Collinsville Copper-Gold Project
Geology
The Collinsville Area occurs within the Palaeozoic to early Mesozoic Tasman Orogenic Zone that spans almost the entire length of the Pacific margin of Australia. From north to south the Orogenic Zone can be divided into three main Fold Belts:
- the Ordovician to Carboniferous Hodgkinson-Broken River Fold Belt;
- the Devonian to Carboniferous Thompson Fold Belt which includes the Lolworth-Ravenswood Block, the Drummond Basin and the Anakie Inlier; and,
- the Silurian to Triassic New England Fold Belt which includes the Connors Arch and the Yarrol Province.
The New England Fold Belt comprises a complex collage of terranes that dominantly reflect tectonic events in the ~100 million year interval from mid-Carboniferous through to the Middle Triassic. The tectonic history was interpreted in terms of three arc-producing orogenic events: the Siluro-Devonian Calliope Arc, which developed as an island arc and subsequently accreted; the Devonian- Carboniferous Connors Volcanic Arc, developed along an Andean-style margin; and the Early Permian Camboon Volcanic Arc, developed mainly on top of the Connors Volcanic Arc.
Early interpretations indicated that arcs were associated with interpreted accretionary complexes to the east as part of a complete subduction complex. However, several unconformities within the volcanic units of this Province are interpreted as evidence for ongoing continental extension. Research in the last decade has recognized two departures from previous models: limited data indicates the existence of an Early Carboniferous volcanic arc that developed coevally with, and to the west of, the subduction complex elements; and a major crustal thermal event in the Late Carboniferous-earliest Permian is recognised that probably records a transition from a convergent to an extensional, possibly back-arc, setting.
The data indicates that the Carboniferous to Late Permian tectonic evolution of the northern New England Fold Belt was controlled by a transition from active continental-arc/accretionary processes to widespread crustal extension. The Early Permian saw major changes in the sedimentation pattern of the New England Fold Belt. A new volcanic arc, the Camboon Volcanic Arc, which includes the Lizzie Creek Volcanics, developed over the site of the old Connors Arc.
Sedimentary basins developed to the west of these systems over the Anakie Inlier and adjacent regions, for example the Drummond Basin. Strike slip faulting may have been associated with extension in forming these Basins and producing their present asymmetry.
In most areas, the Late Carboniferous-early Permian strata are undeformed, except adjacent to major structures. Deformation in the Late Carboniferous formed broad basins and domes formed, which were controlled by basement structure and strike-slip and normal faults.
In the Collinsville Area the Permo-Triassic Bowen Basin separates the Thompson Fold Belt from the New England Fold Belt and is bounded to the north by the Lolworth-Ravenswood Block, to the west by the Drummond Basin and Anakie Inlier, and to the east by the Connors Arch and Yarrol Province. Precious and base metal mineralisation is commonly associated with felsic volcanic and intrusive porphyry rocks throughout the Collinsville Area.