Page 374 - Global Tectonics

PRECAMBRIAN TECTONICS AND THE SUPERCONTINENT CYCLE 357

(a)
120°00
Syncline
A 40
55 56 Anticline
Geological boundary
29 21°00 Fault
48 Facing of bedding
40 D
50 Strike and dip of bedding
Mount Edgar Mount Edgar shear zone
Dome
65 45 Lineation
Zone of sinking
65 40 NW-vergent recumbent isoclinal folds

80
50
60 60
32
Cover 65 C
70 45 Fortescue
70 50 Group
Corunna Downs 50
Dome
70 80 B 0 10
km 21°30
Greenstones Granitic rocks
Gorge Creek Group clastic sedimentary rock Split Rock Supersuite c.2830 Ma High-K monzogranite
Wyman Formation (c.3325–3315 Ma) rhyolite Cleland Supersuite c.3240 Ma High-K monzogranite
Euro Basalt Emu Supersuite (younger) c.3295 Ma High-K monzogranite
Panorama Formation (3458–3426 Ma)
Basalt-dacite, minor rhyolite Emu Supersuite (older) c.3325–3308 Ma High-K monzogranite
Apex Basalt Tambina Supersuite c.3450–3430 Ma TTG
Duffer Formation (3471–3463 Ma) Basalt-dacite Quartz porphyry c.3467 Ma
Talga Talga Subgroup (c.3490–3477 Ma) Callina Supersuite c.3470 Ma TTG
Basalt, minor felsic volcanic rock, chert

(b) Mt. Edgar Mt. Edgar A
A Greenstone Shear Zone Granitic complex Shear Zone Greenstone

V 2
H
(c) Mt. Edgar D
C Greenstone Shear Zone Granitic complex Greenstone

Fig. 11.9 (a) Geologic map of the Mt. Edgar Dome and granitic complex in the Eastern Pilbara (after Van Kranendonk
et al., 2007, with permission from Blackwell Publishing). Map shows the internal structure of the domes and the radial
distribution of 3.32–3.30 Ga metamorphic mineral elongation lineations (arrows) that converge in a vertical zone of
sinking between the Mt. Edgar, Carunna Downs and Shaw (not shown) domes. These features are contemporaneous with
the arcuate shear zones that formed along granite-greenstone contacts (Fig. 11.8). (b,c) Cross-sections showing the
trends of foliation surfaces and shear zones within the Mt. Edgar Dome (after Collins, 1989, with permission from Elsevier).