Geology of New Zealand

New Zealand with the sub- sea continent Zealandia

The geological conditions of New Zealand are to a considerable extent shaped by the tectonic activities of the Pacific and Australian plates . The meeting of the two plates, initially diverging , then later converging , shaped the country with its two main islands over millions of years and still does so today. The outward manifestations of these processes can be observed with mountain folds , volcanism , earthquakes and numerous geothermal activities. In the North Island in particular, the convergence of the two plates leads to increased volcanic activity, with some of the most active volcanoes on earth being in the center of the North Island and north of it and being concentrated in the Taupo Volcanic Zone (TVZ). So that New Zealand is among the countries of the Pacific region, directly on the Pacific Ring of Fire (English: Pacific Ring of Fire ) are, a volcanic belt that the Pacific Ocean surrounds.

Geological review

Play media file

Origin of New Zealand (animated)

Before about 280 million years ago belonged to the land mass that is assigned to New Zealand today to the coastal offshore northeastern part of the supercontinent Gondwana . Under the pressure of the Pacific Plate moving westwards, a mountainous strip began to form in this lake bed about 200 million years ago and to rise out of the sea. With an eastward drift, the elevation was split off from the primary continent about 70 million years ago and gave rise to the below sea level continent Zealandia and the Tasman Sea . The plants and animals already living on the mountain strip developed independently from this point on and thus became endemics .

About 60 million years ago, New Zealand's land mass was much larger than it is today. But constant erosion processes flattened the mountains into hills and plains. The sea shifted the coastline further inland through continuous land erosion. Tectonic processes turned the southern part of the country counterclockwise faster than that could happen to the northern part. The resulting two main islands laid the basis for the division of New Zealand into two parts. Around 35 million years later, around 60% of today's land area was under water. Further progressing and different speed rotation of the two main islands left between the plate and the Pacific plate Australian a grave fraction ( Rift ) arise, the Alpine Fault . Around this fault, the North and South Islands shifted further counterclockwise and aligned New Zealand on an axis running northeast. In addition to the Alpine Fault , the Puysegur Trench formed to the south and the Hikuranki Trench and the Kermadec Trench to the north .

On the North Island, where the Pacific Plate is still pushed under the Australian Plate, volcanically active areas developed, and on the South Island, where the Pacific Plate pushes south-west along the Australian Plate, the New Zealand Alps were formed by folding .

Geological condition

The geological structure of New Zealand can be roughly assigned to three geological cycles based on its history of origin:

• The early to middle Paleozoic , in which the western part of New Zealand arose.
• The late Paleozoic to the early Cretaceous period , when the eastern part was formed.
• From the late Cretaceous to the Cenozoic , when the sediments and rocks of volcanic origin were formed.

One of the oldest known sediment outcrops in New Zealand, around 100 km northwest of Nelson in the Takaka - layer complex of former island arches , consists of Central Cambrian sedimentary sequences of the junction formation , essentially formed by turbiditic sandstones , silt rocks and conglomerates as well as some basaltic and andesitic units. The trilobite fossils contained in the sites of the Haupiri Group are the oldest fossils in New Zealand.

A somewhat more detailed classification of the geological structure of New Zealand can be found on the following map with the associated table.

New Zealand geological map
Data source: Institute of Geological and Nuclear Sciences , New Zealand

Legend for the adjacent map
Item	Rock types	Geological age	Age (mya)
1	Sediments	Chalk Cenozoic	145.5-65.5 and 55.8-0
2	Grauwacken	Permian to Triassic	299-199.6
3	Mica slate	Carbon to chalk	359.2-65.5
4th	volcanic rock	Cretaceous and Cenozoic	145.5-65.5 and 55.8-0
5	Sediments and ophiolites Northland and East Coast units	Cretaceous and Oligocene	145.5-65.5 and 33.9-23.03
6th	Pyroclastics	Triassic to Jurassic	251-145.5
7th	Limestone , clastica and volcanic rock ( central and eastern sedimentary zone )	Cambrian to Devonian	542-359.2
8th	Granitoids	Paleozoic and Cretaceous	542 - 251 and 145.5 - 65.5
9	metamorphic zones ( Western Fiordland zone )	Paleozoic and Cretaceous	542 - 251 and 145.5 - 65.5
10	Ophiolite and pyroclastics	Perm	299-251
11	Pyroclastics and volcanic rocks	Perm	299-251
12	mafic complexes, such as ultramafitite	Paleozoic and Cretaceous	542 - 251 and 145.5 - 65.5
13	Grauwacken ( western sediment zone )	Cambrian to Ordovician	542-443.7

Geological regions

The main islands of New Zealand are determined by a mountain relief that stretches through the two islands in a northeast-southwest orientation and is part of an extensive mountain system that encloses the entire Pacific region along the Pacific Ring of Fire. The two islands show clear differences in relief. These differences result from the different tectonic processes that have shaped New Zealand.

