The mixture of mineral rich water reaches the sea water, the minerals rushing out gives the water the appearance of the black smoke due to the deposits of iron sulfide.
The mineral-rich water generates precipitation of the small particles of the iron sulfide minerals and manganese minerals.
These particles extremely fine-grained of sulfide minerals produced when a hot hydrothermal liquids get mixed with the near freezing sea-water.
When scientists try to use the explanation of the natural world to understand patterns, they are making PREDICTIONS about natural events. For example, volcanic eruptions.