Vein Zone Research Articles

Native gold from alluvial deposits of the Kyvvozhsky district and its probable primary sources (Volsko-Vymskoe rise, Middle Timan)

Based on the study of typomorphic features of gold from alluvial deposits of the Kyvvozh region of Middle Timan, including industrial placers, the most probable genetic types of primary sources were determined. The size of gold particles varies widely, reaching the size of small nuggets; along with rounded ones, there are weakly rounded and unrounded particles. Many of them have undergone repeated deformations in the form of envelope-shaped bends, dents and tears. Most gold coins have high-fineness rims. Gold always contains Ag, sometimes Cu, Pd and Cu. Gold particles with a block structure with high-silver vein zones are often found. In intergrowths with gold and in the form of inclusions are noted in it pyrite, galena, and occasionally minerals of the cobaltine-gersdorfite series, ankerite, galenobismutite, native bismuth, aurostibite, and also sudovikovite (PtSe2), which was first identified in the region. Three types of gold have been identified: 1 – homogeneous silver-containing, 2 – block with highly silvery vein-like zones, 3 – rare silver-containing with impurities of Cu, Pd. The morphology, composition and structure of placer gold indicate its entry into placers from various sources, including nearby sources. Of greatest interest are the zones of development in Riphean rocks of hydrothermal veinlet-disseminated sulfide mineralization, oriented in the northwest direction, partially exposed during the development of placers. Gold with Cu and Pd impurities is most likely associated with derivatives of mafic magmatism. The Volsko-Vymskoe, as well as the Tsilemskoe and Chetlasskoe uplifts of Middle Timan can be considered promising in terms of primary gold content and deserve further study and prospecting.

Quantitative MRI imaging of parenchyma and venation networks in Brassica napus leaves: effects of development and dehydration

BackgroundCharacterisation of the structure and water status of leaf tissues is essential to the understanding of leaf hydraulic functioning under optimal and stressed conditions. Magnetic Resonance Imaging is unique in its capacity to access this information in a spatially resolved, non-invasive and non-destructive way. The purpose of this study was to develop an original approach based on transverse relaxation mapping by Magnetic Resonance Imaging for the detection of changes in water status and distribution at cell and tissue levels in Brassica napus leaves during blade development and dehydration.ResultsBy combining transverse relaxation maps with a classification scheme, we were able to distinguish specific zones of areoles and veins. The tissue heterogeneity observed in young leaves still occurred in mature and senescent leaves, but with different distributions of T2 values in accordance with the basipetal progression of leaf blade development, revealing changes in tissue structure. When subjected to severe water stress, all blade zones showed similar behaviours.ConclusionThis study demonstrates the great potential of Magnetic Resonance Imaging in assessing information on the structure and water status of leaves. The feasibility of in planta leaf measurements was demonstrated, opening up many opportunities for the investigation of leaf structure and hydraulic functioning during development and/or in response to abiotic stresses.

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.

Tungsten mineralization formed by single-pulsed magmatic fluid: Evidence from wolframite-hosted fluid inclusion from the giant Dajishan “five floor” style W-polymetallic deposit

The giant Dajishan W-polymetallic deposit, located in the Nanling metallogenic belt, is a typical steeply dipping wolframite-quartz vein-type deposit. From top to bottom, the W ore grade is highest in the middle and decreases towards both ends. In No. 23 wolframite-quartz vein of the north group, the thickness of the veins increases from 0.1 ∼ 0.2 m thick in the 517 m level to a maximum of 0.6 ∼ 2.0 m in the 267 m level. According to the “Five Floor” prospecting model, the No. 23 vein corresponds to veinlet (517 m), moderate vein (467 ∼ 417 m), and thick vein zones (367 m ∼ 267 m). Primary wolframite-hosted fluid inclusions show homogenization temperatures display a slight but explicit decrease by about 20 °C in average from bottom to top, recording the essential fluid cooling process. The phase ratios (20 to 30 vol% vapor proportions) and salinities (6.3 to 10.0 wt% NaCl equiv.) are constant at all levels, indicating that neither meteoric water mixing nor fluid boiling/immiscibility is obvious during wolframite formation. The fluids contain NaCl and KCl as major salts, B as the subordinate component, with trace elements including Li, Rb, Cs, Zn, Pb, etc. The significant narrow ranges of K/Na (0.296 to 0.664), Rb/Na (0.008 to 0.018), and Cs/Na ratios (0.032 to 0.076) illustrate that wolframite ore-forming fluids come from the initial fluids derived from a highly-evolved granitic magma. In major host metasandstone, muscovitization and tourmalinization lead to the release of Na, B, and Al from the fluid into the wall rock, and liberation of Fe from the wall rock into the fluid. Wall rock composition data show that muscovitization is the main mechanism of changes in Fe contents. Preliminary calculations indicate that fluid-rock interaction may contributes minor iron to the ore-forming fluids. Combining these results, we support that “Five Floor” style W mineralization in Dajishan is formed by a single-pulsed magmatic fluid. The vertical zonation of vein thickness and ore grade in the “Five Floor” model is predominately controlled by temperature, pressure, and local tectonic regime, but it is less dependent on the fluid chemical composition.

