Mangakino caldera complex

{{Short description|A volcanic caldera in New Zealand}}

{{Use New Zealand English|date=April 2024}}

{{Infobox mountain

| name = Mangakino Caldera

| photo = Mangakino.Caldera.Rift.Zone.North.Island.NZ.jpg

| photo_caption = Approximate extent of ignimbrite sheets from Kidnappers (yellow) and Rocky Hill eruptions (orange) as determined from land drill cores sampling. The Kidnappers ignimbrite has been reported in some cores from just beyond the boundaries shown and this map only tries to show where there was full coverage of the then existing landforms and present land surface to convey an idea of the minimal total biosphere disruption.{{harvnb|Cooper|Wilson|Millet|Baker|2016}}

| map=North Island

| elevation_m =

| elevation_ref =

| prominence =

| location = North Island, New Zealand

| coordinates ={{coord|38|23|S|175|47|E|display=inline,title}}

| topo =

| type = Caldera

| age = {{Geological range|1.6|0.93|prefix=Pleistocene (|ref=)}}

| length = {{convert|30|km|abbr=on}}

| width = {{convert|15|km|abbr=on}}

| volcanic_arc/belt = Taupō Volcanic Zone

| last_eruption = 900,000 years ago

}}

File:Maroa.Caldera.Rift.Zone.North.Island.NZ.jpg in the old Taupō Rift (yellow shading). Also shown to its east are the Whakamaru caldera, the more recent Maroa Caldera contained within it and the Ohakuri Caldera which had a paired eruption with the Rotorua Caldera. Also shown is the modern Taupō Rift (red shading), Hauraki Rift (purple shading) and landmarks of Lake Taupō and Lake Rotorua]]

The Mangakino caldera complex (other names are Mangakino volcanic center, Mangakino Caldera) is the westernmost and one of oldest extinct rhyolitic caldera volcanoes in the Taupō Volcanic Zone of New Zealand's North Island.{{Cite journal |doi=10.1080/00288306.1998.9514803 |last1=Krippner |first1=Stephen J. P. |last2=Briggs |first2=Roger M. |last3=Wilson |first3=Colin J. N. |authorlink3=Colin J. N. Wilson |last4=Cole |first4=James W. |year=1998 |title=Petrography and geochemistry of lithic fragments in ignimbrites from the Mangakino Volcanic Centre: implications for the composition of the subvolcanic crust in western Taupo Volcanic Zone, New Zealand |journal=New Zealand Journal of Geology and Geophysics |volume=41 |pages=187–199 |issue=2 |doi-access=free |bibcode=1998NZJGG..41..187K }} It produced about a million years ago (1 Ma) in the Kidnappers eruption of {{convert|1200|km3|cumi|1|sp=us|abbr=on}}, the most widespread ignimbrite deposits on Earth being over {{convert|45000|km2|abbr=on}} in area. This eruption was closely followed in time by the smaller {{convert|200|km3|cumi|1|sp=us|abbr=on}} Rocky Hill eruption.{{cite journal|last= Cooper|first= G.F. |author2=C. J. Wilson|author3=J. A. Baker |author4=M. Millet |year= 2012 |title= Rejuvenation and Repeated Eruption of a 1.0 Ma Supervolcanic System at Mangakino Caldera, Taupo Volcanic Zone, New Zealand |journal= AGU Fall Meeting Abstracts |volume= 2012 |bibcode= 2012AGUFM.V31C2797C | url= https://ui.adsabs.harvard.edu/abs/2012AGUFM.V31C2797C/abstract |accessdate= 2022-05-15 }} The Kidnappers eruption had a estimated VEI of 8 and has been assigned a total eruption volume (not just tephra) of {{convert|2760|km3|cumi|1|sp=us|abbr=on}}.

