Answer:
Invasion of Hydrothermal Solution in Fractured Rocks.
Step-by-step explanation:
The hydrothermal solution consists of water and dissolved minerals. This solution enters into the fractured rocks and cools down. The cooling process leads to formation of mineral crystals in the rock fractures and are called as "veins". Hence, veins deposits are formed in fractured rocks due to invasion of hydrothermal solution in it.