Mount Ada Basalt
The Mount Ada Basalt is the first formation of the Coongan Subgroup belonging to the Warrawoona Group in Western Australia ( Pilbara Kraton ). With an age of 3470 to 3430 million years BP , the basalt formation comes from the Mesoarchean .
stratigraphy
The Mount Ada basalt follows the McPhee Formation or the Dresser Formation discordantly . For its part, it is concordantly overlaid by the Duffer formation , with which it can also interlock laterally. The basalt is intrusively interspersed with Coppin Gap Granodiorite and Munganbrina Monzonite .
The 2,000 to 2,500 meter thick Mount Ada basalt is predominantly made up of massive, tholeiitic cushion basalts into which numerous storage tunnels made of dolerite and gabbro have penetrated. Komatitic basalts, cherts , jaspilites and acidic volcanic plastics also occur subordinately .
Fossil content
The stromatolites appearing for the first time in the underlying Dresser Formation can also be found again in places in Mount Ada basalt.
Deposit
There is a copper - nickel deposit at Farrel Well .
metamorphosis
After its deposition, the Mount Ada basalt was not only affected by the contact metamorphosis caused by the granitic intrusions but also by a regional metamorphosis that took place under the physical conditions of the green slate facies. The newly created metabasalts were transformed into blue-gray, dark green-gray, fine-grain actinolite rocks with chlorite , epidote and plagioclase .
Dating
Van Kranendonk and colleagues (2002) assign the Mont Ada Basalt an age of 3474 to 3463 million years BP .
Individual evidence
- ↑ Van Kranendonk, MJ et al .: Geology and tectonic evolution of the Archaean North Pilbara Terrain, Pilbara Craton, Western Australia . In: Economic Geology . tape 97 , 2002, p. 695-732 .