Gold-bearing Formation Research Articles

Mineralogical Criteria for the Prediction of Gold Mineralization in the Structures of the Siberian Craton

Generalization of the results of the study of placer gold and the mechanisms of its distribution in the east of the Siberian Platform made it possible for the first time to reveal that the ore sources of gold-bearing placers were mainly mineralization of the gold-sulfide formation formed under the influence of hydrothermal metasomatic processes occurred in deep fault zones. It is determined that the gold-bearing hydrothermal-metasomatic formations of the gold-sulfide rock formation are amagmatic, near-surface, low-temperature and spatially confined to deep faults. These formations are widespread in terrigenous-carbonate strata and sand deposits of PZ-MZ age and are observed in the zones of brecciation, silicification, and ferruginization. The analysis of the mechanisms of distribution of hydrothermal-metasomatic gold-bearing formations in the east of the Siberian Platform, based on previously conducted research of predecessors and our field observations, allowed us to establish the following. In the northeast, hydrothermal-metasomatic formations occur in the field of development of the Zhigansky fault, the Molodo-Popigai and Anabar-Eekite fault system, in the central part of the east of the Siberian Platform, the Vilyui paleorift (Kempendyai dislocations), and in the southeast in the Baikal-Patom thrust belt in ancient faults (Bappagai, Khorinsky, etc.). Metasomatites of hydrothermal origin form extended narrow formations along ancient faults activated in the Mesozoic, as well as conformable deposits in the Vendian, Cambrian carbonate strata, Jurassic and Cretaceous sandstones. It is proved that these formations are amagmatic and are not related to the widespread magmatism of the basic composition, which is confirmed by the homogenous mineral composition of metasomatites, independent of the composition of magmatic bodies spatially located with them. Zones of metasomatites with gold mineralization contain Au from 0.5 to 3.0 g/t, and in isolated cases up to 24–32 g/t. Gold is represented from finely-dispersed to visible fine, with a size from 0.01 to 0.5 mm or more. It is known that hydrothermal-metasomatic processes on the territory of Central Aldan contributed to the formation of large deposits such as Kuranakh, Tabornoye and others. It is possible that the identified gold-ore metasomatites, developed along the zones of regional faults and not confined to magmatic formations, widely occurred both in the northeast and in the southeast of the Siberian Platform, represent a huge metallogenic potential.

Evaluating the effectiveness of fine gold extraction technologies on the example of titanomagnetite beach placers of the western coast of Kamchatka

The material on the gold content of coastal-marine deposits of the western coast of Kamchatka is analyzed and the resource potential is briefly characterized. A review of gold technological estimates obtained from the study of gold-bearing samples taken in promising areas of the coastal-marine strip, from the Bolshaya Vorovskaya River in the north to Cape Levashova in the south, is presented. Stock materials supplemented by our studies were used. Gold-bearing deposits with very fine (0.05-0.1 mm) and fine (0.1-1.0 mm) gold amounting to 94.6 % were tested, as well as samples with gold up to 2 mm and more in addition to fine gold The content of freely recoverable gold reached 91.9 %. In the case of significant gold reserves in placers, prospects for their commercial development open up. experiments on the enrichment of gold-bearing coastal-marine deposits of Western Kamchatka indicate the possibility of extraction of free gold and other valuable components from them. Gravity technologies and modern equipment developed by ОАО Irgiredmet and JSC ITOMAK are the most effective for their extraction. enrichment of gold-bearing formations with simultaneous extraction of several useful components from them, which is possible with the use of fluoride technology, can also become economically advantageous.

Peculiarities of search for placer deposits of gold of the south of Ukraine

The long-term high level of world gold prices against the background of depletion of reserves with easily extracted metal leads to the search for and introduction into industrial development of deposits, even with low-tech ores and sands. This, in turn, requires the introduction of effective technologies for the enrichment and extraction of gold, contributes to the improvement of methods of exploration. At present, numerous manifestations of placer gold of various scales are known in the sedimentary strata of Meso-Cenozoic deposits in the south of Ukraine. But the real picture of the distribution and the actual scale of gold deposits in Ukraine are uncompleted and unreliable. This is due to the inconsistency of the applied search technique, which was aimed at identifying near-subglacial valley deposits, to the actual properties of gold-bearing formations. Gold in most Ukrainian placers is represented mainly by small, fine and dispersed particles in a significantly clay substrate. Therefore, the traditional geological samples washing by tray led to excessive losses of fine gold and to a significant underestimation of the gold potential. That is why we need to revise the results of previously obtained geological data. Detection of placer gold deposits of Ukraine is possible under the condition of increasing the efficiency of the local forecast and the reliability of field research. The most favorable situations for the accumulation of a useful component are structural denudation traps in tectonic depressive zones. The technology of sample enrichment must correspond to the actual properties of specific raw materials in the placer object. The types of technological equipment are given and some ways of increase of efficiency and reliability of test are offered. The article continues the series of publications devoted to solving the problems of studying placer gold content with a dominant share of fine and dispersed gold in sedimentary formations of the south of Ukraine.

