Vein Formation and Deformation in Greenstone Gold Deposits

2001 ◽  
pp. 111-155 ◽  
Keyword(s):  
Gold Deposits ◽  
Vein Formation

Nature and evolution of metamorphic fluids associated with turbidite-hosted gold deposits: Hill End goldfield, NSW, Australia

1993 ◽  
Vol 57 (388) ◽  
pp. 423-436 ◽  
Author(s):  
P. K. Seccombe ◽  
J. Ju ◽  
A. S. Andrew ◽  
B. L. Gulson ◽  
K. J. Mizon
Keyword(s):  
Lead Isotope ◽  
Early Carboniferous ◽  
Gold Deposits ◽  
Source Rocks ◽  
Gold Deposition ◽  
Vein Quartz ◽  
Sulphur Isotope ◽  
Hydrous Minerals ◽  
Vein Formation ◽  
The Hill

AbstractThe Hill goldfield, NSW, Australia, is an example of a syntectonic, slate-belt gold deposit formed in a multiply deformed, Late Silurian slate-metagreywacke turbidite sequence. Gold is confined to bedding-parallel veins and discordant leader veins composed of as many as four generations of quartz, accompanied by phyllosilicates, carbonates and minor sulphides. Vein formation and gold deposition was apparently synchronous with Early Carboniferous metamorphism and deformation. Homogenisation temperatures (Th) for fluid inclusions in vein quartz demonstrate five groupings in the temperature intervals 350-280°C 280-250°C 250-190°C 190-150°C and 150-110°C corresponding to a variety of primary and secondary inclusions developed during four periods of vein quartz deposition under a generally declining temperature regime. Inclusion fluids are characterised by a low salinity of around 0.1 to 3.6 wt. % NaCl equivalent. The dominant gas phase present in the inclusion fluids varies from N2 in the early stages of the paragenesis, through CH 4 during the main episode of gold deposition, to CO2- rich fluids associated with late-stage mineralisation. δ18O values for vein quartz (range 15.1-17.1‰) and vein carbonate (range 11.3-13.4‰) are typical of metamorphic mineralisation. δD composition of hydrous minerals and inclusion fluids (range −53 to −138‰) suggest an influx of meteoric water in the later mineralising fluids. This conclusion is supported by δ13C data for vein calcite (range −2.5 to −9.7%0). δ34S composition of vein pyrrhotite and pyrite ranges from 6.9 to 7.8‰ early in the paragenesis, to lighter values (around 4.2 to 5.8%0) accompanying late gold deposition from more oxidising fluids. Sulphur isotope data imply a sulphur source from underlying turbidites and an increase in fluid oxidation state during mineralisation . Lead isotope measurements on vein pyrite, arseno py rite, galena and gold are characterised by two isotope populations with 207Pb/206Pb ratios of 0.862 and 0.860, which define two discrete mineralising events during vein formation. Consistency between data from vein minerals and lead isotope signatures for potential source rocks indicate that lead was derived from the sedimentary pile.

Orogenesis, high-T thermal events, and gold vein formation within metamorphic rocks of the Alaskan Cordillera

1993 ◽  
Vol 57 (388) ◽  
pp. 375-394 ◽  
Author(s):  
R. J. Goldfarb ◽  
L. W. Snee ◽  
W. J. Pickthorn
Keyword(s):  
Gold Mineralization ◽  
Hydrothermal Activity ◽  
Gold Deposits ◽  
Tectonic Deformation ◽  
Alkaline Magmatism ◽  
Metasedimentary Rocks ◽  
South Central ◽  
Vein Formation ◽  
Northern Alaska ◽  
Gold Bearing

AbstractMesothermal, gold-bearing quartz veins are widespread within allochthonous terranes of Alaska that are composed dominantly of greenschist-facies metasedimentary rocks. The most productive lode deposits are concentrated in south-central and southeastern Alaska; small and generally nonproductive gold-bearing veins occur upstream from major placer deposits in interior and northern Alaska. Oreforming fluids in all areas are consistent with derivation from metamorphic devolatilisation reactions, and a close temporal relationship exists between high-T tectonic deformation, igneous activity, and gold mineralization. Ore fluids were of consistently low salinity, CO2-rich, and had δ18O values of 7‰- 12‰ and δD values between −15‰ and −35‰. Upper-crustal temperatures within the metamorphosed terranes reached at least 450-500°C before onset of significant gold-forming hydrothermal activity. Within interior and northern Alaska, latest Paleozoic through Early Cretaceous contractional deformation was characterised by obduction of oceanic crust, low-T/high-P metamorphism, and a lack of gold vein formation. Mid-Cretaceous veining occurred some 50-100 m.y. later, during a subsequent high-T metamorphic/magmatic event, possibly related to extension and uplift. In southern Alaska, gold deposits formed during latter stages of Tertiary, subduction-related, collisional orogenesis and were often temporally coeval with calc-alkaline magmatism.

