Alteration Zones Research Articles

Petrophysics applied in mineralizations, hydrothermal alterations and lithology mapping: A case study from the Zn–Pb (Cu–Ag) epithermal deposit of Santa Maria, Brazil

ABSTRACTThe epithermal Zn–Pb (Cu–Ag) deposit of Santa Maria represents a distal magmatic‐hydrothermal system, whose mineralizations are controlled by fault systems located in the sedimentary units of the upper Camaquã Basin, above the tectonic units of the Sul‐Riograndense Shield. The hydrothermal alteration zones contain illite, chlorite and pyrite, besides galena, sphalerite, chalcopyrite and bornite. To improve the knowledge of this mineral system, this work investigated the petrophysical footprints of samples representing the predominant lithology, altered rocks and hydrothermal mineralization. The core samples of the predominant lithology, altered rocks and hydrothermal deposit mineralizations were used to determine the following petrophysical properties, density, magnetic susceptibility, primary wave velocity, resistivity, conductivity and chargeability. Moreover, the quantitative evaluation of minerals by scanning electron microscopy coupled with an automated image analysis system allowed us to map lithological and alteration processes. The results indicate density as the most effective physical property to map lithology, hydrothermal alteration and the Zn–Pb (Cu–Au) mineralization. Furthermore, all studied physical properties have moderate effectiveness in the alteration zones of known geological and geophysical anomalies in the Santa Maria deposit. Chargeability could be used, especially when sulphides are disseminated, but additional geological factors complicate its interpretation. The mineralogical and petrophysical diversity of the Santa Maria deposit provided vital data for geological–geophysical interpretations while allowing the creation of a key exploration plan to investigate the Zn–Pb (Cu–Au) mineralization. Finally, petrophysics should be used in prospection to help understand complex geological processes, their overlapping subpopulations and to accelerate mineral research while reducing the use of technical and financial resources and expenditure on ineffective geophysical methodologies.

Gold prospectivity mapping and exploration targeting in Hutti-Maski schist belt, India: Synergistic application of Weights-of-Evidence (WOE), Fuzzy Logic (FL) and hybrid (WOE-FL) models

Our study attempts to map gold prospectivity for deriving optimal exploration targets using data-driven, knowledge-driven and hybrid approaches. Prospectivity models viz. Weights of Evidence (WOE), Fuzzy Logic (FL) and a hybrid model that combines the data-driven and knowledge-driven components (WOE-FL) were applied to a part of the auriferous Hutti-Maski schist belt of 1352 km2 area with 20 known gold occurrences. With a pixel resolution of 500 m, 16 spatial evidential raster layers were created on a GIS platform encompassing viable predictive indicators, critical in gold exploration. Modelling inputs include essential ingredients and mappable criteria of the conceived orogenic gold mineral system in the study area. Multi-source geological data such as lithostratigraphic units, favourable litho-contacts, structural deformation sites, geochemical anomalies of selected gold pathfinder elements, and hydrothermal alteration zones derived from digital image processing of Landsat 8 OLI satellite imagery were integrated to generate prospectivity maps for delineation of future targets. A quantitative evaluation of the resulting three prospectivity maps was performed using concentration-area (C-A) fractal analysis, prediction–area (P–A) plot, fitting-rate curve (FRC) and area under curve (AUC). Comparative analysis indicates that the performance of the hybrid model (WOE-FL) stands out to be the most efficient, with a prediction rate of 87% and AUC of 91.40% compared to WOE and FL. A risk assessment was performed combining the outputs of prospectivity models that returned 10% of the study area as potential exploration targets out of which the low-risk exploration targets comprises merely 4.5% representing the optimal targets for gold exploration in the study area.

