Geological, mineralogical and geochemical aspects of Archean Banded Iron-Formation-hosted gold deposits: Some examples from Southern Africa

1990 ◽  
Vol 25 (S1) ◽  
pp. S125-S135 ◽  
Author(s):  
T. Oberthür ◽  
R. Saager ◽  
H. P. Tomschi
Keyword(s):  
Southern Africa ◽  
Gold Deposits ◽  
Iron Formation ◽  
Banded Iron Formation

The application of the mise-a-la-masse electrical technique in Greenstone belt gold exploration

1989 ◽  
Vol 20 (2) ◽  
pp. 113
Author(s):  
L.G.B.T. Polomé
Keyword(s):  
Greenstone Belt ◽  
Electrical Potential ◽  
Gold Deposits ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Current Electrode ◽  
Barberton Greenstone Belt ◽  
A Current ◽  
Ore Zones ◽  
Gold Bearing

Most of the gold deposits in the Barberton Greenstone belt of South Africa are relatively small and in structurally complex geological areas.The mise-a-la-masse electrical technique, where a current electrode is earthed in a mineralised zone, was used on one of our exploration projects consisting of a sulphides/gold-bearing carbonaceous banded iron formation within a succession of mafic, ultramafic and sedimentary rocks. The technique was successful in delineating individual mineralised units within a broad lithological sequence. During the survey, electrical potential measurements were recorded on surface, in underground drives and in twenty five boreholes. Measurements were also repeated by earthing the mineralised zone in a number of boreholes. Major discontinuities were recognised within the ore zones and used to interpret geological structures. These were then used to define specific units for ore reserve calculations and the application of selected mining techniques.

An epigenetic origin for Archean banded iron-formation-hosted gold deposits

1984 ◽  
Vol 79 (1) ◽  
pp. 162-171 ◽  
Author(s):  
G. N. Phillips ◽  
D. I. Groves ◽  
J. E. Martyn
Keyword(s):  
Gold Deposits ◽  
Iron Formation ◽  
Banded Iron Formation

scholarly journals Textural and fluid inclusion constraints on the origin of the banded-iron-formation-hosted gold deposits at Maevatanana, central Madagascar

2007 ◽  
Vol 42 (4) ◽  
pp. 385-398 ◽  
Author(s):  
Prosper Andrianjakavah ◽  
Stefano Salvi ◽  
Didier Béziat ◽  
Damien Guillaume ◽  
Michel Rakotondrazafy ◽  
...  
Keyword(s):  
Fluid Inclusion ◽  
Gold Deposits ◽  
Iron Formation ◽  
Banded Iron Formation

A synopsis of mineral deposits in the Archean and Proterozoic rocks of the Lake Nipigon Region, Thunder Bay District, Ontario

2007 ◽  
Vol 44 (8) ◽  
pp. 1041-1053 ◽  
Author(s):  
Mark C Smyk ◽  
James M Franklin
Keyword(s):  
Sedimentary Rocks ◽  
Gold Deposits ◽  
Hydrothermal Systems ◽  
Mineral Deposit ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Midcontinent Rift ◽  
Copper Nickel ◽  
Ultramafic Intrusion ◽  
Lode Gold Deposits

A variety of metallic and non-metallic mineral deposit types occur within Archean and Proterozoic rocks in the area encompassing the Lake Nipigon Region Geoscience Initiative. Archean deposit types include Algoma-type banded iron formation-hosted iron (e.g., Lake Nipigon iron range); volcanogenic massive sulphide copper–zinc (e.g., Onaman–Tashota belt); ultramafic intrusion-hosted chromium (e.g., Puddy–Chrome lakes); mafic to ultramafic intrusion-hosted copper–nickel – platinum group element (PGE) (e.g., Lac des Iles); and pegmatite-hosted deposits of rare metals (Li, Ta, Be), uranium, and molybdenum (e.g., Georgia Lake field, Black Sturgeon Lake, and Anderson Lake, respectively). Mesothermal lode gold deposits are prominent in the Beardmore–Geraldton camp. Superior-type iron formation occurs in Paleoproterozoic Gunflint Formation. "Red-bed" copper occurs in Mesoproterozoic Midcontinent Rift-related Osler Group volcanic and interflow sedimentary rocks. Native copper and copper sulphides occur in Mesoproterozoic Sibley Group sedimentary rocks, adjacent to ultramafic intrusions. These mafic to ultramafic intrusions, associated with Midcontinent Rift magmatism, host copper–nickel–PGE deposits (e.g., Seagull, Great Lakes Nickel). Silver-bearing veins occur in Paleoproterozoic Animikie Group sedimentary rocks in proximity to Midcontinent Rift-related mafic intrusions (e.g., Silver Islet, Silver Mountain). Lead–zinc–barite veins, uranium-bearing veins, and amethyst vein and replacement-type deposits may be cogenetic and formed at or near the unconformity between Sibley Group basal sandstone and underlying Archean granitic basement (e.g., Dorion, Black Sturgeon Lake, McTavish Township). The hydrothermal systems that produced all of these veins were probably driven by heat associated with Midcontinent rifting. Many occur in structures related to rift-bounding faults. Iron oxide – copper–gold deposits may occur near the English Bay intrusion.

