Prospect dolerite intrusion
| Prospect dolerite intrusion | |
|---|---|
| Stratigraphic range: Early Jurassic or Middle Jurassic | |
| Type | igneous |
| Overlies | Ashfield Shale and Sydney sandstone |
| Area | 2.4 km by 1.4 km |
| Thickness | 76.2 metres (250 ft) |
| Lithology | |
| Primary | picrite, dolerite, prehnite, basalt, calcite, pegmatite, etc |
| Location | |
| Coordinates | 33°49′30″S 150°55′5″E / 33.82500°S 150.91806°E |
| Region | Western Sydney, New South Wales |
| Country | Australia |
| Extent | City of Blacktown and Cumberland City Council |
| Type section | |
| Named for | Prospect, New South Wales |
| Named by | Governor Arthur Phillip and Lieutenant (later Governor) Philip Gidley King |
The Prospect dolerite intrusion, or Prospect intrusion, is a Jurassic picrite or dolerite laccolith that is situated in Sydney, New South Wales, Australia. Lying in the heart of Cumberland Plain, in the suburb of Pemulwuy (previously Greystanes), the igneous intrusion is Sydney's largest body of igneous rock, rising to a height of 117 metres (384 ft) above sea level. The site is formed by an intrusion of dolerite rock into Ashfield Shale and the Hawkesbury sandstone. At least seven different rock types occur in the intrusion.
The site was formed from around 200 million years ago when volcanic material (hot magmatic fluids) from the Earth's upper mantle moved upwards and then sideways, which produced many different minerals in the upper part. Formerly known as Prospect Quarry, the eroded residue of the volcanic core became a quarry of the basalt plug that was carried out from 1820s until the late 2000s, where it contributed most of the crushed rock that were used for building construction and roads in the Sydney area. The intrusion comprises: prospect dolerite and prospect teschenite, in addition to an abundance of coarse grained picrite, olivine and its prehnite specimens.