Distinguishing barren and auriferous veins in the Sigma Mine, Val-d'Or, Quebec

1993 ◽  
Vol 30 (3) ◽  
pp. 413-419 ◽  
Author(s):  
Ross L. Sherlock ◽  
E. Craig Jowett ◽  
Brian D. Smith ◽  
Donald E. Irish
Keyword(s):  
Raman Spectroscopy ◽  
Fluid Inclusions ◽  
Homogenization Temperature ◽  
Lode Gold ◽  
Quartz Veins ◽  
Melting Temperatures ◽  
Abitibi Greenstone Belt ◽  
Significant Difference ◽  
Lode Gold Deposit ◽  
Exploration Tool

The Sigma Mine is an Archean lode gold deposit located in the Abitibi greenstone belt, Quebec. Barren quartz veins occur subparallel to auriferous veins within the mine and also occur north of the mine. The quartz and auriferous veins exhibit a similar mineralogy and alteration and are indistinguishable except for the presence or absence of gold. This study determines differences between (i) a vein that may be auriferous but lacks gold at that location and (ii) a barren vein that formed from fluids that never had the capability of carrying gold. Microthermometry distinguishes two distinct salinities within aqueous inclusions in the barren veins, compared to high salinities only reported in the auriferous veins. The CO2–H2O fluid inclusions within barren veins are remarkably similar to their counterparts in auriferous veins in composition, homogenization temperature, and CO2 effervescence. The most significant difference between the two vein types, and a potential exploration tool, is observed in the CO2-rich inclusions. Tight clustering of first melting temperatures between −57.4 and −56.4 °C and Raman spectroscopy indicate the presence of only CO2 in the barren veins. These results contrast sharply with the −62.5 to −56.0 °C range of first melting temperatures and the presence of H2S indicated by Raman spectroscopy in auriferous veins. Lack of CH4 and H2S gases in the barren CO2-rich inclusions reflects the oxidation state of the fluids, which was too high to permit transport of gold as a reduced complex.

scholarly journals Ore Forming Fluid of Epithermal Quartz Veins at Cisuru Prospect, Papandayan District, West Java, Indonesia

2019 ◽  
Vol 4 (3) ◽  
pp. 170
Author(s):  
Kha Yay Oo ◽  
Wayan Warmada ◽  
Anastasia Dewi Titisari ◽  
Koichiro Watanabe
Keyword(s):  
Fluid Inclusion ◽  
Melting Temperature ◽  
Fluid Inclusions ◽  
Measurement Data ◽  
Homogenization Temperature ◽  
Salinity Range ◽  
Ice Melting ◽  
West Java ◽  
Quartz Veins ◽  
Lapilli Tuff

The Cisuru area is located in Talegong Sub-district, Garut Regency, West Java, Indonesia which is belongs to the central part of Southern Mountain Slope. The aim of this research is to understand the nature and characteristic of fluid inclusion from quartz veins (especially drill core samples) in the study area. Rock units in the area are characterized by Tertiary volcanic rocks and volcaniclastic sequence which is mainly composed of andesite, andesitic breccia, volcanic breccia, lapilli tuff, dacite and related to the intrusion of diorite. The Cisuru epithermal mineralization is dominantly hosted by andesite, dacite, breccia and lapilli tuff, and would probably be controlled by both permeable rocks and NS and NE-SW trending strike-slip faults. The mineralization is shown as void filling and replacement within the silica zone, veinlets along with the open space/fractures and dissemination. Fluid inclusion from quartz veins was studied to know nature, characteristics and origin of hydrothermal fluids. Microthermometric measurements of fluid inclusions were realized by using a Linkam THMSG 600 combined freezing and heating stages. Homogenization temperature and final ice melting temperature were measured for primary two-phase inclusion from quartz veins. Base on the study of the fluid inclusion, the value of homogenization temperature (Th) range from 200 ºC to 395 °C and ice melting temperature range from -0.1 to - 4.5 where salinity range from 0.2 to 7.2 wt. % NaCl equivalent. Fluid inclusion petrography and microthermometric measurement data exhibit that fluid mixing, dilution and boiling were main processes during the hydrothermal evolution.  The formation temperature of each quartz vein is 260 ºC to 290 ºC and also their formation depth is estimated between 560m to 925m respectively. Combination of fluid inclusions petrography, microthermometric measurement, and estimate paleo depth from Cisuru area were suggested under the epithermal environment.

