Editing Magma (section)

==== Alkaline magmas ====
{{See also|Alkaline magma series}}
Some silicic magmas have an elevated content of [[alkali metal oxide]]s (sodium and potassium), particularly in regions of [[continental rifting]], areas overlying deeply [[subduction|subducted]] [[Tectonic plate|plates]], or at intraplate [[Hotspot (geology)|hotspots]].{{sfn|Philpotts|Ague|2009|pp=139-148}} Their silica content can range from ultramafic ([[nephelinite]]s, [[basanite]]s and [[tephrite]]s) to felsic ([[trachyte]]s). They are more likely to be generated at greater depths in the mantle than subalkaline magmas.{{sfn|Philpotts|Ague|2009|pp=606-607}} Olivine [[nephelinite]] magmas are both ultramafic and highly alkaline, and are thought to have come from much deeper in the [[mantle (geology)|mantle]] of the [[Earth]] than other magmas.<ref>{{cite web|url=http://gsc.nrcan.gc.ca/volcanoes/cat/feature_volcano_e.php|work=Catalogue of Canadian volcanoes|title=Stikine Volcanic Belt: Volcano Mountain|archive-url=https://web.archive.org/web/20090307140121/http://gsc.nrcan.gc.ca/volcanoes/cat/feature_volcano_e.php |archive-date=2009-03-07|access-date=23 November 2007}}</ref>
{| style="border:0px solid black;"
|+
!valign="top" |
{| class="wikitable" style="text-align: left;"
|+Examples of magma compositions (wt%){{sfn|Philpotts|Ague|2009|p=145}}
! Component
! Nephelinite
! Tholeiitic picrite
! Tholeiitic basalt
! Andesite
! Rhyolite
|-
| Silica |SiO<sub>2</sub>
| 39.7
| 46.4
| 53.8
| 60.0
| 73.2
|-
| TiO<sub>2</sub>
| 2.8
| 2.0
| 2.0
| 1.0
| 0.2
|-
| Al<sub>2</sub>O<sub>3</sub>
| 11.4
| 8.5
| 13.9
| 16.0
| 14.0
|- 
| Fe<sub>2</sub>O<sub>3</sub>
| 5.3
| 2.5
| 2.6
| 1.9
| 0.6
|- 
| FeO
| 8.2
| 9.8
| 9.3
| 6.2
| 1.7
|- 
| MnO
| 0.2
| 0.2
| 0.2
| 0.2
| 0.0
|- 
| MgO
| 12.1
| 20.8
| 4.1
| 3.9
| 0.4
|- 
| CaO
| 12.8
| 7.4
| 7.9
| 5.9
| 1.3
|- 
| Na<sub>2</sub>O
| 3.8
| 1.6
| 3.0
| 3.9
| 3.9
|-
| K<sub>2</sub>O
| 1.2
| 0.3
| 1.5
| 0.9
| 4.1
|-
| P<sub>2</sub>O<sub>5</sub>
| 0.9
| 0.2
| 0.4
| 0.2
| 0.0
|}
! valign="top" | {{Pie chart
| radius = 100
| thumb = 
| caption = Tholeiitic basalt magma
| other = 
| label1 = SiO<sub>2</sub> 
| value1 = 53.8
| label2 = Al<sub>2</sub>O<sub>3</sub>
| value2 =13.9
| label3 =FeO
| value3 =9.3
| label4 =CaO
| value4 =7.9
| label5 =MgO
| value5 =4.1
| label6 =Na<sub>2</sub>O
| value6 =3.0
| label7 = Fe<sub>2</sub>O<sub>3</sub>
| value7=2.6
| label8 = TiO<sub>2</sub>
| value8=2.0
| label9 = K<sub>2</sub>O
| value9 = 1.5
| label10 = P<sub>2</sub>O<sub>5</sub>
| value10 = 0.4
| label11 = MnO
| value11 = 0.2
}}
! valign="top" |{{Pie chart
| radius = 100
| thumb = 
| caption = Rhyolite magma
| other = 
| label1 = SiO<sub>2</sub> 
| value1 = 73.2
| label2 = Al<sub>2</sub>O<sub>3</sub>
| value2 = 14
| label9 =K<sub>2</sub>O
| value9 = 4.1
| label6 =Na<sub>2</sub>O
| value6 = 3.9
| label3 =FeO
| value3 = 1.7
| label4 = CaO
| value4 = 1.3
| label7 = Fe<sub>2</sub>O<sub>3</sub>
| value7= 0.6
| label5 = MgO
| value5= 0.4
| label8 = TiO<sub>2</sub>
| value8 = 0.2
| label10 = P<sub>2</sub>O<sub>5</sub>
| value10 = 0.
| label11 = MnO
| value11 = 0.
}}
|}