5. Gold deposits of French Guyana, Guyana, Venezuela

Guyana 2018 - El Dorado feeding ourselves - Gold 100 dollars

5. Gold deposits of French Guyana, Guyana, Venezuela – V140418

Contents

0. Introduction

1. Geology

2. Le projet « Montagne d’or » French Guyana

3. Montagne d’Or – Norgold

4. French Guiana – Montagne d’Or – Columbus Gold Corporation

5. Geological and metallogenic environments of gold deposits of the Guiana Shield; a comparative study between St-Elie (French Guiana) and Omai (Guyana) – Jean Lafrance, Marc Bardoux, Gabriel Voicu, Ross Stevenson, Nuno Machado (1999).

6. Gold deposits (gold-bearing tourmalinites, gold-bearing conglomerates, and mesothermal lodes), markers of the geological evolution of French Guiana: geology, metallogeny, and stable-isotope constraints – Jean-Pierre MILESI et. al.

7. Guyana: Gold board moving towards minted gold coins – Apr 15, 2018 – Kaieteur News

8. Guyana: Maps major gold deposits

Gold - El Callao - MCAL
  • facebook
  • Twitter
  • LinkedIn
Gold – El Callao – Venezuela – MCAL

0) Introduction

The first years of my career as a geologist in Venezuela were as a hard-rocker and field mineral exploration consultant.

With the Ministerio de Energia y Minas (Ministry of Energy and Mines, Geological Survey), headquarters El Silencio, Torre Norte, Caracas.

One of my assignments was to assist with exploration in Minerven, Gold Company, in the town El Callao, eastern Venezuela. This area once was the major gold producing area in the world. My task included exploration surveys in the giant gold mine ” Colombia ” and surrounding area. As a ” gold digger “. Exploration? A simple focus. Discover, map and indicate where the quartz veins are with lots of gold.

Gold mine, Colombia - El Callao - MCAL
  • facebook
  • Twitter
  • LinkedIn
Gold mine, Colombia – El Callao – MCAL

El Callao https://en.wikipedia.org/wiki/El_Callao_Municipality:

El Callao is a most interesting mining town.

Where you can have a golden time. As it is all about gold in this town. From the gold shops on the plaza Bolivar. To the golden morning sun and golden sunset.

Where surprisingly, though deep in the Venezuelan hinterland, on the Early Proterozoic of some 2,2 billions years old, you can hear original Caribbean calypso music.

Where surprisingly you can meet native trigueñita beauties with gold blond hair and sparkling green eyes. A precious human cocktail thanks to the lovesome interaction of fortune seekers from diverse countries that came in rushing for the gold. Vintage, limited editions.

Where you can dance calypso. Till the golden morning sun, in the weekends.(https://youtu.be/XsOH4rtE1lI). 

Many first generation Callao miners came from Trinidad, in the former centuries. The older generations still spoke english when I worked there.

Gold Deposits - Guyana Greenstone Belt - MCAL
  • facebook
  • Twitter
  • LinkedIn
Gold Deposits – Guyana Greenstone Belt – MCAL

The gold mine at El Callao, started in 1871, was for a time one of the richest in the world, and the goldfields as a whole saw over a million ounces exported between 1860 and 1883. The gold mining was dominated by immigrants from the British Isles and the British West Indies, giving an appearance of almost creating an English colony on Venezuelan territory.

The Trinidadian immigrants brought the music of Calypso with them, which later became very popular in the city. The folk music is a mixture of Venezuelan and Caribbean genres and is sung in Spanish and/or Caribbean English. It is closely associated with the Carnival festival, a tradition also brought by the West Indian people (https://youtu.be/h1nnL1mmGsg).

In the carnival months, Calypso is performed with competitions, where the winners are crowned Calypso King and Queen. Calypso or as the town’s people call it “Calipso” is one of the most popular cultural tradition that the city is well known for in the rest of the country. Popular instruments used in the performance of the music are the drums, cuatro, maracas, guitar, bandolin, violin and the steel drum.