Archaean precious-metal hydrothermal systems, Dome Mine, Abitibi Greenstone Belt. II. REE and oxygen isotope relations

1979 ◽  
Vol 16 (3) ◽  
pp. 440-458 ◽  
Author(s):  
R. Kerrich ◽  
B. J. Fryer
Keyword(s):  
Oxygen Isotope ◽  
Greenstone Belt ◽  
Precious Metal ◽  
Igneous Rocks ◽  
Lode Gold ◽  
Quartz Veins ◽  
Hydrothermal Quartz ◽  
Abitibi Greenstone Belt ◽  
Chemical Sediments ◽  
Gold Bearing

The Porcupine District, Abitibi Greenstone Belt, is one of the most extensive areas of Archaean auriferous mineralisation. At least two stages of lode-gold emplacement are recognised: the first stage involves gold-bearing carbonate–chert chemical sediments within the lower mafic volcanic sequence; the second stage is represented by auriferous hydrothermal quartz veins which postdate deformation of the greenstone assemblage and transect diverse host rocks.Rare-earth element (REE) concentrations in the stratiform carbonates are typical of the distinctive patterns recorded for Archaean chemical sediments. Chert in these rocks has a δ18O value averaging 17.1‰, implying exchange from heavier 18/16 ratios during diagenesis and metamorphism. Metabasic volcanic rocks and quartz–feldspar porphyry stocks with background gold abundances have mean whole-rock δ18O values of 9.1‰ and 10.7‰ respectively. This enrichment in 18O relative to primary igneous rocks is attributed to oxygen isotope exchange with seawater at low temperatures during fluid transport through the oceanic crust.Quartz in all of the five hydrothermal vein systems present has a δ18O of 14‰ to 15‰, and quartz-muscovite fractionations are 3.4‰ to 3.8‰. Ambient temperatures of mineralisation are estimated to have been 400 °C to 450 °C, from oxygen isotope thermometers, fluid inclusion filling temperatures, and metamorphic mineral assemblages. The calculated δ18O of the mineralising solutions is~10‰, implying fluids of metamorphic origin. REE patterns in hydrothermal quartz veins suggest that they have been derived from high-temperature solutions in equilibrium with source rocks having relatively flat (chondrite normalised) REE distributions, such as tholeiitic and komatiitic volcanics. Adjacent to hydrothermal veins, quartz in igneous rocks approaches isotopic equilibrium with vein quartz, at 15‰, and whole-rock δ18O values for metabasalts shift to ~11‰, implying extensive water-rock interaction. Strong depletions in heavy REE of metabasic schists adjacent to veins provides further evidence for pervasive hydrothermal alteration. The Eu enrichment of all lode gold deposits analysed at Dome Mine is consistent with the reduced state of the solutions involved in their deposition, as recorded by the predominance of Fe2+. The gold-bearing veins are believed to have formed by focussed flow of fluids outgassed at the greenschist–amphibolite transition. Source volumes for Au in the Porcupine District exceed 600 km3, the carrier fluid volume for mineralisation was 60–90 km3, the Au solute concentration in the low nanogram mL−1 range, and transport distances were of the order of 10 km. Such veins may be the precursors of precious-metal-bearing chemical sediments if fluids debouche into the hydrosphere.

scholarly journals Fluid evolution from quartz veins in micaschists from the thermal aureole around the Acari batholith, Northeast Brazil

2021 ◽  
Vol 21 (4) ◽  
pp. 13-30
Author(s):  
Laécio Cunha de Souza ◽  
Regina Celia de Oliveira Brasil Delgado ◽  
Heitor Neves Maia
Keyword(s):  
Fluid Inclusions ◽  
Aqueous Fluid ◽  
Fluid Circulation ◽  
Two Phase ◽  
Quartz Veins ◽  
Melting Temperatures ◽  
Three Phase ◽  
Higher Temperature ◽  
Homogenization Temperatures ◽  
Liquid Vapor

