Fitzroy Island, Far North Qld

Being adjacent to Cairns, the mountainous Fitzroy Island has become a popular tourist destination distinct from the low-lying sand cay of Green Island. A tourist resort, walking tracks and snorkelling opportunities are attractive to day visitors as well as longer-staying guests. The island is composed entirely of granite, which can be seen in huge boulders outcropping on the slopes and around the headlands and beaches. It is a uniform, light coloured medium to coarse-grained biotite granite. It is probably part of the northern end of the huge Bellenden Ker Batholith intruded in the early Permian (about 280 million years ago), which extends from Babinda to False Cape near Yarrabah, although cut in two along the Mulgrave River Valley by the Russell- Mulgrave Shear Zone (see page 80). It is uncertain whether Fitzroy Island, and Cape Grafton and Granite Hill on the nearby mainland, are part of the main batholith, or are three discrete bodies separated by obscured meta-sediments of the Hodgkinson  Province or the older Barnard Province. Fitzroy Island was connected to the mainland at times of lower sea level and has assumed its present shape only after 7400 years ago.

Warwick Willmott, Rocks and Landscapes of National Parks of North Queensland, Geological Society of Australia (Qld)