Here's a breakdown:
* Assimilation: This process involves the incorporation of surrounding rock (country rock) into the magma. As the magma melts the country rock, the chemical composition of the magma changes, becoming more similar to the melted rock.
It's important to distinguish assimilation from another process called contamination.
* Contamination: This is a broader term that refers to any change in the composition of magma, including assimilation but also other processes like mixing with other magmas or reacting with surrounding fluids.
So, while contamination is the overarching term, assimilation specifically refers to the change in magma composition due to melting of surrounding country rock.
