Geology and Mineralization
The Castelo de Sonhos property encompasses a 15km by 12km plateau in the Tapajós region of Pará state. It has an average elevation of 650 meters (a.s.l.) and around 300-350 meters above the surrounding plains.
The Castelo de Sonhos Formation is a package of sandstones and conglomerates which form a roughly circular plateau. The plateau lies within the Amazon Craton, bounded on the east by volcanic, plutonic and sedimentary rocks of the Iriri-Xingu domain of the Central Amazon Province with ages dating back to ~3Ga (Santos et al., 2001; Bizzi et al., 2003), and on the west by the 2,030 – 1,860 Ma Tapajós-Parima Province, consisting of granodiorites, monzogranites and syenogranites that belong to the Creporizao and Parauari Suites. Both are intruded by the slightly younger monzo- and syeno-granite stocks of the Maloquinha Suite. The predominantly granitic Tapajós-Parima Province borders the Castelo de Sonhos Formation on the north and west.
The gold mineralization is intimately associated with the conglomerates. The main alteration types are hematite and silicification.
Two billion years ago, a large continent lay near the South Pole, with a chain of lode gold deposits along its central mountain ridge. Gold accumulated in placer deposits down-slope, in alluvial fans, on beaches and in the near-shore marine environment. In modern times, these now include gold deposits at Tarkwa, Jacobina and Castelo de Sonhos.
There are at least two styles of paleoplacer deposits: Witwatersrand (the largest single gold producing district in the world) and Tarkwa. There are many differences such as age, type of iron in the matrix and size, but two fundamental differences are:
- Wits contains detrital carbon; Tarkwa is carbon-free
- Wits pebbles are gold-free (Frimmel, pers. comm.). Tarkwa pebbles sometimes contain gold
Where We Operate
Brazil is the world’s 5th largest country, and Latin America’s largest country. Brazil includes 26 states plus a Federal District. The mining sector of the country comprises almost 7% of its GDP 1. With rich mineral resources, Brazil is a leading mineral exporter.
Brazil produces 72 different mineral substances due to its diversified geological formations. It exports Niobium, Iron Ore Vermiculite, Graphite Bauxite, Kaolin, Nickel, Tin, Magnesite, Manganese, Chrome, Gold and Ornamental Stones2.
Gold in Brazil has a long history stretching as far back as the 1700s, when a gold rush in the then-Portuguese colony opened the country up to the major gold-producing region of Ouro Preto — Portuguese for “black gold.”
Brazil has recently made changes to its decades-old mining laws, aimed at making the local industry more competitive and sustainable.
Pará state hosts many of the minerals and is the second largest producer of Iron Ore, Brazil’s dominant mineral production.
Geology of Brazil
About two-thirds of Brazil is underlain by Precambrian rocks, including ancient cratonic (long stable) regions and orogenic (“mobile”) belts that were active largely from about two billion years ago through the end of the Precambrian and extending into the earliest Paleozoic. The richest iron, tin, and nickel deposits formed in Archean and Paleoproterozoic rocks, as did much of the gold and platinoid metals found in placer deposits3.
Castelo de Sonhos was one of the most famous and gold rich alluvial garimpos in all the Tapajós region. The main gold rush took place there between 1985 and 1990 and it is estimated that 300,000 ounces of gold has been produced.
By early 1995, Barrick Gold began to pay attention and soon recognised that the source of the alluvial gold was the Castelo de Sonhos plateau. So, in June 1995, after optioning the property, Barrick started an aggressive exploration program and discovered the conglomerate hosted gold mineralization.