Geology and geochronology of the Don Javier Cu-Mo porphyry deposit, southern Peru

The Don Javier porphyry Cu-Mo deposit is located in the Yarabamba district of the Arequipa region, Peru, which represents the northwestern end of the Paleocene-early Eocene Cu belt of the central Andes, extending from northern Chile into southwestern Peru. The deposit occurs around the contacts of a dacite porphyry stock emplaced into the pre-mineralization and Yarabamba granodiorite batholith. The intrusions display a telescoped sequence of alteration, from shallow sericitic to deeper chloritic-sericitic, with minor remnant potassic assemblages, which are surrounded by propylitic zones. EB-, M-, EQ-, SQ-, and D-type veinlets occur in all alteration zones. The higher Cu and Mo grades are mainly associated with the widely distributed sulfide-quartz veinlets within the potassic and chlorite-sericite overlapping zones. The mineralized zone measures ∼500 m in width (NE-SW) by ∼800 m in length (NW-SE). Uranium-Pb zircon ages show that the Yarabamba granodiorite plutons were emplaced at ∼ 64.6 Ma and subsequently intruded by the inter-mineralization dacite porphyry intrusions at ∼ 59.9 to 59.5 Ma. Molybdenite Re-Os ages indicate that the deposit formed between ∼ 60.5 and 59.6 Ma. Younger molybdenite Re-Os ages (∼45.4 to 44.4 Ma) obtained in the deep parts of the altered rocks suggest that the deposit might have been overprinted by later hydrothermal activity in the Eocene. The success of exploration at Don Javier emphasizes that traditional methods such as geologic and geophysical mapping followed by timely drilling tests can still be effective in a mature metallogenic belt.

Alteration Characteristics and Precious Metal Availability in Gunung Gembes & Surroundings, Jeruk Village, Pacitan Regency, East Java Province

The research area is located in the area of Mount Gembes, Jeruk Village in Pacitan (East Java). This study aims to determine the characteristic and temperature in the formation of alteration which refers to petrography with the help of samples taken in the study area. The petrographic observations carried out were thin section observations which were then analyzed for the mineral content contained in the sample rock. After knowing the minerals contained in the sample rock, it is then entered into the mineral formation temperature diagram (White & Hedenquist, 1995). The method used in this study includes primary data in the form of geological observations such as lithology, geological structure geomorphology, environmental geology and alteration observations and combined with secondary data. Alteration observations in this study were carried out descriptively (megascopic) and subjective (microscopic). The geomorphic unit that works is of volcanic origin, with high hilly sub-units of porphyry dacite intrusion (volcanic neck). Geological structures that develop in the study area are faults, namely the left horizontal fault of Jeruk 1, the left horizontal fault of Jeruk 2 and the interpretation of the oranges right horizontal fault. Geological resources or sources found in the research area are mineral potential resources that are economical, and negative sources are in the form of mass movement of debris flow type. The Zonation and the type of alteration that developed in the research area are the clay alteration zone and silicification. The clay zone is formed at a temperature >100⁰C-220⁰C with a pH of 3-5 and a silicification zone is formed at a temperature>100⁰C-300⁰C with a pH <2 which is directly controlled by the faults found in the study site.

Impact of fluorine-bearing hydrothermal fluid on deep burial carbonate reservoirs: A case study from the Tazhong area of Tarim Basin, northwest China

Deep burial carbonate reservoirs (>4000 m) have great potential of reserves for oil and gas exploration, although the matrix reservoirs generally become extremely heterogeneous and tight due to various diagenesis. Hydrothermal dissolution is supposed to be important for formation of high-quality deep burial carbonate reservoirs. However, few studies have focused on influence of minor fluorine-bearing fluid on carbonate reservoir quality. This study integrates petrography, geochemistry and fluid inclusion data to understand impact of fluorine-bearing fluid on deep burial carbonate reservoirs. Mineralogy and mineral distribution suggest that fluorite and concomitant calcite are found in the Ordovician and Cambrian strata of the whole Tazhong area, especially in the vicinity of faults. Calcite associated with fluorite is probably derived from progressive mixture between formation water and fluorine-bearing hydrothermal fluid, which is supported by REY pattern of concomitant calcite, surrounding limestone and fluorite, and fluid inclusion microthermometric data of concomitant calcite and fluorite. Fluorine-bearing hydrothermal fluid was responsible for the concomitant C2 calcite of high Y/Ho ratio. Therefore, the superchondritic Y/Ho ratio of concomitant calcite can be probably used as proxy for identifying distribution of minor fluorine-bearing hydrothermal fluid. For thick fluorite bed, influx of fluorite-rich fluid resulted in surrounding limestone dissolution and altered zones between fluorite and limestone. This process simultaneously improves porosity and permeability of high-energy sedimentary facies reservoirs. In contrast, the fluorine-rich hydrothermal fluid through the low-energy sedimentary facies mainly enhanced permeability of the tight carbonate reservoirs rather than porosity. For widespread tight reservoir of high-energy and low-energy sedimentary facies, even minor fluorite-bearing fluids still enhance permeability. The fluorine-bearing hydrothermal fluid may influence carbonate reservoirs away from hydrothermal-altered zones. Significance of minor fluorine-bearing hydrothermal fluid for widespread tight carbonates has probably been underestimated for deep burial carbonate reservoir.