North island

The mountain landscapes of the North Island are determined by fracture tectonics and volcanism , with flatter regions being shaped by sediment deposits. The regions in detail:

• Along the main fault system, which runs from south to north through the North Island and is split up by the Wellington Fault , Mohaka Fault , Ruahine Fault and then almost parallel to it, the Waiohau Fault , Whakatane Fault , Waimana Fault , has one for the North Island formed an important mountain region. Grauwacke is the defining rock in the Rimutara Range , Tararua Range , Ruahine Range , Kaweka Range , Huiarau Range , Ikawhenua Range , Raukumara Range .
• The Taupo Volcanic Zone (TVZ), which extends from the submarine Whakatane volcano , about 80 km north-northeast of White Island , extends in a south-south-west direction to Mount Ruapehu over a length of 350 km and was originally up to 100 km wide the most volcanically active part of New Zealand. The Taupo Volcanic Zone has been divided into three categories over the so-called "old zone" (2 to 0.34 million years ago) and the "young zone" (0.34 million years ago to 65,000 years) down to the "modern zone" (65,000 years ago to today), which is continually reduced in width. Today the major faults and the most active volcanic areas are in a band of up to 50 km. Several large lakes, such as Lake Taupo , Lake Rotorua and Lake Tarawera , as well as the largest volcanoes, Mount Ruapehu with its 2797 m, Mount Ngauruhoe with 2291 m and Mount Tongariro with 1967 m are on a line there . The continental crust in the Taupo Volcanic Zone measures around 15 km thick, in contrast to the usual 35 km below the plains.
• The Central Volcanic Plateau is a central plateau in the middle of the North Island, which includes the southern part of the Taupo Volcanic Zone . Noteworthy here is the Rangipo Desert , a barren desert-like landscape with sand dunes and bizarre erosions, which make the layer structure visible. Rangipo is located in the southeastern part of the plateau.
• The eastern part of the North Island with the regions Wairarapa , Hawke's Bay , Gisborne and Eastland , and the western part with the regions Taranaki up to the North Island Volcanic Plateau and the western part of the Waikato region up to just before Auckland consist of flat-lying sandstone of the Cretaceous period and deposits from the Miocene and Pliocene . Alluvial land is found in the lower river landscapes of the largest rivers, Manawatu River and Waikato River , as well as in the coastal lowlands of Hawke Bay .
• The area around Mount Taranaki is of volcanic origin and is therefore an exception in the surrounding sediment-determined regions.

South island

Most of the South Island, but especially in the western part of the island, is characterized by mountain folds and glaciation . The subsoil in flatter regions consists primarily of sediments. The regions in detail:

• The mountainous landscape, which continues from the north of the North Island and runs lengthways through the South Island, has an alpine character and culminates in the glacier area around the highest mountain in the country, the Aoraki / Mount Cook . Mesozoic gneiss , greywacke and mica schist are mainly involved in the rock structure of the New Zealand Alps .
• A narrow band on the west coast from Haast up to the area around Nelson is characterized by sedimentary rocks, whereby the northern part is interspersed with regions in which granite is the dominant rock in the subsurface. An area running north to Golden Bay is of volcanic origin and interspersed with limestone deposits .
• East of the New Zealand Alps to the edge of the Canterbury Plains , the subsoil consists mainly of greywacke, with a narrow band of mica slate extending down to the Otago region, where it is the predominant rock.
• The Canterbury Plains in the central eastern coastal area consists entirely of sediments.
• The few areas of purely volcanic origin are located on the South Island on the Banks Peninsula not far from Christchurch and further south the urban area of Dunedin including the Otago Peninsula and Otago Harbor .
• Fiordland , in the extreme southwest of the South Island, on the other hand, consists mainly of metamorphic rocks and, with its rugged coastal landscape and mountains up to over 2,700 m high, represents the southern extension of the New Zealand Alps.

Geological outcrop

• During the recording work on Dun Mountain near Nelson, Ferdinand von Hochstetter explored a rock type that was not yet classified at the time and named it dunite after this type of locality . He published the first scientific description of the rock in 1864.