Micaschists that host the Acari batholith (Ediacaran age, 572 to 577 My) are characterized by a large number of quartz veins. The veins are more abundant in higher-temperature metamorphic zones and, together with lower metamorphic zones, form an aureole centered in the batholith. Most of the fluid inclusions are two-phase (H2O-CO2 and liquid/vapor), but three-phase varieties (liquid/vapor/salt cubes; liquid/liquid/vapor) occur locally. The analyzed veins come from the biotite + chlorite + muscovite, biotite + garnet, cordierite + andalusite, and cordierite + sillimanite metamorphic zones. CO2 melting temperatures (TmCO2) vary from -62.6 to -56.7°C, suggesting CH4 and/or N2. Eutectic temperatures (Te) in quartz veins show average values of -30.8°C in the biotite + chlorite + muscovite and biotite + garnet zones, and -38.6°C in the cordierite + andalusite and cordierite + sillimanite zones. Ice-melting temperatures (Tmice) are lower in the higher-temperature metamorphic zones. The mode values are -3.8, -5.5, -5.6, and -7.3°C, corresponding respectively to the biotite + chlorite + muscovite, biotite + garnet, cordierite + andalusite, and cordierite + sillimanite zones. A fluid characterized by the H2O-Na-Cl (KCl)-MgCl2-FeCl2-CaCl2 system is defined by: Tmice from near -1.9 to -32°C, the presence of salt cubes mainly in the cordierite + andalusite and cordierite + sillimanite zones, and recorded eutectic temperatures (Te) from -16.5 to -59.1°C. In addition, total homogenization temperatures (Tht) ranging from 117 to 388°C were obtained for primary aqueous fluid inclusions. This indicates a long period of fluid circulation under conditions of falling temperatures. Our results are consistent with an increase in the salinity of the aqueous fluid across the thermal aureole toward the granitic batholith.

An Update on the Geology of the Lupin Gold Mine, Nunavut, Canada

2004 ◽  
Vol 13 (1-4) ◽  
pp. 1-13 ◽  
Author(s):  
P.A. GEUSEBROEK ◽  
N.A. DUKE
Keyword(s):  
Iron Formation ◽  
Western Boundary ◽  
Dome A ◽  
Banded Iron Formation ◽  
Lode Gold ◽  
Quartz Veins ◽  
Slave Province ◽  
Lode Gold Deposit ◽  
World Class ◽  
Recrystallization Front

Abstract The Lupin mine, located in the central Slave province just east of the western boundary of Nunavut Territory, is a world-class example of a Neoarchean-aged banded iron formation (BIF)-hosted lode-gold deposit. At the minesite the gold-mineralized Lupin BIF, separating stratigraphically underlying psammitic wacke and overlying argillaceous turbidite sequences, delineates the Lupin dome, a hammerhead-shaped F2/F3 interference fold structure occurring at the greenschist to amphibolite facies metamorphic transition within the thermal aureole of the Contwoyto batholith. Detailed paragenetic relationships indicate that peak thermal metamorphism coincided with the switch from regional D2 compression to rapid D3 unroofing of the Neoarchean orogenic infrastructure. Gold initially precipitated with pyrrhotite, replacing amphibolitic BIF at the apex of the Lupin deformation zone, separating the east and west lobes of the Contwoyto batholith. Over the course of associated prograde/retrograde metasomatic overprints, gold was further remobilized during garnet and loellingite/arsenopyrite growth in chlorite-altered selvages of late-forming ladder quartz veins. A metamorphic model of ore genesis, with gold being scavenged and transported by metamorphic fluid that was shed and structurally trapped at the amphibolite recrystallization front, is favored over the previously proposed syngenetic and exogenic models of gold concentration that have tended to polarize genetic interpretations to date.

scholarly journals Evaluating the Use of the Molybdenite Re-Os Chronometer in Dating Gold Mineralization: Evidence from the Haigou Deposit, Northeastern China

2019 ◽  
Vol 114 (5) ◽  
pp. 897-915 ◽  
Author(s):  
Degao Zhai ◽  
Anthony E. Williams-Jones ◽  
Jiajun Liu ◽  
David Selby ◽  
Chao Li ◽  
...  
Keyword(s):  
North China ◽  
Gold Mineralization ◽  
Northeastern China ◽  
Orogenic Belt ◽  
Central Asian Orogenic Belt ◽  
Lode Gold ◽  
Quartz Veins ◽  
The North ◽  
Central Asian ◽  
Lode Gold Deposit