Interpretation of Airborne Gravity Data over Kushaka Schist Belt, Northwestern Nigeria

The Kushaka Schist Belt has a peculiar importance due to its minerological potential. The area is located on the Latitudes 10°30’-110 and Longitude 6°30’-7° in the northwestern part of Nigeria. Kushaka airborne dataset (Sheet 222) obtained from Nigerian Geological Survey Aagency was interpreted to delineate litho- structural architectures that could favour the exploitation of potential economic minerals over the area. The analyzed results of the bouguer map of Kushaka show the distribution of the gravity anomalies and magnitudes of the concealed shear and weak zones being characterized by low to very high gravity anomalies. The upward continued bouger anomaly map at distance of 3000m reveal the regional trends so as to generate a subsequent residual field where several filtering operations were carried out. Several enhancement techniques were carried out on the airborne gravity data to reveal the locations, edges/boundaries, trends, and depths of gravity anomalies. The analytic signal gravity and its superimposed maps reveal areas with low to high amplitude signals. Low amplitude regions are suggested to be dominated by highly fractured schistose, quartzitic rocks and fractures. On the other hand, high amplitude regions are likely occupied by denser biotite granitic and gneissic rocks. Also, the First Vertical Derivative gravity anomaly map shows low gravity region which indicate the presence of fracture. The horizontal gravity gradient map shows high, positive gravity regions which may be attributed to the presence of a regional structure trend in the area. Low gradient anomalies can also denote presence of graben-like structures or other geological depressions. The depth analysis over Kushaka schist Belt suggests depth to top for shallow bodies ranging from 385m to 560 m with an average depth of 440.55 m while the deep sources have depths ranging from 1910m to 2480m with an average depth of 2111.1m. The obtained Euler anomalies depths ranged from <2607m to >5858m suggesting that mineralization around the study area is structurally controlled, an evidence of hydrothermal alteration zones. The structural solution (S.I=0) result displays two NW-SE trending short linear features, an indication of tectonic metamorphic phases of Pan-African orogeny that harbor mineralization. The results therefore, suggested intensed deformation of the basement rocks with tectonic framework suitable for mineralization.

Unravelling the hydrothermal system of Laguna del Maule restless volcanic field, in the Andean Southern Volcanic Zone (36° 10′S)

Laguna del Maule Volcanic Field (LdMVF, 36° 10′ S), located in the Southern Andean Volcanic Zone, concentrates an extraordinary postglacial (<25 ka) rhyolitic volcanism and records one of the highest world rates of surface uplift (>20 cm/yr since 2007). Different papers have been published concerning magmatism and geophysical survey but no research has been performed concerning the associated hydrothermal system present in the area. In this work, we analyze both past and present-day hydrothermal manifestations present in the LdMVF. Seven hydrothermal fossil alteration zones were described, with different mineral assemblages suggesting paleo-fluids temperatures ranging between 150 °C - 250 °C for hydrothermal alteration. Additionally, five active fluid discharge zones were also recognized. Based on their spatial distribution, and new data on surficial water/gas geochemistry including stable isotopic composition (δ18O-δD-H2O and δ13C-CO2), the Laguna del Maule Hydrothermal System is here defined. A conceptual two-layer model is proposed, which consists in a deep reservoir with estimated temperature of 178 °C -195 °C and over this a shallow aquifer system with temperature of 116 °C -143 °C. Water composition from outflow zones revealed fluid-rock interaction, due to carbonates and sulphates dissolution of Mesozoic sedimentary units. The upflow fluid discharges, which are spatially coincident with the ongoing surface uplift, provides geochemical evidence of deep origin, and consequently the arrival of fluids capable of increasing pressure in the upper crust. The spatial distribution of both past and present hydrothermal manifestations suggests a strong structural control promoting fluid circulation due to enhanced permeability, throughout the entire lifetime of the volcanic field.

