Deformation Events
Last updated:8 April 2016
| Deformation event | Timing (Ma) | West and Central Pilbara | East Pilbara | Comments and additional references to this study where appropriate |
|---|---|---|---|---|
| D1 | 3515-3471 | Basement not exposed | Tight folds and axial planar schistosity steep E-dip (pre refolding) in Coonterunnah Group. Bedding parallel fabric in Talga-Talga | Pre-Strelley Pool Chert (Van Kranendonk 1997) |
| D2a | ca. 3445-3380 | Basement not exposed | Main schistose fabric and isoclinal folds in Warrawoona Group, variable trends now envelopes post-D2a granitoid complexes. E-striking foliation in later crenulation (S2b); Talga-Talga anticline | Orogenic Au, Bamboo Creek Shear Zone (Zegers, 1996); Klondyke orogenic Au. Fabrics cut by (3330) Mount Edgar B. (Williams, 1998) |
| D2b | 3380-3330 | Basement not exposed | Shear zones West Coongan Belt; Southern Mount Edgar B. mylonites; thrusting Coppin Gap. N-striking crenulation cleavage in Warrawoona Belt | Cut by 3270 Ma pegmatite dykes Cooper et al 1983; Zegers 1996; Sulphur Springs Grp u/c above (Van Kranendonk, 1997) |
| D2c | ca. 3325 | Basement not exposed |
Main shear fabric in Warrawoona Belt Metamorphic zircon in Mount Edgar |
Equivalent to S4 of Collins et al, 1998 McNaughton et al, 1993 |
| D2d | 3260 | Isoclinal and rootless folds; E-NE plunging folds cut by Harding Granite (3260 Ma); S-directed thrusts | Smith et al, 1998 | |
| D3a | ca. 3200 | Lower amphibolite metamorphism Roebourne Group; horizontal asymmetrical folds; layer parallel faults; doming of Karratha Granodiorite | Main fabric and folds NNE Wodgina, NE North Shaw in Gorge Ck & Sulphur Springs Groups; Tambourah Dome folding; NE-trending crenulations and folds in older groups |
Bickle et al, 1985 Krapez & Eisenlohr, 1998 Orogenic Au at Lallah Rookh |
| D3b | ca. 3100 | Earliest fabric in Whundo Group preserved in microlithons of later fabrics; 3107 Ma metamorphism | Maximum age of gneiss in western Whundo Nelson, 1999. | |
| D3c | ca. 3015 | Main NW-trending greenschist to amphibolite schistosity to crenulation cleavage (Whundo Group); NNW-SSE folds in Cleaverville Fm; sinistral transtension on Sholl Shear Zone | NW trending steeply dipping crenulation in Wodgina and Pilgangoora Belts | Cleaverville u/c overlain by 3010 Whim Creek Group (Hickman et al, 1998) |
|
D4a progressive | ca. 3000-2950 | NE-plunging tight upright folds (Whundo & Cleaverville); E-W macroscale folds (eg Powereena folds) N-dipping cleavage; S-directed thrusting Sholl Shear Zone; crenulation cleavage in Whundo Group | E-W crenulations; sinistral N-S oriented shear zones (eg. West Wodgina); reworking main fabric to a crenulation or shear bands. Mosquito Creek ENE plunging S-verging folds | Progressive deformation with early transtension and later transpression in the developing De Grey Group basins (Van Kranendonk, 1997; Smithies, 1998; Krapez & Eisenlohr, 1998) |
| D4b | <2950 | N-S upright folds and steep slaty cleavage (eg Croydon anticline); pencil cleavage intersection (with S4a) plunge steep north; normal-sinistral shear on Sholl Shear Zone; NNE crenulations; normal shear in Chirratta Batholith | N-S crenulations of D4 shear zones (West Wodgina); N-S upright folds (eg Pilgangoora syncline); Sinistral N-S shear (Mulgandinnah Shear Zone); dextral shear zones (E-W) Mosquito Creek Belt, Kurrana Shear Zone |
F4b folds cut by 2950 Ma granites - Smithies 1998 Zegers, 1996 |
| D4c | 2935-2880 | NE to ENE folds tight, steeply inclined with SE dipping axial surface; reworked S4/S6 fabric (ENE-trend) in Mallina Basin; dextral shear on Sholl Shear Zone (40km) with gentle E-NE plunging lineations |
ENE-trending moderate N-dipping crenulations; sinistral shear zones reworking west Pilgangoora belt (orogenic Au); N-NW verging folds and thrusts in Mosquito Creek Belt probably controlling Au | Last major deformation; Mount York Au (Neumayr, 1993); Mosquito Creek Au; deformation associated with Satirist Granite in west (Smithies, 1998); Smith et al 1998. |
| D4d | ca. 2850 | NW thrusting on steep faults (eg Loudens Fault?); shallow dipping S-directed thrusts at Point Sansom; conjugate fault arrays along Sholl Shear Zone | Weak E-W steep dipping crenulations with E-plunging fold hinges. Weak to moderate E-W foliation in 2950 Ma Sn granites |
Maybe associated with post-tectonic tin granites (2850); Smithies, 1998; Krapez & Eisenlohr, 1998 |
| Extension | 2780 | Hamersley Basin initiated, Normal N-down Mallina Fault, Loudens Fault | Hamersley Basin initiated; N-NW trending dextral faults, sinistral reworking along ENE structural grain of Mosquito Creek Belt |
extension; Opaline Well Intrusion; epithermal Au systems |
| D5 | <2780 | NW to N-trending folds, crenulations, kinks; gentle upright subhorizontal folds trend NW in Negri Volcanics | NW-trending folds and crenulations | Hickman, 1983; Krapez & Eisenlohr, 1998 |
| D6+ | ca. 2100 to Neoproterozoic. | Western margin reworking - east-directed thrusting in Cape Preston (Ophthalmia Orogeny?); Elevated Ar temperatures on Sholl Shear Zone | Eastern margin reworking (Paterson Orogen) - thrusting, NNW-trending strike slip faults, NW-SE folds, metamorphism (6 phases of post Archean deformation in the Rudall Complex). |
Hickman & Strong, 1998; K. Beintema (Utrecht) email communication 1999. Bagas et al, 1995, Williams & Trendell, 1998 |