ГЕОЛОГО-ГЕОМОРФОЛОГИЧЕСКИЕ УСЛОВИЯ ФОРМИРОВАНИЯ И СОХРАННОСТИ РОССЫПЕЙ ЗОЛОТА В БЕЛЬСКОЙ МЕЖГОРНОЙ ДЕПРЕССИИ (ЮЖНЫЙ УРАЛ)

An analysis of the geological and geomorphological features of the formation and preservation of gold placers in the Pribelsky placer zone located in the central part of the Belsky intermountain depression in the Southern Urals revealed the following. Valley of River Belay within Belsky depression, inheriting a zone of the Zyuratkulsky deep break, has complex two-level structure. The upper tier is represented by a wide (up to 5 km) trough-like paleovalley with complexes of polygenic and polychronic Miocene-Pliocene formations, both preserved in deep (up to 20–37 m) erosion-karst depressions and in some places coming to the surface. In Beloretsky and Burzyansky prospective sites of these complexes gold-bearing was revealed. As a result of the Eopleistocene – Early Neopleistocene phase of the neo-tectonic uplift of the mountainous part of the Bashkir Urals and subsequent river incision into the bottom of the paleo-valley to a depth of 30 to 130 m, a complex of sediments of the lower tier of the modern Belay river valley was formed. Due to the incision and reworking of goldbearing formations of the upper tier, the weight contents of gold are also established in the braid deposits of the river Belay. It has been shown that the areas of paleo-valley river Belay with karst troughs-traps of placer gold associated with zones of increased fracturing and permeability at the junctions of the submeridional and secant transverse faults. Attention is also drawn to the sites of the inheritance of the paleo-valley by a modern network with a predicted greater concentration of metal in them, even if weakly gold-bearing loose formations.

SPATIALLY-PARAGENETIC, POLYGENIC-POLYCHRONOUS GOLD ORE SYSTEM OF THE SOLONYANSKYE ORE FIELD

During the geological development of the territory within the Solonyansky ore field of Middle Dnipro granite-greenstone region, a spatially paragenetic series of different and heterogenetic gold-bearing formation units was formed, which are united by cause-effect relationships and have a significant resource in the aggregate. An integrated approach to the evaluation of objects that spatially and paragenetically combine the bedrock, hypergenic and placer gold content significantly expands the prospects of the Solonyanskye ore field and enhances its investment attractiveness.

PLACERS OF MAJOR VALLEYS IN THE LENA GOLD-PLACERS REGION

The morphology and inner structure of the placers in the maj or valleys of the Lena gold-bearing area are considered. The morphology of placers in the plan and the distribution of gold within the contours of the valleys are determined by the morphodynamic type of the channels and their evolution in different parts of the valley. The influence of the major tributaries on the placers structure is found out. They determine the presence of the gold-bearing formations, transverse to the axis of the valley, as well as the abrupt changes of the elevation values of the bottom of the metal-bearing layers, which are located on the outcrops of different height levels and in the erosion hollows - paleochannels of the tributaries. Taking these facts into account allow predicting the position and morphology of the gold formations in buried valleys, to identify undiscovered fragments of placers and to increase the accuracy of delimitation blocks for the estimation of the gold reserves.

THE AURIFEROUS SUBMARINE FANS SANDSTONES OF THE IONIAN ZONE (EPIRUS, GREECE)

During recent decades many studies have be done on the rocks that developed in the area of Western Greece and especially in Epirus, known in geoscientific literature as Ionian Zone of External Hellenides. These rocks have undergone geological research (basic geological mapping, research for hydrocarbons, metals and inert materials) and exploitation (inert materials). Recently, within the sedimentary succession of the Ionian zone submarine fans, in the region of Peta–Kompoti, in the prefecture of Arta, have been identified positions where sedimentary gold is present. Recently, positions where sedimentary gold is present, within the sedimentary rocks of the submarine fans, in the region of Peta–Kompoti, prefecture of Arta, have been identified. For the continuation and the practical application of these positive results, it was necessary to obtain a documented reference of geological parameters. After a series of new sampling and detailed analysis of the samples, this work presents the detected gold concentrations, illustrates the limits of grouping areas of interest as well as delineating and illustrating palaeogeographic factors that have contributed to the creation of gold-bearing formations. The highest gold concentration found was in the Ta Bouma sequence. The observation of constant indications of high gold values above background that suddenly increase in certain places up to 260 ppb, leads to the conclusion that in the broader area and within locations with equivalent formations procedure, there could be gold pockets of exploitable concentrations.

