Hydrothermal vents HW2B
1. In total, how much metal is present on the seafloor in metal sulfide deposits? How much of this is Copper plus Zinc? Assuming all this copper + zinc is copper, how much is this worth? (note that tonne is a metric ton = 1000 kilograms) you will need to look up how much copper is worth per kilogram, then calculate the total value of this.
1. 600 million of metric tons of metal present on the seafloor.2. 30 million of metric tons of copper and zinc.3. 30 million metric tons* 1000 kilograms = 30 billion kilograms * $6.67/kilogram= around 200 billion USD.
2. How do black smoker chimneys grow? ( you could divide this into 2 or 3 stages)
1. Hot fluids that contain calcium and cold seawater that contains sulfate and calcium form anhydrite == incipient chimney. 2. The cooling and mixing with seawater. 3. Metals precipitate as metal sulfide metals lining chimney walls, chimney grows
5. The TAG metal sulfide deposit is 3 million metric tons, and contains 5% Copper. How much is this deposit worth? (you need to look up the price of copper per kilogram; A metric ton is 1000 kilograms)
3 million* 5%= 150000 metric tons 150000 metric tons*1000 kilograms= 150 million kilograms * $6.67/ kilograms= 1.0005 billion
3. The TAG hydrothermal metal sulfide deposit has black smoker vents, but it also has "white smoker" vents, with different fluid compositions. What do these white smoker fluids and the presence of anhydrite (CaSO4) deep within the TAG sulfide mound tell us about processes within the mound?
It shows that the cold seawater was mixing with hot hydrothermal fluids in the mound and forming anhydrite and metal sulfides within the mound.
4. How old is the TAG hydrothermal deposit? What does its cycle of activity and quiescence and the presence of breccias (broken rock cemented by different minerals) tell us about how the deposit formed?
The TAG hydrothermal deposit is tens of thousands of years. The cycle of activity and quiescence and the presence of breccias tell us that there have been multiple cycles of mound material reworking over a long period of time. When the fluid ceases, the anhydrite dissolves, and the chimneys collapse. When the fluid flows resume, anhydrite precipitates and mounds materials in breccia deposits.
2. At what type of mid-ocean ridge are the biggest metal sulfide deposits found (Fast-spreading or Slow-spreading?) Why do you think the biggest deposits are found here? (Shouldn't fast spreading ridges have bigger deposits since they have a greater magmatic budget, and it's the magma that is the heat source to drive hydrothermal circulation, right?) We will discuss this in class, as it may not be obvious, but try to come up with a reason for this.
The biggest metal sulfide deposits are found in slow-spreading ridges. They are found here because even though there are fewer deposits, they grow large over a long time span. However, the lavas in the fast-spreading ridges covers up the deposits before they grow. Slow-deposits not covered by lavas, fractures from fluid flow at the same place
1. What causes precipitation of metal sulfides in black smoker chimneys?
The cooling of hot hydrothermal fluids mixing with seawater produces metal sulfides.
6. In 6A and 6C pdf readings, Cyprus (in the eastern Mediterranean) is mentioned: What is the origin of these rocks in Cyprus? Why do we care about them in a class on Ocean Resources?
The origin of these rocks in Cyprus is Troodos Ophiolite. They contain metal sulfide deposits that are mined for copper.
