exploration target. This gold mineralization is hosted in rocks of the Pine Lake greenstone belt that is within the Glennie domain of the larger Paleoproterozoic Trans-Hudson orogen. Mineralization is focused within shear zones, including the Santoy shear system that extends south onto the Fisher property. The role of ore-adjacent intrusions, systematics of gold mineralization, and relationship between the mineralization of the properties are largely undefined. In this study, hydrothermally-altered samples from locations along the Santoy shear system, namely the Santoy 7, Santoy Gap, and the Fisher property, were analyzed to identify and compare the mineralogical and geochemical characteristics related to sulfide-gold mineralization and associated alteration.The altered host rocks primarily comprise upper greenschist to lower amphibolite-grade sheared metabasalt to chlorite-hornblende-biotite ± garnet schist, and intrusive rocks dominated by granodiorite and tonalite. These lithologies are cut by similar quartz vein generations and are associated with similar alteration assemblages and mineralization, including (i) syn-late-D3 “distal” (∼0.4 to 3 m wide) sericite-biotite-chlorite-clinozoisite ± albite, titanite to vein-adjacent coarse-grained diopside-K-feldspar-albite-actinolite ± apatite, titanite calc-silicate alteration, associated with main-stage Py2a, 2b-Cpy2-Po1-Au (syn-late-D3) mineralization; (ii) remobilized, fracture-filling Py3-Po2-Cpy3-Au-BiTel (late-D3) mineralization within the calc-silicate assemblage; and (iii) early colloform Py1a (pre-syn-D3) and intrusion-hosted, inclusion-rich Py1b (pre-D3). Microprobe analyses reveal similar mineralogical trends between Fisher and Santoy alteration minerals typical of orogenic gold systems. Empirical geothermobarometric calculations of gold-associated vein-adjacent and vein-hosted chlorite and biotite exhibit orogenic-style formation conditions (∼320–330 °C, 3 kbar, ∼9 km depth). As such, these analyses suggest that the Fisher property and Santoy Mine Complex underwent inter-connected, multi-stage hydrothermal processes. These stages comprise (i) a potential early introduction of gold into the system closer to the timing of plutonism (Py1b magmatic-hydrothermal; pre-D1) or during the onset of gold mineralization (Py1a; orogenic; late-D2 to early-syn-D3) during the evolution of the Reindeer zone; (ii) orogenic main-stage mineralization (syn-late-D3) concurrent with late- to post- collisional deformation throughout the Reindeer zone; and (iii) remobilization during continuous deformation (late-D3) where elevated cyclical fluid fluxes and higher fracture density at Santoy produced higher-grade mineralization.

Alteration Mapping for Porphyry Cu Targeting in the Western Chagai Belt, Pakistan, Using ZY1-02D Spaceborne Hyperspectral Data

Abstract The Chagai porphyry Cu belt in Pakistan is an important metallogenic terrain extending approximately 400 km in an east-west direction. Most of the known porphyry Cu deposits, such as the world-class Reko Diq deposit and Saindak deposit, are located in the western Chagai belt. In this study, the ZY1-02D hyperspectral data acquired by a recently launched spaceborne imaging spectrometer with 166 bands within a 0.4- to 2.5-μm spectral region were used to map mineral information over 8,000 km2 for exploring potential targets of porphyry Cu mineralization in the western Chagai belt. False color composite, spectral angle mapper, and wavelength position mapping methods were used in this research leading to the identification of a series of alteration minerals (including muscovite [sericite], kaolinite, alunite, epidote, chlorite, and calcite) from ZY1-02D data. The alteration mineral maps derived from ZY1-02D data match well with the known deposits and field inspections. Twenty-three new targets were identified as potential porphyry Cu mineralization targets for further exploration in the study area. Three targets, north of Saindak, Koh-i-Sultan, and Durban Chah, and six alteration sites in the southwest of Durban Chah, were inspected in the field, and Cu-Au mineralization was confirmed in all these inspected areas. As the ZY1-02D hyperspectral data covers most of the land area of the earth, this study provides new insights for mineral exploration and lithologic mapping in remote regions.

