Three-dimensional structure along the inverted Palaeoproterozoic Fiery Creek Fault System, Mount Isa terrane, Australia

The NW-dipping Fiery Creek Fault System, located in the northern Mount Isa terrane, comprises numerous sub-parallel faults that record multiple episod es of Palaeo- to Mesoproterozoic movement. Hanging wall wedge-shaped strata l geometries and marked stratal thickness variation across the fault system indicate that the earliest movement occurred during episodic intracontinen tal extension (Mount Isa Rift Event; ca. 1710-1655 Ma). Reactivation of the fault system during regional shortening and basin inversion associated wit h the Mesoproterozoic Isan Orogeny (ca. 1590-1500 Ma) resulted in complex t hree-dimensional hanging wall geometries and highly variable strain in the hanging wall strata along the fault system. This has resulted in the develo pment of discrete hanging wall deformation compartments, that are character ised by different structural styles. High strain compartments are character ised by relatively intense folding and the development of break-back thrust s, whereas low strain compartments are only weakly folded. Variations in ha nging wall strain are attributed to selective reactivation of normal fault segments, controlled by the pre-inversion fault dip and lithological contra sts across the faults. Variation of the pre-inversion fault dip is interpre ted to have been caused by episodic tilt-block rotation during crustal exte nsion. Moderately dipping faults active early in the Mount Isa Rift Event s how the greatest degree of reactivation, whereas younger and steeper normal faults have behaved as buttresses during inversion with strain focussed in zones of upright folding in the hanging wall. (C) 2001 Elsevier Science Lt d. All rights reserved.