Since my Minerven assignment I have stayed interested and been keen on gold exploration and genesis, specifically in the Guyana gold and greenstone belt. Extending from Venezuela, Guyana, Suriname to French Guyana. And the twin sister Birimian gold belt in West Africa.

Long before clever petroleum geologists finally realised that the Cretaceous plays on the continental shelf of northern South America were the mirror brothers & sisters of the Jubilee discovery in Ghana, gold ore geologists had already discovered and using this mirror concept for exploration. Which applies for the Guyana – Birimanian goldbeld in the precambrian craton.

El Callao - Venezuela - MCAL
  • facebook
  • Twitter
  • LinkedIn
El Callao – Venezuela – MCAL

Explorer ? Discoverer ? Gold Digger ?

Venezuela seems to have some 7000 tons of gold reserves, in the subsurface.(https://pubs.usgs.gov/bul/2062/report.pdf).

Gold subsurface exploration in the main ” Colombia ”  mine is not so much romantic but very hard work.

Visiting and exploring in the small hand-digged “private” gold mines and concessions is even tougher and more dangerous. Many miners die inside their own mines due to accidents (collapses, toxic gases etc.).

On the photo one of such mines that I visited. Where you only get in and, hopefully also out, with a private lift, a simple bucket.

Gold Deposits - Guyana Greenstone Belt - MCAL
  • facebook
  • Twitter
  • LinkedIn
Gold Deposits – Guyana Greenstone Belt – MCAL

Explorers, gold diggers?

Do not panic and do not get claustrophobic when descending in these mini-handcrafted mines.

Certainly good luck, God Bless You. Enjoy being in the Subsurface.

It is invaluable to have this field Surface and Subsurface experience and knowledge? As additional help, when sitting most comfortable in an ergonomic chair, in front of the multiple wide screens with the virtual subsurface world in front of you, on your workstation.

Or simply making your interpretation by strolling around with your hands in your pockets in the immersive visionarium or visualisation room.

When trying to figure out, as a digital native, from your desktop on floor 33 in a mid-town skyscraper with a most splendid panoramic city view. How the subsurface should really look like and should behave. According to Homo Sapiens Geologica Softwaretialis.

According all the smart programs which perfectly explain how Mother Earth is obliged to behave and should function.

Enjoy.

El Callao - Small, hand-digged private gold mines - MCAL
  • facebook
  • Twitter
  • LinkedIn
El Callao – Small, hand-digged private gold mines – I have been in several of these ” dangerous ” mines – MCAL

Afterward I switched to black gold, petroleum exploration.

Credit for all pictures: published and available on internet.

”  All-in-1 Consultant,  Available-to-Serve-You.

For grounded, vintage stewardship to successfully find lots of oil, mineral resources, develop your business and get sustained value for money ?

See <Contact & Contract Me> at marcelchinalien@gmail.com “.

Doei, salu2, ciao, até logo, grüssen, cordialement, salut, добрый день, ajoo, tur kos bon mi dushi hendenan na Switi Sranan i mi famiri na switi Korsou, tan bun allamala !

Geologic Map El Callao - Choco Gold Area - MCAL
  • facebook
  • Twitter
  • LinkedIn
Geologic Map El Callao – Choco Gold Area – MCAL

1) Geology and gold mineralization of the El Callao District, Bolivar State, Venezuela.

Baxter Peter, 1995: Simposio International del Oro en Venezuela 3 (Pages 143-147)

https://eurekamag.com/research/022/716/022716386.php

The El Callao Mining District located 130 kilometres southeast of Puerto Ordaz has been the most prolific gold mining district in Venezuela and the longest lasting hard rock mining district in the Guayana Shield. Published production is between 124 and 180 tonnes of gold (4 to 5.8 million ounces).

The majority of this production has been from a small number of highgrade underground mines located north and south of the town of El Callao.

Geologic Column - El Callao - Choco Gold Area - MCAL
  • facebook
  • Twitter
  • LinkedIn
Geologic Column – El Callao – Choco Gold Area – MCAL

Mining has been continuous since 1829 with current production from the Columbia mine at approximately 1.86 tonnes of gold per year (60.000 ounces).