However this was only in its most recent caldera forming phase from 1.21 to 0.91 million years ago as it had its earliest caldera generating phase from 1.62 to 1.51 million years ago. There are at least 11 major historic eruptions assigned to this complex.{{cite web |title=Mangakino |url=http://www.bgs.ac.uk/vogripa/searchVOGRIPA.cfc?method=detail&id=950 |publisher=VOGRIPA |access-date=9 December 2018 |archive-url=https://web.archive.org/web/20181209124038/http://www.bgs.ac.uk/vogripa/searchVOGRIPA.cfc?method=detail&id=950 |archive-date=9 December 2018 |url-status=live }} At least 5 of these contributed significant welded ignimbrite deposits that represent major pyroclastic events in the central North Island.{{Cite web|title= Rift Architecture and Caldera Volcanism in the Taupo Volcanic Zone, New Zealand |url=https://ir.canterbury.ac.nz/handle/10092/4944| year=2005 |last1=Spinks |first1=Karl D. }} Ongatiti Ignimbrite (Hinuera Stone) from a 7 VEI event,{{sfn|Yousef Zadeh|2020|pp=ii}} about 1.3 million years ago, has now been found over a wider area and several meter thick tephra deposits from the eruption exist on drill samples from both Auckland and Wellington.{{sfn|Yousef Zadeh|2020|p=38}}{{harvnb|Yousef Zadeh|Pittari|Lowe|Danišík|2023|loc=Conclusions}}

The earliest characterised eruptives from the complex are andesitic{{Harvnb|Yousef Zadeh|2020|loc=table 1.1}} and the mechanism of transition from this to the more explosive later rhyolitic eruptions is related to increased heat flow from the magma sources.{{Harvnb|Yousef Zadeh|2020|p=9}}

Later many of these deposits were covered over by deposits from other eruptive centres such as those of the Oruanui eruption.

The caldera can be defined by gravitational measurements as {{convert|30|km|abbr=on}} by {{convert|15|km|abbr=on}} and its "basement" floor is at least {{convert|4|km|abbr=on}} below the present ground surface.{{harvnb|Pittari|Prentice|McLeod|Yousef Zadeh|2021}}

class="wikitable" |+ Assigned eruptions for the Mangakino Caldera (note Unit F not definitely assigned)
Formations	Layer names	Age range estimate by various methods (if only one method ± error)	Eruptive volume
Marshall	Unit I (Marshall A and B) Ignimbrite Unit H (Kaahu) Ignimbrite Unit G	0.95 ± 0.03 Ma
Whakaahu	Rhyolite dome	1.02 ± 0.02 Ma
Raepahu (Potaka Tephra)	Rocky Hill Ignimbrite Kidnappers Unit E Ignimbrite and fall deposit	0.95 to 1.15 Ma 0.93 to 1.07 Ma	{{convert|200|km3}} >{{convert|1200|km3}}
Mangaokewa	Ahuroa Ignimbrite Unit D Ignimbrite and fall deposit	1.16 to 1.33 Ma 1.20 ± 0.04 Ma
Ongatiti	Ongatiti Ignimbrite (Oparau tephra, K12a Kauroa Ash Formation, K12){{sfn|Yousef Zadeh|2020|p=150}} Tumai Rd dome	1.37 ± 0.04 Ma (1.31 ± 0.09 Ma, 1.38 ± 0.06 Ma, 1.38 ± 0.05 Ma){{sfn|Yousef Zadeh|Pittari|Lowe|Danišík|2023|loc=Compilation of published ages and new (Usingle bondTh)/He data}} 1.16 to 1.34 Ma 1.27 ± 0.05 Ma	>{{convert|1000|km3}} DRE
Pouakani	Unit C Ignimbrite	1.68 ± 0.07 Ma (This age inconsistent with position)
Tolley	Unit B Ignimbrite	1.53 ± 0.04 Ma
Ngaroma	Ngaroma (Unit A) Ignimbrite	1.31 to 1.6 Ma
Link (source unknown)	Unit F Ignimbrite	1.60 ± 0.09 Ma

{{#tag:mapframe|{{Wikipedia:Map data/Northern North Island Volcanics}}|frameless=1

|align=center

|text=Map of selected surface volcanic deposits centered to include all the present surface Mangakino caldera ignimbrites. Tephra and buried ignimbrite from these eruptions were even more widespread as illustrated elsewhere on this page. The present surface ignimbrite is various light violet shades which are identical for any single source, but other eruptions breakup the mutual ignimbrite sheets. Thus clicking on the map enlarges it, and enables panning and mouseover of volcanic deposits name/wikilink and ages before present for wider volcanic context. The key to the shading of other volcanics that are shown (active in last million years odd) with panning is rhyolite - violet, dacite - purple, basalt - brown, monogenic basalts - dark brown, undifferentiated basalts of the Tangihua Complex in Northland Allochthon - light brown, arc basalts - deep orange brown, arc ring basalts -orange brown, andesite - red, basaltic andesite`- light red, and plutonic - gray. White shading has been used for postulated calderas (usually subsurface now).

|width=500

|height=520

|latitude=-38.25

|longitude=175.57

|icon=no

|zoom=9

}}