Haast Schist

Haast Schist
Stratigraphic range: Carboniferous-Jurassic ~320–180 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Sample of Haast Schist, containing biotite
Type	Metamorphic
Unit of	Austral Superprovince
Sub-units	Otago & Alpine Schist
Lithology
Primary	Schist
Other	Greenschist, jade
Location
Region	Canterbury, Marlborough & Otago Regions Chatham Islands
Country	New Zealand
Type section
Named for	Haast Pass

The Haast Schist, which contains both the Alpine and Otago Schist, is a metamorphic unit in the South Island of New Zealand. It extends from Central Otago, along the eastern side of the Alpine Fault to Cook Strait.[1] 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. The Haast Schist can be divided geographically from north to south into the Kaimanawa, Terawhiti, Marlborough, Alpine, Otago and Chatham schist.[2]

Description

The metamorphic grade progresses from greenschist, biotite, garnet and finally orthoclase. Myrmekitic textures occur within oligoclase within the garnet zone.[3] The schist's protoliths were the greywacke and argillite of the Caples Terrane and Torlesse Composite Terrane. 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 (Jade) is found as isolated pods in the higher metamorphic grades near the Alpine Fault.[4]

See also

• Geology of Canterbury, New Zealand
• Stratigraphy of New Zealand

References

1. "New Zealand Geology: an illustrated guide" (PDF). www.geotrips.org.nz.
2. Mortimer, N; Rattenbury, MS; King, PR; Bland, KJ; Barrell, DJA; Bache, F; Begg, JG; Campbell, HJ; Cox, SC; Crampton, JS; Edbrooke, SW; Forsyth, PJ; Johnston, MR; Jongens, R; Lee, JM; Leonard, GS; Raine, JI; Skinner, DNB; Timm, C; Townsend, DB; Tulloch, AJ; Turnbull, IM; Turnbull, RE (2014). "High-level stratigraphic scheme for New Zealand rocks". New Zealand Journal of Geology and Geophysics. 57 (4): 402–419. Bibcode:2014NZJGG..57..402M. doi:10.1080/00288306.2014.946062. ISSN 0028-8306.
3. Cooper, A. F. (1972). "Progressive Metamorphism of Metabasic Rocks from the Haast Schist Group of Southern New Zealand". Journal of Petrology. 13 (3): 457–492. Bibcode:1972JPet...13..457C. doi:10.1093/petrology/13.3.457.
4. Cooper, Alan F.; Ireland, Trevor R. (2015). "The Pounamu terrane, a new Cretaceous exotic terrane within the Alpine Schist, New Zealand; tectonically emplaced, deformed and metamorphosed during collision of the LIP Hikurangi Plateau with Zealandia". Gondwana Research. 27 (3): 1255–1269. Bibcode:2015GondR..27.1255C. doi:10.1016/j.gr.2013.11.011. ISSN 1342-937X.

Further reading

• The Rise and Fall of the Southern Alps, G. Coates 2002