Gold mineralization occurs within metavolcanics and metasediments of the Precambrian Guayana Shield, which underlies most of Bolivar State and extends through the neighbouring countries of Guyana, Surinam and northern Brazil.

There are four major lithological units of Proterozoic age in the area, from the oldest to the youngest the El Callao Formation, the Cicapra Formation, the Yuruari Formation, and the Caballape Formation. These units have been subject to amphibolite to greenschist grade regional metamorphism. Structural trends of foliation, folding, faulting and shearing in the EI Callao District are primarily oriented to the northeast with dips mostly to the southeast.

Choco Gold mine - MCAL
  • facebook
  • Twitter
  • LinkedIn
Choco Gold mine – MCAL

The shear hosted gold mineralization consists of quartz veins, quartz stockworks, and massive silicification. Alteration consists of silicification, carbonitization, sericitization, and propylitization. Accessory minerals in the quartz veins include tourmaline, pyrite, arsenopyrite, chalcopyrite and scheelite.

Tropical weathering is only moderately developed in the area with laterite generally not deeper than 3 meters and the saprolitic zone typically less than 30 meters.

El Callao Mining Corporation is a junior exploration company, with majority ownership and management by Bema Gold Corporation. The company has been conducting a gold exploration program primarily on the Lo Increible 2 and 4 concessions since September 1993. Other companies active in the area include, Bolivar Gold, Goldfields of South Africa, Minoven, Teck-KinRoss, and Golden Star.

2) Le projet « Montagne d’or » French Guyana – V.220817

serait à l’origine de la première mine d’or industrielle de Guyane. Ici, le site minier aurifere de Yaou, le 17 septembre 2011, à Maripasoula, en Guyane française.
L’opposition au projet de mine d’or industrielle en Guyane grandit – Le Monde.fr avec AFP – Le 22 août 2017 à 10h59

Une pétition lancée par les opposants a reçu près de 166 000 signatures en cinq mois, alors que le gouvernement n’a toujours pas autorisé la construction de la mine.
Le sujet n’en finit pas de soulever les critiques en Guyane. Pour dénoncer le plus grand projet d’extraction d’or jamais proposé en France, l’opposition a lancé une pétition en mars, qui a déjà récolté 165 800 signatures, et est soutenue par 110 organisations nationales et internationales.

« Il y a cent cinquante ans que la Guyane a eu une histoire d’amour avec l’or, mais il faut que cela cesse. Ce ne sont pas les meilleures orientations économiques pour la Guyane », a expliqué à l’Agence France-Presse (AFP) Nora Stephenson, porte-parole du collectif Or de question. Treize chefs coutumiers de Guyane se sont déclarés contre ce projet industriel inédit, évoqué pour 2022. « Au nom de l’économie, vous êtes prêts à écraser une nouvelle génération », a déploré au début d’août Bénédicte Fdjéké, présidente des chefs coutumiers. « Faire des trous partout, dans le sol qui nous nourrit, c’est une mauvaise chose », a aussi jugé Christophe Pierre, leader du collectif Jeunesse autochtone, lors d’une réunion publique à la fin de juillet.

La raison de leur colère : le projet « Montagne d’or », prévu près de Saint-Laurent-du-Maroni, dans l’Ouest guyanais, et détenu à 55 % par le russe Nordgold et à 45 % par le canadien Columbus gold. Il suscite une telle controverse qu’il n’a pas encore été autorisé par le gouvernement français.

Guyana Shield Gold Deposits
  • facebook
  • Twitter
  • LinkedIn
Guyana Shield Gold Deposits

Lire aussi : L’or de Guyane, un test politique pour Macron
Ampleur économique hors norme

« Montagne d’or » est « hors normes par ses aspects économiques », souligne une « note d’information » interministérielle de février 2016 obtenue par l’AFP, qui prévient également que les « empreintes spatiale et écologique sont de dimensions inconnues en France ».

Selon cette note, les taxes associées à la production minière représenteraient « 80,6 millions d’euros » et celles à l’importation « 325,5 millions d’euros ».

