New data on the reduced intrusion-related Au mineralization of Central Kolyma gold region: age, formation conditions, composition, orecontrolling factors

2021 ◽  
pp. 68-89
Author(s):  
Nikolay Pachersky ◽  
Sergei Kryazhev ◽  
Eugene Naumov ◽  
Darya Desyatova ◽  
Svetlana Dvurechenskaya ◽  
...  

New data are presented on the formation conditions and ages of the reduced intrusion-related Au mineralization of the Vetrenskaya area in the Central Kolyma region. The mineralization is predominantly confined to intersections of Late Jurassic minor intrusive bodies and NE-trending fracture systems and is represented by zones of thin quartz veinlets with sericite-quartz halos. The major ore mineral is gold-bearing arsenopyrite (up to 10%), while minor minerals are represented by lellingite, pyrite, chalcopyrite, and pyrrhotite. Microscopic native gold of a low fineness is paragenetically associated with bismuth minerals (bismuthine, native bismuth, andtellurides of Bi and Au), forming microinclusions (1–10 μ) in the arsenopyrite. Isochronous Re-Os age of the goldbearing arsenopyrite is 137–117 Ma, which suggests the mineralization was formed significantly later than the hosting granitoids (147–153 Ma). The reduced intrusionrelated Au ore deposit was formed at shallower depths in comparison with orogenic Au deposits, and at lower temperatures in comparison with rare metal (W, Mo) ore deposits.

2008 ◽  
Vol 72 (4) ◽  
pp. 953-970 ◽  
Author(s):  
T. Oberthür ◽  
T. W. Weiser

AbstractGold mineralization at the Viceroy Mine is hosted in extensional veins in steep shear zones that transect metabasalts of the Archaean Arcturus Formation. The gold mineralization is generally made up of banded or massive quartz carrying abundant coarse arsenopyrite. However, most striking is a distinct suite of Au-Bi-Te-S minerals, namely joseite-A (Bi4TeS2), joseite-B (Bi4Te2S), hedleyite (Bi7Te3), ikunolite (Bi4S3), ‘protojoseite’ (Bi3TeS), an unnamed mineral (Bi6Te2S), bismuthinite (Bi2S3), native Bi, native gold, maldonite (Au2Bi), and jonassonite (AuBi5S4). The majority of the Bi-Te-S phases is characterized by Bi/(Se+Te) ratios of >1. Accordingly, this assemblage formed at reduced conditions at relatively low fS2 and fTe2. Fluid-inclusion thermometry indicates depositional temperatures of the main stage of mineralization of up to 342°C, in the normal range of mesothermal, orogenic gold deposits worldwide. However, melting temperatures of Au-Bi-Te phases down to at least 235°C (assemblage (Au2Bi + Bi + Bi7Te3)) imply that the Au-Bi-Te phases have been present as liquids or melt droplets. Furthermore, the close association of native gold, native bismuth and other Bi-Te-S phases suggests that gold was scavenged from the hydrothermal fluids by Bi-Te-S liquids or melts. It is concluded that a liquid/melt-collecting mechanism was probably active at Viceroy Mine, where the distinct Au-Bi-Te-S assemblage either formed late as part of the main, arsenopyrite-dominated mineralization, or it represents a different mineralization event, related to rejuvenation of the shear system. In either case, some of the gold may have been extracted from pre-existing, gold-bearing arsenopyrite by Bi-Te-S melts, thus leading to an upgrade of the gold ores at Viceroy. The Au-Bi-Te-S assemblage represents an epithermal-style mineralization overprinted on an otherwise mesothermal (orogenic) gold mineralization.


