Carbon in Archean rocks of the Abitibi belt (Ontario–Quebec) and its relation to gold distribution

1985 ◽  
Vol 22 (12) ◽  
pp. 1945-1951 ◽  
Author(s):  
Janet S. Springer
Keyword(s):  
Hydrothermal Fluids ◽  
Carbonate Content ◽  
Gold Leaching ◽  
Independent Evidence ◽  
Quartz Veins ◽  
Mass Balancing ◽  
Gold Enrichment ◽  
Carbonaceous Rocks ◽  
Hydrothermal Event

In the Abitibi belt of Ontario and Quebec, sedimentary black argillites with carbon contents of up to 5% C contain up to 0.5 ppm gold. Sheared black argillites, now graphitic schists, reflect the values of the sedimentary precursors, although their appearance is very different. Gold values of 15 ppm and more are found in graphitic schists only where alteration, shown by quartz veins and increased carbonate content, gives independent evidence of a later hydrothermal event. Gold-rich graphitic schists are characterized by veining; raised gold values closely follow vein margins. As mass balancing shows gold leaching and redeposition to be unlikely, gold enrichment is interpreted to reflect introduction of gold and its preferential deposition in carbonaceous rocks by reduction at vein margins. Natural carbons in these rocks may have been surface activated by both shearing and hydrothermal fluids.

Fluid flow and faulting history of the Iano tectonic window (Southern Tuscany, Italy).

2021 ◽  
Author(s):  
Paolo Fulignati ◽  
Martina Zucchi ◽  
Andrea Brogi ◽  
Enrico Capezzuoli ◽  
Domenico Liotta ◽  
...  
Keyword(s):  
Fluid Inclusions ◽  
Hydrothermal Fluids ◽  
Normal Faults ◽  
High Angle ◽  
Quartz Veins ◽  
History Of ◽  
Tectonic Window ◽  
Liquid Vapor

<p>In the Iano area (Southern Tuscany) a small tectonic window of Tuscan metamorphic units is observed. This belongs to the northernmost part of the so-called Mid-Tuscan ridge and, during Pliocene, formed a submarine high, now defining the easternmost shoulder of the Volterra Pliocene basin. The area gives the opportunity to investigate the complete cycle of negative inversion from crustal thickening to crustal thinning, which characterizes Southern Tuscany. Our new data focus on the western margin of the Iano ridge, and in particular on a system of high angle normal faults that represents the youngest structures of the investigated area. These structures, deformed low angle regional detachments locally juxtaposing the uppermost units of contractional nappe stack (the ophiolite-bearing Ligurian units), with the Tuscan metamorphic units, with an almost complete excision of at least 3.5 Km thick Mesozoic to Tertiary Tuscan nappe succession. The high angle normal faults show variable Plio-Quaternary vertical displacements from few meters to about 500 meters, and acted as pathways for the upwelling of hydrothermal fluids, as revealed by Pleistocene travertine deposits, hydrothermal alteration and occurrence of different generations of fluid inclusions in hydrothermal veins associated with these fault systems. Fluid inclusions were studied in quartz veins hosted in the Verrucano metasediments forming the top of the Tuscan metamorphic unit, as well as in some carbonate lithotypes (Cretaceous to Tertiary in age) of the overlying Tuscan Nappe. Two different kinds of fluid inclusions were documented. The Type 1 are multiphase (liquid + vapor + 1 daughter mineral) liquid-rich fluid inclusions whereas the Type 2 are two-phase (liquid + vapor) liquid-rich fluid inclusions. Type 1 fluid inclusions are primary in origin and were found only in quartz veins present in Verrucano metarudites, whereas Type 2 fluid inclusions occur in quartz veins present in both Verrucano phyllites and quartzites and in the carbonate units of the Tuscan Nappe. These are secondary and can be furthermore distinguished in two sub-populations (Type 2a and Type 2b) on the basis of petrographic observation and microthermometric data. Fluid inclusion investigation evidenced an evolution of the hydrothermal fluids from relatively high-T (~265°C) and hypersaline (35 wt.% NaCl<sub>equiv.</sub>) fluids trapped at about 100 MPa, to lower temperature (~195°C) and salinity (~9.5 wt.% NaCl<sub>equiv.</sub>) fluids, having circulated in the high-angle fault system. Based on the new data and a revision of the local tectonic setting a fluid-rock interaction history has been reconstructed with new hints and constraints for the Plio-Quaternary extensional history of the Volterra basin.</p>