scholarly journals Invisible Gold in Pyrite from Epithermal, Banded-Iron-Formation-Hosted, and Sedimentary Gold Deposits: Evidence of Hydrothermal Influence

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 447 ◽  
Author(s):  
Yuichi Morishita ◽  
Napoleon Q. Hammond ◽  
Kazunori Momii ◽  
Rimi Konagaya ◽  
Yuji Sano ◽  
...  
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Gold Deposits ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Field Range ◽  
Invisible Gold ◽  
Epithermal Deposits ◽  
As Relationship ◽  
Low Sulfidation ◽  
The Relationship

“Invisible gold” in pyrite is defined as an Au solid solution of the pyrite lattice, sub-microscopic Au nanoparticles (NPs) in the pyrite, or other chemisorption complexes of Au. Because the relationship between the Au and As concentrations in pyrite could indicate the genesis of the deposit, the purpose of this study is to assess the micro-analytical characteristics of the Au–As relationship in pyrite from epithermal and hydrothermally affected sedimentary Au deposits by secondary ion mass spectrometry. The Au and As concentrations in pyrite vary from 0.04 to 30 ppm and from 1 to 1000 ppm, respectively, in the high-sulfidation Nansatsu-type epithermal deposits; these concentrations are both lower than those of the low-sulfidation epithermal Hishikari deposit. The Au concentrations in pyrrhotite and pyrite reach 6 and 0.3 ppm, respectively, in the Kalahari Goldridge banded-iron-formation-hosted gold deposit, and Au in pyrrhotite may sometimes exist as NPs, whereas As concentrations in pyrrhotite and pyrite are both low and lie in a narrow range from 6 to 22 ppm. Whether Au is present as NPs is important in ore dressing. The Au and As concentrations in pyrite from the Witwatersrand gold field range from 0.02 to 1.1 ppm and from 8 to 4000 ppm, respectively. The shape of the pyrite grains might prove to be an indicator of the hydrothermal influence on deposits of sedimentary origin, which implies the genesis of the deposits.

sPhysicochemical conditions of fluid–wall rock interaction at amphibolite-facies conditions in two Archean hydrothermal gold deposits in the Mt. York District, Pilbara Craton, Western Australia

1995 ◽  
Vol 32 (7) ◽  
pp. 993-1016 ◽  
Author(s):  
P. Neumayr ◽  
J.R. Ridley ◽  
D.I. Groves
Keyword(s):  
Western Australia ◽  
Gold Mineralization ◽  
Wall Rock ◽  
Gold Deposits ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Rock Interaction ◽  
Wall Rock Alteration ◽  
Geochemical Analyses ◽  
Pilbara Craton

Synamphibolite facies Archean gold mineralization in the Mt. York District, Pilbara Craton, Western Australia, is hosted in metamorphosed banded iron formation (Main Hill–Breccia Hill prospect), amphibolites, and ultramafic schists (Zakanaka prospect). Mineralization at Main Hill occurs in quartz breccias with sulfide matrices and in altered wall rock adjacent to quartz–biotite–amphibole ± clinopyroxene veins. Alteration associated with quartz veins is zoned, with biotite—pyrrhotite vein selvedges and a distal calcic-amphibole, arsenopyrite–lôllingite zone. Hydrothermal biotite and actinolite have highest Mg/(Mg + Fe) ratios where associated with abundant sulfarsenides in the distal alteratin zone. Whole-rock geochemical analyses and calculated metasomatic reactions indicate the addition of K, Al, S, As, Au, Ag, and Ni during hydrothermal alteration. Mineralization at Zakanaka is characterized by a broad wall rock alteration halo of biotite–amphibole, and zoned quartz–calc silicate veins proximal to ore. Wall rock adjacent to the veins contains pyrrhotite, pyrite, and gold. The alteration is explained by K-metasomatism distal to mineralization and K and Ca metasomatism proximal to mineralization. Balanced metasomatic reactions and mass-balance calculations indicate addition of K and depletion of Na, Ca, Mg, and Fe in distal alteration zones and addition of K, Ca, Mg, Fe, and Ti in proximal zones. Gold precipitation at both prospects occurred through loss of S, and possibly As, from the ore fluid during sulfidation reactions with Fe-rich amphiboles and biotites to form Mg-enriched equivalents and sulfarsenides. Changes in the oxidation state of the ore fluid may have enhanced gold precipitation, though pH changes are unlikely to have been important. The controls on mineralization are thus similar to those at many lower temperature, mesothermal deposits. The lack of consistently increasing Mg ratios of calc-silicate phases with increasing intensity of alteration and sulfidation at Main Hill may be the result of coupled substitutions in amphiboles and biotites during infiltration of a fluid with high-S, but low-As, activities.

Sign in / Sign up

Export Citation Format

Share Document