Les industriels, qui prévoient d’extraire « 6,7 tonnes » d’or par an pendant « douze ans », soit une valeur estimée à plus de 3 milliards d’euros, souhaitent un débat public resserré. « Après consultation des élus locaux, tout le monde est pour un débat qui serait guyanais », a affirmé le représentant des industriels, Rock Lefrançois.

Il a saisi la commission nationale de débat public (CNDP) pour lui demander d’organiser un débat local. Au début de juillet, la CNDP a rejeté la demande en l’état, au motif que les coûts initiaux du projet étaient flous et considérant « l’importance considérable des enjeux sociaux, économiques et environnementaux ». La compagnie minière Montagne d’or a annoncé qu’elle organiserait un débat « au cours du quatrième trimestre » avec « le public directement concerné » par le projet.

Impact écologique inquiétant

Mais les opposants craignent pour les conséquences écologiques du projet industriel. S’il était validé par le gouvernement, les miniers creuseraient en pleine forêt tropicale une fosse grande comme trente-deux Stades de France. Les détracteurs du projet s’alarment de la proximité du site avec des massifs à haute biodiversité, dont la plus vaste réserve biologique intégrale de France.

Ils s’inquiètent aussi des déchets qu’engendrerait l’extraction de l’or. Des millions et des millions de mètres cubes de roche devraient être charriés et traités au cyanure pour extraire les 85 précieuses tonnes d’or que Nordgold pense possible de récupérer en quinze ans.

Le déblai entraînerait la création artificielle et permanente de deux dômes de roches de 100 mètres de haut, ainsi que d’un mont endigué de 70 m de haut renfermant, selon les industriels, « 54 millions de tonnes » de boues issues du processus de traitement de la roche avec le cyanure.

Face aux craintes environnementales dans un territoire caractérisé par des retards structurels, notamment en gestion et prévention des pollutions, Rock Lefrançois précise que des « forages […] surveilleront les eaux souterraines pour voir s’il y a des traces ou des niveaux élevés de certains métaux » libérés par la roche à nu ou par les traitements physico-chimiques pour récupérer l’or. « Les forages resteront sur site pendant cinq ans après la fermeture, ensuite il y aura un suivi environnemental sur trente ans », assure-t-il.

« Le drainage minier acide peut durer des centaines d’années, c’est très difficile à maîtriser et ça coûte cher », rétorque Thibault Saint-Aubin, de l’association Ingénieurs sans frontières systèmes extractifs et environnements, soutien d’Or de question. Pour fonctionner, la mine demandera aussi des investissements publics importants (routes, énergie, port, exonérations), dans un territoire où 15 % des foyers du littoral et 30 % des foyers de l’intérieur n’ont pas accès à l’électricité.

French Guyana - Gold mine - MCAL
  • facebook
  • Twitter
  • LinkedIn
French Guyana – Gold mine – MCAL

3)  MONTAGNE D’OR – Norgold

http://www.nordgold.com/operations/development-projects/mondgne/

Guiana Gold Belt - Montagne d'Or - MCAL
  • facebook
  • Twitter
  • LinkedIn
Guiana – Birimian Gold Belt – Montagne d’Or – MCAL

Project Background

The 4.8 million ounce of Mineral Resources Montagne d’Or gold deposit is located in north-west French Guiana, 180 kilometers west of the capital, Cayenne, and 80 kilometres south of the department capital, Saint-Laurent-du-Maroni. The Project’s base camp can accommodate 65 people.

In mid-March 2017, Nordgold earned-in a 55.01% interest in the Montagne d’Or project by spending a minimum of US$30 million and completing a Bankable Feasibility Study by 13 March 2017.

Nordgold also holds ~9% of Columbus Gold Corp.(“Columbus Gold”, CGT: TSX-V), the Company’s partner in the Montagne d’Or project. In October 2014, Mr. Oleg Pelevin, Director of Strategy and Corporate Development for Nordgold, was appointed to Columbus Gold’s board of directors.

Montagne d’Or official website (French)

Montagne d’Or Presentation 2017

Reserves and Resources

Montagne d’Or is located within the northern greenstone belt of the Guiana Shield in French Guiana. The mineral deposits of the Guiana Gold Belt are very similar to those in other greenstone terrains such as in West Africa. This will enable Nordgold to apply its deep knowledge of West African geology to the Project and other projects in the region. Columbus Gold, with its many years of operational experience in French Guiana and unique local knowledge will serve a strong partner in the advancement of the project.