Physiological TLR4 regulation in human fetal membranes as an explicative mechanism of a pathological preterm case.

The integrity of human fetal membranes is crucial for harmonious fetal development throughout pregnancy. Their premature rupture is often the consequence of a physiological phenomenon that has been exacerbated. Beyond all the implied biological processes, inflammation is of primary importance and is qualified as 'sterile' at the end of pregnancy. In this study, complementary methylomic and transcriptomic strategies on amnion and choriodecidua explants obtained from the altered (cervix zone) and intact fetal membranes at term and before labour were used. By cross-analysing genome-wide studies strengthened by in vitro experiments, we deciphered how the expression of toll-like receptor 4 (TLR4), an actor in pathological fetal membrane rupture, is controlled. Indeed, it is differentially regulated in the altered zone and between both layers by a dual mechanism: (1) the methylation of TLR4 and miRNA promoters and (2) targeting by miRNA (let-7a-2 and miR-125b-1) acting on the 3'-UTR of TLR4. Consequently, this study demonstrates that fine regulation of TLR4 is required for sterile inflammation establishment at the end of pregnancy and that it may be dysregulated in the pathological premature rupture of membranes.

Active structures and thermal state of the Piton de la Fournaise summit revealed by combined UAV magnetic and thermal infrared measurements

In this study, we demonstrate the strong potential of combining Unmanned Aerial Vehicle (UAV)-based thermal infrared (IR) and magnetic measurements to image the thermal state of volcanic edifices, as well as the distribution of active volcano-tectonic features at depth. Since magnetization is strongly dependent on temperature and alteration, thermally active structures are also associated with a decrease in magnetization. Based on the analysis of recent combined magnetic and infrared acquisitions, we focus on the recent evolution of the summit activity at Piton de la Fournaise. The comparison clearly highlights zones of major thermal activity, alteration and high permeability, and potentially areas of low mechanical resistance. Those observations provide information on preferential pathways for future activity, and also provide constraints on fluid transfer, diffusion, and cooling processes occurring within the volcano subsurface. Through reiterations, such combined UAV measurements are therefore particularly relevant in monitoring volcanic hazards before, during and after eruptions.

Active structures and thermal state of the Piton de la Fournaise summit revealed by combined UAV magnetic and thermal infrared measurements

In this study, we demonstrate the strong potential of combining Unmanned Aerial Vehicle (UAV)-based thermal infrared (IR) and magnetic measurements to image the thermal state of volcanic edifices, as well as the distribution of active volcano-tectonic features at depth. Since magnetization is strongly dependent on temperature and alteration, thermally active structures are also associated with a decrease in magnetization. Based on the analysis of recent combined magnetic and infrared acquisitions, we focus on the recent evolution of the summit activity at Piton de la Fournaise. The comparison clearly highlights zones of major thermal activity, alteration and high permeability, and potentially areas of low mechanical resistance. Those observations provide information on preferential pathways for future activity, and also provide constraints on fluid transfer, diffusion, and cooling processes occurring within the volcano subsurface. Through reiterations, such combined UAV measurements are therefore particularly relevant in monitoring volcanic hazards before, during and after eruptions.

