Chapter 9: Orogenic Gold Deposits of the Kibali District, Neoarchean Moto Belt, Northeastern Democratic Republic of Congo

2020 ◽  
pp. 185-201
Author(s):  
Andrew Allibone ◽  
Carlos Vargas ◽  
Etienne Mwandale ◽  
Justus Kwibisa ◽  
Richard Jongens ◽  
...  
Keyword(s):  
Democratic Republic ◽  
Gold Mineralization ◽  
Democratic Republic Of Congo ◽  
Shear Zones ◽  
Gold Deposits ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Republic Of Congo ◽  
Lithostratigraphic Units ◽  
Host Rocks

Abstract The Kibali district in the Democratic Republic of Congo hosts the large Karagba-Chaffeur-Durba (KCD) deposit and smaller satellite deposits that together contained 20 million ounces (Moz) of gold when mining recommenced in 2013. An additional 3 Moz of gold was probably mined from the district before 2013. Gold deposits in the Kibali district are located along the KZ trend, a series of folds, contractional shear zones, and altered lithostratigraphic units that coincide with the margin of an earlier 2630 to 2625 Ma intraorogenic basin within the Neoarchean Moto belt. Fluids first responsible for barren carbonate-quartz-sericite alteration, and later for siderite and/or ankerite (±quartz, magnetite, pyrite, and/or chlorite) alteration with associated auriferous pyrite ± rare arsenopyrite veinlets, infiltrated and replaced the siliciclastic, banded iron formation (BIF), and chert host rocks via fold axes, shear zones, and reactive BIF horizons. The complex shape and gentle northeast plunge of the lodes across the Kibali district reflect the shape and plunge of coincident folds that formed during early barren alteration. Many other folded BIF horizons across the wider Moto belt remain barren or only weakly mineralized, suggesting deep extensional structures that may have developed in the vicinity of the KZ trend during basin opening and prior to gold mineralization, were important fluid pathways during later contractional deformation and mineralization.

scholarly journals A Fonte dos Metais da Mina de Ouro do Schramm, Santa Catarina: Evidências de Dados de Isótopos de Pb e Elementos Terras Raras

2005 ◽  
Vol 32 (1) ◽  
pp. 51
Author(s):  
FLÁVIO FRANÇA NUNES DA ROCHA ◽  
ARTUR CEZAR BASTOS NETO ◽  
MARCUS VINÍCIUS DORNELLES REMUS ◽  
VITOR PAULO PEREIRA
Keyword(s):  
Gold Mineralization ◽  
Isotope Composition ◽  
Shear Zones ◽  
Iron Formation ◽  
Gold Mine ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Santa Catarina ◽  
Lead Isotope Composition ◽  
Ree Patterns

The source of the ore elements in the Schramm gold mine, localized in central part of Santa Catarina shield, has been constrained based on lead isotope composition of galena and sulfosalts, and the rare earth element (REE) patterns of the ore. The Pb207/ Pb206 model age obtained in galena and lillianite-gustavite series from the mineralization yields an age of 1.88 Ga. It is higher than the estimated age of the deposit (» 534 Ma). The Pb isotopic composition obtained in these minerals indicates that the age of Schramm mine source is similar to that of the galena of the Ribeirão da Prata mine (Pb-Zn-Cu-Ag). This mine is located 25 Km southwest of the Schramm gold mine witch is hosted in the tension fracture zone conjugated with the first order shear zone that contains the Ribeirão da Prata deposit. The similarities between Pb-isotope compositions of both deposits could indicate that they were contemporaneous and derived from the same regional lead source. The REE patterns of the ore samples of Schramm mine are similar to that of the pyroxenites and banded iron formations from the Archean Santa Catarina Granulitic Complex that host the Schramm gold mine. They present low REE contents with flat patterns and lack Eu anomalies. The comparison among the isotopic data from this mine with those from other places indicates that the banded iron formation and mafic-ultramafic granulitic gneisses are the source of the gold mineralization. This evidence agreed with the hypothesis that the ore fluids were derived from retrogressive metamorphism reactions of Santa Catarina Granulitic Complex in the shear zones during the final stage of Brasiliano orogenic cycle.

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.

Chapter 13: Boddington: An Enigmatic Giant Archean Gold-Copper (Molybdenum-Silver) Deposit in the Southwest Yilgarn Craton, Western Australia

2020 ◽  
pp. 275-288
Author(s):  
Stephen J. Turner ◽  
Graeme Reynolds ◽  
Steffen G. Hagemann
Keyword(s):  
Western Australia ◽  
Melt Inclusion ◽  
Gold Mineralization ◽  
Extended Period ◽  
Granite Gneiss ◽  
Shear Zones ◽  
Gold Deposits ◽  
Yilgarn Craton ◽  
Local Evidence ◽  
Host Rocks

Abstract Boddington is a giant, enigmatic, and atypical Archean Au-Cu deposit hosted in a small, remnant greenstone belt within granite-gneiss and migmatite of the Southwest terrane of the Yilgarn craton, Western Australia. Primary Au and Cu (and Mo) mineralization consists of a network of thin fractures and veins, controlled by shear zones, and dominantly hosted by early dioritic intrusions and their immediate wall rocks, which comprise felsic to intermediate-composition volcanic and volcaniclastic rocks. The pre-~2714 Ma host rocks are typically steeply dipping and strongly deformed, with early ductile and overprinting brittle-ductile fabrics, and have been metamorphosed at mid- to upper greenschist facies. Features consistent with porphyry-style mineralization, classic orogenic shear zones, and intrusion-related Au-Cu-Bi mineralization are all recognized, giving rise to a variety of genetic interpretations. It is clear that Boddington does not fit any classic Archean orogenic gold deposit model, having a general lack of quartz veins and iron carbonate alteration, a Cu (Mo and Bi) association, zoned geochemical anomalism, and evidence of high-temperature, saline ore-forming fluids. Detailed petrographic, geochemical, and melt inclusion studies suggest a late-stage ~2612 Ma, monzogranite intrusion as one of the principal sources of the mineralizing fluids. However, there is also local evidence for older, perhaps protore, porphyry-style Cu (±Au) in the dioritic intrusions and patchy, locally high-grade, orogenic-style gold mineralization associated with enclosing shear zones and brittle-style deformation, which was focused on the relatively competent dioritic intrusions. The relative contributions of metals from these components to the system may not be resolvable. It appears that the Boddington deposit has been a locus for multiple episodes of intrusion, alteration, and mineralization over an extended period of time, as has been demonstrated in a number of other large Canadian and Australian gold deposits, including the Golden Mile near Kalgoorlie.