The current model of gold mineralization is a high sulphidization, volcanogenic type. Significant portions are thought to have been emplaced as replacement style mineralization. Subsequently, the mineralization has been deformed and partly remobilised within structural controls. Gold mineralization is associated with primary sulphide minerals as replacements within pyrite and chalcopyrite.

CATEGORY TONNES (M) GRADE (AU G/T) AU (MOZ)
RESERVES *
Proven and Probable 54.11 1.58 2.75
RESOURCES **
Measured and Indicated 85.1 1.41 3.85
Inferred 20.2 1.5 0.96
Total (M+I+I) 105.3 1.4 4.81

 

  • * Proven and Probable Reserves were estimated using a gold price of US$1,200/oz at varied cut-offs dependent on lithological rock types, economics and estimated metallurgical recovery. Felsic Tuffs have CoG of 0.617 g/t Au, Granodiorites have a CoG of 0.622 g/t Au, Mafics have a CoG of 0.665 g/t Au, Saprolite and Saprock have a CoG of 0.552 g/t Au.
  • ** Mineral Resources estimated within pit shell that is defined by an US$1,300/oz price and CoG of 0.4 g/t Au.

4) French Guiana – MONTAGNE D’OR – Columbus Gold Corporation

http://www.columbusgoldcorp.com/s/MontagnedOr.asp

Montagne d’Or is part of the Paul Isnard project which is comprised of eight mining concessions covering an area of 190 km2 and is accessible via an all season forest road from the town of Saint-Laurent-du-Maroni, for a distance of 120 kilometres, and by small aircraft to the project’s base camp. Several roads crisscross the mining concessions providing truck access.

At Montagne d’Or, the gold mineralisation is hosted within a 400 metre thick sequence of intercalated felsic and mafic volcanic and subordinate volcaniclastic rocks that strike east-west and dip steeply south.

The near surface gold resources are contained within four (4) closely-spaced stratiform, sub-parallel, east-west-striking and south-dipping sulphide mineralised horizons, which include the principal UFZ (Upper Felsic Zone) and LFZ (Lower Favorable Zone) having average thicknesses of 50 metres and 17.5 metres, respectively.

Gold mineralisation is associated with disseminated and stringer sulphides with occasional semi-massive seams to several centimetres in width, mainly as pyrite, and is accompanied by pervasive alteration, which includes sericite, secondary biotite (retrograded to chlorite) and secondary K-feldspar ± quartz. Only a small portion of the deposit has been subjected to upper level oxidation.

Montagne d’Or occurs within the Guiana Gold Belt which stretches from western Venezuela eastward through Guyana, Suriname and French Guiana and into Brazil. Mineral deposits are typical of those in other greenstone terrains such as in Canada, Australia and West Africa. Many (8) significant gold deposits and prospects have been identified on the Guiana Gold Belt, including Las Cristinas, Choco, Toropoaru, Aurora, Omai, Gros Rosebel, Merian and Camp Caiman.

Numerous other prospects, mostly in Guyana and Surinam are undergoing active exploration.

Guyana - Africa Gold Areas
  • facebook
  • Twitter
  • LinkedIn
Guyana – Africa Gold Areas

5) Geological and metallogenic environments of gold deposits of the Guiana Shield; a comparative study between St-Elie (French Guiana) and Omai (Guyana)

http://emg.geoscienceworld.org/content/8/1-2/117

Jean Lafrance, Marc Bardoux, Gabriel Voicu, Ross Stevenson, Nuno Machado
Published on April 1999, First Published on April 01, 1999 – ArticleInfo & Metrics – GeoRef, Copyright 2004, American Geological Institute.
Abstract

Paleoproterozoic gold is found in two (2) different volcano-sedimentary sequences and intrusive bodies separated by 600 km within the Guiana Shield.

The 2148 Ma St-Elie granite intruded volcanic-arc sequences of the Paramaca Group.