Magnetotelluric study on a vapor-dominated geothermal reservoir in the Matsukawa area, Japan

Vapor-dominated geothermal areas produce only vapor from geothermal reservoirs and have been reported worldwide (e.g., Larderello, Italy; The Geysers, United States; and Kamojang, Indonesia) and studied from several perspectives. White et al. (1971) proposed a typical vapor-dominated reservoir model, which has been applied to numerous vapor-dominated fields. The Matsukawa area, located in Iwate prefecture, is one of the few vapor-dominated geothermal areas in Japan that contains an operational power plant; therefore, it has been the site of many geological and drilling studies. For example, Ozeki et al. (2001) proposed a geological conceptual model of this area. In this study, we investigated the characteristic resistivity structure in a vapor-dominated geothermal reservoir in the Matsukawa geothermal area. We performed a three-dimensional (3D) inversion with ModEM (Egbert and Kelbert, 2012) for magnetotelluric data obtained from 68 stations. We determined an optimized solution according to the results with the smallest root mean square value by considering various calculation conditions, including the smoothing parameter and Lagrange multiplier. The 3D inversion results were used to confirm clay alteration zones, faulting, basement rocks, and low-permeability lateral shielding, which characterizes the vapor-dominated geothermal system in this area. The 3D resistivity structure is considered valid because it is consistent with logging data. In addition, we estimated the 3D temperature structure using the neural kriging method (e.g., Ishitsuka et al., 2018) based on the obtained resistivity structure, temperature logging data, and electrical logging data.

Integrating remote sensing data, GIS analysis and field studies for mapping alteration zones at Wadi Saqia area, central Eastern Desert, Egypt

Remote sensing data, spectral analyses, Geographic Information System (GIS) tools and field work were integrated for detecting the spatial distribution of the alteration zones in the study area. Remote sensing studies including; spectral signatures analyses and satellite image processing, were used for identifying the alteration minerals setting of the study area then extracting the alteration zones. A field study was carried out to the study area and several tens of samples were collected. The spectral behavior of the collected samples was obtained using the “Advanced Spectral Devices (ASD) TerraSpec Halo mineral identifier” handheld spectro-radiometer. Spectral analyses were carried out on signatures of selected samples to obtain the characterizing absorption features and to reveal the identity of the alteration minerals (end-members) representing the alteration zones in the area. The identified end-members included; Clay minerals, white Mica, Epidote and Iron oxides. Spectral Angle Mapper (SAM), Spectral Feature Fitting (SFF), Constrained Energy Minimization (CEM), and Mixture Tuned Matched Filtering (MTMF) alteration mapping techniques were used to map the abundance of the identified alteration minerals from ASTER satellite image data. Lineaments were extracted automatically using combined hill-shade images obtained at multi-azimuths derived from Allos PALSAR 12.5 m Digital Elevation Model (DEM) data. The alteration and lineament data were integrated together using the GIS “Weighted Overlay Analysis” tool to delineate the most potential areas for alteration zones existence. The results were validated through plotting the field observation points on the resulted final alteration map; the accuracy was estimated by about 80%.

Detecting Buried Porphyry Cu Mineralization in a Glaciated Landscape: A Case Study from the Gibraltar Cu-Mo Deposit, British Columbia, Canada

Abstract At the Gibraltar porphyry Cu-Mo deposit in south-central British Columbia, Canada, geochemical and mineralogical anomalies in till around a cluster of mineral occurrences form amoeboid-shaped dispersal patterns controlled by three phases of ice movement. The glacial dispersal patterns defined by elevated concentrations of ore (Cu, Mo) and pathfinder (Ag, Zn) elements and alteration oxides (Al2O3, K2O) in the till matrix (clay and silt plus clay fractions) extend over areas of 6–36 km2 and are centered on the main economic mineralization. Mineralogical dispersal trains were identified by the high abundances of chalcopyrite, pyrite, jarosite, titanite, and epidote, which were derived from the mineralization and its associated oxidation and alteration zones. These mineralogical anomalies in till extend approximately 30 km2 for chalcopyrite, 62 km2 for jarosite, and up to 136 km2 for epidote. Epidote grains in till with a trace element composition of &amp;gt;10 ppm As, &amp;gt;4 ppm Sb, &amp;lt;200 ppm total rare earth elements (ΣREEs), &amp;lt;45 ppm Y, &amp;lt;100 ppm Sc + Cr + Y, and/or &amp;lt;2 ppm Th + Hf are interpreted as being either principally derived from the intrusive rocks or from hydrothermal alteration of the porphyry mineralization. Rare epidote grains with &amp;gt;30 ppm Cu, interpreted to be related to the porphyry Cu mineralization, were detected in till up to 7 km down-ice from the economic mineralization. This study demonstrates that till geochemistry and mineralogy, combined with geochemical analyses of specific minerals such as epidote, are efficient methods for identifying porphyry Cu mineralization in terrains covered by glacial sediments.