Classification of Polymetallic Ore-Forming Processes and Transitional VMS–SEDEX–MV-type: the Example of the Giant Ozernoe Deposit in Transbaikalia, Russia

This article discusses the general classification approaches and key features of different families of polymetallic deposits, with particular attention to the largest in Eurasia Ozernoe polymetallic deposit located in Western Transbaikalia and thoroughly explored 50 years ago. The main groups (or families) of polymetallic deposits in the English-language literature are identified by brief names: volcanogenic massive sulphide (VMS), sedimentary exhalative (SEDEX), and Mississippi Valley type (MVT). Within these three families of deposits, there are many additional types/subtypes, a large number of which are mostly due to the incompleteness and inconsistency of accumulated knowledge on the genesis of polymetallic deposits. Overall, all Pb–Zn(Ag,Cu) deposits—both those that are considered syngenetic, forming on and near the seafloor (VMS and SEDEX), and epigenetic low-temperature ones (MVT)—demonstrate a wide range of features that distinguish and bring together these families. This also applies to the types and subtypes of mineral deposits identified within them. One of the most complex objects for geological–genetic classification is the Ozernoe deposit studied by the authors, which, in terms of the nature of the host rocks, is intermediate between the end members of all three families: SEDEX, VMS and MVT. The deposit is localized in volcanic–carbonate–terrigenous rocks of the Cambrian Oldynda formation, but the age and stratigraphic affiliation of the ore-bearing series remain a matter of debate. The Ozernoe deposit is a combination of massive sulfide and siderite ore beds, ore breccia horizons, low-carbonate aleuropelite members, limestones, fine detrital tuffites, lavas, and tuffs. The sulfide bodies are confined to several stratigraphic levels, and the main productive unit thickness reaches 230 m. The thickness is comprised of 12 mineral lodes, a series of stratified ore bodies separated by gangue layers of sedimentary and volcaniclastic rocks. The primary ore minerals are pyrite, sphalerite, and galena, while the minor minerals include magnetite, chalcopyrite, marcasite, tetrahedrite, and arsenopyrite. There are two main theories regarding the origin of the ore: volcanogenic–sedimentary and hydrothermal–metasomatic. The hydrothermal–sedimentary theory remains the prevailing hypothesis, but there are many indications that epigenetic hydrothermal–metasomatic and dynamic metamorphic processes have contributed to the formation of the deposit. These include the appearance of sulfide–quartz and quartz–carbonate–sulfide veins and vein zones in fine-grained “layered” ores, with large crystalline sphalerite and galena; multiple signs of ore recrystallization, including the formation of pyrite porphyroblasts and arsenopyrite metacrystals; and the formation of solid pyrrhotite and pyrrhotite–magnetite ores with a lenticular-striped, gneissic structure. These observations suggest that different processes, both hydrothermal–sedimentary and metamorphogenetic–metasomatic, were involved in the formation of the Ozernoe deposit. In other words, primary hydrothermal–sedimentary ores were redeposited by late hydrothermal solutions. Nevertheless, many issues concerning the genesis of the Ozernoe deposit remain unresolved.

The Birkachan Epithermal Au–Ag Deposit in the Kedonsky Middle Paleozoic Volcanic Belt (Russian Northeast)

The Birkachan deposit in the Middle Paleozoic Kedonsky Volcanic Belt (KVB) is unique in Northeast Russia for its stockwork epithermal Au–Ag ores. The deposit is located in the northeastern part of the Gurnik volcanotectonic depression, in the Kedonsky segment of the KVB. The deposit is localized in the lying side of a large sublatitudinal thrust fault, due to which it was overlain in the Jurassic–Early Cretaceous by allochthon rocks and, therefore, was slightly eroded, as evidenced by the preserved fragments of the argillisite cap. The ore-bearing Gurnik sequence is composed of felsic tuffs and lavas with intercalations of ignimbrites. The main ore-bearing zone of the Birkachan deposit is 4.5 km long and 200–300 m wide consists of several echelon-like vein zones of northeast strike, falling to the southeast at angles of 55°–70°. Most of the ore bodies are linear stockworks. Single, lenticular rich ore bodies represented by mineralized breccias have been found at deep horizons. In the section, the system of ore bodies of the Birkachan deposit forms a fan-shaped structure. The main textures of ores are vein-disseminated, breccia, and rhythmically banded. The ores are enriched in comparison with the upper continental crust in a rather narrow range of elements (Au, Ag, Sb, As, Mo, W, and Li) and are poor in rare-earth elements, among which light lanthanides predominate. The sulfide grade of ores is 0.1–0.5%. The vein minerals in ores are dominated by quartz, sericite, and siderite. Among the ore minerals, pyrite dominates, with fahlore, native gold and chalcopyrite, and minerals of the series acanthite → Se–acantite → naumannite, pearceite, and Se–pearceite being less common. The average fineness value of native gold is 643‰. The parameters of mineral-forming solutions correspond to typical medium-temperature fluids of epithermal low-sulfidized deposits: homogenization temperature of 93–291°С, salt concentration of 0.2–7.0 wt % eq. NaCl, and fluid density of 0.71–0.99 g/cm3. The main indicators of fluid composition are CO2/CH4 = 15.8–23.6, Na/K = 2.3–4.3, and K/Rb = 2007. The prospects for increasing the reserves of Au and Ag are associated with further study and exploration of the flanks and deep horizons of the deposit.

