Archean Zircons of Erawondoo Hill

Erawondoo Hill, part of the Jack Hills Range, is located in the Murchison District of Western Australia. Geologically, it is in the northern part of the Yilgarn Craton in a structural/ metamorphic terrane known as the Narryer Terrane, a northeast-trending belt of folded and metamorphosed supracrustal rocks between 3.1-3.2 billion years old. The Jack Hills range is comprised of vertically-dipping Precambrian rocks and the detrital zircons over 4 billion years old occur within pebble conglomerates therein. Locally are interlayered sheets of massive sandstone and cross-bedded sandstone. Hard and heat-resistant, zircon is capable of persisting even after the primary features of the host or parent rock have been destroyed. These ancient zircon crystals provide the only geological evidence to provide insight into this time period. In fact, these zircons being older than the sedimentary rocks in which they occur represent rocks that no longer exist or can no longer be identified. The exact age of deposition of the pebble conglomerate in which the crystals are found is still unknown and is one of the unresolved questions surrounding this ancient fragment of Earth’s early crust in this part of Western Australia.