Volcanic Ash from the June 17, 1962 Eruption of Yakedake Volcano: Stereomicroscopic, XRD, and Water-Soluble Components Analyses

We performed stereomicroscopic, X-ray diffraction (XRD), and water-soluble components analyses on volcanic ash discharged from the June 17, 1962 eruption of Yakedake volcano. Ash samples were collected without surface soil and rainfall contamination. Pyrite and gypsum were identified, as well as other previously reported constituent minerals, and 1,250 mg/kg of Cl and 10,800 mg/kg of SO4 as water-soluble components. The presence of hydrothermal alteration minerals and large amounts of water-soluble components indicates that the eruption was a phreatic event that originated in a hydrothermal alteration zone.

Machine-learning techniques for quantifying the protolith composition and mass transfer history of metabasalt

The mass transfer history of rocks provides direct evidence for fluid–rock interaction within the lithosphere and is recorded by compositional changes, especially in trace elements. The general method adopted for mass transfer analysis is to compare the composition of the protolith/precursor with that of metamorphosed/altered rocks; however, in many cases the protolith cannot be sampled. With the aim of reconstructing the mass transfer history of metabasalt, this study developed protolith reconstruction models (PRMs) for metabasalt using machine-learning algorithms. We designed models to estimate basalt trace-element concentrations from the concentrations of a few (1–9) trace elements, trained with a compositional dataset for fresh basalts, including mid-ocean ridge, ocean-island, and volcanic arc basalts. The developed PRMs were able to estimate basalt trace-element compositions (e.g., Rb, Ba, U, K, Pb, Sr, and rare-earth elements) from only four input elements with a reproducibility of ~ 0.1 log10 units (i.e., ± 25%). As a representative example, we present PRMs where the input elements are Th, Nb, Zr, and Ti, which are typically immobile during metamorphism. Case studies demonstrate the applicability of PRMs to seafloor altered basalt and metabasalt. This method enables us to analyze quantitative mass transfer in regional metamorphic rocks or alteration zones where the protolith is heterogeneous or unknown.

Influence of fluid-rock interaction on gold mineralization in the Dongwan deposit, East Qinling, China: Constraints from systematic sulfur isotope and trace element geochemistry

The Dongwan gold deposit is located in the Xiong'ershan area, East Qinling, China, with gold ore bodies hosted in NE-trending hydrothermal alteration zone and quartz + sulfides veins in structures. Here we present systematic field investigation, petrographic observations, in-situ trace elements and sulfur isotope of pyrite, and sulfur isotope of galena and barite to elucidate the genesis and effect of fluid-rock interaction during hydrothermal evolution of the Dongwan gold deposit. Four types of pyrite are recognized based on their occurrences in different hydrothermal veins, structures and paragenetic sequences, as follows: i) Py1 in the stage I quartz-pyrite vein is composed of coarse-grained cubic pyrite (Py1-1) and medium-grained cubic pyrite (Py1-2); ii) Py2 is characterized by fine-grained disseminated pyrite in stage II vein; iii) Py3 is represented by pyrite that occurs together with galena, sphalerite and chalcopyrite in stage III vein. The early stage Py1-1 and Py1-2 are characterized by high Co/Ni ratios and low contents of As, Au and Ag. The main ore-forming stages represented by Py2 and Py3 show lower Co/Ni ratios and higher concentrations of As, Sb, Au, Ag, Pb and Cu. The Ni contents of all pyrite types are < 10 ppm, indicating that the ore-forming fluid was derived from felsic rocks. The δ34S values of the different pyrite generations range between −16.0‰ and −7.4‰, which are attributed to the fractionation between barite and sulfide minerals. The sulfur isotopic composition of the hydrothermal fluid calculated from co-genetic barite and pyrite is 1.2‰, suggesting that the ore-forming materials were possible derived from mantle source, and were correlated with the Late Mesozoic granitic magmatism. The main mechanisms of gold precipitation are fluid-rock interaction and decrease of temperature, which promote the Fe2+ rich Xiong’er Group wall rocks to reduce the hydrothermal fluid and disequilibrate the gold-sulfur complex causing the precipitation of gold. The overall trace elements and sulfur isotopic signatures suggest that the pyrite is of magmatic-hydrothermal origin, and that the ore-forming materials of the Dongwan gold deposit are probably related to post-magmatic fluids derived from the Early Cretaceous granitoid magmatism in the region.

