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

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