2019 ◽  
Vol 487 (4) ◽  
pp. 424-427
Author(s):  
L. N. Kogarko

Detailed studies have shown that changing the forms of eudialyte release (and the time of its crystallization) is a new geochemical criterion for the ore - bearing of alkaline magmas for rare metal (eudialyte ores). A new ore-bearing principle of alkaline magmas has been formulated: a prerequisite for the formation of an ore deposit is the early saturation of alkaline magmas with respect to the ore mineral. If the concentration of the ore component is significantly lower than the cotectic concentration (saturation), then the melt saturation and crystallization of the ore mineral will be carried out at the later stages of rock formation in a small volume of interstitial melt, when the phenomena of convective-gravity differentiation and segregation of mineral phases in the form of ore deposits are hampered. This leads to the dispersion of ore components in the form of xenomorphic forms of accessory minerals. Rocks of the differentiated complex (lower zone of the Lovozero deposit), and of the Khibiny massif, containing xenomorphic eudialyte, are not promising for eudialyte ores. Eudialyte deposits are associated with the upper zone of the Lovozero intrusion containing idiomorphic early eudialyte. The saturation of the initial magma in relation to eudialyte occurs after crystallization of about 80% of the intrusion. The proposed criterion is applicable to the largest alkaline massifs in the world. With the Ilimaussaksky massif (Greenland), in the rocks of which early, crystallized, idiomorphic eudialyte, there is a superlarge eudialyte ore deposit while in the Khibiny eudialyte ore is absent.


Author(s):  
V. Yu. Chikatueva ◽  
S. A. Sitkevich

New data on the mineral composition of the Drazhnoye gold deposit, located within the Taryn ore field, have been presented. The samples from the central and flank areas of the deposit, which characterize ore and barren zones, have been studied. Based on the detailed studies of the interrelationship and the form of mineral exhalations and their aggregates, the stages of mineral formation have been proposed, including two main stages: sediment-diagenetic and hydrothermal-metasomatic. It has been revealed that the main precipitator of early native gold was pyrrhotite, which later, with an increase in fugacity of sulfur, was almost replaced by later pyrite. At the end of hydrothermalmetasomatic stage, native gold is formed from gold-bearing solutions and is located often in quartz and quartzcarbonate veinlets as independent precipitates, less commonly associated with polymetallic minerals, pyrite and arsenopyrite. Previous researchers of the Drazhnoye deposit established its genetic relationship with hydrothermal solutions. The data obtained confirm this. According to the type of gold ore mineralization and the type of prospective deep source of solution, this field is previously attributed to a hydrothermal pluton-related gold — quartz formation.


Author(s):  
С.Г. Парада ◽  
М.Ю. Маркин ◽  
В.В. Столяров ◽  
Х.О. Чотчаев

Проведен сопоставительный анализ документации керна буровых скважин и результатов химикоаналитических определений золота в керновых пробах из рудных интервалов золотоносных скарнов Зыгыркольской зоны. Показано, что содержания золота в рудных интервалах не зависят от типа, форм проявления, количества и состава рудных минералов. Отсутствие связи концентраций золота с сульфидами, магнетитом и гематитом подтвердилось и при исследовании пробпротолочек, составленных из хвостов 50 бороздовых проб, отобранных из рудных интервалов, в которых содержания золота по результатам химического анализа составили от 0,6 до 9,9 г/т. Результаты минералогического анализа шлихов показали крайнюю бедность их рудными минералами. В минералогических пробах руд с максимальными содержаниями золота установлены частицы самородного золота, при полном отсутствии в этих пробах сульфидов и других рудных минералов. Множественная корреляция, выполненная по массиву химикоаналитических данных, полученных по результатам кернового опробования золотоносных скарнов Зыгыркольской рудоносной зоны, показала, что золото достаточно сильно положительно коррелируется только с висмутом. Это соответствует минералогическим данным о наличии ассоциации самородного золота с самородным висмутом, установленной по результатам электронномикроскопических исследований. Установлено также отсутствие значимой корреляции золота и серебра, что может свидетельствовать о разных этапах золотой и серебряной минерализаций. Относительно сильная положительная корреляция серебра со свинцом, сурьмой, цинком, мышьяком, марганцем и оловом свидетельствует о связи этого элемента с проявлениями сульфидной минерализации, содержащими галенит, пираргирит и другие сульфоантимониты, сульфоарсениды и сульфостанаты, а также алабандин. Таким образом, установлено, что золотое оруденение в скарнах Зыгыркольской зоны является монометалльным (чисто золотым), образовавшимся раньше так называемых сопутствующих сульфидных и сульфидномагнетитовых минерализаций Тырныаузского рудного поля The correlative analysis of borehole core documentation and results of gold determination in core samples from ore intervals of gold bearing skarns of the Zygyrkol zone has been carried out. It was shown that gold contents in the ore fntervals does not depend on the type, forms of manifestation, number and composition of ore minerals. Absence of connection of gold concentration with sulphides, magnetite and hematite has been also confirmed at investigation of crush samples, composed of tails of 50 trench samples, taken from ore intervals, in which gold contents by results of chemical analysis made from 0.6 to 9,9 g/t. Results of mineralogical analysis of blacksands have shown their extreme poverty in ore minerals. In the mineralogic samples of ores with maximal gold contents there were established particles of native gold, at full absence of sulphides and other ore minerals in these samples. Plural correlation carried out on the array of chemicalanalytic data, obtained by results of core sampling of goldbearing skarns of the Zygyrkol ore bearing zone, has shown that the gold is sufficiently strong correlated only with bismuth. This corresponds to the mineralogical data about existence of association of native gold with native bismuth, established on results of electronmicroscopic research. There is established also absence of significant correlation of gold and silver, what can testify in favor of different stages of golden and silver mineralizations. Relatively strong positive correlation of silver with lead, antimonium, zinc, arsenic, maqnganese and tin, testify about link of this element with manifestations of sulphide mineralization, containing galenite, pyrargyrite and other sulphoantimonites, sulphoarsenides and sulphostannates, and also alabandite. So it has been stated that golden mineralization in skarns of the Zygyrkol zone is monometallic (pure golden), formed earlier than so called attendant sulphide and sulphidemagnetite mineralizations of the Tyrnyauz ore field