The Application of Geologic Mapping, Core Logging, and 3-D Geoscientific Data Integration in the Exploration and Resource Expansion of Porphyry Copper-(Gold) Deposits: Examples from Recent Discoveries in Ecuador and Chile

Abstract The collection of accurate geologic data is critical in minerals exploration. The successful visualization, integration, and interpretation of quantitative vein abundance data, associated selvages of wall-rock alteration mineralogy, sulfide mineral proportions, and metal zoning facilitate the path to discovery and orebody delineation. The application of the Anaconda method, developed by the Anaconda Copper Mining Company geologists in the 1960s, to geologic mapping and drill core logging has facilitated the discovery and resource expansion in the giant Alpala porphyry Cu-Au-Ag deposit in northern Ecuador and the Cortadera porphyry Cu-Au-Mo deposit cluster in northern Chile. In both porphyry systems, high-grade zones have been targeted through the delineation of an intrusion and vein chronology that allows for the recognition of early-stage causal intrusions, zones of abundant porphyry-style quartz veins, and elevated chalcopyrite to pyrite ratios. Increased amounts of molybdenum, as molybdenite along fractures and in quartz veins, as well as anhydrite veins and disseminations, correlate with proximity to the deposit cores. The field-based methods presented in this article have proven useful in porphyry exploration for decades. The application of the Anaconda method of geologic mapping and core logging by geologists can assist in the targeting of high-grade cores of deposits and improved estimation of metal resources.

Epithermal Au–Ag–Se–Te Deposits of the Chukchi Peninsula (Arctic Zone of Russia): Metallogeny, Mineral Assemblages, and Fluid Regime

Abstract Numerous epithermal Au–Ag deposits and ore occurrences of the Chukchi Peninsula are localized in the Cretaceous Okhotsk–Chukotka (OCVB) continent-marginal and Late Jurassic–Early Cretaceous Oloi (OVB) island arc volcanic belts and in Early Cretaceous postcollisional volcanic troughs. Volcanotectonic depressions, calderas, and volcanic domes control the location of the deposits. The orebodies of the deposits are quartz–adularia veins, sometimes en-echelon ones forming extending vein zones, as well as isometric and linear stockworks. The auriferous veins of most deposits display complex breccia–crustification structures. The vein ores have rhythmically and colloform–banded structures, with a predominantly fine distribution of ore mineral grains, often with banded clusters of ore minerals (ginguro). Native gold is of low fineness; the dispersion of this index varies from low to high. Acanthite is widespread in the ores. Its highest contents are specific to deposits with the repeated redistribution of substance (Kupol, Corrida, and Valunistoe). Based on the results of mineralogical studies, most of the epithermal Au–Ag deposits of the Chukchi Peninsula can be assigned to the Se type. The ores of some deposits (Valunistoe, Dvoinoe, etc.) contain both Se and Te minerals. The telluride-richest sites of the Sentyabr’skoe and Televeem deposits are far from the main orebodies. Most of the Chukchi epithermal Au–Ag deposits have many common characteristics (low and moderate temperatures of fluids, low fluid salinity, domination of carbon dioxide over methane, etc.) typical of low-sulfidation deposits. The maximum temperatures and salinity are specific to fluids in the Central Chukchi sector of the OCVB and in the Baimka zone of the OVB, and the minimum ones are typical of fluids in the East Chukchi flank zone and inner zone of the OCVB. The average salinity of mineral-forming fluids in the inner zone of the OCVB is half as high as the salinity of fluids in the East Chukchi flank zone of this belt, although the sulfate content is higher. At the same time, the fluids in the inner zone of the OCVB are richer in carbon dioxide and bicarbonate ion than the fluids in the East Chukchi flank zone of this belt. The fluid inclusion data permit the Vesennee deposit (Baimka zone) to be regarded as an intermediate-sulfidation one and suggest the presence of epithermal high-sulfidation deposits in the inner zone of the OCVB.

