U-spatial statistic data modeled on a probability diagram for investigation of mineralization phases and exploration of shear zone gold deposits

2010 ◽  
Vol 104 (1-2) ◽  
pp. 27-33 ◽  
Author(s):  
R. Ghavami-Riabi ◽  
M.M. Seyedrahimi-Niaraq ◽  
R. Khalokakaie ◽  
M.R. Hazareh
Keyword(s):  
Shear Zone ◽  
Gold Deposits ◽  
Spatial Statistic

scholarly journals A NEW GOLD ORE REGION IN TANZANIA

2018 ◽  
pp. 55-59
Author(s):  
V. Mykhailov ◽  
А. Tots
Keyword(s):  
Gold Deposit ◽  
Shear Zone ◽  
Gold Mineralization ◽  
Lake Victoria ◽  
Gold Deposits ◽  
Mobile Belt ◽  
Gold Content ◽  
Gold Ore ◽  
Metallogenic Zone ◽  
The Republic

Tanzania is one of the leading gold mining countries in the world and the discovery of new gold resources on its territory is an actual task. Known gold deposits are concentrated mainly in the northwest of the country, in the metallogenic zone of Lake Victoria, where they are associated with the Archean greenstone belts, and to a lesser extent – in the southwest, in the ore regions of Lupa and Mpanda, confined to the Ubendian Paleoproterozoic mobile belt. With regard to the eastern regions of Tanzania, where the Proterozoic structures of the Uzagaran mobile belt are developed, until recently in this region any significant manifestations of gold mineralization were not known. As a result of our research in the northern part of the Morogoro province of the Republic of Tanzania, a new previously unknown gold deposit Mananila was discovered. It is represented by a large volume, up to 400–450 m long, up to 60–80 m thick, mineralized shear zone over intensely leached and schistosed migmatites, gneisses, amphibolites, penetrated by echelon systems of quartz veins and veinlet, steeply dipping bodies of quartz breccia up to 1.0–1.5 m thick. Gold contents range from 0.61 to 8.11 g/t, the average zone content is 2.5–3.0 g/t. Parallel to the main zone, similar structures are developed on the site, although they are of lower thickness. The forecast resources of the deposit are estimated at 20 tons of gold. 2.8 km to the east from the Mananila field, the recently discovered Mazizi gold deposit is located, and a number of small occurrences of gold are also known in the region. All these objects are located within a large shear zone of the northeastern strike, up to 4–5 km width, over 20 km in length. This serves as the basis for the identification of a new gold ore region in the northern part of the Morogoro province of the United Republic of Tanzania, within the Proterozoic mobile belt of Usagaran, the possible gold content of which has never been previously discussed in geological literature.

Gold Deposits of the ~15-Moz Ahafo South Camp, Sefwi Granite-Greenstone Belt, Ghana: Insights into the Anatomy of an Orogenic Gold Plumbing System

2021 ◽  
Author(s):  
Quentin Masurel ◽  
Paul Morley ◽  
Nicolas Thébaud ◽  
Helen McFarlane
Keyword(s):  
Rock Mass ◽  
Shear Zone ◽  
Gold Mineralization ◽  
Hanging Wall ◽  
Spatial Association ◽  
Sedimentary Rocks ◽  
Shear Zones ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Plutonic Rocks