Efficacy of Three Remineralizing Agents on Erosion of Root Dentin by Cola Drink: An In Vitro Study

Abstract Objective The aim of the study was to investigate the effects of silver diamine fluoride (38% SDF), sodium fluoride (NaF) varnish, and casein phosphopeptide-amorphous calcium phosphate fluoride (CPP-ACPF) on cola-eroded root dentin microhardness and mineral alteration in vitro. Materials and Methods Forty human root dentin slabs were exposed to alternating 10 cycles of cola drink and artificial saliva, repeated 3 times at 6-hour intervals. Specimens were randomly assigned to four groups: control (deionized water), 38% SDF, NaF varnish, and CPP-ACPF. All specimens underwent the second erosion process. Microhardness was measured at baseline (KHN0), pretreatment (KHN1), and posttreatment (KHN2). The mean difference of microhardness (ΔKHN2-1) was analyzed using one-way analysis of variance (ANOVA) and Tukey's post hoc tests (α = 0.05). The chemical composition and surface morphology were assessed using energy dispersive spectroscopy (EDS) and scanning electron microscope (SEM). Results All experimental groups exhibited dentinal tubule occlusion. Both 38% SDF and NaF varnish demonstrated a statistically significant increase in microhardness compared to CPP-ACPF. However, CPP-ACPF was comparable to the control group. EDS analysis showed an increase in weight percentage of fluorine in all groups. Furthermore, silver and chlorine were detected in the 38% SDF group. Conclusion All treatments enhanced eroded root dentin microhardness, with 38% SDF and NaF varnish demonstrating superior acid resistance and preventing morphological changes induced by cola re-immersion.

Weathering alteration in the Antarctic environment as seen in the Miller Range (MIL) 090030 Martian meteorite

Abstract The analysis of Martian meteorites is a key research to understand the mineralogical composition of Mars. However, they suffer different types of alteration due to the environment where they fall on Earth. These differences should be identified in order to characterize correctly the original Martian compounds. Most of the meteorites found on Earth are collected in Antarctica where the environmental conditions are such that, in general and based on many previous investigations, produce fewer alterations compared with other terrestrial environments such as hot deserts. In this study, the weathering alterations of minerals from the MIL 090030 Martian Nakhlite found in Antarctica were analyzed to determine which minerals are formed by Antarctic environmental conditions. It was confirmed that the south-polar region environment can contaminate Martian meteorites and, in this study, several minerals like halite, nitratine and niter, were detected as weathering alteration products that have not been referenced in the literature before.

Selection of Landsat-8 Operational Land Imager (OLI) Optimal Band Combinations for Mapping Alteration Zones

In typical alteration extraction methods, e.g., band math and principal component analysis (PCA), the bands or band combinations unitized to extract altered minerals are usually selected based on empirical models or previous rules. This results in significant differences in the alteration of mineral mapping even in the same area, thus greatly increasing the uncertainty of mineral resource prediction. In this paper, an intelligent alteration extraction approach was proposed in which an optimization algorithm, i.e., a genetic algorithm (GA), was introduced into the PCA; this approach is termed GA-PCA and is used for selecting the optimized band combinations of mineralized alterations. The proposed GA-PCA was employed to map iron oxides and hydroxyl minerals using the most commonly adopted multispectral data, i.e., Landsat-8 OLI data, at the Lalingzaohuo polymetallic deposits, China. The results showed that the spectral characteristics of GA-PCA-selected OLI band combinations in the research area were beneficial for enhancing alteration information and were more capable of suppressing the interference of vegetation information. The mapping alteration zones using the GA-PCA approach had a higher agreement with known ore spots, i.e., 25% and 33.3% in ferrous-bearing and hydroxyl-bearing deposits, compared to the classical PCA. Furthermore, two predicted targets (not shown in the classical PCA results) were precisely obtained via analyzing the GA-PCA alteration maps combined with the ore-forming geological conditions of the mine and its tectonic characteristics. This indicated that the intelligent selection of mineral alteration band combinations increased the reliability of remote sensing-based mineral exploration.

Study on the Hydrothermal Superposition Period: Mineralization–Alteration Zoning Model and Zoning Mechanism of the Dahongshan Fe-Cu Deposit in Yunnan Province

