长时间的地热和高压作用使这些页岩发生了变质作用，形成了新的矿物。

The prolonged geothermal heat and pressure led to ___metamorphism of these shales, forming new minerals.

这座城市经过几十年的发展，经历了惊人的蜕变。

The city has undergone remarkable ___metamorphosis over decades of development.