Author(s):  
A. N. Glukhov ◽  
◽  
M. I. Fomina ◽  
E. E. Kolova ◽  
◽  
...  

The authors briefly characterize the geology and structure of the Shtokovoye ore field attached to the area where the Khurchan-Orotukan zone of tectonic-magmatic activation overlays the structures of the Yana-Kolyma ore-bearing belt. Studied are mineral associations and physicochemical conditions of gold ore bodies, located both in granites and in hornfelsed sedimentary masses. By the main features of its geological structure, ore composition, and physicochemical formation conditions, the Shtokovoye ore field mineralization corresponds to the "depth" group of the gold-rare-metal formation, analogous to the Butarnoye, Basugunyinskiye, Dubach, and Nadezhda occurrences. Its ores are peculiar in the late epithermal mineralization, which is associated with the Okhotsk-Chukotka volcanic belt and overlays the sinaccretional gold-rare-metal mineralization.


2019 ◽  
Vol 61 (1) ◽  
pp. 18-38
Author(s):  
L. B. Damdinova ◽  
B. B. Damdinov ◽  
M. O. Rampilov ◽  
S. V. Kanakin

This study examines the compositions of the ore and the ore formation solutions, conditions of formation, and sources of Be mineralization using the Aunikskoye F-Be deposit, which is an integral part of the Western Transbaikal beryllium-bearing provinces, as a representative example. Further, the main factors responsible for the formation of beryllium mineralization were evaluated. The ore deposits are presented by the feldsparic–fluorspar–phenacite–bertrandite metasomatites formed in the carboniferous limestones during their metasomatic alternation with hydrothermal solutions by introducing F, Be, and other associated elements. The formation of early phenacite–fluorspar association occurred in high-fluorite СО2-containing solutions of elevated alkalinity with a salinity of ~10.5%–12% wt eq. NaCl in a temperature range of ~ 370–260 °С at pressures ranging from 1873 to 1248 bar. More recent fluorite and bertrandite deposits were formed by solutions with a salinity of 6.4%–7.7% wt eq. NaCl in a temperature range of ~156 °C–110 °C and a pressure range of 639–427 bar. The examination of the isotopic signature of the ore association minerals confirmed the apocarbonate nature of the main ore deposit and allowed the determination of the magmatogene nature of the ore-forming paleothermal springs, which are the source of subalkaline leucogranites. The primary factors that influenced the formation of the F-Be ore included the reduction of the F activity in solutions because of the binding of Ca and F in fluorite as well as because of the decrease in temperature during the ore deposition process. The elevated alkalinity of the ore-formation solutions resulted in the low solubility of the Be complexes, which caused a relatively low Be content in the ore and a relatively small amount of mineralization in the deposit.


2019 ◽  
Vol 10 (2) ◽  
pp. 375-404 ◽  
Author(s):  
N. G. Murzintsev ◽  
I. Yu. Annikova ◽  
A. V. Travin ◽  
A. G. Vladimirov ◽  
B. A. Dyachkov ◽  
...  