scholarly journals Fracture Fillings and Implication of Fluid Activities in Volcanic Rocks: Dixi Area in Kelameili Gas Field, Junggar Basin, Northwestern China

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 154 ◽  
Author(s):  
Mingyou Feng ◽  
Tian Liu ◽  
Tong Lin ◽  
Xiaohong Liu ◽  
Ningxin Li ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Volcanic Rocks ◽  
Junggar Basin ◽  
Hydrothermal Fluids ◽  
Northwestern China ◽  
Volatile Components ◽  
Gas Field ◽  
Weakly Alkaline ◽  
Quartz Veins ◽  
Calcite Veins

The Carboniferous Batamayineishan Formation of the Kelameili Gas Field is a specific weathered crust-related volcanic reservoir that has a significant production rate in the Junggar Basin, Northwestern China, attributed to debatable processes of fluid evolution. The results suggest that various types of fluids occurring in volcanic rocks lead to the filling of quartz and calcite in fractures and their associated alteration haloes. The silica that formed quartz veins was mainly derived from deep hydrothermal fluids, while the carbon dioxide that formed calcite veins originated from sources characterized by mixing and alteration of deep hydrothermal and hydrocarbon fluids. Siliceous hydrothermal fluids rich in sulphur dioxide and other volatile components were driven by a pressure gradient and buoyancy, and circulated both laterally and vertically along the fractures, forming quartz veins and tension fractures under different temperature conditions. Moreover, changes in salinity, pressure, and carbon dioxide of deep fluids, varying from acidic to weakly alkaline, resulted in earlier calcite precipitation in contraction fractures and weathered fractures. Tectonic uplift resulted in the long-term exposure of volcanic rocks, where fresh water mixed with the partially alkaline fluid escaping the basin to form calcite cements, thus retaining the characteristics of a seepage environment in the weathered fractures. Structural fractures occurred due to tectonic movements during the burial period. Filling and leakage of hydrocarbons caused pore fluids to convert from acidic to alkaline, precipitating late sparry calcite in dissolution fractures. Late hydrothermal fluid metasomatism, brought about by infiltration into the permeable zone, caused partial dissolution of local calcite along cleavage cracks.

Carbon-isotope systematics of Archean Au–Ag vein deposits in the Superior Province

1990 ◽  
Vol 27 (1) ◽  
pp. 40-56 ◽  
Author(s):  
R. Kerrich
Keyword(s):  
Hydrothermal Fluids ◽  
Superior Province ◽  
Ambient Temperatures ◽  
Rayleigh Fractionation ◽  
Clastic Sediments ◽  
Isotopic Equilibration ◽  
Vein Deposits ◽  
Carbonaceous Rocks ◽  
Isotope Systematics ◽  
Main Population