X-ray computed tomography study for drill core of the Drazhnoe orogenic-type gold deposit (Sakha (Yakutia), Russian Federation)

2022 ◽  
pp. 43-59
Author(s):  
Victoria Chikatueva ◽  
Nikita Stepanov ◽  
Andrey Chitalin ◽  
Dmitry Korost
Keyword(s):  
Computed Tomography ◽  
Three Dimensional ◽  
Distribution Patterns ◽  
Gold Deposits ◽  
X Ray ◽  
Vein Formation ◽  
Study Results ◽  
Ore Minerals ◽  
Ore Mineralization ◽  
X Ray Computed

Orogenic gold-quartz deposits have a clear structural control and are accompanied by wallrock metasomatic alteration. However, in detailed modeling of such deposits, there is often a mismatch between the structural plans for high-grade ore zone distribution and metasomatite zones, and the latter are not always associated with faults. This is explained by the evolution of the hydrothermal process and the pulsating nature of the development of the territory. In the early stages of the mineral deposit study, it is very important to reliably determine the distribution of ore zones, since the correct targeting of the drilling program and the economic deposit assessment depend on it. The problem can be solved using the method of X-ray computed tomography (СТ) in the core study. This paper presents the methodology of studying fullsize core samples of gold deposits by using CT. A core sample characterizing the central part of ore body of Drazhnoye deposit (Tarynskoye ore field, Republic of Sakha (Yakutia)) was used as the study material. The sample studied was scanned by a SIEMENS Somatom Perspective tomograph at two energies (80 and 130 keV). As a result, a detailed three-dimensional stereological model of the core was obtained, which made it possible not only to study the distribution of ore minerals in the volume of the entire sample, but also to identify vein bodies of different ages, as well as to study their morphology and trace the distribution patterns of ore mineralization in them. Based on the study results, we can offer a preliminary interpretation of ore mineralization and vein formation sequence.

40Ar/39Ar dating of ribbon-textured veins and wall-rock material from Meguma lode gold deposits, Nova Scotia: implications for timing and duration of vein formation in slate-belt hosted vein gold deposits

1998 ◽  
Vol 35 (7) ◽  
pp. 746-761 ◽  
Author(s):  
Daniel J Kontak ◽  
Richard J Horne ◽  
Hamish Sandeman ◽  
Douglas Archibald ◽  
Jim KW Lee
Keyword(s):  
Nova Scotia ◽  
Wall Rock ◽  
Gold Deposits ◽  
Rock Composition ◽  
Lode Gold ◽  
Rock Samples ◽  
Vein Formation ◽  
Quartz Veining ◽  
Meguma Terrane ◽  
Lode Gold Deposits

Results of 15 40Ar/39Ar age spectra for whole-rock argillite samples collected from within and adjacent to veins from eight Meguma gold districts in the Meguma Terrane of southern Nova Scotia are presented. The samples give excellent plateau ages (i.e., concordance of plateaux, correlation, and integrated ages) that range from ca. 379 to ca. 403 Ma, and there is no apparent correlation of age with bulk rock composition (K2O, Al2O3) or sampling localities. In addition, apparent ages for samples from a district are similar within analytical error, except for one deposit, and there is no difference for samples from within ribbon-textured veins versus samples collected outside of the gold districts (i.e., in areas free of quartz veining). The results of this work compare well to previous whole-rock 40Ar/39Ar dating of Meguma Group samples and we concur with previous workers that the range in dates (i.e., 380-410 Ma) reflects diachronous cooling of the area through the intracrystalline retention temperature for argon in mica (i.e., approx. 300-350°C). However, with respect to the vein samples, there is a marked difference between the 40Ar/39Ar ages of vein-hosted whole-rock samples and hydrothermal minerals (amphibole, muscovite, biotite) from the same deposits previously dated, which indicates that whole-rock samples have retained their metamorphic ages and have not been reset by the later hydrothermal event responsible for vein formation, despite being incorporated within the high-temperature fluids (approx. 400-450°C). This discrepancy in ages indicates that the wall rocks and veins were in thermal disequilibrium, as the vein temperatures were well above that required to cause diffusion of argon out of mica phases within the whole-rock samples, and implies therefore that the fluids must have been derived from depth. The results have the following important implications for models of vein formation: (i) vein formation was rapid and is consistent with models of hydrofracturing due to fluid overpressure, and (ii) the vein-forming fluids were derived from depth and cannot have been produced by a lateral secretion processes whereby fluids and gold are derived from the Meguma Group.

Studi Awal Geologi di Daerah Beruang Kanan Kabupaten Gunung Mas Propinsi Kalimantan Tengah

PROMINE ◽  
2018 ◽  
Vol 6 (1) ◽  
pp. 1-11
Author(s):  
Retno Anjarwati ◽  
Arifudin Idrus ◽  
Lucas Donny Setijadji
Keyword(s):  
Gold Mineralization ◽  
Volcanic Rocks ◽  
Gold Deposits ◽  
Central Kalimantan ◽  
Magmatic Arc ◽  
Tertiary Sediment ◽  
Copper Gold ◽  
Regional Tectonic ◽  
Mineralization Processes ◽  
High Yields

The regional tectonic conditions of the KSK Contract of Work are located in the mid-Tertiary magmatic arc (Carlile and Mitchell, 1994) which host a number of epithermal gold deposits (eg, Kelian, Indon, Muro) and significant prospects such as Muyup, Masupa Ria, Gunung Mas and Mirah. Copper-gold mineralization in the KSK Contract of Work is associated with a number of intrusions that have occupied the shallow-scale crust at the Mesozoic metamorphic intercellular junction to the south and continuously into the Lower Tertiary sediment toward the water. This intrusion is interpreted to be part of the Oligocene arc of Central Kalimantan (in Carlile and Mitchell 1994) Volcanic rocks and associated volcanoes are older than intrusions, possibly aged Cretaceous and exposed together with all three contacts (Carlile and Mitchell, 1994) some researchers contribute details about the geological and mineralogical background, and some papers for that are published for the Beruang Kanan region and beyond but no one can confirm the genesis type of the Beruang Kanan region The mineralization of the Beruang Kanan area is generally composed by high yields of epithermal sulphide mineralization. with Cu-Au mineralization This high epithermal sulphide deposition coats the upper part of the Cu-Au porphyry precipitate associated with mineralization processes that are generally controlled by the structure

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