Структурні зміни плечового суглоба при експериментальному відтворенні його порушеної біомеханіки

Деформуючий остеоартроз плечового суглоба — актуальна та малодосліджена проблема. Одним з основних чинників розвитку артрозу є травматичне ушкодження капсулярно-зв’язкового апарату суглоба, порушення рухомості суглоба та запалення. Разом із тим залишається невстановленим місце аномальної біомеханіки у розвитку остеоартрозу плечового суглоба як монофактора патологічного стану. Мета. Дослідити роль обмеженої біомеханіки плечового суглоба як монопатогенетичного чинника в розвитку остеоартрозу плечового суглоба. Матеріали та методи. В експерименті морським свинкам відтворювали модель остеоартрозу і через 3 місяці досліджували структурні зміни суглоба. Із декальцинованих зразків плечового суглоба отримували кріозрізи, проводили гістологічне та морфометричне дослідження. ­Результати та обговорення. Встановлено структурні порушення суглобової поверхні головки плечової кістки і западини лопатки, зміну контура субхондральної кісткової тканини, проліферативні зміни капсули суглоба. Порушена рухливість і змінена зона навантаження спричинили втрату 48 % (р &lt; 0,01) товщини хрящової суглобової поверхні плечової кістки та 14 % з боку гленоїду (р &lt; 0,01). Тобто суттєве обмеження мобільності (біомеханіки) плечового суглоба призводить до дистрофічних змін хрящових елементів в обох суглобових поверхнях. Висновки. Результати експериментальних досліджень підтвердили, що порушена біомеханіка рухів плечового суглоба є одним із монопатогенетичних чинників остеоартрозу.

Mapping of Hydrothermal Alteration Zones in the Kelâat M’Gouna Region Using Airborne Gamma-Ray Spectrometry and Remote Sensing Data: Mining Implications (Eastern Anti-Atlas, Morocco)

The mapping of hydrothermal alteration zones associated with mineralization is of paramount importance in searching for metal deposits. For this purpose, targeting alteration zones by analyzing airborne geophysical and satellite imagery provides accurate and reliable results. In the Kelâat M’Gouna inlier, located in the Saghro Massif of the Moroccan Anti Atlas, natural gamma-ray spectrometry and ASTER satellite data were used to map hydrothermal alteration zones. Natural gamma-ray spectrometry data were processed to produce maps of Potassium (K in %), Uranium (eU in ppm), Thorium (eTh in ppm) and ratios of K/eTh and K/eU. In addition, four-band ratios were computed, on ASTER data, to map the distribution of clay minerals, phyllitic minerals, propylitic minerals, and iron oxides. The combined results obtained from geophysical and satellite data were further exploited by fuzzy logic modelling using the Geographic Information System (GIS) to generate a mineral prospectivity map. Seven hydrothermal alteration zones likely to be favorable for mineralization have been identified. They show a spatial correlation with (i) known surface prospects and mineral occurrences, (ii) the granite-encasing contact zone, and (iii) the fault zones (Sidi Flah and Tagmout faults). This research therefore provides important information on the prospecting of mineral potential in the study area.

