Wood and land are very precious commodities in South America. Agriculture is getting more and more aggressive, taking over the land previously covered by rainforest. Due to rapid growth of South American economies, a significant percentage of the pristine rainforest was destructed for cattle ranching, logging, mining and oil and gas exploration.
In my short travelling life, I have had a chance to see various environments but one of the most spectacular I have ever had the opportunity to see was a rainforest in Suriname. On a small hill called Brownsberg I had a small glimpse of that magical world of species of plants and animals unknown to me before. I wish everyone had, at least once in their lives, a chance to see this - and we would all probably appreciate the greatness and importance of this fragile ecosystem better than we do now.
A trip to Surinamese rainforest may be long and adventurous. Unfortunately, we did not have enough time to explore the jungle properly, so we were forced to choose just one-day trip to Brownsberg National Park (Brownsberg means Brown Hill). The tour was organised by TourBox which has a small office located at Kleine Waterstraat street, opposite the Royal Torarica hotel in Paramaribo. The trip was supposed to last 8 hrs and included transportation, guide, food and water. Everything costed 65 Euro.
We set off at 7am from Zus & Zo restaurant (nota bene a good restaurant/coffee shop at Grote Combweg street) and it took us approximately 2-3 hrs to reach the Brownsberg National Park (park fee was included in the tour price). We drove through some Maroon villages before reaching an unpaved, muddy road which steeply climbs on the Brownsberg hill (507 m a.s.l.). At the top of the hill is an information centre and a small restaurant.
The view from the hill is outstanding. You can see the greatness of the rainforest and a large water reservoir called Brokopondo lake. Brokopondo lake was created in 1965 by inundation of a significant area of the rainforest (not-funny fact: according to World Bank, the entire investment was mismanaged as the electricity production is not efficient). Until now, some dead tree trunks stick out of the water. The dam and power plant were constructed to provide electricity for the bauxite mining and aluminium production.
With our guide we entered the dark, humid forest. Our main goal was to reach two small waterfalls (Irene and Leon waterfalls), about 2 hr walk from the information centre. As we walked, admiring the variety of exotic plants (e.g. pipe tree, lemon tree), we were constantly targeted by flies and followed by spider monkey family. It is amazing how many different species of trees, flowers, insects and other animals you can encounter even on such a short trip.
The walk was rather hard. The weather wasn't very nice for strolling - horribly hot and sticky. Also, the entire area is hilly so you can lose some weight. There is, however, a reward at the end. It is brilliant to take a short break and take a shower in one or two of the waterfalls.
Green forest canopies which prevent sunlight from reaching the surface, birds flying and monkeys hauling... At first glance you may think that this was the real Paradise described in Genesis. But if you look closer, you will see it is not heaven as you may think. Forest is full of enemies: animals, viruses, even plants, all want to kill you.
There is also another dark side of Brownsberg Park which is not immediately visible if you are a tourist. In 1999 gold was found and mining activity started. According to WWF, there are approximately 40 recorded mining pits in the area. You can see how damaging this activity is for the forest simply by looking at the google earth aerial photo (see below).
Geologically speaking, Brownsberg National Park is located on the metamorphosed sedimentary and volcanic rocks (metaarenites and metarhyolites) of Lower Palaeozoic age. In the area, a few granitic intrusions are also recognised. The metamorphosed sandstones belong to the Lower Palaeozoic Armina Formation. These are most likely the source of gold in the area.
(The metamorphosed sedimentary and volcanic rocks are believed to be part of much wider geological unit known as Transamazonian belt (it is an old orogen which in literature is known as greenstone belt). This old orogenic suture was probably related to collisions of several Island Arcs. Radiogenic dating of zircons yield ages of 2.2-2.08 Ga).
It is interesting that geology is still not well recognised over there. Geological maps are not detailed and relationships between different unit types are not clear. The reason is quite simply - thick vegetation hampers geological reconnaissance (see simplified map below).
So what about gold in Brownsberg area? Why Guinea Shield is so gold-prone?
Gold in the Guyanas brought all sort of adventurous people. One of the most famous was Sir Walter Raleigh (1554-1618), Queen Elizabeth I’s lover. He set off in 1595 travelling along Orinoko river and sailed almost 400 km inland eventually reaching Guyana Highlands. This guy claimed that somewhere inside that land exists a legendary hidden golden city known as El Dorado. Although never found, it sparked the imagination of many. Until now, the gold bonanza continues.
Gold is a really rare element. The average gold concentration in the crust is very low - for every billion particles you will find one gold particle (1 ppb). Sometimes, however, due to some geological processes, the concentration of this valuable precious metal is much higher and its extraction is possible.
Most of the gold deposits are associated with magmatic activity and some related hydrothermal processes. Hydrothermal processes, as the name suggests (hydro - water), is associated with hot water (or more generally hot fluids). When intrusive magmatic rocks start to crystallise from hot melt, this same melt starts to release portions of fluids. These fluids then circulate within the fracture network developed around the magmatic (plutonic) body, often reacting with host rocks. If those fluids are rich in various ions, they may start producing some minerals, gold being one of them.
The age context of gold deposits seems to be important as well. It is known that some periods in the Earth history produced more gold deposits than others. These were Late Archean (2.7-2.6 Ga (billion years)), Palaeoproterozoic (2-1.6 Ga) and Phanerozoic (0.6 Ga). Currently, geologists suggest that gold "production" is associated with fluid fluxes from the mantle (Walshe & Cleverly, 2009), which is the source of gold as an element. The process of gold concentration in gold-prone areas is a totally different story.
Gold can be found in some sedimentary rocks, such as conglomerates and sandstones, due to gravitational segregation of gold nuggets (heavier, more dense stuff (such as gold) will be transported for a shorter distance than the lighter stuff). One of the most famous sedimentary type gold deposits are in South Africa (Witwatersrand). Gold deposits in-situ (i.e. within the magmatic rocks) formation suggest totally different processes involved. The gold deposition must have occurred in chemical environments far from equilibrium.
In Brownsberg area, gold can be found mostly in sandstones and conglomerates. Miners (mostly illegal) try to extract gold using mechanical methods. Unfortunately, these are not easy processes and some chemical processing must be applied. This industrial activity is unfortunately associated with harmful Mercury. This highly-toxic liquid metal was once used throughout the world in gold processing (amalgamation). In modern mining technology it is not used anymore as it has been replaced by more efficient and less environmentally damaging techniques. However, in developing countries (such as Suriname) this technique is still in use. It is extremely dangerous for miners (mainly illegal workers from Brazil) and toxic for environment. WWF was monitoring the site and the results are alarming.
It is unknown how much gold is extracted from Brownsberg area. This activity however continues and the consequences may not be fully understood.
If you want to see a good movie about gold prospecting why don't you go to the cinema watch Stephen Gaghan's "Gold" movie.
With all the logging and mining activity going on around the world it seems quite clear to me that our civilisation still does not understand that by destroying our planet's truncus pulmonalis (which I believe is the rainforest), we are destroying ourselves and our future. The Brownsberg National Park may open your eyes and you may start to appreciate the great nature.
Wlashe, J., L., Cleverly, J., S. 2009. Gold deposits: where, when and why. Elements 5. 288.
Gimlette J. 2012. Wild Coast : Travels on South America's Untamed Edge.
Alimoenadi A. Gillian ; Bhoelan Rayiez ; Patadien S. Raysree. 2011. Geological field mapping at the northern part of the Brownsberg area. A comparison study between field data and the geologic map published by the Geological and Mining Services of the Government. Poster at 12 Symposio de Geologia de Amazonia.