The 2096 Ma Omai stock penetrated back-arc/island-arc sequences of the Barama-Mazaruni Group.

Positive epsilon Nd values suggest that both suites lack Archean crustal contaminants, which is consistent with an origin in an oceanic arc setting.

4.1 The St-Elie deposit is characterized by quartz-dominant vein systems with minor metallic minerals, represented chiefly by pyrrhotite and pyrite. Biotite, calcite, and chlorite are the main gangue minerals. The alteration haloes at St-Elie feature a strong potassic zone, which is absent at Omai.

The ore-controlling structures are ductile and the vein emplacement is related mainly to contemporaneous, high-angle ductile shear zones.

The St-Elie deposit formed at temperatures >350 degrees C. The stable isotopes values are compatible with a magmatic or metamorphic source.

4.2 The Omai deposit is characterized by quartz-dominant vein systems with minor metallic minerals, represented mainly by pyrite. Ankerite, scheelite, albite, and chlorite are common gangue minerals.

The vein emplacement is syn-to post-deformation and it is related mainly to brittle shear zones with low-angle, stockwork networks and breccia zones.

The Omai deposit formed in a temperature range between 250 degrees C and 170 degrees C, much lower than the St-Elie deposit. The stable isotope values are compatible with mixing between deep-seated fluids of metamorphic or magmatic origin with surface-derived fluids.

These differences between St-Elie and Omai are interpreted in terms of their depth of formation. Alteration patterns, structural elements, and paragenetic assemblages indicate that the gold at St-Elie was most probably emplaced at a mesozonal depth, whereas the Omai setting yields evidence for epizonal conditions.

6) Gold deposits (gold-bearing tourmalinites, gold-bearing conglomerates, and mesothermal lodes), markers of the geological evolution of French Guiana: geology, metallogeny, and stable-isotope constraints

https://www.researchgate.net/publication/309669698_Gold_deposits_gold-bearing_tourmalinites_gold-bearing_conglomerates_and_mesothermal_lodes_markers_of_the_geological_evolution_of_French_Guiana_geology_metallogeny_and_stable-isotope_constraints

Jean-Pierre MILESI (1), Catherine LEROUGE (1) Claude DELOR (1), Patrick LEDRU (1) Mario BILLA (1), Alain COCHERIE (1) Emmanuel EGAL (1), Anne-Marie FOUILLAC (1) Didier LAHONDÈRE (1) Jean-Louis LASSERRE (2) Alain MAROT (1), Bruno MARTEL-JANTIN (1) Philippe ROSSI (1), Monique TEGYEY (1) Hervé THÉVENIAUT (2) Denis THIÉBLEMONT (1)

Les minéralisations aurifères (tourmalinites, conglomérats et gîtes mésothermaux) marqueurs de l’évolution géologique de la Guyane

Olivier VANDERHAEGHE

Géologie de la France, 2003, n° 2-3-4, 257-290, 12 fig., 7 tabl.
Mots clés : Minéralisations aurifères, Conglomérats, Tourmalinites, Gîtes mésothermaux, Guyane. Key words: Gold deposits, Conglomerates, Tourmalinites, Mesothermal lodes, French Guiana.

Abstract

In French Guiana, three (3) types of Proterozoic gold deposits can be recognized (gold-bearing tourmalinites, gold-bearing conglomerates, and mesothermal ore deposits).

And used as metallogenic markers in the two-stage (2) geodynamic evolution proposed by Vanderhaeghe et al. (1998) and updated at the Guiana Shield scale by Delor et al. (2000, 2001, 2003a, b this volume).

During the first stage of crustal growth by calc-alkalic and TTG magmatic accretion, an early (pre-D1 deformation) stock of gold and disseminated sulphides associated with regional tourmalinization accumulated in the Paramaca volcaniclastic sequences in subaquatic conditions (example of the stratiform/stratabound Dorlin deposit). These gold-bearing tourmalinites were locally modified under upper–middle crust conditions during emplacement of discordant mesothermal quartz veins.

