The Tyennan Domain of western Tasmania is a structurally emplaced, complexly deformed lithotectonic sheet (allochthon). It comprises stacked, isoclinally folded slabs of allochthonous high-grade schist including garnet schist and quartzite, amphibolite and rare eclogite (uppermost unit), overlying low-grade pelite, overlying low-grade quartzite and platy quartzite (middle unit), overlying parautochthonous low-grade dolomitic pelite, quartzite and dolostone (lowermost unit). It is a product of Cambrian continental margin subduction, rebound and exhumation coupled with ophiolite obduction. Tyennan rocks were transported to maximum depths of ∼60–80 km sufficient to generate high-P metamorphism. Their deformation involved progressive shear, large shear strains and large shear displacements with a bulk west-over-east sense of shear related to the direction of subduction and buoyant exhumation. The Tyennan Domain shows a unique crustal architecture, including: (1) metamorphic sheets with 100 km lengths, 50 km widths and 5–10 km structural thicknesses, (2) a leading edge fold nappe with ∼200 km axial surface trace length, (3) megasheath folds with 20–25 km dimensions, and (4) asymmetric folds within regional scale shear lozenges as macro-augen. It provides an unparalleled window beneath the now, largely eroded, obducted ophiolite sheet and provides structural insight into the mechanics of continental margin subduction–obduction. Deformation has been partitioned through the composite exhumed 'slab' with domains of isoclinal macrofolds transitioning into regional scale sheath folds bounded by zones of higher strain. The higher strain zones are characterised by transposition foliation, rootless mesoscopic isoclinal folds, small-scale sheath folds, overprinting crenulation cleavages and platy mylonitic to schistose zones in quartzite. The uppermost, high-grade part of the Tyennan allochthon is clearly a composite, ∼1 km thick 'sheet' made up of a 'welded' amalgam of largely pelitic fragments that had been subducted to different depths, assembled and deformed during buoyant ascent to the current structural level. The Tyennan Domain represents the subducted part of a microcontinent during a Cambrian arc–microcontinent collision outboard of the eastern Pacific margin of Gondwana. The Tyennan Domain consists of stacked, recumbent and isoclinally folded slabs of allochthonous high-grade schist and low-grade pelite-quartzite, overlying parautochthonous low-grade dolomitic marl, quartzite and dolostone. Isoclinal, asymmetric, macrofold 'wave trains', megasheath folds and a 'leading edge' fold nappe with ∼200 km length scale dominates the structure of the Tyennan Domain. [ABSTRACT FROM AUTHOR]