Detection of alteration zones using the Dirichlet process Stick-Breaking model-based clustering algorithm to hyperion data: the case study of Kuh-Panj porphyry copper deposits, Southern Iran

Detection of hydrothermal alteration zones (HAZs) associated with porphyry copper systems using remote sensing imagery is a crucial stage for discovering high potential zone of ore mineralization. Statistical model-based clustering methods have great potential for automatic and accurate detection of hydrothermal alteration minerals using hyperspectral remote sensing imagery. In this research, the Dirichlet Process based on Stick-Breaking (DPSB) model-based clustering algorithm was implemented to hyperion remote sensing imagery to discriminate HAZs associated with the Kuh-Panj porphyry copper deposit, south, Iran. The DPSB clustering algorithm was implemented and subsequently compared with the k-means algorithm, CLARA clustering, hierarchical clustering, Gaussian finite mixture model (GFMM), Gaussian model for high-dimensional (GMHD) and spectral clustering as well as spectral angle mapping (SAM). Results derived from the DPSB model-based clustering algorithm show 88.6% accuracy in distinguishing propylitic, argillic, advanced argillic, propylitic-argillic and phyllic alteration zones. The DPSB algorithm can be broadly implemented to hyperspectral remote sensing imagery for detecting alteration zones associated with porphyry systems.

Spectral introductions of typical minerals during the periods of skarn formation and evolution at Zhuxi tungsten polymetallic deposit in Jiangxi Province

朱溪是近年来在江西塔前-赋春成矿带发现的一个世界级超大型钨铜矿床。本文采用短波红外+热红外光谱技术对矿区13个钻孔进行了光谱测量，结合岩石-矿物地球化学分析，探讨了朱溪矿床矽卡岩中典型蚀变矿物的形成与演化过程，厘定了矽卡岩形成不同阶段矿物组合的光谱特征，构建了朱溪矿床的短波红外+热红外光谱勘查模型。研究发现:（1）区内不同矿物组合形成了明显的蚀变分带，由内向外依次为绢云母（富Si）+长石（岩体顶层蚀变，多期流体叠加综合作用）→外矽卡岩:钙铝榴石+透辉石+（绢云母）→透辉石+蛇纹石+绿泥（帘）石+滑石→绢云母（富Al）+绿泥（帘）石（基底不整合面蚀变）；（2）Al-OH波长的移动可指示成矿流体压力、温度及pH值的变化；（3）研究区透辉石的形成、演化与矿体之间关系密切，虽然富矿体赋存于矽卡岩形成早期的透辉石-石榴子石蚀变带，但大量矿体则赋存于矽卡岩退蚀变阶段的蛇纹石-绿泥石蚀变带；（4）矿体的形成与流体的混合作用关系极大，伊利石光谱吸收特征能够指示外部冷水（大气降水或地下水）的灌入轨迹。;The Zhuxi tungsten polymetallic giant deposit is located in the Taqian- Fuchun metallogenic belt, Jiangxi Province. By measuring 13 drill cores with SWIR and TIR spectroscopy combined with geochemical analysis, we discussed the formation and evolution process of typical skarn minerals in the Zhuxi deposit, summarized their spectral characteristics, and constructed a spectral exploration model. It was found that:(1) different mineral assemblages form obvious alteration zones, i.e., sericite+feldspar (the top layer of the rock mass, caused by multistage fluid superposition probably) → grossular+diopside+(sericite) → diopside+serpentine+chlorite (epidote+talc) → sericite+chlorite (epidote) (alteration on the basement); (2) the shift of the Al-OH wavelength 2200nm can indicate the changes in pressure, temperature, and pH value of the ore-forming fluid; (3) diopside formation and evolution have a close relationship with ore bodies. Bonanza occurs in the grossular+diopside alteration zone, and a large number of ore bodies occur in the serpentine+chlorite alteration zone. It evidenced the importance of the fluid mixing and cooling for mineralization. The ore body emerged in the early stage of skarn formation, but the real enrichment stages occurred in the retrograde alteration stage; (4) the mixing fluid plays a key role in forming the deposit, and the illite spectrum can indicate the trace of the external cold water (atmospheric precipitation or groundwater).