Industrial Рerspectives for Аpplication of a New Environmental Protection Technology in Processing of Gold-bearing Technogenic Formations

Industrial Рerspectives for Аpplication of a New Environmental Protection Technology in Processing of Gold-bearing Technogenic Formations

TARGET ORIENTED EXPERT SYSTEMS FOR GEOLOGICAL OBJECTS

The target of the paper is a conceptual presentation of the problem for implementation into geological practice of target oriented expert systems (TOES) basing upon principles of geological objects complex modeling on the basis of modern computer technologies with a perspective of artificial intellect elements introducing. The methodological basis of TOES is represented with complex evaluation of geological medium, and a tool of this evaluation realization is expressed with complex model of the proper issue. The latter includes a structural-litho-logical model, as a basic, matrix one, and a number of subordinate models (hydrogeological, geomechanic, engineering-geological etc.), a set and content of the latter are defined with TOES direction (resources, underground construction, geological environment protection etc.). A scheme of TOES types and content is presented. The examples of target oriented structural-lithological models and complex models are demonstrated, the latter provide a basis for TOES concerning geological objects within the limits of salt, titanium-zirconium and gold-bearing formation types. A subsequent development of this directory comprises the expansion of experience for complex modeling experience, the foundation of knowledge bases, containing expert rules sets for data obtained processing and pertinent mathematic apparatus development, and finally - the development of completed expert systems.

A study on the genetic relations between Permian Longtan Formation coal series strata and Carlin-type gold deposits, southwestern Guizhou Province, China

A large number of the Carlin-type gold deposits occur in the Longtan Formation in southwestern Guizhou Province. The Longtan Formation contains abundant basalt, tuff and siliceous rocks. All rocks of the Longtan Formation are enriched in gold, which were deposited in a limited platform environment in the transition zone from marine to continental. The process of sedimentation was accompanied by the eruption of Emeishan basalt and hydrothermal deposition controlled by co-sedimentary submarine deep faults in the west, which led to the formation of a peculiar gold-bearing formation with coal series strata. This formation controlled the occurrence of the Carlin-type gold deposits in southwestern Guizhou Province. In response to the remobilization of the Emei mantle plume during the Yanshanian period, As, Au and other ore-forming materials were continuously extracted by deeply circulating waters from the Emeishan basalt and coal seams, thereafter forming ore-forming hydrothermal solutions. When these elements were transported in the coal seams, large amounts of As, Au and other elements were enriched in pyrite within the coal seams, thus forming high-As coal and Carlin-type gold deposits in the Longtan Formation coal series strata.

Causes and Consequences of a Tropical Forest Gold Rush in the Guiana Shield, South America

Statistical and spatial analyses of both historical time series and remotely sensed data show a link between the spatial distribution and growth of gold production across the Guiana Shield in northeast Amazonia. Results indicate that an exponential rise in production across an expanding area is primarily a delayed response to the 1971-1978 market flotation of international gold prices. The subsequent 10-fold (2-fold) average nominal (real) price increase has provided a compelling economic incentive to mass exploitation of lower-grade gold deposits. The ground-based and remotely sensed distributions of mining activity are strongly attached to these deposits that dominate the region's gold geology. The presence of these gold-bearing formations in conservation and sustainable timber zones has sparked social conflict and environmental degradation across the region. Left unmanaged, more than a quarter-million square-kilometer area of tropical forest zoned for protection and sustainable management could ultimately be compromised by the price-driven boom in gold mining through poorly integrated resource use planning, lack of reclamation effort, and control of illegal operations. Serious public health issues propagated through the unregulated mining environment further erode the financial benefits achieved through gold extraction. This study demonstrates in part how international economic policies successfully stabilizing more conspicuous centers of the global economy can have unintended but profound environmental and social impacts on remote commodity frontiers.