Abundant carbonate is a characteristic feature of most Archean mesothermal Au–Ag vein deposits, but the source of the C is controversial. For Superior Province deposits collectively, the maximum variation of average δ13C values is from −9.0 ± 0.7‰ (1σ, n = 19; Darius) to −0.6 ± 1.6‰ (1σ, n = 7; Cochenour–Willians), and limiting δ13C values are−13.6 and + 1.3‰. At the deposit scale, Fe dolomites in nongraphitic lithologies are for the most part isotopically uniform, where δ13C = −3.4 ± 0.4 (1σ) (Hollinger), −3.2 ± 0.3 (McIntyre), −4.7 ± 1.7 (Dome), −2.8 ± 0.6 (Buffalo Ankerite), −3.6 ± 0.5 (Macassa), −3.2 ± 0.3 (Bousquet), −5.4 ± 0.9 (Lamaque), and −5.3 ± 0.5‰ (Hasaga): the restricted individual ranges of δ13C values imply a corresponding uniformity to the ambient temperature and δ13CΣC of the ore-forming fluids.Within individual deposits, small systematic variations of δ13C carbonate arise from (i) interaction of hydrothermal fluids with carbonaceous rocks, (ii) immiscible separation of CO2 + CH4, or (iii) Rayleigh fractionation effects. Positive shifts in δ13C result from buffering of the fluid to lower Eh by reaction with reduced C, whereas negative shifts reflect partial isotopic equilibration between 13C-depleted C (δ13C ≈ −26‰) and aqueous hydrothermal C species. Transient immiscibility of CO2 + CH4 acts to precipitate carbonates enriched relative to the main population of Fe dolomites. The δ13C values of carbonates in unmineralized alteration halos (−2.2 ± 1.1‰, n = 42) at the McIntyre deposit are enriched in 13C relative to the main gold-bearing vein systems (δ13C = −3.2 ± 0.3‰): the enrichment is attributed to a Rayleigh fractionation accompanying progressive consumption of CO2 as hydrothermal fluids infiltrate laterally from veins into wall rocks. Fe dolomite and calcite are variably enriched in 18O with respect to equilibrium quartz-carbonate fractionations for ambient temperatures of 270–340 °C. Carbonate δ18O values diminish in an irregular manner with depth, converging on values of ~11‰ (Fe dolomite, 6800 ft (2073 m), McIntyre). Variable degrees of oxygen-isotope disequilibrium represent overprinting of carbonates by post-Archean brines in the Canadian Shield.Synvolcanic vesicle calcite in three groups of metabasalts (δ13C = −4.3 ± 2.1; −2.8 ± 1.5; −2.7 ± 1.3‰) and calcite in two groups of clastic sediments (−6.4 ± 1.8; −4.6 ± 2.5‰) remote from deposits are systematically depleted of 13C relative to average Precambrian limestones (~0 ± 1‰), owing to the involvement of CO2 derived from 13C-depleted organic matter. Consequently, calcite in greenstone belt supracrustal rocks is not restricted to approximately 0‰. The total spread of average δ13CFe dol values (−9.0 ± 0.7 to −0.6 ± 0.6‰) in the Au deposits, which goes in hand with a geographical provinciality in O-, Sr-, and Pb-isotope compositions of the ore-forming fluids, is too large to be accounted for by mantle CO2 (−6 ± 2‰) or magmatic CO2 (−6 ± 2‰) alone but rather is interpreted as reflecting generation of hydrothermal fluids in crustal or subcreted rocks heterogeneous in terms of the distribution of 13C-enriched (carbonate) and 13C-depleted (reduced C) lithologies.

scholarly journals Amethyst Occurrences in Tertiary Volcanic Rocks of Greece: Mineralogical, Fluid Inclusion and Oxygen Isotope Constraints on Their Genesis

Minerals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 324 ◽  
Author(s):  
Panagiotis Voudouris ◽  
Vasilios Melfos ◽  
Constantinos Mavrogonatos ◽  
Alexandre Tarantola ◽  
Jens Gӧtze ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Open System ◽  
Volcanic Rocks ◽  
Hydrothermal Fluids ◽  
Northern Greece ◽  
Quartz Veins ◽  
Low Salinity ◽  
Moderate Salinity ◽  
Host Rocks ◽  
Of Greece