The article presents an event correlation of the Permian‐Triassic granites of the Altai collision system, which are associated with industrial ore deposits and occurrences (Mo‐W, Sn‐W, Li‐Ta‐Be). The multi‐system and multi‐mineral isotope datings of igneous rocks and ore bodies (U/Pb, Re/Os, Rb/Sr, Ar/Ar‐methods) suggest the postcollisional (intraplate) formation of ore‐magmatic systems (OMS), the duration of which depended on the crustmantle interaction and the rates of tectonic exposure of geoblocks to the upper crustal levels.Two cases of the OMS thermal history are described: (1) Kalguty Mo‐W deposit associated with rare‐metal granite‐leucogranites and ongonite‐ elvan dykes, and (2) Novo‐Akhmirov Li‐Ta deposit represented by topaz‐zinnwaldite granites and the contemporary lamprophyre and ongonit‐elvan dykes. For these geological objects, numerical modeling was carried out. The proposed models show thermal cooling of the deep magmatic chambers of granite composition, resulting in the residual foci of rare‐metal‐granite melts, which are known as the petrological indicators of industrial ore deposits (Mo‐W, Sn‐W, Li‐Ta‐Be). According to the simulation results concerning the framework of a closed magmatic system with a complex multistage development history, the magmatic chamber has a lower underlying observable massif and a reservoir associated with it. A long‐term magmatic differentiation of the parental melt (a source of rare‐metal‐granite melts and ore hydrothermal fluids) takes place in this reservoir.


2021 ◽  
Vol 48 (1) ◽  
pp. 1
Author(s):  
José Cabello

A review of gold and gold bearing base metals deposits in Chile, indicate the existence of at least six different type of ore deposits, most largely formed during the Cenozoic with predominance in the Miocene. Mesozoic deposits are common but less relevant regarding their size and gold content. These hydrothermal ore deposits are genetically associated with subduction related Andean arc magmatism. Due to its relationship with episodic magmatism migrating eastward, there is a tendency for the deposits to be in distinct, north-south trending, belts with a progressive west to east decrease in mineralization age. After analysing 82 cases in total, main gold concentration can be assigned to high-sulfidation epithermal and porphyry type deposits. Low-sulfidation epithermal, IOCG and mesothermal type appears as less relevant. Gold bearing copper deposits constitute an important part of Chile’s total gold production. Both IOCG type but especially porphyry copper deposits are and will remain as a substantial source to supplement the future output of the gold in the country. The 82 deposits with their tonnage and grade studied, represent a total gold content of 11,662 t equivalent to 375 Moz, excluding past production for those exploited. A number of probable gold bearing base metals high tonnage deposits (IOCG and porphyry copper) do not include their gold content in public format, hence the number delivered could be estimated conservative. Methodical geochronological, ore types and zonation studies are required to better appreciate this metallogenic setting widening current understanding and future exploration results.


Author(s):  
John D. Greenough ◽  
Alejandro Velasquez ◽  
Mohamed Shaheen ◽  
Joel Gagnon ◽  
Brian J. Fryer ◽  
...  

Trace elements in native gold provide a “fingerprint” that tends to be unique to individual gold deposits. Fingerprinting can distinguish gold sources and potentially yield insights into geochemical processes operating during gold deposit formation. Native gold grains come from three historical gold ore deposits; Hollinger, McIntyre (quartz-vein ore), and Aunor near Timmins, Ontario, at the western end of the Porcupine gold camp and the south-western part of the Abitibi greenstone belt. Laser-ablation, inductively-coupled plasma mass spectrometry (LA ICP MS) trace element concentrations were determined on 20 to 25 µm wide, 300 µm long rastor trails in ~ 60 native gold grains. Analyses used Ag as an internal standard with Ag and Au determined by a scanning electron microscope with an energy dispersive spectrometer. The London Bullion Market AuRM2 reference material served as the external standard for 21 trace element analytes (Al, As, Bi, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Pd, Pt, Rh, Sb, Se, Si, Sn, Te, Ti, Zn; Se generally below detection in samples). Trace elements in native gold associate according to Goldschmidt’s classification of elements strongly suggesting that element behavior in native Au is not random. Such element behavior suggests that samples from each Timmins deposit formed under similar but slightly variable geochemical conditions. Chalcophile and siderophile elements provide the most compelling fingerprints of the three ore deposits and appear to be mostly in solid solution in Au. Lithophile elements are not very useful for distinguishing these deposits and element ABSTRACT CUT OFF BY SOFTWARE


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