Establishing the mining deposit groups and the gold exploration network patterns in the Attapeu area, Lao PDR

This paper initially clarified the context of primary gold mineralization in the Attapeu area, Lao People's Democratic Republic. It proposed the priority for the exploration, using the conventional technique combined with the geological mathematic method. The research essentially summarized that the study area had a complex geological and structural setting; the mineralization zones or gold orebodies most likely formed as a lens shape and/or mineralized single vein or vein zone, extending from a few tens of meters to greater than 500 meters long, within a single dipping angle of 450÷800; the geometric of orebodies likely illustrated as small to medium size. The mineralization zone significantly extended following the geological setting, indicating consistent to the strongly inconsistent group (Vm = 8.9÷116.8%). Medium- to high-grade gold ores are commonly found in each ore body and identified as a homogeneous to strongly inhomogeneous group (Vc = 58.3÷785%). Regarding the exploration criteria, exploring primary gold mineralization in the Attapeu area fits well with the mineral exploration group III. To estimate the ore reserve in category 112 significantly requires conducting the parallel exploration grid or rectangular grid with the exploration grid interval of 40÷60 meters within the space of the exploration grid line between 20 to 30 meters. The exploration guidelines proposed in this research are efficiently applicable for exploring other primary gold mineralization elsewhere with the geological settings and mineralogical characteristics identically to the primary gold mineralization in the Attapeu area.

Geotechnical risks of above-standard losses in shallow mining

The geotechnical risks and the operational loss risks in mining shallow subsurface zones of veins under conditions of extremely unstable rock mass are assessed as a case-study of the vein gold–quartz deposit of Dzhamgyr. The risk management and control are proposed. The method of surface exploration and access cutting is substantiated. The vein gold–quartz deposit Dzhamgyr occurs in the Pre-Cambrian granite block. Thin and continuous gold–quartz veins 0.1 to 1.5–2 m thick (on average to 0.8 m) are located inside the vein bodies in healed faults. In the field, the zones of the Riedel shears with pre-mineral and syn-mineralization faulting are identified. The vein zones enclosing pay sections develop as a spindle of veins which grow in number, length, density, branches and thickness toward ground surface. The mining system, which is the underhand cut-and-fill with cemented backfill, is described. The comparative economic performances with regard to the geotechnical risk and its reduction activities are presented. The advanced planning including the geotechnical risk management in shallow mining in instable rock mass areas, the use of the accessing, development and extraction technologies consistent with the existing geological situation, as well as the stoping under the manmade crowns ensure safe operating conditions and allow anticipating essential economic effect in terms of reduced losses of ore and precious metal.

New Data on Hydrogeochemical and Isotopic Composition of Natural Waters of the Baidar Valley (Crimean Peninsula)

Abstract —Results of study of natural waters of the Baidar valley (southwestern Crimean Peninsula) obtained during the 2018–2019 field works are presented. Major groundwater resources of the study area are confined to the Upper Jurassic aquifer complex, which serves as a recharge source for the aquifer systems of the Plain Crimean and the Azov–Kuban’ artesian basins and hydrogeologic folded region of the Crimean Mountains mega-anticlinorium. The regional waters are fresh and ultrafresh, predominantly of calcium bicarbonate composition, with TDS varying from 208 to 1269 mg/dm3. The study enabled their classification into eight geochemical groups: (1) waters of a regional fracture zone in carbonate-terrigenous rocks affected by continental salinization; (2) waters of a regional fracture zone affected by leaching of aluminosilicates and sulfide oxidation; (3) waters of a regional fracture zone dominated by sodium aluminosilicates in the fracture filling (long-term interaction in the water–rock system), affected by continental salinization; (4) regional fracture zones dominated by sodium aluminosilicates affected by anthropogenic continental salinization; (5) groundwaters in fracture–vein aquifers affected by leaching of aluminosilicates and sulfide oxidation; (6) fracture–vein aquifers affected by leaching of sodium aluminosilicates (long-term interaction in the water–rock system); (7) waters in fractured karst aquifers; and (8) surface waters subjected to continental salinization. Fracture karst waters, which were found to be most protected against human impact and continental salinization processes, are slightly alkaline (pH = 7.7), fresh (with average TDS = 444 mg/dm3), with low silicon concentrations (2.23 mg/dm3), and of calcium bicarbonate composition. Waters residing in regional fracture and fracture–vein zones are affected by continental salinization and anthropogenic load and are neutral to alkaline (pH = 7.1–8.6), predominantly fresh (TDS = 269–1269 mg/dm3), with average silicon concentrations of 4.61–4.70 mg/dm3, of calcium bicarbonate composition, with high concentrations of sulfate ion, magnesium, and sodium. The waters of the Chernaya River, Chernorechensk reservoir, and lakes, which are also affected by continental salinization, are slightly alkaline (pH = 8.3), brackish (TDS = 207–364 mg/dm3), with an average silicon concentration of 1.18 mg/dm3, of calcium bicarbonate composition, with high concentrations of chlorine ion, magnesium, and sodium. The calculated intensity of chemical-element migration in waters of the background composition follows the descending order: very strong, I17.7 > Br14.4; strong, Se2.83 > B2.22 > Sr1.46 > Sb1.12 > Be1.07 > Hg1.06; moderately strong, Zn0.74 > Mo0.50 > Li0.46 > Sc0.41 > Ag0.18 > As0.16 > Si0.123 > Ba0.122; weak, Cr0.10 > Cu0.096 > Bi0.080 > Sn0.068 > Tl0.067 > P0.062 > Ni0.043 > Ta0.040 > Ge0.034 > Cd0.028 > Fe0.026 > Rb0.024 > Co0.023 > Pb0.020 > W0.017 > V0.012; very weak (inert), Nb0.008 > Hf0.0033 > Mn0.0031 > La0.0029 > Cs0.0022 > Ti0.0018 > Ga0.0016 > Y0.0013 > Al0.0008 > Zr0.0008. All the studied waters are found to be of atmospheric origin and located along the global (GMWL) and local (LMWL) meteoric water lines. Their δ18O value varies from –9.9 to –3.3‰, and δD value, from –64.2 to –32.5‰. Sedimentary carbonate rocks, atmospheric carbon dioxide, organic compounds, and hydrolysis of aluminosilicate minerals serve as the source of δ13C bicarbonate ion in natural waters of the Baidar valley. Surface waters have a heavier carbon isotope composition (δ13C = –9.2 to –6.2‰), which is due to atmospheric CO2, plant growth, and associated microbial activity. Fracture karst waters are characterized by a lighter carbon isotope composition (δ13C = –12.8 to –11.0‰) because of their interaction with dispersed organic matter. Waters of the regional fracture and fracture–vein zones display the widest variation in δ13C (–15.5 to –6.9‰), which is associated with a mixed type of “isotope supply” to the waters. A complex hydrogeochemical field that has formed in the Baidar valley tends to be increasingly affected by the anthropogenic factor.