Epithermally altered volcanic rocks in Greece host amethyst-bearing veins in association with various silicates, carbonates, oxides and sulfides. Host rocks are Oligocene to Pleistocene calc-alkaline to shoshonitic lavas and pyroclastics of intermediate to acidic composition. The veins are integral parts of high to intermediate sulfidation epithermal mineralized centers in northern Greece (e.g., Kassiteres–Sapes, Kirki, Kornofolia/Soufli, Lesvos Island) and on Milos Island. Colloform–crustiform banding with alternations of amethyst, chalcedony and/or carbonates is a common characteristic of the studied amethyst-bearing veins. Hydrothermal alteration around the quartz veins includes sericitic, K-feldspar (adularia), propylitic and zeolitic types. Precipitation of amethyst took place from near-neutral to alkaline fluids, as indicated by the presence of various amounts of gangue adularia, calcite, zeolites, chlorite and smectite. Fluid inclusion data suggest that the studied amethyst was formed by hydrothermal fluids with relatively low temperatures (~200–250 °C) and low to moderate salinity (1–8 wt % NaCl equiv). A fluid cooling gradually from the external to the inner parts of the veins, possibly with subsequent boiling in an open system, is considered for the amethysts of Silver Hill in Sapes and Kassiteres. Amethysts from Kornofolia, Megala Therma, Kalogries and Chondro Vouno were formed by mixing of moderately saline hydrothermal fluids with low-salinity fluids at relatively lower temperatures indicating the presence of dilution processes and probably boiling in an open system. Stable isotope data point to mixing between magmatic and marine (and/or meteoric) waters and are consistent with the oxidizing conditions required for amethyst formation.

scholarly journals Amethyst occurrences in Tertiary volcanic rocks of Greece: mineralogical and genetic implications

2013 ◽  
Vol 47 (1) ◽  
pp. 477 ◽  
Author(s):  
P. Voudouris ◽  
I. Psimis ◽  
C. Mavrogonatos ◽  
C. Kanellopoulos ◽  
M. Kati ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Hydrothermal Activity ◽  
Hydrothermal Fluids ◽  
Calc Alkaline ◽  
Northern Greece ◽  
Volcanic Arc ◽  
Quartz Veins ◽  
High Sulfidation ◽  
Host Rocks ◽  
Of Greece

Epithermal-altered volcanic rocks in Greece host gem-quality amethyst veins in association with various silicates, carbonates, oxides, sulfides and halides. Host rocks are Oligocene to recent calc-alkaline to shoshonitic lavas and pyroclastics of intermediate- to acid composition. The amethyst-bearing veins occur in the periphery of porphyry-type and/or high-sulfidation epithermal mineralized centers in northern Greece (e.g. Sapes, Kirki, Kornofolia/Soufli, Lesvos island) and on Milos island in the active Aegean Volcanic Arc. Hydrothermal alteration around the quartz veins includes sericitic, K-feldspar (adularia), argillic, propylitic and zeolitic types. Precipitation of amethyst in the northern Greece occurrences, took place during the final stages of the magmatic-hydrothermal activity from near-neutral to alkaline fluids, as indicated by the presence of gangue adularia, calcite, smectite, chlorite, sericite, pyrite, zeolites (laumontite, heulandite, clinoptilolite), analcime and minor amounts of barite, halite, epidote and fluorite in the quartz veins. Amethyst at Milos Island (Chondro Vouno and Kalogries-Vani areas), is accompanied by barite, smectite and lepidocrocite. Colloform-crustiform banding with alternations of amethyst, chalcedony and/or carbonates is a common characteristic of the studied amethyst-bearing veins. Fluid inclusion- and mineralogical data suggest that the studied amethyst were formed at: 174-246 °C (Sapes area), 100-175 °C (Kirki and Kornofolia areas) and 223-234°C (Lesvos island). The amethyst formation requires oxidizing conditions and is probably the result of mixing between meteoric or seawater with upwelling hydrothermal fluids. The involvement of seawater in the studied mineralization is supported by the presence of halite and abundant barite in the veins. Finally, the studied amethyst deposits should be evaluated as potential gemstone sources in Greece.

