Lineament tectonics of the Willyama block and relationship to the adelaide aulocogene
Titel:
Lineament tectonics of the Willyama block and relationship to the adelaide aulocogene
Auteur:
Katz, M.B.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 23 (1976) nr. 3 pagina's 275-285
Jaar:
1976-09
Inhoud:
The tectonics of the Willyama Block are controlled by fundamental deep-seated northeasterly-trending faults of the Darling River Lineament system. Regional dextral shear coupling along this lineament system has caused attenuated folds which in places show strong NE dextral vergence. Compressional forces of this regional NE couple has formed conjugate latitudinal- and northwesterly-trending faults. The tensional force of this regional couple has formed west-northwesterly-trending lineaments. High-grade metamorphic and deep-seated igneous activity, as well as mineralization events are also controlled by these lineaments, especially between the northeasterly-trending en echelon faults, at lineament intersections, and along WNW zones of tension. En echelon NE dextral faults in the vicinity of Broken Hill have formed a local 'hot spot' with associated Broken-Hill type mineralization. Maficultramafic rocks in the area are closely related to lineaments, especially lineament intersections. A prominent dolerite dyke-swarm trending WNW northeast of Broken Hill is aligned along the zone of tension. These primary and secondary lineaments were activated during the Willyama event at about 1700 m.y. This event, recorded in the Broken Hill area by medium-to high-grade metamorphism, igneous activity, and structural deformation is related to activity on the Darling River transform, which played an important role in the formation of the Adelaide aulacogene. A late phase of this activity included the emplacement of the Mundi Mundi granite at about 1560 m.y. along WNW zones of tension and NW lineaments. At this time the NW lineaments appeared to play a more active role, especially to the northeast of the Willyama Block. These high-angle NW lineaments under the influence of NE dextral transform movement formed rifts and structural troughs that served as sites for accumulating Adelaidean System sediments. The next conspicuous event dated at about 500 m.y. strongly reactivated the faults of the Willyama Block, as further movement along the Darling River transform contributed to the Delamerian orogeny.
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