Fluid-assisted localized embrittlement in an overall ductile fold-and-shear belt: A case study from Cap de Creus

The Cap de Creus massif in the eastern Pyrenees is a renowned late Variscan fold-and-shear zone belt characterized by partitioning of an overall ductile strike-slip-dominated dextral transpression into coeval folding, ductile shearing and localized embrittlement. The local partitioning of deformation mode (fracture vs. ductile flow) can be related to rheologically contrasting lithologies and syntectonic infiltration of hydrothermal fluids that were likely residual fractions of earlier pegmatite intrusion. In particular, the influx of hydrothermal fluids results in cm-to m-sized damage zones of localized fractures and veins with associated hydrothermal alteration across most lithological units. Such damage zones systematically formed at a low angle to the axial surfaces of contemporaneous folds, even in cases with minimal shortening. In higher strained areas, evident by tighter folding and shearing, cataclasites developed along these same damage zones. This study provides an example of contemporaneous ductile and brittle structures, in this case resulting from localized embrittlement due to fluid flow.

Mineralization and hydrothermal alteration in the Mamão orogenic gold deposit, Andorinhas greenstone belt, Carajás Province, Brazil

The Mamão gold deposit, located in the eastern portion of the Amazonian Craton, northern Brazil, is hosted by mafic rocks of the Mesoarchean Andorinhas greenstone belt. An underground mine was operated in this area by Troy Resources Ltd., which produced approximately 350 koz of gold between 2008 and 2015. The hydrothermal alteration halos are characterized by a distal zone (10- to 80 m wide) with a chlorite-albite-epidote-actinolite assemblage, an intermediate zone (5- to 20 m wide) marked by calcite-albite-chlorite-actinolite-quartz, a proximal zone (0.5–5 m wide) composed of biotite-quartz-calcite-pyrite-(gold) and a quartz vein-hosted orebody zone (0.5- to 6 m wide) composed by quartz-calcite-pyrite-(gold). Geochemical data indicate that the metabasalt, metandesite and metadacite host rocks display a tholeiitic N-MORB signature, suggesting that they were formed in ancient oceanic spreading centers. Hydrothermal chlorite of the Mamão deposit is classified as ripidolite and brunsvigite. Biotite is the main mica and increases in modal content from the distal alteration to the vein zone, displaying compositions within the annite domain. Muscovite occurs as very fine lamellae and is generally located in the intermediate zone of the altered region. Amphiboles are calcium-rich and display compositions mostly varying from hornblende (Mg-hornblende to Fe-hornblende) in the distal zone, to actinolite in the intermediate zone. Sulfidation occurs in all hydrothermal alteration zones, with both fine- and coarse-grained pyrite as the main sulfide phase, and lesser amounts of chalcopyrite, pyrrhotite, cobaltite and sphalerite. Fine-grained pyrite contains many gold inclusions and is typical of the orebody zone preferentially in close contact with the proximal hydrothermal zone, whereas coarse-grained pyrite (without recoverable gold) occurs in the veins. From the edges to the core of the hydrothermal alteration halos, the As, Sb, Ag and Au contents in the pyrite increase, whereas Pb, Co and Mo decrease. Gold occurs as free crystals (2- to 0.1 mm) disseminated within the gangue or as inclusions in the fine-grained pyrite. Temperature estimated via chlorite geothermometer ranges from 284- to 320 °C, with pressure between 1.12 and 1.34 kbar according to biotite geobarometer calculations for the hydrothermal zones. The C–O–S isotope analyses of the calcite and pyrite from the orebody zone yielded δ13C, δ18O and δ34S values ranging from −4.23 to −3.54‰, 8.60–9.77‰ and 3.37–3.52‰ respectively, which suggests that the hydrothermal fluid is predominantly of metamorphic origin. The εNd (3.0) calculated using isotopic analyses of the metavolcanic host rocks varies between +0.11 and + 4.25. A whole-rock Sm–Nd isochron age of 2952 ± 14 Ma was obtained from the host rocks, while a post-mineralized pyrite yielded a Sm–Nd isochron age of 2446 ± 35 Ma. The deposit exhibits mineralogical and isotopic characteristics consistent with those of orogenic type containing gold-bearing, sulfide-rich quartz veins. The Mamão deposit's host rocks are among the oldest rocks described so far in the Carajás Province. The age of the mineralizing event is limited between 2.95 and 2.45 Ga (probably ca. 2.7 Ga), which is the major metallogenic event of gold-deposit formation in several granite-greenstone terrains worldwide.

