It's somewhat more involved than just "volcano lava."

https://en.wikipedia.org/wiki/Porphyry_copper_deposit Porphyry copper deposits are copper ore bodies that are formed from hydrothermal fluids that originate from a voluminous magma chamber several kilometers below the deposit itself. Predating or associated with those fluids are vertical dikes of porphyritic intrusive rocks from which this deposit type derives its name. In later stages, circulating meteoric fluids may interact with the magmatic fluids.

There's also this idea: https://www.earthmagazine.org/article/studies-re-examine-how...