Geology, geochemistry and genesis of the Hongshijing gold deposit in Ruoqiang, Xinjiang

The Hongshijing gold deposit, which occurs in the Middle and Late Carboniferous volcanic and pyroclastic rocks, is of the brittle-ductile shear zone type controlled by a rift belt. The Hongshijing gold deposit is one controlled by a brittle shear zone located in the Late Paleozoic rift zone. The altered-rock type and quartz type orebodies are contained in the gold-bearing formation, which consists of basalt and tuffaceous sandstone. The major mineralizing stage is at 267 - 261 Ma and reiteration mineralizing stage at 220 - 209 Ma. The ore minerals include pyrite, magnetite, copper, bornite, ferrohydrite, native gold, and the gangue minerals include quartz, sercite, calcite, Fe-dolomite, leucoxene, anorthose, biotite, baria, cajuelite, and agustite. The wall rock alteration associated with gold mineralization comprises silicification, carbonization, pyritization, sericitization and chloritization. The contents of gold are 2.4 × 10−9 in the gold-bearing formation, 5.7 × 10−9 in the tuffaceous sandstone and 1.4–1.5 × 10−9 in the basalt. Au is associated with Te, Se, Ni, Cu. Au = 74.331 × Te +0.0335 × Ni−0.0211 × Cu-2.650. Geochemical investigations revealed that the mineralizing materials came from the basalt and tuffaceous sandstone in the gold-bearing formation. Under the action of ductile brittle shear structure, the gold-bearing formation was metamorphosed and altered, and the ore-forming materials activated, migrated and mineralized. The mineralizing fluid shows three mineralizing stages, with the characteristics of middle to low temperature (381-115°C) and middle to low mass fractions of NaCl (2.18%-16.77%). The fluid is of the Ca2+ -Mg2+ -Na+ -Cl− type and H2O-NaCl system. According to the data from hydrogen and oxygen isotopic composition (δD = −114.6%= −68.8%, δ18OH 2O = −2.47%−5.91%), the conclusion can be drawn that the mineralizing fluid of the Hongshijing gold deposit was a kind of mixed hydrothermal solution composed mainly of meteoric water, magmatic water and formation water in basalt and tuffaceous-sandstone or metamorphic water. The results show the mineralizing fluid and mineralizing materials came from the basalt and suffaceous-sandstone in the gold-bearing formation in Late Variscan orogeny. Under the action of brittle shearing, the gold-bearing formation was metamorphosed and altered, and the ore-forming material activated, migrated and mineralized withT andP going down and changes in pH, Eh,f O 2 andf S 2 under the earth’s surface from 1.57 to 2.25 km.

Influence of gold mine on groundwater quality (Efemçukuru, Izmir, Turkey)

Currently, exploration of gold ores is under discussion in Turkey, without considering its adverse affect on the environment. Studying the adverse affect on environment is extremely important because significant civic activities are already taking place on the geological units that contain gold ore bodies in Turkey. Such an area is located at the southeast of Izmir City (Turkey), and approximately 2-km-long gold-bearing ore veins occur close to the Efemcukuru Village. The objective of this study was to describe the characteristics and seasonal variation of the groundwater chemistry and pollution of the aquifer in the ore deposit site, and to determine the impact of ore deposits on groundwater quality. The gold-bearing formation is highly weathered and fractured. The fractures in the geological units control the permeability and the depth of groundwater in the area. The concentrations of Al, Ag, Cu, Cd, Cr, Fe, Pb, Mn, Zn, Ni, and Sb were determined for four well samples and two stream waters for wet and dry seasons. The results showed that the concentrations of most of these elements were below the USA EPA (Environmental Protection Agency) limits; however, Pb and Cd concentrations are slightly above the limits. The results indicate that minerals in gold bodies do not dissolve although the weathering of formations is high. The low concentration of elements in groundwater and streams may be attributed to the high velocity of ground and surface water.

Genesis and organic geochemical characteristics of the carbonaceous rock stratabound gold deposits, South China

The organic matter of three different chronological major carbonaceous rock gold-bearing formations of South China (Middle Proterozoic Shangqiaoshan group of northeastern Jiangxi, Lower Cambrian Shuikou group of northern Guangxi and Devonian Shetianqiao group of eastern Hunan) and related carbonaceous stratabound gold deposits such as Jinshan, Longshui and Shixia deposits, respectively, has been characterized by organic geochemical techniques. These organic geochemical results show that the average total organic carbon (TOC) content of the three chronological carbonaceous rock gold-bearing formations of South China ranges from 0.15% to 1.56%. The thermal maturity of the organic matter of host rocks in the three gold-bearing formations is high. The micro-component of the organic matter of the host rocks consists primarily of solid bitumen and graphite. The organic carbon and gold of the host rocks appear to syndeposit in situ during the formation of the gold-bearing formations. The organic carbon played a certain role in controlling the geochemical environment of the gold-bearing formations. The metallogenetic mechanism of the carbonaceous rock stratabound gold deposits of South China is closely associated in genesis with the sedimentation, diagenesis and thermal evolution history of the organic matter of host rocks in the gold-bearing formations.