scholarly journals Caracterização da Alteração Hidrotermal Micácea do Tipo Greisen e dos Reequilíbrios de Baixa Temperatura em Áreas Graníticas: o Exemplo do Distrito Estanífero de Encruzilhada do Sul, RS

2007 ◽  
Vol 34 (2) ◽  
pp. 75
Author(s):  
ROBERTO DOS SANTOS TEIXEIRA ◽  
JOSÉ CARLOS FRANTZ ◽  
ANDRÉ SAMPAIO MEXIAS ◽  
JULIANA CHARÃO MARQUES ◽  
JORGE ALBERTO COSTA
Keyword(s):  
High Temperature ◽  
White Mica ◽  
Hydrothermal Fluids ◽  
Hydrothermal Conditions ◽  
Quartz Veins ◽  
Upper Limit ◽  
Argillic Alteration ◽  
Granitic Intrusions ◽  
Homogenization Temperatures ◽  
Phyllic Alteration

The hydrothermal alteration associated with the tin mineralization in the Encruzilhada do Sul Tin District is characterized by zones with different compositions. The most important of these hydrothermal zones are the phyllic and the argillic. The first one is composed mainly by white mica and quartz with tourmaline. The argillic alteration is composed by kaolinite. The phyllic zones represent associations with greisens and disseminated pervasive white mica on the granitic wall rocks. The argillic zones are constrained to the top zones of some granitic intrusions associated with greisens and quartz-veins in the stockworks. The hydrothermal fluids associated with the alteration show homogenization temperatures ranging from about 450˚C to 120˚C. The first temperature is the upper limit for the hydrothermal system, related with the white mica high temperature alteration. The second temperature is the lower limit of the argillic alteration under the hydrothermal conditions. The white mica related with the phyllic alteration range from phengite to muscovite. The argillic alteration has the presence of halloysite, probably as a weathering product.

Fe-Mn phosphate associations as indicators of the magmatic-hydrothermal and supergene evolution of the Jálama batholith in the Navasfrías Sn-W District, Salamanca, Spain

2012 ◽  
Vol 76 (1) ◽  
pp. 1-24 ◽  
Author(s):  
T. Llorens ◽  
M.C. Moro
Keyword(s):  
Hydrothermal Fluids ◽  
Granitic Pegmatite ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Magmatic Differentiation ◽  
Metasedimentary Rocks ◽  
Quartz Veins ◽  
Ore Minerals

AbstractThe residual melts that remained after the consolidation of the Jálama batholith crystallized to form a group of intra-granitic pegmatite dykes, which are hosted by its outermost facies (the External Unit), and the most evolved residual melts migrated through fractures to form the Cruz del Rayo field of pegmatite dykes, which are hosted by pre-Ordovician low-grade metasedimentary rocks. The increasing activity of phosphorus as magmatic differentiation took place led to the crystallization of primary phosphates, including members of the triplite–zwieselite and the amblygonite–montebrasite series. A strong albitization of the granitic and pegmatite rocks led to the replacement of the primary assemblage by other phosphates such as alluaudite. The influx of post-magmatic hydrothermal fluids, produced quartz veins, gave rise to the crystallizationof ore minerals and triplite, and altered the granites, aplites and pegmatites, replacing some of the phosphate minerals and feldspars and depositing goyazite, montebrasite and childrenite–eosphorite. The interaction of the residual hydrothermal fluids with those from the surrounding metamorphic rocks during later alteration events resulted in the influx of large quantities of Ca and Mg, and produced phosphate assemblages enriched in those elements. Finally, late goyazite, hydroxylapatite and an unidentified Fe-rich phosphate were formed as a result of supergene alterationby percolating meteoric waters, which added Ca, Sr and other elements into the system, and increased fO2.