Natural resources

New Zealand is rich in natural resources . Above all metals , such as gold , silver and platinum metals , as well as coal , various economically important minerals occur in large quantities and are mined under economic conditions. Here are the most important:

coal

New Zealand has extensive lignite deposits , mainly found in the Waikato and Taranaki regions of the North Island and on the west coast , in Otago and in the south of the South Island. The resource is estimated at around 15 billion tons, with 80% of the deposits being distributed over the South Island. The lignite of the South Island is suitable for studies resulting in u. a. as a raw material for the production of fuels , briquettes and fertilizers in large petrochemical plants.

gold

Compared to other countries in which gold is mined worldwide, the amount of gold mined in New Zealand is comparatively small at around 13.5 tons in 2009. But gold, along with silver, is one of the most important raw materials in New Zealand that is mined.

Gold deposits are present on both islands, whereby they can come from four different deposit situations:

• Mesothermal quartz veins in Grauwacke, formed in the Paleozoic ,
• Mesothermal quartz veins in shale , formed in the Mesozoic ,
• Epithermal quartz veins in volcanic rock, formed in the Cenozoic ,
• Soaps in gravel or sand, also originated in the Cenozoic .

Other mineralizations of gold can be found in copper and in hydrothermal deposits, but are not of great importance in relation to their occurrence.

Major gold deposits are found on the Coromandel Peninsula , the Taupo Volcanic Zone , the West Coast and in Otago , which is also home to the country's largest gold mine, the Macraes Gold Mine . A total of 50 different places in the country are mining for gold. In 2006, the total gold deposits in New Zealand were estimated to be around 1230 tons.

silver

Silver mining is a by-product of New Zealand gold mining. Gold and silver usually appear together at their source. The classification of the four deposit types for gold (see above) also applies to silver in the same way. In 2009, around 14.3 tons of silver were still mined in New Zealand, and the trend is falling. Production peaked in 2005 at 43 tons.

Almost all of the silver mined in New Zealand comes from the country's second largest mine, the Martha Mine , along with the Favona Mine 2 km away . The share of silver in total production there is around 85%. The rest is gold.

Platinum metals

In the Longwood Range , about 40 km northwest of Invercargill , the government of New Zealand suspects deposits of platinum metals ( ruthenium , rhodium , palladium , osmium , iridium and platinum ) worth NZ $ 2 billion  . It is estimated that up to 1 million troy ounces (around 31 tons) of the rare metals can be found in an area of ​​12 by 32 km .

Greenhills , a few kilometers north of Bluff , is another important site on an area of ​​14 km². The Anglem field on Stewart Island is 35 by 14 km and near Riwaka a band extends 45 km in length and up to 3 km Width. With 400 km² by far the largest area where platinum metals are found is the region around Rotoroa .

Heavy mineral sands

As early as 1839, Ernst Dieffenbach , hired by the London New Zealand Company , described the occurrence of sand containing titanium minerals on the coast of Taranaki . In 1841 this was confirmed again by the head of the New Zealand expedition of the Plymouth Company of New Zealand , George Cutfield . A year later, Frederic Alonzo Carrington , surveyor for the New Zealand Company , sent samples of so-called iron sand to England to have it tested for its suitability for iron extraction . The run on this raw material began.

Heavy mineral sand in the form of iron sand occurs on many of the western coastal sections of the two main islands. Probably the largest deposits exist on the 480 km long stretch of coast of the North Island from Kaipara Harbor down to Whanganui . The black material, eroded by the volcanic rock of Mount Taranaki and the North Island Volcanic Plateau , was once carried into the sea by the rivers, the Rangitikei River up to the Waikato River , and deposited in the shelf area off the coast.

The Trans-Tasman Resources Limited (TTR), founded in September 2007, received a permit to mine iron sand for two sea areas in front of this coastal area, which cover an area of ​​almost 10,000 km² . Investigations in this area showed that around 4.5 billion tons with an iron content of 6.23% can be mined economically. The ore also contains 0.7% vanadium (V) oxide and shares of titanium (IV) oxide . The deposits seem to be so gigantic that the Taranaki Daily News had already brought the term " ocean of iron ore " (German: iron ore ocean ), coined by the TTR company, to the public.

In 2009, around 2 million tons of iron sand were extracted across New Zealand. The bulk of it came at the time from Barrytown and Westport , on the west coast of the South Island. The sand that is mined there is 4.5% ilmenite in Westport and 13.8% in Barrytown. It is assumed that deposits are in the order of 122 million tons or 50 million tons.