The Dahongshan large-scale iron (Fe)–copper (Cu) polymetallic deposit is in the Proterozoic metallogenic domain on the western margin of the Yangtze Block. It is a typical representative of Fe-Cu polymetallic composite mineralization in the Kangdian area. The deposit comprises a group of layered orebodies formed by volcanic exhalation sedimentation and metamorphism, and a group of vein-like orebodies formed by hydrothermal superposition. The large-scale mapping of altered lithofacies in the deposit has resolved issues of weak links and unclear mineralization and alteration zoning of hydrothermal superimposed deposits within the study area. The mineralization type, hydrothermal alteration type and intensity, mineral assemblage, and mineral structure of the vein-type Cu polymetallic deposits during the hydrothermal superposition period are meticulously analyzed and studied. Finally, the zoning relationships of vein orebodies (mineralization) are summarized. On the basis of the results of the study of the distribution pattern of this mineral body, a mineralization alteration zoning model of the hydrothermal superposition period is constructed. The results show that the alteration is primarily silicification, carbonation, and chloritization, and the mineralization is chalcopyrite, bornite, chalcocite, and pyrite. The Dibadu anticline and the cutting layer faults and fractures strictly control the hydrothermal alteration zoning. The mineralization alteration zoning from the core to the flank is divided into coarse vein zone (I) → stockwork zone (II) → veinlet zone (III). The corresponding mineral assemblages are quartz–calcite–chalcocite–bornite–(native copper) (I) → calcite–dolomite–quartz–bornite–chalcopyrite–chlorite (II) → dolomite–quartz–chalcopyrite–(pyrite) (III), where the stockwork zone has the most substantial mineralization. The mineral assemblages of each alteration zone, the characteristics of rare earth elements of typical samples, and the test results on the fluid inclusions confirm that pH and Eh primarily control the zoning mechanism. This study has significance for deepening the understanding of the composite metallogenic system, guiding deep and peripheral prospecting, and providing significant enlightenment for the study of this type of deposit.

Lineaments Characterization and their Tectonic Significance in Mineralization using Landsat TM Data and Field Studies along Mambilla Plateau, Northeast, Nigeria

Lineament characterization and their tectonic significance in mineralization using Landsat TM data and field studies Along the Mambilla Plateau and environs, northeast Nigeria .The area forms part of the mineralized shear zone of the Northeastern, part of the Basement Complex. The Basement Complex rocks underlie more than two-thirds of the plateau and date back to the Precambrian to early Paleozoic eras. While the remaining part of the plateau and its surroundings are made up of volcanic rocks of the upper Cenozoic to Tertiary and Quaternary ages. Remote sensing imagery data and field measurements were integrated for mapping the structural elements and hydrothermal alteration zones related to mineralization. Tectonically the lineaments trends NE-SW, NNW-SSE, NW-SE, and NS, are the main trends controlling mineralization in the area based on data from remote sensing and field measurements. On the other hand, applying band ratios and the constrained energy minimization (CEM) technique to Landsat-8 data pointed out alteration minerals associated with the hydrothermal fluids. Silica, sericite, and chlorite are the common alteration minerals detected, while goethite and epidote are less common in the alteration zones of the area under study. A combination of CET structural complexity, circular features, and alteration zones produced a potential mineralization map, pointing out numerous prospective zones for mineralization that are proximate to areas where artisanal mining activities are carried out. The predictive map was validated by projecting the known prospect zones in the study area, reflecting an agreement between the known occurrences and the higher classes of the predictive zone. The techniques in the current research can be adopted as a direct indicator for structural mapping and detecting alteration zones related to mineralization elsewhere.

Halogen Cycling in the Solid Earth

Each of the halogens constrains a different aspect of volatile cycling in the solid Earth. F is moderately incompatible in the mantle and has a low mobility at Earth's surface, meaning that it is preferentially retained in the mantle and continental crust. In contrast, Cl, Br, and I are strongly incompatible and highly soluble. Chloride is the dominant anion in seawater and many geofluids and a major component of evaporite minerals. Br and I are essential for life and significantly incorporated into organic matter that accumulates in marine sediments. Surficial fluids circulated into continental and oceanic crust incorporate surface-derived halogens into alteration minerals. As a result, subducting slabs and arc lavas are weakly enriched in F and strongly enriched in Cl, Br, and I. Subduction has maintained mantle Cl and Br concentrations at relatively constant levels since Earth's early differentiation, but mantle I/Cl has decreased over time. ▪Halogen abundances on the early Earth were affected by I partitioning into Earth's core and possible loss of hydrophilic Cl, Br, and I in an early formed ocean.▪Halogens are powerful tracers of subduction zone processes on the modern Earth, with Cl, Br, and I having a dominantly subducted origin in Earth's mantle.▪The deep subduction cycles of Cl, Br, and I are more similar to that of H2O than they are to F, but the geochemical cycle of each halogen differs in detail.▪Halogen abundance ratios and stable isotope ratios vary systematically in Earth's surface reservoirs, meaning that halogens are powerful tracers of geological fluids and melts.