Percurso da Serra Amarela

NAME OF INTEREST - Rose coloured granite

CONCEPT - Geological Heritage

On the other side of the valley the granitic landscape stands out with a reddish tone. This feature, caused by a process known as episyenitisation of granite, is very common in this region. The phenomenon occurred at or after the final stages of solidification of the granite magma, when processes of hydrothermal alteration were occurring (a combination of chemical processes that affect rocks, induced by hot aqueous solutions of varying origin – magmatic, metamorphic, amongst others – that circulate inside the earth’s crust) preferentially along fractures in the granites. These processes gave the granite a reddish colour, this sometimes accompanied by an intense modification of the original composition, transforming the rock into episyenite. Another feature that will become noticeable from this point on in the walk is the large amount of coarse sand. These sediments that can be referred to as gravel, granitic sand rotten granite or grit, result from the process of arenitisation caused by the disaggregation that the rock suffers when water infiltrates and circulates through fractures within it. Ice (cryoclastic) action can accelerate this process.