The age of shear zones on western King Island

<p>Several shear zones occur within Neoproterozoic granites on the north and west coasts of King Island. We have<br>applied the chemical U-Th-Pb dating method to monazite and xenotime from five of these shear zones to show<br>that they were formed at 740 ± 9 Ma, immediately after granite intrusion. The strongest reactivation on the shear<br>zones occurred at 500 Ma and was probably associated with sinistral movement. This event may have occurred at<br>the same time as the regional cleavage was developed in the Grassy Group. Further reactivation occurred during<br>the Devonian. There is evidence for brittle reactivation of the Disappointment Bay West Shear Zone in the early<br>Permian that may correlate with movement on the Grassy River Fault and possibly sinistral transpression on the<br>eastern margin of Gondwana.</p>