Lachlan Fold Belt

The Lachlan Fold Belt, also called the Lachlan Orogen, is a special area of folded and broken rocks in the eastern part of Australia. It covers much of New South Wales and Victoria, and also reaches into Tasmania, the Australian Capital Territory, and Queensland.

This belt was formed a very long time ago, between 450 and 340 million years back, during a time called the Middle Paleozoic. Today, the Lachlan Fold Belt spans a huge area of about 200,000 square kilometers, making it an important part of Australia's landscape and history.

Characteristics

The Lachlan Fold Belt is a large area of folded and cracked rocks in eastern Australia. It mainly covers parts of New South Wales and Victoria, and also reaches into Tasmania, the Australian Capital Territory, and Queensland.

This area is bordered by different rock features. To the west lies the Delamerian Orogen, and to the east are the Narooma terrane and the New England Orogen. The belt is part of a larger system called the Tasman Orogenic System in Australia. It has been shaped by many natural processes, including folding and the movement of Earth's plates. Over time, the width of the belt has changed because of these processes.

History

The Lachlan Fold Belt is a part of eastern Australia made from very old ocean rocks. It formed long ago when Australia had a shoreline along what is now New South Wales and Victoria. In ancient times, shallow seas covered parts of Australia, and layers of mud and sand settled on the ocean floor.

Later, underwater volcanoes formed chains of islands, and deep water sediments collected between these islands and the mainland. Over millions of years, these sediments were pushed and folded into mountains. Today, we can still see evidence of these ancient processes in the rocks of New South Wales and Victoria.

Lithology

The Lachlan Fold Belt is made of many kinds of rocks that formed under the water. These rocks include sandstone and shale, as well as other materials like chert and changed volcanic rocks. They came from deep-sea fans, trenches, volcanic arcs, ocean crust, and small pieces of continents.

Subdivisions

The Lachlan Fold Belt has three main parts: Western, Central, and Eastern. The Western Lachlan is in Victoria and includes areas like Stawell and Melbourne. The Central Lachlan has the Tabberabbera Zone and the Wagga-Omeo Metamorphic Belt. The Eastern Lachlan lies east of the Gilmore Fault Zone.

The Macquarie Volcanic Arc formed far off the coast. West of Parkes, you can find the Yarrimbah Formation, made of deep-water rocks. Near Oberon, there is the Budhang Chert Member, and between Cowra and Boorowa lies the Molong Volcanic Belt. The Adaminaby Group moved north over the Molong Volcanic Belt. Rocks in the Wagga Belt were pushed east over another volcanic belt.

Western Lachlan Orogen

The upper crust here has folded layers of sediment. The lower crust has old ocean floor rocks and magma support from below.

Central Lachlan Orogen

Eastern Lachlan Orogen

In the Eastern part, rock structures run north to south. The western side has thick rock layers moved, while the eastern side has thinner layers moved.

Economically significant mineralisation

The Lachlan Fold Belt has many places where valuable minerals like gold, copper, silver, lead, zinc, and tin are found. These minerals have helped people make things and earn money. There is still a chance to find more minerals here in the future.