During the second stage of crustal recycling and tectonic accretion, a wide variety of syntectonic ore deposits including gold-bearing conglomerate and gold mesothermal types were emplaced during all increments of D2 transcurrent deformation, which was responsible for the progressive deformation of the North Guiana Trough, from its creation through to its burial and final exhumation:

The gold-bearing conglomerate type of ore deposit, hosted by the Upper Detrital Unit in the North Guiana Trough, presents several facies markers of the progressive burial of the deposits, e.g.

(i) gold-oxide “paleoplacer” of “Banket” type,

(ii) debris-flow type with syndiagenetic and/or epigenetic deposits,

(iii) epigenetic disseminated- sulphide facies, and

(iv) epigenetic mesothermal quartz stockworks.

Overall, it formed under low to medium-grade metamorphic conditions with, however, relicts of an earlier hydrothermal event as indicated by preserved hydrothermal pebbles in polygenic conglomerates.

The gold mesothermal type of ore deposit (dominant Au- Fe-Cu type associated with brittle-ductile faults and rare Au- As mesothermal deposits), hosted by the metavolcanic and metasedimentary rocks of the Paramaca Series and also by late-D2 small granite stocks, is always associated with major fault zones.

Overall, it formed under low-grade metamorphic conditions. It is characterized by hydrothermal chlorite+ muscovite+albite+carbonates±biotite alteration. Muscovite +chlorite+carbonates predominate in hydrothermally

(1) Brgm, 3, avenue Claude-Guillemin, BP 6009, 45060 Orléans cedex 2, France.
(2) Brgm Guyane, Domaine de Suzini, Route de Montabo, BP 522, 97333 Cayenne cedex 2, France. (3) CNRS-Univ. Poincaré, Nancy, France.

GÉOLOGIE DE LA FRANCE, N° 2-3-4, 2003 – GEOLOGY OF FRANCE AND SURROUNDING AREAS, N° 2-3-4, 2003

257

GOLD DEPOSITS AND GEOLOGICAL EVOLUTION OF FRENCH GUIANA

Altered metavolcanic and metasedimentary rocks, whereas albite+carbonates predominate in hydrothermally altered granites.

Hydrothermal fluids have a variety of origins. Stable-iso- tope (C, H, O) data indicate a dominant participation of external fluids, near seawater, in the Dorlin subaquatic stratiform/stratabound deposit, whereas metamorphic fluids become dominant in ore deposits formed at deeper levels, such as gold-bearing conglomerates and mesothermal deposits. Sulphur isotopes, trace elements, and sulphide min- eralogy show a consistent magmatic component, represented by magmatic fluids or by leaching of magmatic rocks.

Résumé

En Guyane, trois (3) types de minéralisations d’or d’âge protérozoïque ont été distingués (tourmalinites aurifères, conglomérats aurifères et or orogénique mésothermal) et utilisés comme marqueurs métallogéniques dans le scénario en deux stades d’évolution géodynamique proposée par Vanderhaeghe et al. (1998) et mis à jour, à l’échelle du bouclier guyanais, par Delor et al. (2000, 2001, 2003a, b ce volume).

Durant le premier stade de croissance crustale par accré- tion magmatique calco-alcaline et TTG, un premier dépôt de sulfures disséminés et d’or (pré-déformation D1), associé à une tourmalinisation régionale se met en place dans les séquences volcanoclastiques du Paramaca en conditions sub- aquatiques (cas du gîte stratiforme/”stratabound” de Dorlin). Ces tourmalinites aurifères ont été ensuite portées dans les conditions de la croûte supérieure à moyenne et localement remaniées par des veines de quartz mésothermales.