scholarly journals Structural Control on Banded Iron Formation (BIF) and Gold Mineralization at Abu Marawat Area, Central Eastern Desert, Egypt

2011 ◽  
Vol 22 (2) ◽  
pp. 155-183
Author(s):  
Mohamed K. El-Shafei Mohamed K. El-Shafei
Keyword(s):  
Structural Control ◽  
Gold Mineralization ◽  
Early Stage ◽  
Pure Shear ◽  
Shear Zones ◽  
Iron Formation ◽  
Low Grade ◽  
Brittle Deformation ◽  
Banded Iron Formation ◽  
Quartz Veins

Abu Marawat area is considered as a promising site for exploration of gold mineralization, where many ancient gold mines, hydrothermal alteration zones, and intervening quartz veins are present. This study is a field-based structural analysis that aims at revealing the relationship between mineral occurrences and local structural setting. The area is a part of a back-arc volcanosedimentary sequence associated with banded iron formation (BIF) that has undergone extensive ductile and brittle deformation history. This multiple deformation is manifested by four phases. D1 and D2 are the product of compressional stresses and are expressed by F1, F2 and F3 folds in low-grade regionally metamorphosed rocks. D1 was a progressive deformational phase started with F1 folds, which in a later stage were overprinted by F2 folds. It resulted from NW-SE-oriented pure shear and is associated with imbricate thrust stacks, which control the locations of listwanite bearing gold. NE-SW-oriented compressive stress during D2 is displayed by F3-slip folds at the early stage followed by N-S- to NW-trending dip-slip normal faults and related shear zones. Mineralized quartz veins (MQV) were developed post-D2 and pre-D3. Folding and refolding in addition to thrust movement play a significant role in shortening and thickening of the iron formation bands located at the summit of Gebel Abu Marawat. D3 and D4 are expressed by brittle deformation. D3 is displayed by conjugate shear planes represented by sinistral-NW-oriented and dextral-NE–oriented strike-slip faults that led to the dislocation and redistribution of gold mineraliztion associated with both MQV and listwanite. Barren quartz veins trending E-W were also developed along gash fractures formed during this phase of deformation.

A progressive episode of deformation in the foreland of the West-Congo Belt: From folding to brittle shearing, in Republic of Congo

2021 ◽  
Author(s):  
Hardy Medry Dieu-Veill Nkodia ◽  
Florent Boudzoumou ◽  
Timothée Miyouna ◽  
Alex Ibarra-Gnianga ◽  
Damien Delvaux
Keyword(s):  
Kinematic Analysis ◽  
Structural Model ◽  
Democratic Republic ◽  
Democratic Republic Of Congo ◽  
Structural Data ◽  
Shear Zones ◽  
The West ◽  
Republic Of Congo ◽  
The Republic ◽  
Late Neoproterozoic

<p>The West Congo belt is a Panafrican orogenic belt that evolved and resulted from the collision of the Sao Francisco craton and the Congo Craton during late Neoproterozoic (630 Ma)  to late Cambrian (490 Ma ?). It constitutes the counterpart of the most studied Araçuaì belt in Brasil. Over the past decades, most structural analysis focused in Araçuaì belt while few structural data were obtained from the West-Congo Belt. Understanding the West Congo belt and particularly in its foreland is relevant to establish a unified structural model for its evolution, as the late phases of deformation of both orogens are still debated. In the Comba basin at Mont Bélo, Loutété, Mfouati, most of the folds are gently plunging, upright to moderately inclined fold, with sometimes chevron shape, circular shape and box shape. Some of the folds show decollement within their limbs. Most of these fold display flexural slip displacements along the layers where slickensides are associated with calcite fibres. Most of the limbs developed boudinage in the carbonate layers. The folds are oriented WNW-ESE and they are cut by a system of conjugate NW-SE striking strike-slip dextral fault and NNE-SSW striking sinistral fault. A kinematic analysis from fault slip data using the Win-Tensor program reveal that faults originate from NNE-SSW shortening and ESE-WNW extension. This kinematic analysis is consistent with the orientation of the fold according the Riedel model. The brittle deformation occurred in continuity of the deformation after the folding as folds hinges are displaced in certain localities.This episode of progressive deformation probably ends with intense shearing of the belts, as several dominating regularly spaced NE-striking shear zones cut the orogen from the Republic of Congo to the democratic Republic of Congo. Further investigations will be conducted in the continuity of the west Congo Belt in the Democratic Republic of Congo in order to enlarge the regional perspective.</p>

The Role of Gender in Agent Banking: Evidence from the Democratic Republic of Congo

2020 ◽  
Author(s):  
Richard Chamboko ◽  
Robert Cull ◽  
Xavier Gine ◽  
Soren Heitmann ◽  
Fabian Reitzug ◽  
...  
Keyword(s):  
Democratic Republic ◽  
Democratic Republic Of Congo ◽  
Republic Of Congo
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