Major fault zones related to the Omeo Metamorphic Complex, Northeastern Victoria
Titel:
Major fault zones related to the Omeo Metamorphic Complex, Northeastern Victoria
Auteur:
Morand, V. J. Gray, D. R.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 38 (1991) nr. 2 pagina's 203-221
Jaar:
1991-05
Inhoud:
Major faults bounding the Omeo Metamorphic Complex in Victoria have wide mylonite zones containing mylonitized schist, gneiss and granite. The northwest-striking Kiewa, Kancoona and Ensay Faults show no evidence of movement pre-dating Late Silurian to Early Devonian time, but all had major dextral strike-slip movement at this time, as shown by mylonite fabrics and stretching lineations. Estimated displacement on the Kiewa Fault is about 50 km. The Indi Fault is a moderately west-dipping thrust striking north-northeast, with mylonite fabrics indicating east-directed thrusting. This thrusting occurred during the Late Silurian to Early Devonian, contemporaneous with folding and cleavage development in adjacent Silurian strata. Thus major displacement on these boundary faults occurred after the Early to Middle Silurian metamorphism, and they do not appear to be associated with the formation of the Omeo Metamorphic Complex. After cessation of dextral movement on the Kiewa, Kancoona and Ensay Faults, and thrusting on the Indi Fault, mylonitic fabrics were overprinted by a Middle Devonian crenulation cleavage. Most of the major faults have undergone reactivation. The Kiewa and Kancoona Faults underwent sinistral strike-slip in the Middle Devonian to Early Carboniferous, with the Middle Devonian Yackandandah Granite being sinistrally offset by 7 km along the Kancoona Fault. During the Late Devonian to Early Carboniferous period a conjugate fault set was established in northeastern Victoria, with dextral northeast-striking faults and sinistral northwest-striking faults, indicating limited east-west crustal shortening. The northeast-striking Beech worth and Tawonga Faults were probably initiated at this time and they dextrally offset the Kancoona and Kiewa Faults. Reactivation of the Beechworth and Tawonga Faults with dip-slip motion occurred during the Cainozoic and possibly Mesozoic.
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