Pendant le deuxième stade de recyclage crustal et d’accrétion tectonique, une grande variété de minéralisations syntectoniques comprenant des conglomérats aurifères et des minéralisations mésothermales aurifères se sont mises en place durant tous les incréments de la déformation D2 transcurrente, responsable d’une déformation progressive du Sillon Nord Guyanais, depuis son initiation jusqu’à son enfouissement et son exhumation finale :

– les conglomérats aurifères, portés par l’unité Détritique Supérieure du Sillon Nord Guyanais, comprennent plusieurs faciès, marquant l’enfouissement progressif des dépôts, i.e. (i) « paléoplacers » à or-oxydes de type « Banket », (ii) coulées de débris à minéralisations syn-diagénétiques et/ou épigéné- tiques, (iii) faciès de sulfures disséminés épigénétiques, jus- qu’aux (iv) stockwerks de quartz épigénétiques mésothermaux. Ils se sont formés sous un métamorphisme de degré faible à moyen, préservant des reliques d’un événement hydrothermal précoce, comme l’indique la présence de galets hydrothermaux dans les conglomérats polygéniques ;

– les minéralisations aurifères orogéniques mésother- males (à Au-Fe-Cu dominant associé à des failles ductiles

– fragiles et à Au – As plus rare), encaissées par les séries volcaniques et sédimentaires métamorphisées du Paramaca et par de petits stocks de granite tardi-D2, sont toujours associées à des zones de failles majeures. Elles se sont généralement formées dans des conditions métamor- phiques de bas degré et sont caractérisées par une altéra- tion hydrothermale à chlorite + muscovite + albite + carbonates ± biotite. Muscovite + chlorite + carbonates sont dominants dans les encaissants volcaniques et sédi- mentaires, tandis que albite + carbonates sont dominants dans les encaissants granitiques.

Les fluides hydrothermaux ont plusieurs origines. Les isotopes du soufre, les éléments en trace et la minéralogie des sulfures provenant des différents types de gisements indiquent une composante magmatique constante, issue soit de l’extraction des fluides magmatiques au cours de la mise en place des magmas et de leur cristallisation, soit du lessivage de roches magmatiques riches en sulfures. Les isotopes stables (C, H, O) indiquent une participation dominante de fluides externes. Dans le cas du gisement aurifère de Dorlin de type stratiforme/”stratabound” et mis en place dans des conditions sub-aquatiques, les fluides externes ont une composition proche de l’eau de mer. Dans le cas des minéralisations formées à plus grande profondeur, comme les conglomérats (pro parte) et les gîtes mésothermaux aurifères, les fluides hydrothermaux ont une signature métamorphique. Ce sont des fluides d’origine indéterminée (magmatique, marine, météorique ?), équilibrés avec les roches encaissantes dans les conditions du métamorphisme régional.

7. Guyana: Gold board moving towards minted gold coins – Apr 15, 2018 – Kaieteur News

The Guyana Gold Board (GBB) has started the groundwork for the implementation of minted gold coins and ingots, allowing persons to make certified purchases similar to what can be obtained in the United States and other countries.

Chairman of the Board, Gabriel Lall, told Kaieteur News that the senior managers are working closely with both local and foreign companies to design and be ready to deliver for approval various designs for consideration and the associated cost for production.     

“We are expecting some progress reports within the next several weeks,” Lall stated.

He revealed that the board is pursuing local input in the designs and would later rely on overseas companies for the production since Guyana doesn’t have the capabilities to undertake the minting of the coins.

“We want to enshrine in the design, national attributes. We want local fingerprints on this at the initial stages in terms of design and appearance,” Lall stated.

He said further discussions will surround quality control between Guyana and the overseas company which will undergo the minting process.

“We plan to deal with reputable overseas organizations. We can do our own testing in terms of quality control, but we have been using several reputable companies for years,” Lall noted.

He said the Minister of Natural Resources, Raphael Trotman, has given the board a mandate to utilize gold-minted coins as a revenue earning for the board. According to Lall, the Management team of the Gold Board has been moving to get something tangible to deliver.

Guyana has previously issued commemorative gold coins, which were released by the Bank of Guyana. Businesses and individuals tend to hold or invest in gold through gold coins, gold bars, and gold bullion. These items can then be traded.

Minister Trotman stated that Government envisions that the Gold Board will move away from just burning gold and shipping it overseas.

“This year, we will be moving to producing commemorative coins and ingots so that people can come and buy gold as Guyanese.

If I am a citizen of Canada or visitor to Canada or the U.S, I can go and buy gold and it comes with a certificate and a number. I believe that is where we are heading. I am happy that the board is responding to this,” Trotman stated.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.