Abstract The ~15-Moz Ahafo South gold camp is located in southwest Ghana, the world’s premier Paleoproterozoic gold subprovince. Major orogenic gold deposits in the camp include Subika, Apensu, Awonsu, and Amoma. These deposits occur along an ~15-km strike length of the Kenyase-Yamfo shear zone, a major tectonostratigraphic boundary juxtaposing metamorphosed volcano-plutonic rocks of the Sefwi belt against metamorphosed volcano-sedimentary rocks of the Sunyani-Comoé basin. In this study, we document the geologic setting, structural geometry, and rheological architecture of the Ahafo South gold deposits based on the integration of field mapping, diamond drill core logging, 3-D geologic modeling, and the geologic interpretation of aeromagnetic data. At the camp scale, the Awonsu, Apensu, and Amoma deposits lie along strike from one another and share similar hanging-wall plutonic rocks and footwall volcano-sedimentary rocks. In contrast, the Subika gold deposit is hosted entirely in hanging-wall plutonic rocks. Steeper-dipping segments (e.g., Apensu, Awonsu, Subika) and right-hand flexures (e.g., Amoma, Apensu) in the Kenyase-Yamfo shear zone and subsidiary structures appear to have represented sites of enhanced damage and fluid flux (i.e., restraining bends). All gold deposits occur within structural domains bounded by discontinuous, low-displacement, sinistral N-striking tear faults oblique to the orogen-parallel Kenyase-Yamfo shear zone. At the deposit scale, ore-related hydrothermal alteration is zoned, with distal chlorite-sericite grading into proximal silica-albite-Fe-carbonate mineral assemblages. Alteration halos are restricted to narrow selvages around quartz-carbonate vein arrays in multiple stacked ore shoots at Subika, whereas these halos extend 30 to 100 m away from the ore zones at Apensu and Awonsu. There is a clear spatial association between shallow-dipping mafic dikes, mafic chonoliths, shear zones, and economic gold mineralization. The abundance of mafic dikes and chonoliths within intermediate to felsic hanging-wall plutonic host rocks provided rheological heterogeneity that favored the formation of enhanced fracture permeability, promoting the tapping of ore fluid(s). Our interpretation is that these stacked shallow-dipping mafic dike arrays also acted as aquitards, impeding upward fluid flow within the wider intrusive rock mass until a failure threshold was episodically reached due to fluid overpressure, resulting in transient fracture-controlled upward propagation of the ore-fluid(s). Our results indicate that high-grade ore shoots at Ahafo South form part of vertically extensive fluid conduit systems that are primarily controlled by the rheological architecture of the rock mass.

scholarly journals The Mustajärvi orogenic gold occurrence, Central Lapland Greenstone Belt, Finland: a telluride-dominant mineral system

2020 ◽  
Vol 55 (8) ◽  
pp. 1625-1646
Author(s):  
Matthias Mueller ◽  
Petri Peltonen ◽  
Pasi Eilu ◽  
Richard Goldfarb ◽  
Eero Hanski
Keyword(s):  
Shear Zone ◽  
Greenstone Belt ◽  
Gold Deposits ◽  
Orogenic Gold ◽  
Fault System ◽  
Near Surface ◽  
Gold Occurrence ◽  
Metavolcanic Rocks ◽  
Host Rocks ◽  
Central Lapland Greenstone Belt

Abstract The Mustajärvi gold occurrence lies in the southern part of the Paleoproterozoic Central Lapland Greenstone Belt, in proximity to the first-order transcrustal Venejoki thrust fault system. The gold occurrence is structurally controlled by the second-order Mustajärvi shear zone, which is located at the contact between siliciclastic metasedimentary and mafic to ultramafic metavolcanic rocks. The main mineralization comprises a set of parallel veins and sulfidized rocks that are slightly oblique to the shear zone and are hosted by third-order structures likely representing Riedel R-type shears. The gold-mineralized rock at Mustajärvi is associated with pyrite that is present in 0.15- to 1-m-wide quartz-pyrite-tourmaline veins and in zones of massive pyrite in the host rocks with thicknesses ranging from 1.15 to 2 m. In unweathered rock, hypogene gold is hosted by Au- and Au-Bi-telluride micro-inclusions in pyrite, whereas strong weathering at near surface levels has caused a remobilization of gold, resulting in free gold deposited mainly in the cracks of oxidized pyrite. The geochemistry of both mineralization styles is typical of orogenic gold systems with strong enrichments comprising Au, B, Bi, CO2, Te, and Se; and less consistent anomalous amounts of Ag, As, Sb, and W. Unusual for orogenic gold deposits is the strong enrichment of Ni and Co, which leads to the classification of Mustajärvi as orogenic gold occurrence with atypical metal association.

Metallogenesis of the São Martinho and Mosteiros Gold Deposits, Tomar Cordoba Shear Zone, Portugal

2007 ◽  
Vol 49 (10) ◽  
pp. 907-930 ◽  
Author(s):  
D. P. S. de Oliveira ◽  
L. J. Robb ◽  
C. M. C. Inverno ◽  
E. G. Charlesworth
Keyword(s):  
Shear Zone ◽  
Gold Deposits

Geology of the shear-hosted Brookbank gold prospect in the Beardmore–Geraldton belt, Wabigoon subprovince, Ontario