P-47 HISTOPATHOLOGICAL ANALYSIS OF 10-YEAR PROTOCOL LIVER ALLOGRAFT BIOPSY OF ASYMPTOMATIC PEDIATRIC RECIPIENTS FROM A SINGLE BRAZILIAN CENTER

Liver transplant (LT) is the main therapeutic procedure for irreversible liver failure. Protocol liver biopsies during post-transplant follow-up in pediatric recipients with stable graft function have been done in order to identify structural changes. A more specific score, LAFSc, to analyze fibrosis and inflammation on liver allografts has been validated recently. To describe the prevalence of histological liver abnormalities in asymptomatic pediatric patients after ten years following LT from a Brazilian single center comparing two different scoring methods. Cross-sectional study of analysis of protocol percutaneous liver biopsies performed in patients who underwent liver transplant before the age of 18 years, of both genders, asymptomatic, using Tacrolimus for immunosuppression and at least 10-years post-liver transplant. From 97 recipients, 21 met inclusion criteria and had stable liver graft function. A single experienced pathologist assessed histopathological features comparing METAVIR scoring system and LAFSc. Mean follow-up was 12.8 (+/- 2.1) years after post-LT. TAC mean daily dose during biopsy time was 4mg (+/- 1.7) with mean serum level of 4.04. METAVIR scoring system pointed 10 recipients with any degree of fibrosis and 13 with inflammation findings in protocol biopsies. However, using LAFSc scoring system, 13 patients scored for abnormal findings in any of the three zones analysed, although 8 of these had total score of mild fibrosis (1-3). Of the three zones analysed in LAFSc, the highest scores were found in portal space. Centrilobular vein zone was the most affected, documented in 11 recipients. We observed a higher prevalence of abnormal findings using the new allograft fibrosis scoring system – LAFSc. It also showed more specifically the degree and location of fibrosis within hepatic lobule compared to METAVIR. Compared to other LT reports, we observed lower rates of chronic allograft hepatitis and fibrosis at 10 years.

Application of magnetic and induced polarization method for delineating gold-bearing vein zones at Cibaliung, Pandeglang Regency, Banten

Magmatic processes occurred during the Miocene period caused the formation of epithermal gold deposits in Cibaliung area. The deposit has previously been investigated through geological surveys which basically only covers the surface aspect, so in this study a subsurface analysis was carried out through magnetic and IP surveys to determine the distribution and continuity of the gold deposits. The magnetic survey was conducted over an area of about 3 km2 with sampling interval 20 m east and 100 m north. The magnetic data were processed using Oasis Montaj with magnetic intensity map as an output, which was then interpreted to determine the presence of structures and magnetite destruction zones as mineralization clues. The IP survey was conducted on 20 east-west oriented lines with length of about 1.2 km. The electrode configuration used is Wenner with 25 m spacing. IP data were processed using RES2DINV software to eliminate bad datum points and invert the apparent chargeability values into the true ones. IP data are then interpreted to clearly determine the position, direction, and distribution of gold mineralization body by detecting the presence of sulfide minerals as ligands carrying gold. Magnetic data analysis shows that gold mineralization tends to occur at low magnetic anomaly, ranging from 37 nT to 240 nT and generally associated with northwest-oriented structures. The mineralization zone is found in four main vein zones with resistivity and chargeability values < 51 Ωm and > 50 ms.

