Tectonic Petrameter

Geologists study the Earth to learn our planet’s natural history. But the reason behind the planet’s birth still remains a mystery. Won’t you join me on a very special journey through geologic time? Four billion, six hundred million years have passed so please don’t mind me if I move somewhat fast through the story. Rocks are the geologist’s inventory of information. They give us clues to their formation. Ever since its creation, the Earth has been dynamic and constantly changing. All of our panoramic views are always rearranging themselves ever so slowly over time. The oldest slice of time is called the Precambrian which is broken into three, beginning with Hadean, and as you can see, our Earth is thought to have been covered by a sea of magma! Could you have handled it? A bombardment of meteorites also hit and continue to hit our planet.

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v18n1 From the Editors

In this issue, we follow the halogen group elements (fluorine, chlorine, bromine, and iodine) from the Earth’s interior to surface—and even beyond! In a similar vein to two previous Elements issues that also explored groups of elements united by common properties (Rare Earth Elements; October 2012 and Platinum Group Elements; August 2008), this issue similarly showcases the wide diversity of research that is encompassed by halogen mineralogy and geochemistry. Over the last several decades, the halogens have increasingly come into the spotlight, possibly due to improving methods for measuring ultra-low abundance bromine and iodine in geologic materials, as well as isotopes of chlorine and bromine. The result of this increased enthusiasm for halogens is deftly covered over six articles by this issue’s authors—from halogens in Earth and planetary systems to experimental petrology and analytical developments, there truly is something for everyone.

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