There are currently no ideas about the size of the total deposits of heavy mineral sands in New Zealand.

Other mineral raw materials

Other non-mineral raw materials that are industrially mined and recycled are in alphabetical order: bentonite , pumice stone , diatomite , dolomite , halloysite 7Å , limestone , perlite , silicon dioxide , various clay minerals and zeolites .

Well known geologists in New Zealand

• Ernst Dieffenbach (1811–1855) was a German physician, geologist and naturalist who lived and researched in New Zealand for more than two years and who also made a name for himself in the field of geology for New Zealand through his publication " Travels in New Zealand ".
• Julius von Haast (1822-1887), was a German-New Zealand geologist and naturalist, professor of geology at Canterbury College .
• Ferdinand von Hochstetter (1829-1884), was an Austrian geologist and began geological mapping of New Zealand on behalf of the governor at the time.
• James Hector (1834-1907), was a Scottish-New Zealand physician, geologist, researcher, director of various New Zealand institutes and from 1885 to 1903 Chancellor of the University of New Zealand.
• Frederick Wollaston Hutton (1836-1905), was an English-born natural scientist who was appointed first director of the Otago School of Mines and was the curator of the Otago Museum . He is known through the systematic description of fossils and through work on the theory of evolution .
• Alexander McKay (1841-1917), was a Scottish geologist who dealt with fault zones in New Zealand and left an extensive collection of fossil evidence.
• James Park (1857-1946), was a Scottish geologist who was the director of the Thames School of Mines and who made merits in New Zealand's mining geology .
• Patrick Marshall (1869-1950), was an English-born geologist who studied volcanic rocks in the Pacific. The terms ignimbrite and andesite lineage come from him .
• Charles Andrew Cotton (1885–1970) was an internationally recognized scientist in the field of geomorphology .
• Francis John Turner (1904–1985), was a petrologist and earned merit in the study of metamorphic rocks.
• Harold Wellman (1909–1999), was an expert in plate tectonics and a member of the Royal Society of New Zealand .
• William Sefton Fyfe (1927–2013), was a professor emeritus of geology, studied at the University of Otago , later taught at universities in the United States , England and most recently in Canada .

See also

• Geography of New Zealand

literature

• JJ Aitken : Plate Tectonics for curious kiwis . Ed .: Institute of Geological & Nuclear Sciences Limited . Lower Hutt 1996, ISBN 0-478-09555-4 (English).
• PJ Forsyth : Geology of the Waitaki Area . Ed .: Institute of Geological & Nuclear Sciences Limited . Lower Hutt 2001, ISBN 0-478-09739-5 (English).
• Australia, Oceania, Antarctica . In: The Great Encyclopedia of the Earth . tape 15 . Novaria Verlag, Munich 1973.

media

• Crown Minerals - Ministry of Economic Development (Ed.): Mineral Resources of New Zealand . 2009, ISSN  1836-5752 (English, CD-ROM - Disc 1 + 2 ).

Web links

• Eileen McSaveney, Simon Nathan : Geology - overview . Te Ara - the Encyclopedia of New Zealand , accessed January 30, 2012 . 
• New Zealand Geology Web Map . GNS Science,accessed November 25, 2015(English, interactive geological map of New Zealand). 

