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°°Environment 1: (Where we find deposits) Black Smokers and Massive Sulphide Ore Deposits°°
°°°-Tectonic environment: mid-ocean ridges (spreading centers)°-Magma upwelling, pour out on ocean surface, basaltic flow°-Normal faults around spreading centers, ocean water above. Water is going to go downwards- heated- and eventually it will rise back up again (to surface of earth).°°-When water moves down, it has the potential to remove (leach) metals from rock. How?Depends on components of the sea water to make those metals more soluble. Ex. Take iron (insoluble) in rock, if it sees the water, and sees chlorine, it will react with chlorine to create a soluble (specie) elementThe water alters minerals- causes them to break down. In the case of iron, it reacts with chlorine in the water to create a specie (iron chloride). The water can therefore extract iron from rocks.
This is what happens with rusty cars°°Why do vehicles rust? Salt on the roads. Back in the day, Japanese carswould last 3 years because they weren’t designed for rust. They would fall apart. °So we have the sea water going down, and will lead out small amounts of copper, zinc, etc. The solution is now pretty hot, and pours out on the ocean surface.°°°°-Diagram: Vent on sea floor. Water rises at 350. Black color because it is precipitating metals (creation of a solid).Before (Review): Solubilize/extract metals from the rocks by allowing sea water to interact with them, and forms strong species in solution which start to deposit as they come out. The metals in solutions are precipitating (forming a solid) as sulfide minerals (iron sulfide…). Why? (precipitating and why as sulfide minerals?oPrecipitating because the fluid is at 350 degrees, but the water in to which its moving into is 4 degrees. The hot water is cooling extremely rapidly. (Most substances are more soluble (able to be dissolved) in hot water than in cold water). Cooling the fluid down extremely rapidlyoThe sulfur:
The fluids, as they interact with rock, are going to become very reducing. Up here we have oxygenated sea water, as it moves down, moves into rock, reactionsare going to consume a lot of oxygen. As they pour out, sulfur in the form of sulfate, will be converted into sulfide. [Sea water has a lot of sulfate, will react with H2to form sulfide.]The earlier reaction was producing a lot of hydrogen, adding hydrogen to fluid, then (when going up) the sulfur was taken out of the sea water, reducing to H2S, then as we showed before , Fe2+ + H2S = FeS2What we have here: a geological environment on the ocean floor where we can see metals being concentrated in real time. If we were to dive down, you’ll see a mound, the mound is covered with little chimneys, if you dig into the mound, the mound itself is just chimneys that have fallen over. The mound of material is just solid FeS2, or other material (these metals- iron, copper, zinc, are highly concentrated here- economically exploitable).