2007 ◽  
Vol 44 (7) ◽  
pp. 925-946 ◽  
Author(s):  
Jerry C DeWolfe ◽  
Bruno Lafrance ◽  
Greg M Stott
Keyword(s):  
Shear Zone ◽  
Hanging Wall ◽  
Shear Zones ◽  
Gold Deposits ◽  
Iron Formation ◽  
Alteration Zone ◽  
Gold Deposition ◽  
Low Grade ◽  
Metasedimentary Rocks ◽  
Polymictic Conglomerate

The Beardmore–Geraldton belt consists of steeply dipping, intercalated panels of metavolcanic and metasedimentary rocks along the southern margin of the granite–greenstone Wabigoon subprovince in the Archean Superior Province, Ontario. It is an important past-producing gold belt that includes classic epigenetic iron-formation-hosted deposits near Geraldton and turbidite-hosted deposits, north of Beardmore. The Brookbank gold prospect belongs to a third group of related gold deposits that formed along dextral shear zones localized at contacts between panels of metasedimentary and metavolcanic rocks. The Brookbank prospect occurs along a steeply dipping shear zone at the contact between footwall polymictic conglomerate and hanging-wall calc-alkaline arc basalt. Early during shearing the basalt acted as a structural and chemical trap that localized brittle deformation, veining, and gold deposition, ankerite–sericite–chlorite–epidote–pyrite alteration, and the replacement of metamorphic magnetite and ilmenite by gold-bearing pyrite. This produced a low grade (≤5 g/t Au) ankerite-rich alteration zone that extends up to 20 m into the hanging-wall basalt. Later during shearing, gold was deposited within higher grade (≤20 g/t Au) quartz–orthoclase–pyrite alteration zones superimposed on the wider ankerite-rich alteration zone. Auriferous quartz–carbonate veins oriented clockwise and counter-clockwise to the shear zone walls are folded and boudinaged, respectively, consistent with dextral slip along the shear zone. A key finding of the study is that different groups of gold deposits in the belt, including epigenetic iron formation gold deposits near Geraldton, formed during post-2690 Ma regional dextral transpression across the belt.

scholarly journals Aeromagnetic and digital elevation model constraints on the structural framework of southern margin of the Middle Niger Basin, Nigeria

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Naheem Banji Salawu
Keyword(s):  
Shear Zone ◽  
Digital Elevation Model ◽  
Gold Mineralization ◽  
High Sensitivity ◽  
Structural Data ◽  
Structural Features ◽  
Gold Deposits ◽  
Significant Implication ◽  
Digital Elevation ◽  
Elevation Model

AbstractHigh resolution aeromagnetic anomaly and topographic data using enhancement filtering techniques have resulted in better understanding of the nature of structures at the margins of the Middle Niger Basin. Due to the lack of structural data, the gold deposits within the margins of the Middle Niger Basin were variably excavated, leading to land degradation. The newly-produced structural map highly constrained the mineralization, which makes the study area and its periphery safe for gold exploration. Structural map has been produced from the integration of derivative maps to assess the pattern of surface and subsurface structural features within the studied area. The structural map unravels structural features with major and minor structural trends, in addition to a prominent crustal partitioning, characterized by the Ifewara shear zone. These structural features correlate very well with known gold mineralized locations and also predict new zones for structurally controlled gold and associated mineralization. The structural patterns are directly related with tectonic episodes in the basement. In fact, the Ifewara shear zone appears more pronounced on the total gradient and 3-D Euler deconvolution maps, which reveal various lineaments within the shear zone. The topographic maps (digital elevation model) clearly shows the surface morphology of the region under study while the resulting shaded-relief map reveal the continuity of the deduced magnetic lineaments that coincide with the valleys of River Niger which exploits zones of weakness from the lineaments. The results suggest high sensitivity of fluvial network to deduced lineaments with possible significant implication for alluvial gold mineralization.

scholarly journals Comparison of Dighem EM and Magnetic Results for Detecting Epithermal And Shear Zone gold Deposits

2010 ◽  
Vol 2010 (1) ◽  
pp. 1-1
Author(s):  
Mohsen Shademan ◽  
Gholam H Noroozi ◽  
AliReza Arab Amiri
Keyword(s):  
Shear Zone ◽  
Gold Deposits

scholarly journals Fluid inclusion study of shear zone hosted lode gold type deposits: El Bagre mining district, Antioquia-Colombia