Kerogen—as a sort of organic bearer of gold in gold-bearing formations

Organic component, organic carbon and gold content analyses were used to study the relationship between gold mineralization and organic matter in major host rocks of three different chronological gold-bearing formations of South China. The results show that the organic matter of host rocks in various chronological major gold-bearing formations of South China has associated with gold mineralization in genesis. There is a positive correlation between gold and organic carbon in the host rocks of gold-bearing formations. Gold element was mainly enriched in insoluble organic matter—kerogen. Gold content of the kerogen is commonly higher from a few tens to several hundred times than that of the whole rocks, up to 5%–40% gold of the whole rocks. Gold remaining in the kerogen was considered an organic group of the kerogen to combine with ionic gold in solution through surface absorption, ion exchange complex reaction and chelation so that the kerogen could have become an important sort of organic bearer of gold in gold-bearing formations.

Ore-controlled Mechanism and Geochemical Characteristics of Gold-bearing Formation in Northwest Jiangxi Terrain

Based on the geological and geochemical studies on the Middle Proterozoic Jiuling Group in the Northwest Jiangxi Terrain, it is ascertained that this group is a kind of Au-bearing formation with Au-Ag-As association, and the volcanism is the key to its foundation. The Jiuling Group can be divided into two geochemical groups: high-Au layers and low-Au layers, which is due to the inhomogeneous metamorphic reformation. The discriminant functions F_1 F_2 can be established by means of Au, Ag, As, Ti, Cr, V, etc. eleven elements, and the diagram of F_1-F_2 is the distinguishing sign of the Au-bearing formation. Based on the systematic studies on two types of gold mineralization, namely, solo gold with metamorphic fluid and Au, Ag, etc. polymetallic association with magmatic fluid, the authors establish the metallogenic model of gold deposits in the area.

Concentration of gold during retrograde metamorphism of Archean banded iron formations, Slave Province, Canada

Gold-bearing iron formations are widely distributed within extensive metasedimentary terranes of the Archean Slave Province, situated in the northwestern Canadian Precambrian Shield. Mineralized iron formations occur within thick turbidite sequences overprinted by a protracted history of deformation, metamorphism, and plutonism. Economically significant gold prospects are specifically sited at structural culminations characterized by polyphase folding. Based on garnet–biotite geothermometry on the stable prograde metamorphic assemblage of enveloping metapelites, peak metamorphic conditions are approximated to be 570 °C and 4 kbar (1 kbar = 100 MPa). Diagnostic prograde mineralogy reveals that two facies of silicate iron formation are represented at the five gold occurrences investigated: (1) amphibolitic iron formation (AIF), characterized by quartz + grunerite + hornblende + pyrrhotite ± garnet ± graphite + ilmenite, and (2) pelitic iron formation (PIF), consisting of quartz + biotite + garnet + ilmenite ± grunerite ± hornblende. Textures reveal that grunerite crystallization preceded hornblende and garnet. Within AIF, banded pyrrhotite is in textural equilibrium with prograde metamorphic minerals. Retrograde hornblende, garnet, zoisite, apatite, carbonate, ferroactinolite, and gold-bearing sulphide minerals replace the prograde mineral assemblages on the margins of quartz veins that intensify at AIF fold hinges.It is hypothesized that the iron-formation-hosted gold deposits of the Slave Province are a result of multistage processes. Gold concentrated at high background levels within pyrrhotite-bearing AIF was remobilized during fluid migration into brittle AIF fold hinges in subsequent metamorphic and deformational events. Metamorphic fluid, ponded in fractured AIF hinge domains, caused retrogressive replacement, quartz veining, and gold-bearing sulphide precipitation during waning temperature. Although the mineralized hinge zones commonly display evidence of late chloritization, this alteration did not further affect gold distribution. The gold precipitated with destabilization of thio complexes due to sulphidation prior to low-temperature hydrothermal activity.

Geology of unmineralized and gold-bearing iron formation, Contwoyto Lake – Point Lake region, Northwest Territories, Canada: Reply

Numerous gold occurrences, including the Lupin mine, exist in Archean iron formation within the Contwoyto Lake – Point Lake region of the Slave Province. Early studies suggested that gold was a syn...

Geology of unmineralized and gold-bearing iron formation, Contwoyto Lake – Point Lake region, Northwest Territories, Canada: Discussion

Geology of unmineralized and gold-bearing iron formation, Contwoyto Lake – Point Lake region, Northwest Territories, Canada: Discussion

Metamorphism and hydrothermal alteration of the Homestake gold-bearing formation

Metamorphism and hydrothermal alteration of the Homestake gold-bearing formation