How can an intrusive igneous body alter the surrounding country rock?

An intrusive igneous body can alter the surrounding country rock through a process called contact metamorphism. This occurs when hot magma invades the Earth's crust, increasing the temperature of the nearby rocks. The extent of this alteration, known as a contact aureole, depends on the size and shape of the igneous intrusion.1

These contact aureoles can vary in thickness from centimeters around small intrusions like dikes and sills to kilometers around large granitic bodies. The rocks within the aureole zone may undergo changes in their mineral composition and texture due to the heat from the magma. This process is distinct from regional metamorphism, which affects larger areas under high pressure and temperature conditions.123