What was the principal source of Portuguese wealth in its colony of Brazil?

sea trade

Explanation:

The control of sea trade, the chief source of Portuguese wealth in the East, was assured by the defeat of Muslim naval forces off Diu in 1509.

Portugal's main natural resources include fish, forests (cork), iron ore, copper, zinc, tin, tungsten, silver, gold, uranium, marble, clay, gypsum, salt, arable land and hydropower.

i think the reason that they immagrated was to find freedom of religion