The Haast Schist, which contains both the Alpine and Otago Schist, is a metamorphic unit in the

South Island The South Island, also officially named , is the larger of the two major islands of New Zealand in surface area, the other being the smaller but more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman ...

of New Zealand. It extends from Central Otago, along the eastern side of the

Alpine Fault The Alpine Fault is a geological fault that runs almost the entire length of New Zealand's South Island (c. 480 km) and forms the boundary between the Pacific Plate and the Indo-Australian Plate. The Southern Alps have been uplifted on the fa ...

Cook Strait Cook Strait ( mi, Te Moana-o-Raukawa) separates the North and South Islands of New Zealand. The strait connects the Tasman Sea on the northwest with the South Pacific Ocean on the southeast. It is wide at its narrowest point,McLintock, A H, ...

. There are also isolated outcrops of the Haast Schist within the central North Island. The schists were named after Haast Pass on the

West Coast West Coast or west coast may refer to: Geography Australia * Western Australia *Regions of South Australia#Weather forecasting, West Coast of South Australia * West Coast, Tasmania **West Coast Range, mountain range in the region Canada * Britis ...

. The Haast Schist can be divided geographically from north to south into the Kaimanawa, Terawhiti, Marlborough, Alpine, Otago and Chatham schist.

Description

The

metamorphic grade Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of che ...

progresses from

greenschist Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically and 2–10 kilobars (). Greenschists commonly have an abundance of green minerals such as chlorite ...

biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more alumino ...

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different s ...

and finally

orthoclase Orthoclase, or orthoclase feldspar (endmember formula K Al Si3 O8), is an important tectosilicate mineral which forms igneous rock. The name is from the Ancient Greek for "straight fracture," because its two cleavage planes are at right angles t ...

. Myrmekitic textures occur within

oligoclase Oligoclase is a rock-forming mineral belonging to the plagioclase feldspars. In chemical composition and in its crystallographic and physical characters it is intermediate between albite ( Na Al Si3 O8) and anorthite ( CaAl2Si2O8). The albite:an ...

within the garnet zone. The schist's protoliths were the greywacke and

argillite :''"Argillite" may also refer to Argillite, Kentucky.'' Argillite () is a fine-grained sedimentary rock composed predominantly of indurated clay particles. Argillaceous rocks are basically lithified muds and oozes. They contain variable amounts ...

of the Caples Terrane and

Torlesse Composite Terrane The Torlesse Composite Terrane is a plate tectonic terrane forming part of the South Island of New Zealand. It contains the Rakaia, Aspiring and Pahau Terranes and the Esk Head Belt. Greywacke (or Torlesse Greywacke) is the dominant rock type of ...

. The schists were originally brought to the surface of the Earth's crust in the Cretaceous and again during the Kaikoura Orogeny along the Alpine Fault.

Pounamu Pounamu is a term for several types of hard and durable stone found in southern New Zealand. They are highly valued in New Zealand, and carvings made from pounamu play an important role in Māori culture. Name The Māori word , also used ...

(

Jade Jade is a mineral used as jewellery or for ornaments. It is typically green, although may be yellow or white. Jade can refer to either of two different silicate minerals: nephrite (a silicate of calcium and magnesium in the amphibole group of ...

) is found as isolated pods in the higher metamorphic grades near the Alpine Fault.

References

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Description

See also

References

Further reading