Abstract The Haigou lode gold deposit (>40 tons [t] at 3.4 g/t), which is located near the eastern boundary of the Central Asian orogenic belt and the North China craton, is one of the largest gold deposits in northeastern China. Native gold is intergrown with molybdenite and pyrite in auriferous quartz veins hosted by a monzogranite-monzonite stock and locally by Proterozoic gneiss, thereby offering an excellent opportunity to directly date the mineralizing event. Uranium-Pb age determinations for zircon yielded ages for the monzogranite and monzonite of 327.1 ± 1.1 and 329.5 ± 1.0 Ma, respectively. Numerous mafic to felsic dikes, which are crosscut by ore veins (pre-ore), parallel to these veins (possibly synore), or crosscut by them (post-ore), were carefully examined and dated. Their zircon 206Pb/238U ages are 318.3 ± 1.0, 310.9 ± 1.1, and 134.9 ± 0.4 Ma, respectively, thereby placing the timing of gold mineralization within the relatively large interval of 318.3 ± 1.0 to 134.9 ± 0.4 Ma. The age of mineralization was determined directly using the Re-Os method applied to molybdenite. A total of 19 molybdenite samples separated from auriferous quartz veins yielded widely differing Re-Os model ages of 467 to 155 Ma, and replicate analyses of individual samples also yielded widely differing ages. Significantly, the wide range is attributable entirely to the results obtained for some coarse-grained molybdenite samples and is interpreted to be due to Re and Os isotope decoupling, the considerable spatial Re heterogeneity, the analytical procedure (e.g., use of small sample aliquots), and the post-ore deformation. Nine of the samples, which are all fine grained, yielded a robust weighted mean model age of 310 ± 3 Ma and an isochron age of 309 ± 8 Ma. Thus, the molybdenite Re-Os ages are identical, within uncertainty, to those of the dikes that are parallel to the ore veins, indicating that these dikes were emplaced contemporaneously with the ore and that they and the Haigou gold mineralization are of late Paleozoic age (ca. 310 Ma). Finally, a sericite sample obtained from an auriferous vein returned a 40Ar/39Ar plateau age of 165.3 ± 1.2 Ma, which is much younger than the age of the mineralization constrained by Re-Os age determinations of molybdenite. This indicates that the 40Ar/39Ar isotope system was reset by post-ore thermal events. Our new geochronological data provide evidence for late Paleozoic gold mineralization in Haigou, which makes it the oldest known lode gold deposit in the easternmost Central Asian orogenic belt, a finding that has important implications for precious metal mineral exploration in the eastern part of the Solonker-Xar Moron-Changchun-Yanji suture zone between the Central Asian orogenic belt and the North China craton. This study also indicates that accurate and reproducible molybdenite Re-Os ages representing the true timing of ore deposition need an integrated combination of careful petrography, proper sampling procedures, sufficiently large analyzed aliquots, multiple analyses of individual samples, and multiple dating methods.

scholarly journals Mineralogy and Magnetic Behavior of Yellow to Red Xuanhua-Type Agate and Its Indication to the Forming Condition

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 877
Author(s):  
Danyi Zhou ◽  
Guanghai Shi ◽  
Suzhen Liu ◽  
Bailing Wu
Keyword(s):  
Raman Spectroscopy ◽  
Magnetic Susceptibility ◽  
Iron Oxides ◽  
Fluid Inclusions ◽  
Remanent Magnetization ◽  
Magnetic Behavior ◽  
Homogenization Temperature ◽  
Isothermal Remanent Magnetization ◽  
Magnetic Minerals ◽  
Forming Condition

Iron oxides/hydroxides are important magnetic minerals to provide information about changes in the forming environment. However, the magnetic behavior in agate has been rarely investigated. In this study, the magnetic behavior of the Xuanhua-type agate with intense yellow to red colors from the Xuanhua District (China) was investigated by temperature dependence of magnetic susceptibility, hysteresis loop, isothermal remanent magnetization and the analysis of remanent coercivity components from the gradient acquisition plot. Yellow goethite and red hematite can be quantitatively identified by XRD and Raman spectroscopy due to their relatively higher content. Results showed that the red, yellow and orange Xuanhua-type agate had different magnetic behavior, and magnetite existed in the yellow and orange ones. Fluid inclusions in such agate had the homogenization temperature of ~168 °C to 264 °C. All results suggested that the dehydration of goethite to form hematite was the main reason for the high remnant coercivity (above 1000 mT) of hematite in the red agate. The co-existence of magnetite and goethite in the yellow and orange agate reflects the transformation from Fe2+ to Fe3+, indicating the change in the redox property of the environment. Unique patterns mainly formed by hematite and goethite make it a popular gem-material with high research value.

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