Why does the Tsumeb mine in Namibia have such a huge variety of rare minerals?

Answer 1

Tsumeb is a hydrothermal vein with lead, zinc and copper sulfides and arsenides, and though it is large that is not in itself unusual. It gets a little help from the comparative abundance of some unusual elements, germanium and gallium, but the real difference is made by the karst environment. The ore body and surrounding rock is brecciated and crossed by fractures. This allows surface water to penetrate to great depth, circulating in unusual patterns.
Your standard textbook hydrothermal vein has an 'oxidation zone' near the surface - this is where you find most of the pretty so-called 'secondary minerals' with brightly colored crystals in cavities. It is formed by the action of surface waters, carrying oxygen and carbon dioxide, on the sulfide and arsenate ores. The ore is oxidized, sulfide oxidizes to sulfate, arsenide to arsenate. The metals, predominantly copper, zinc and lead, are also brought into solution and depending on the local conditions, minerals precipitate. These are carbonates, sulfates and arsenates of copper, zinc and lead, sometimes incorporating other elements as well. These minerals are often colorful, and well-known examples include Azurite, Malachite, Cerussite, Brochantite, and Linarite.

Answer 2

Dormant volcanos.

Rare minerals are rare because they contain things like gold and platinum, and these materials do not occur on the surface of the earth. They are more abundant deep inside the earth. The surface of the earth is known as the crust. It is mostly silicon, calcium and oxygen. The mantle is about six miles under the crust. It is mostly silicon and oxygen but is semi-liquid and contsins much higher concentrations of rare minerals. Just after the earth formed, it melted and heavier material sank further inside the planet. Lighter material rose to the top. This is how the crust and mantle formed. Most of the iron sank to the very center of the earth and is now a sphere about the size of the moon.

Volcanos form when sections of the earth's crust slide under each other. As one section gets pushed under the edge of another section, it begins to melt. The surface of the earth contains light materials like sulfur and carbon. These materials travel deep inside the earth and begin expanding as they mix with the semi-liquid rock in the mantle. They form pools of lighter material just under the surface of the crust. This material is under enormous pressure and lighter than the surrounding rocks. If a crack develops in the crust, this liquid can seep back up to the surface of the earth. It then flows out onto the surface as liquid volcanic rock.

Because of the sulfur, carbon and other surface materials, this volcanic rock can dissolve rare minerals and bring them to the surface. South Africa was once covered with active volcanos. They are now all dormant. The liquid rock has solidified into great channels running down to the mantle of the earth. Miners bore into this material to extract the rare minerals like gold and platinum. Diamonds form when carbon dissolves in liquid iron like sugar dissolving in coffee. If the coffee is frozen, the sugar can begin to crystalize. This is how diamonds grow deep inside the mantle. Volcanos then bring diamonds to the surface.

Answer 3

i just want to say that I lived in tsumeb and these two answers were very interesting because i have often wondered the same thing that was asked, thanks.