Multiscale Synchrotron-Based Imaging Analysis for the Transfer of PEGylated Gold Nanoparticles In Vivo.

High spatial resolution imaging analysis is urgently needed to explore the biodistribution, transfer and clearance profiles, and biological impact of nanoparticles in the body, which will be helpful to clarify the efficacy of nanomedicine in clinical applications. Herein, by combination with multiscale synchrotron-based imaging techniques, including X-ray fluorescence (XRF) spectrometry, Fourier transform infrared (FTIR) spectroscopy, and micro X-ray phase contrast computed tomography (micro-XPCT), we visually displayed the transfer patterns and site-specific distribution of PEGylated gold nanoparticles (PEG-GNPs) in the suborgans of the liver, spleen, and kidney after an intravenous injection in mice. A combination of XRF and FTIR imaging analysis showed that the PEG bands presented similar distribution patterns with Au in the intraorgans, suggesting the stability of PEGylation on GNPs. We show that the PEG-GNPs presented heterogeneous distribution in the hepatic lobules with a large amount around the portal vein zone and then a gradient decrease in the sinusoidal region and the CV zone; in the spleen, it gradually accumulated in the splenic red pulp over time; and in the kidney, it quickly transported via the bloodstream to the renal pyramids and renal pelvis, and parts of PEG-GNPs finally accumulated in the renal medulla and renal cortex. Multidimensional micro-XPCT images further show that the PEG-GNP transfer in the liver induced hepatic blood vessel dilatation while they transferred in the liver, providing evidence of GNP transport across the blood vessel endothelial barrier.

ЗАВИСИМОСТЬ КАЧЕСТВЕННО-КОЛИЧЕСТВЕННЫХ ПОКАЗАТЕЛЕЙ ЗАПАСОВ РУДЫ ОТ МАКСИМАЛЬНО ДОПУСТИМОГО ИНТЕРВАЛА НЕКОНДИЦИОННЫХ РУД НА СОТКСКОМ ЗОЛОТОРУДНОМ МЕСТОРОЖДЕНИИ

At the Sotk gold ore deposit, the following morphological types of ore bodies can be distinguished: vein zones; veins and vein-like bodies; mineralized dykes and a vein zone in gabbro - massifs. The deposit is characterized by rather difficult mining and technical conditions. The enclosing rocks of the near-ore bodies have undergone intense hydrothermal changes at a distance of 5,0...10,0 m to 50,0 m, as a result of which, within the boundaries of these zones, the enclosing rocks have lost their strength and stability. The stability of the host rocks is also greatly influenced by postore tectonic faults, which are widespread in the field. The ore is also volatile. The strength factor of ore and host rocks varies from 3 to 20, with a predominance of 8...13. Hydrothermally altered metasomatites, which make up the mineralized zones, are prone to caking. The ore loosening factor is 1,25...1,40. The average bulk density of ore is 2,6 t / m3, and the bulk density of the host rocks is 2,3... 3,2 t / m3. At the deposit, conditioned and substandard intervals alternate with each other and there is no clearly expressed regularity of their spatial location, which predetermines the use of the ore-bearing factor when calculating ore reserves. The ore content ratio is determined by the ratio of the amount of conditioned ores to the total amount of ore mass, and the amount of conditioned ores is determined using the condition parameter “maximum - allowable range of substandard ores or waste rocks” included in the reserve calculation. For the Sotk gold ore deposit, the regularities of changes in ore reserves in the subsoil, the gold content in the ore massif and the ore content factor from the “maximum allowable to an increase in ore reserves in the subsoil and the ore content ratio with a decrease in the gold content in the ore massif and vice versa are revealed.

ХЕМОГЕННЫЕ ОТЛОЖЕНИЯ МУТНОВСКОГО ГЕОТЕРМАЛЬНОГО КОМПЛЕКСА (ЮЖНАЯ КАМЧАТКА)

By studying the processes taking place at the operating geothermal stations it is possible to model and understand some features of formation of minerals of geothermal origin, processes of transfer by hydrothermal solutions and concentration of some metals by analogy with the ore-forming processes at the formed deposits. During the release of steam-water mixture and outpouring of water from the wells silica gel is deposited, a number of elements (including noble metals) migrate and accumulate in the sediments. A great role during exploitation of wells, operation of turbines, separators and other structural elements of geothermal stations is played by the chemical composition of the coolant. Because of its high mineralization deposition on various units and parts of equipment occurs, what may complicate the operation of a geothermal plant. We describe the composition of chemogenic deposits on various technological elements of the Mutnovskaya geothermal power plant. Data on sediments sampled in boreholes, on turbine blades and separator are presented. We have revealed a wide variety of such deposits, both oxide compounds and ore phases (from magnetite, chalcopyrite, minerals of faint ore group to native gold, tellurides, selenides and sulfides of gold and silver). We suppose that the processes currently taking place at the Mutnovskoye steam hydrothermal field are similar to the hydrothermal processes that contributed to the formation of vein zones of the gold-silver-polymetallic deposit of the same name.