scholarly journals In–Situ LA-ICP-MS Trace Elements Analysis of Pyrite and the Physicochemical Conditions of Telluride Formation at the Baiyun Gold Deposit, North East China: Implications for Gold Distribution and Deposition

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 129
Author(s):  
Chang-Ping Li ◽  
Jun-Feng Shen ◽  
Sheng-Rong Li ◽  
Yuan Liu ◽  
Fu-Xing Liu
Keyword(s):  
Gold Deposit ◽  
Hydrothermal Fluids ◽  
Coarse Grained ◽  
Late Triassic ◽  
Invisible Gold ◽  
Northern Margin ◽  
Compositional Evolution ◽  
Quartz Veins ◽  
North East ◽  
Icp Ms

The Baiyun gold deposit is located in the northeastern North China Craton (NCC) where major ore types include Si-K altered rock and auriferous quartz veins. Sulfide minerals are dominated by pyrite, with minor amounts of chalcopyrite, sphalerite and galena. Combined petrological observations, backscattered electron image (BSE) and laser ablation analysis (LA-ICP-MS) have been conducted on pyrite to reveal its textural and compositional evolution. Three generations of pyrite can be identified—Py1, Py2 and Py3 from early to late. The coarse-grained, porous and euhedral to subhedral Py1 (mostly 200–500 μm) from the K-feldspar altered zone is the earliest. Compositionally, they are enriched in As (up to 11541 ppm) but depleted in Au (generally less than 10 ppm). The signal intensity of Au is higher than background values by two orders of magnitude and shows smooth spectra, indicating that invisible gold exists as homogeneously or nanoscale-inclusions in Py1. Anhedral to subhedral Py2 grains (generally ranging 500–1500 μm) coexist with other sulfides such as chalcopyrite, sphalerite and galena in the early silicification stage (gray quartz). They have many visible gold grains and contain little amounts of invisible Au. Notably, visible gold has an affinity with micro-fractures formed due to late deformation, implying that native gold may have resulted from mobilization of preexisting invisible gold in the structure of Py2 grains. Subsequently Py3 occurs as very fine-grained disseminations of euhedral crystals (0.05–1 mm) in late silicification stage (milky quartz) and coexists with tellurides (e.g. petzite, calaverite and hessite). They contain the highest level of invisible gold with positive correlations between Au-Ag-Te. In the depth profiles of Py3, the smooth Au spectra mirror those of Te with high intensities, revealing that gold occurred as homogeneously/nanoscale-inclusions and submicroscopic Au-bearing telluride inclusions in pyrite grains. The high Te and low As in Py3, combined with high Au content, imply that invisible gold can be efficiently scavenged by Te. Abundant tellurides (petzite, calaverite and hessite) have been recognized in auriferous quartz veins. Lack of symbiosis sulfides with the tellurium assemblages indicates crystallization under low fS2 and/or high fTe2 conditions and coincides with the result of thermodynamic calculations. High and markedly variable Co (from 0.24 to 2763 ppm, average 151.9 ppm) and Ni (from 1.16 to 4102 ppm, average 333.1 ppm) values suggest that ore-forming fluid may originate from a magmatically-derived hydrothermal system. Combined with previous geochronological data, the textural and compositional evolution of pyrite indicates that the Baiyun gold deposit has experienced a prolonged history of mineralization. In the late Triassic (220,230 Ma), the magmatic hydrothermal fluids, which had affinity with the post-collisional extensional tectonics on the NCC northern margin, caused initial gold enrichment. Then, as a result of deformation or the addition of new hydrothermal fluids, visible gold-rich Py2 was formed. The upwelling of mantle–derived magma brought in a lot of Te-rich ore-forming hydrothermal fluids during the peak of the destruction of the NCC (~120 Ma). Amount of visible/invisible gold and Au-Ag-Te mineral assemblages precipitated from these mineralized fluids when the physical and chemical conditions changed.