2020 ◽  
Vol 24 (3) ◽  
pp. 245-257
Author(s):  
Edwin Naranjo Sierra ◽  
Mauricio Alvaran Echeverri
Keyword(s):  
Fluid Inclusion ◽  
Shear Zone ◽  
Gold Deposits ◽  
Fluid Inclusion Study ◽  
Mining District ◽  
Type I ◽  
Lode Gold ◽  
Calcite Veins ◽  
Inclusion Study ◽  
Homogenization Temperatures

The shear zone hosted lode gold type deposits are located at the northeast part of Antioquia department of Colombia. The characteristics of ore-forming fluids were discussed using fluid inclusion petrography and microthermometry analysis. Two stages, namely quartz-pyrite pre-mineralization stage (1) and reactivation-sulfides-tellurides mineralization stage (2) were included in this study. Two types of fluid inclusions were observed: primary aqueous-carbonic inclusions (type I) are characterized by the presence of clathrate, with salinities between 1.5 and 8.3 %wt NaCl equiv. and homogenization temperatures (to liquid) occurs between 238.1° and 297.1°C. Secondary aqueous inclusions (type II) were trapped in reactivated quartz (type IIa) and cross-cutting calcite veins (type IIb), salinity estimates display a mixing trend from a relatively saline with 9.21 %wt NaCl member (type IIa) to a low salinity one with 3.82 %wt NaCl (type IIb), homogenizations to a liquid phase occur between 150.8° and 184.6°C for type IIa inclusions and 130.3° to 190.4°C for type IIb. Based on these results, the shear zone hosted lode gold type deposits from El Bagre mining district, share similar characteristics with orogenic gold deposits.

Polyphase gold mineralisation at the Yaou deposit, French Guiana

2021 ◽  
pp. SP516-2020-29
Author(s):  
Vincent Combes ◽  
Aurélien Eglinger ◽  
Anne-Sylvie Andre-Mayer ◽  
Yoram Teitler ◽  
Arnauld Heuret ◽  
...  
Keyword(s):  
Shear Zone ◽  
French Guiana ◽  
Primary Source ◽  
Gold Deposits ◽  
Low Grade ◽  
Gold Content ◽  
Icp Ms ◽  
Multiple Deformation ◽  
Penetrative Foliation

AbstractThe Yaou deposit, located in French Guiana within the Guiana Shield, is one of the most promising gold deposits of the regional Palaeoproterozoic greenstone belt. It displays numerous quartz monzodiorite bodies aligned along a sinistral shear zone where a five-deformation phases model is established at the camp scale. The ductile D1/2YA phase is responsible for the main penetrative foliation while the D3YA phase is related to shearing. An intrusive event is identified as being pre to syn-D3YA. The following phase D4YA represents a brittle quartz-carbonate veining set hosted preferentially within intrusive bodies and along the shear zone. A local D5YA brecciation event crosscuts the D4YA veins. Among this deformation history, two auriferous events (D3YA and D4YA) control the overall grade of the Yaou gold deposit. More specifically, most of the Au grade is associated with the main economic D4YA veining event, where the gold is visible and linked to Py4 within an ankerite/hematite rich alteration halo. At the microscopic scale, results of in situ analyses using LA-ICP-MS on pyrite show that metasediment-hosted Py0 is a primary source of submicroscopic gold having a low contribution to the total endowment. Py3 shows some gold content due to possible remobilisation of AuD0YA. Gold in Py4 is found as submicroscopic gold, as micro-inclusions and as infilling fractures in association with elements such as Te, Ag and Bi. Most contribution to the Au grade is from micro-inclusions and, to a lesser extent, from free and submicroscopic gold. The ore shoot locations are lithologically controlled for AuD0YA (metasedimentary unit-hosted), structurally controlled (shear zone-hosted) for AuD3YA and rheologically controlled for the AuD4YA (intrusion-hosted). The deposit is clearly polyphase both at the macroscopic and the microscopic scales, invisible gold is associated with As whereas visible gold is observed as inclusions in pyrite with high contents of Ag, Te and Bi. We define an early low-grade enrichment of AuD0YA to AuD3YA followed by a later high-grade event, AuD4YA supporting polyphase mineralisation processes. This study confirms that orogenic gold deposits can be formed by remobilisation and/or new gold inputs during multiple deformation, veining and hydrothermal events.

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