Prospects for Degdekan Gold Project in the North-East of Russia

The article describes the analytical, mineralogical and technological studies into enclosing rocks of Degdekan gold deposit. It is found that ore composition is dominated by silicon oxide (62.2–70.4 %), the ore-forming minerals are mainly iron, sulfur and arsenic in sulfide and oxide forms. The clustering analysis distinguishes three representative geochemical associations: Au-Ag-Pb-Sb; As-Mo-Cu; Co-Ni-Cr-Zn-W. Mineralization is pyrite, arsenopyrite, free gold, seldom fahlore, pyrrhotine, chalcopyrite, galena, sphalerite, etc. Pyrite contains As and Ni impurities. By the criteria of association and recovery, gold is present in 4 varieties: free gold recoverable by amalgamation and cyanation; fine gold associated with sulfides and disengageable after oxidizing roasting; fine and very fine gold associated with iron hydroxides, carbonates and chlorites, and extractable in cyanation after HCl treatment; fine gold associated with carbon black and recoverable by cyanation after oxidating roasting at a temperature of 650 °C. The bulk (from 41.6 to 86 %) is represented by free gold extractable in cyanation and gravity separation. This gold features large particles and occurs at the zones of quartz veins, both in veins and in strings. Percentage of fine gold (–0.04 mm) in metasomatic quartz–cericite rocks (nearby veins) varies from 2 to 11 %. There are also platinoid group metals, highly concentrated in sulfide concentrates. Potential resources of platinoids as associated metals are estimated as 10 t (around 10 % of gold resources). The authors arrive at the conclusion on feasibility of joint concentration of gold and platinoids in an integrated process circuit by gravity separation with end product as a Doré bar containing platinoids.

The Cerro Negro epithermal district, northwestern Deseado Massif (Patagonia, Argentina): New insights from telescoped volcanic-hydrothermal systems

The Cerro Negro district, northwestern Deseado Massif (Patagonia, Argentina), is one of two world-class Au–Ag epithermal mines in the Patagonian region, with combined reserves, resources, and production of about 8 Moz of Au equivalent. The epithermal deposits are hosted by volcanic and intrusive rocks and are related to the evolution of distinct Jurassic magmatic events. Major WNW trending depocenters were filled by a thick sequence of andesitic-dacitic flows and ignimbrites. In the western part of the district, the sequence is intruded by subvolcanic bodies of the same composition and is grouped into the 159-156 Ma Eureka Volcanic Subvolcanic Complex (EVSC). Hydrothermal activity took place during the last stages of the EVSC, producing epithermal Au- and Ag-rich veins of low to intermediate sulfidation style in the Eureka West (156 Ma) and the Marianas-San Marcos veins (155-154 Ma) that were emplaced in NW striking extensional faults and in WNW to E-W trending strike-slip faults. In the eastern part of the district, basal units of the EVSC are overlain by a thick package of 154 Ma rhyodacitic ignimbrites, hosting the NW to EW-striking Vein Zone deposit and the NW-striking Bajo Negro, Silica cap and Gato Salvaje veins. NNE-trending block faulting formed horsts in the western and eastern parts of the district, separated by a central graben. Uplift of the western and eastern horst blocks lowered the water table and caused erosion, exhumation, and telescoping of the vein systems. Volcanism culminated in a late-to post-mineral rhyolitic event composed of lava-domes and volcaniclastic deposits grouped into the Eureka Rhyolitic Complex (ERC). Continued hydrothermal-volcanic explosive activity produced breccias which cap some of the Au–Ag vein deposits. The high geothermal gradient during ERC volcanism generated renewed hydrothermal activity, and hot springs discharged along the boundary faults of the central graben and within the graben in a fluvio-lacustrine environment.The Au–Ag epithermal veins associated with the EVSC (Eureka and Marianas-San Marcos) show a complex paragenetic history. High Au–Ag grades are related to early sulfide-rich ginguro bands formed at 290–230 °C from meteoric and volcanic fluids due to boiling/flashing mechanism at ~600–800 m below the paleowater table. Low-grade to barren quartz stages followed the early Au–Ag stage, and late calcite was deposited due to the collapse of steam heated CO2 waters. The highest Au–Ag grades are related to a late supergene event extending to 400 m depth. The eastern group of epithermal deposits (Vein Zone, Bajo Negro, Silica cap and Gato Salvaje) were emplaced ~300–400 m below the paleowater table indicated by a silica cap on Cerro Negro hill. They are dominated by silica replacement after lattice calcite texture with high Au grades related to low temperature quartz and late hematite-stained brecciation. We conclude that all deposits are genetically related to intrusive activity, and that additional Au–Ag mineralization may be concealed beneath post-mineral volcanic and sedimentary rocks in the central graben.