Hydrothermal solutions associated with magma bodies Black smokers - Sea water percolates through newly formed oceanic crust, dissolving out metallic sulfide minerals. The hot sea water rises along fractures and pours from vents in the seafloor as black clouds of dark mineral-rich water. The processes of compaction and recrystallization change the texture of rocks during metamorphism. The grains move closer together. The rock becomes more dense.
Porosity is reduced.
No changes in overall chemistry. New crystals grow from the minerals already present. A preferred orientation of minerals commonly develops under applied pressure. Platy or sheet-like minerals such as muscovite and biotite become oriented perpendicular to the direction of force. This preferred orientation is called foliation .