Steep structure
{{short description|Zones of high strain characterised by the rotation of regional foliation into subvertical attitude}}
A steep structure is a unique structural feature found in the O'okiep Copper District (OCD), Namaqualand, Northern Cape Province, South Africa. These structures occur as narrow, east-west trending, antiformal and/or monoclinal zones of high strain characterised by the rotation of regional foliation into subvertical attitude.{{Cite journal|last1=Kisters|first1=Alexander F. M.|last2=Guy Charlesworth|first2=E.|last3=Gibson|first3=Roger L.|last4=Anhaeusser|first4=Carl R.|date=1996-06-01|title=Steep structure formation in the Okiep Copper District, South Africa: bulk inhomogeneous shortening of a high-grade metamorphic granite-gneiss sequence|url=http://www.sciencedirect.com/science/article/pii/S0191814196800083|journal=Journal of Structural Geology|language=en|volume=18|issue=6|pages=735–751|doi=10.1016/S0191-8141(96)80008-3|bibcode=1996JSG....18..735K|issn=0191-8141}}{{Cite journal|last=Watkeys|first=M. K.|date=1996-06-01|title=The Klondike steep structure, Okiep Copper District, South Africa|url=https://journals.co.za/content/journal/10520/EJC-92ec28309|journal=South African Journal of Geology|language=en|volume=99|issue=2|pages=169–183|issn=1012-0750}} These structures commonly host plug- and dyke-like mafic- to intermediate cupriferous bodies of the Koperberg Suite in their central portions.{{Cite journal |last1=Clifford |first1=Tom N. |last2=Barton |first2=Erika S. |date=2012-12-01 |title=The O'okiep Copper District, Namaqualand, South Africa: a review of the geology with emphasis on the petrogenesis of the cupriferous Koperberg Suite |journal=Mineralium Deposita |language=en |volume=47 |issue=8 |pages=837–857 |doi=10.1007/s00126-012-0403-x |bibcode=2012MinDe..47..837C |s2cid=129735687 |issn=1432-1866}} Steep structures are interpreted to have formed at the same time as the [https://www.britannica.com/science/granulite-facies granulite-facies metamorphism] during the waning stages of the Namaqua Orogeny.{{Cite journal|last1=Gibson|first1=R. L. |last2=Robb |first2=L. J. |last3=Kisters |first3=A. F. M. |last4=Cawthorn |first4=R. G. |date=1996-06-01 |title=Regional setting and geological evolution of the Okiep Copper District, Namaqualand, South Africa |url=https://journals.co.za/content/journal/10520/EJC-92e742794 |journal=South African Journal of Geology |language=en |volume=99 |issue=2 |pages=107–120 |issn=1012-0750}} Steep structures are also intimately related to megabreccias, a term coined by geologists in the OCD for granite-gneiss and metasedimentary country rocks cemented by granitic material {{Cite journal|last1=Kisters |first1=Alexander F. M. |last2=Gibson |first2=Roger L. |last3=Charlesworth|first3=E. Guy |last4=Anhaeusser |first4=Carl R. |date=1998-02-01 |title=The role of strain localization in the segregation and ascent of anatectic melts, Namaqualand, South Africa |url=http://www.sciencedirect.com/science/article/pii/S0191814197000813 |journal=Journal of Structural Geology |series=Structures and Properties of High Strain Zones in Rocks |language=en |volume=20 |issue=2 |pages=229–242 |doi=10.1016/S0191-8141(97)00081-3 |bibcode=1998JSG....20..229K |issn=0191-8141}}