Individual evidence

1. ^ ^{A b} J. J. Aitken : Plate Tectonics for curious kiwis . Ed .: Institute of Geological & Nuclear Sciences Limited . Lower Hutt 1996, p.  38-41 (English).
2. ^ Geology and Mineral Resources . (PDF 1.3 MB) Ministry of Economic Development , archived from the original ; accessed on February 8, 2016 (English, original website no longer available).  
3. ^ Carsten Münker, Roger Cooper : The Cambrian arc complex of the Takaka Terrane, New Zealand: An integrated stratigraphical, paleontological and geochemical approach . In: The Royal Society of New Zealand (Ed.): New Zealand Journal of Geology and Geophysics . Volume 42, Issue 3 . Wellington 1999, p. 415-445 , doi : 10.1080 / 00288306.1999.9514854 (English).
4. ^ New Zealand Stratigraphic Lexicon - Takaka Terrane . Institute of Geological and Nuclear Sciences , accessed June 16, 2012 .  
5. ^ MS Rattenbury, RA Cooper, MR Johnston : Geology of the Nelson Area . Ed .: Institute of Geological and Nuclear Sciences . Lower Hutt 1998, ISBN 0-478-09623-2 , pp.  67 (English).
6. ^ New Zealand Active Faults Database . GNS Science , accessed April 12, 2018 .  
7. ^ Wellington Land District . In: Alexander Hare McLintock (Ed.): An Encyclopaedia of New Zealand . Wellington 1966 ( online [accessed August 16, 2011]).
8. ^ Hawke's Bay Land District . In: Alexander Hare McLintock (Ed.): An Encyclopaedia of New Zealand . Wellington 1966 ( online [accessed August 16, 2011]).
9. ^ Gisborne Land District . In: Alexander Hare McLintock (Ed.): An Encyclopaedia of New Zealand . Wellington 1966 ( online [accessed August 16, 2011]).
10. ↑ JA Gamble, IC Wright, JA Baker : Seafloor geology and petrology in the oceanic to continental transition zone of the Kermadec ‐ Havre ‐ Taupo Volcanic Zone arc system, New Zealand . In: The Royal Society of New Zealand (Ed.): New Zealand Journal of Geology and Geophysics . Volume 36, Issue 4 . Wellington 1993, p.  417-435 , doi : 10.1080 / 00288306.1993.9514588 (English).
11. ^ ^{A b} P. Villamor & KR Berryman : Evolution of the southern termination of the Taupo Rift, New Zealand . In: The Royal Society of New Zealand (Ed.): New Zealand Journal of Geology and Geophysics . Volume 49, Issue 1 . Wellington 2006, p.  23–37 , doi : 10.1080 / 00288306.2006.9515145 (English).
12. ^ JJ Aitken : Plate Tectonics for curious kiwis . Ed .: Institute of Geological & Nuclear Sciences Limited . Lower Hutt 1996, p.  39 (English).
13. ^ Judy Grindell : Volcanic Dunes of the Rangipo Desert . Landcare Research New Zealand , December 22, 2010, archived from the original on February 9, 2013 ; accessed on April 12, 2018 (English, original website no longer available).  
14. ↑ ^{a b} Australia, Oceania, Antarctica . In: The Great Encyclopedia of the Earth . tape  15 . Novaria Verlag, Munich 1973.
15. ^ F. Hochstetter: Geology of New Zealand. Contributions to the geology of the provinces of Auckland and Nelson . Vienna 1864, p. 218.
16. ↑ ^{a b} Ministry of Economic Development (ed.): Crown Minerals - Report 2009/2010 . 2010, ISSN 1178-4512 , p.   20 (English).
17. ↑ ^{a b c d} Introduction to New Zealand's Mineral Resources - Gold . In: Crown Minerals - Ministry of Economic Development (Ed.): Mineral Resources of New Zealand . 2009, ISSN 1836-5752 (English, CD-ROM - Disc 1 ).  
18. ^ GA Partington, AB Christie, MS Rattenbury : GIS Modeling of Gold Prospectivity in New Zealand . In: The Australasian Institute of Mining and Metallurgy, New Zealand Branch (Ed.): Geology and Exploration of New Zealand Mineral Deposits . Alexandra 2006, p.  21–28 (English, online [PDF; accessed on August 16, 2011]).
19. ^ New Zealand Silver Production by Year . Index Mundi , accessed June 12, 2012 .  
20. ^ Gold and silver production in New Zealand . Museum of New Zealand Te Papa Tongarewa , accessed June 11, 2012 .  
21. ↑ Alex Fensome : Platinum potential in the Longwood hills . The Southland Times - Online , September 21, 2011, accessed June 12, 2012 .  
22. ↑ ^{a b} Iron and steel - Iron - an abundant resource . Te Ara - the Encyclopedia of New Zealand , accessed June 12, 2012 .  
23. ↑ Iron sand to Steel - Chronology . Techhistory.co.nz , accessed June 12, 2012 .  
24. ^ Offshore Iron Ore Harvesting . Trans-Tasman Resources , accessed June 12, 2012 .  
25. ^ Offshore Iron Ore Harvesting . (PDF 4.6 MB) Trans-Tasman Resources , accessed June 12, 2012 (English, roadshow document).  
26. ↑ Rob Maetzig : Ironsand deposits exceed estimates . Taranaki Daily News - Online August 16, 2011, accessed June 12, 2012 .  
27. ↑ Introduction to New Zealand's Mineral Resources - Gold . In: Crown Minerals - Ministry of Economic Development (Ed.): Mineral Resources of New Zealand . 2009, ISSN 1836-5752 (English, CD-ROM - Disc 2 ).