Magnesium

Magnesium is the chemical element in the periodic table that has the symbol Mg and atomic number 12. Magnesium is the eighth most abundant element and constitutes about 2% of the Earth's crust by weight, and it is the third most plentiful element dissolved in seawater. This alkaline earth metal is primarily used as an alloying agent to make aluminium-magnesium alloys, sometimes called "magnalium" or "magnelium".

Isotopes

Magnesium-26 is a stable isotope that has found application in isotopic geology, similar to that of aluminium. Mg-26 is a radiogenic daughter product of Al-26, which has a half-life of 717000 years. Large enrichments of stable Mg-26 have been observed in the Ca-Al-rich inclusions of some carbonaceous chondrite meteorites. The anomalous abundance of Mg-26 is attributed to the decay of its parent Al-26 in the inclusions. Therefore, the meteorite must have formed in the solar nebula before the Al-26 had decayed. Hence, these fragments are among the oldest objects in the solar system and have preserved information about its earliest history.

Related Topics:
Isotopic - Geology - Aluminium - Radiogenic - Half-life - Ca-Al-rich inclusions - Carbonaceous chondrite - Meteorite - Solar nebula - Solar system

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It is conventional to plot Mg-26/Mg-24 against an Al/Mg ratio. In an isochrone plot, the Al/Mg ratio plotted is Al-27/Mg-24. The slope of the isochron has no age significance, but indicates the initial Al-26/Al-27 ratio in the sample at the time when the systems were separated from a common reservoir.

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