Editing Magma (section)

==== Non-silicate magmas ====
Some lavas of unusual composition have erupted onto the surface of the Earth. These include:
* [[Carbonatite]] and [[natrocarbonatite]] lavas are known from [[Ol Doinyo Lengai]] volcano in [[Tanzania]], which is the sole example of an active carbonatite volcano.<ref>[http://www.geology.sdsu.edu/how_volcanoes_work/Unusual%20lava.html Vic Camp, ''How volcanoes work'', Unusual Lava Types] {{Webarchive|url=https://web.archive.org/web/20171023185741/http://www.geology.sdsu.edu/how_volcanoes_work/Unusual%20lava.html |date=2017-10-23 }}, [[San Diego State University]], Geology</ref> Carbonatites in the geologic record are typically 75% carbonate minerals, with lesser amounts of silica-undersaturated silicate minerals (such as [[mica]]s and olivine), [[apatite]], [[magnetite]], and [[pyrochlore]]. This may not reflect the original composition of the lava, which may have included [[sodium carbonate]] that was subsequently removed by hydrothermal activity, though laboratory experiments show that a calcite-rich magma is possible. Carbonatite lavas show [[stable isotope ratio]]s indicating they are derived from the highly alkaline silicic lavas with which they are always associated, probably by separation of an immiscible phase.{{sfn|Philpotts|Ague|2009|pp=396-397}} Natrocarbonatite lavas of Ol Doinyo Lengai are composed mostly of sodium carbonate, with about half as much calcium carbonate and half again as much potassium carbonate, and minor amounts of halides, fluorides, and sulphates. The lavas are extremely fluid, with viscosities only slightly greater than water, and are very cool, with measured temperatures of {{cvt|491|to|544|C}}.<ref>{{cite journal |last1=Keller |first1=Jörg |last2=Krafft |first2=Maurice |title=Effusive natrocarbonatite activity of Oldoinyo Lengai, June 1988 |journal=Bulletin of Volcanology |date=November 1990 |volume=52 |issue=8 |pages=629–645 |doi=10.1007/BF00301213|bibcode=1990BVol...52..629K |s2cid=129106033 }}</ref>
* [[Iron oxide]] magmas are thought to be the source of the [[iron ore]] at [[Kiruna]], [[Sweden]] which formed during the [[Proterozoic]].<ref name="IronOxidelava"/> Iron oxide lavas of [[Pliocene]] age occur at the [[El Laco (volcano)|El Laco]] volcanic complex on the Chile-Argentina border.<ref name="ChileIronOxideLava"/> Iron oxide lavas are thought to be the result of [[Miscibility|immiscible]] separation of iron oxide magma from a parental magma of [[Calc-alkaline magma series|calc-alkaline]] or alkaline composition.<ref name="IronOxidelava"/> When erupted, the temperature of the molten iron oxide magma is about {{cvt|700|to|800|C}}.<ref name="Jonsson_etal_2013">{{cite journal | title=Magmatic origin of giant 'Kiruna-type' apatite-iron-oxide ores in Central Sweden | first1=E. | last1=Jonsson | first2=V.R. | last2=Troll | first3=K. | last3=Högdahl | first4=C. | last4=Harris | first5=F. | last5=Weis | first6=K.P. | last6=Nilsson | first7=A. | last7=Skelton | journal=Scientific Reports | date=2013 | volume=3 | page=1644 | doi=10.1038/srep01644| pmid=23571605 | pmc=3622134 | bibcode=2013NatSR...3.1644J }}</ref>
* [[Sulfur]] lava flows up to {{convert|250|m|0|abbr=off}} long and {{convert|10|m|0|abbr=off}} wide occur at [[Lastarria]] volcano, Chile. They were formed by the melting of sulfur deposits at temperatures as low as {{convert|113|°C}}.<ref name="ChileIronOxideLava"/>