Haast Schist
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]
| Haast Schist Stratigraphic range: Carboniferous-Jurassic ~320–180 Ma | |
|---|---|
 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 |  |
| Type section | |
| Named for | Haast Pass |
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]
References
- "New Zealand Geology: an illustrated guide" (PDF). www.geotrips.org.nz.
- 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. doi:10.1080/00288306.2014.946062. ISSN 0028-8306.
- 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.
- 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