scholarly journals Effect of paleoseawater composition on hydrothermal exchange in midocean ridges

2017 ◽  
Vol 114 (47) ◽  
pp. 12413-12418 ◽  
Author(s):  
Michael A. Antonelli ◽  
Nicholas J. Pester ◽  
Shaun T. Brown ◽  
Donald J. DePaolo
Keyword(s):  
Low Temperature ◽  
Negative Feedback ◽  
Chemical Exchange ◽  
Hydrothermal Systems ◽  
Hydrothermal Fluids ◽  
Sr Isotope ◽  
Seawater Chemistry ◽  
Quartz Veins ◽  
Midocean Ridges ◽  
Temperature Exchange

Variations in the Mg, Ca, Sr, and SO4 concentrations of paleoseawater can affect the chemical exchange between seawater and oceanic basalt in hydrothermal systems at midocean ridges (MOR). We present a model for evaluating the nature and magnitude of these previously unappreciated effects, using available estimates of paleoseawater composition over Phanerozoic time as inputs and 87Sr/86Sr of ophiolite epidosites and epidote-quartz veins as constraints. The results suggest that modern hydrothermal fluids are not typical due to low Ca and Sr relative to Mg and SO4 in modern seawater. At other times during the last 500 million years, particularly during the Cretaceous and Ordovician, hydrothermal fluids had more seawater-derived Sr and Ca, a prediction that is supported by Sr isotope data. The predicted 87Sr/86Sr of vent fluids varies cyclically in concert with ocean chemistry, with some values much higher than the modern value of ∼0.7037. The seawater chemistry effects can be expressed in terms of the transfer efficiency of basaltic Ca and Sr to seawater in hydrothermal systems, which varies by a factor of ∼1.6 over the Phanerozoic, with minima when seawater Mg and SO4 are low. This effect provides a modest negative feedback on seawater composition and 87Sr/86Sr changes. For the mid-Cretaceous, the low 87Sr/86Sr of seawater requires either exceptionally large amounts of low-temperature exchange with oceanic crust or that the weathering flux of continentally derived Sr was especially small. The model also has implications for MOR hydrothermal systems in the Precambrian, when low-seawater SO4 could help explain low seawater 87Sr/86Sr.

scholarly journals Structure of the Golets Vysochaishy gold deposit (Northern Transbaikalia)

2021 ◽  
Vol 12 (1) ◽  
pp. 60-75
Author(s):  
V. A. Vanin ◽  
A. M. Mazukabzov
Keyword(s):  
Cross Section ◽  
Structural Elements ◽  
Subsequent Transformation ◽  
Quartz Veins ◽  
Crenulation Cleavage ◽  
Deformation Processes ◽  
Carbonaceous Rocks ◽  
Axial Surface ◽  
Ore Zones ◽  
Gold Bearing

The article describes the fold-thrust structure of the Golets Vysochaishy deposit located at the Baikal-Patom Upland in the Marakan-Tunguska megasyncline. The latter is composed of terrigenous-carbonate carbonaceous rocks metamorphosed in greenschist facies conditions. The deposit is detected in the hanging wing of the asymmetric Kamenskaya anticline. In a cross section, the anticline is an S-shaped structure extending in the latitudinal direction. The main feature of the Golets Vysochaishy deposit is the development of interlayer sulfidization zones (pyrite, pyrrhotite), including gold-bearing ones. Its gold-ore zones tend to occur in layered areas of interlayer sliding in the rocks of the Khomolkhinskaya suite.Four structural markers revealed within the deposit area are indicative of repeated deformation processes: (1) sublatitudinal folding, cleavage of the axial surface and its subsequent transformation into schistosity; (2) crenulation cleavage; (3) interlayer sliding and rock breakdown with interlayer drag folds, parallel microfractures and polished slickensides; (4) large quartz veins and veinlets that cross cut the main structural elements in plan.

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