The correct statements about slavery in Brazil are:
A. Plantations and mining operations fed the demand for slaves - This is true as both sugar plantations and gold/diamond mining were major industries in colonial Brazil that relied heavily on enslaved labor.
B. Slavery began during the Portuguese colonization of Brazil - This is also true; slavery was established soon after the Portuguese began colonizing Brazil in the 16th century.
D. More than one third of all enslaved people transported from Africa went to Brazil - This statement is true as Brazil was the largest destination for enslaved Africans, receiving a significant portion of the transatlantic slave trade.
Therefore, the correct answers are A, B, and D.