Potrillo Volcanic Field - Isotope Geochemistry

Isotope Geochemistry

Potrillo volcanic field contains alkaline basanitic lavas and cinder cones in the southernmost New Mexico. La Mesa is a surface which formed between 900 and 700 Ka, which holds the lavas in the central and eastern region of the field. There are three separate eruptive centers; Afton eruptive center which resides directly against La Mesa central province, the Aden complex which is a crater that lies above the Afton flows, lastly the Black Mountain, which is adjacent to a series of cinder cones. When performing 3He surface exposure dating, the upper 3 centimetres (1.2 in) of flow surfaces is sufficient enough for collecting samples desired. It is essential to collect samples with primarily display flow features, such as spatter, flow lineation, and cooling rinds. 3He surface dating is a technique that is optimal when working with well preserved young surface lavas (<700 ka). All samples are analyzed on a static mass spectrometer equipped with ion counting detection. The mineral is first crushed in a vacuum, and the magmatic component of the mash is analyzed for its amount and isotropic composition of helium and neon. 3He is calculated by taking the difference of total 3He component equal to the total 4He released in the heating process times 3He/4He released in the crush step. Cosmogenic 3He/21Ne confirm that 3He is retained be the samples taken. Cosmogenic isotopes are rare isotopes created when a high-energy cosmic ray interacts with the nucleus of an atom. These isotopes are produced within earth materials such as rocks or soil, in Earth's atmosphere, and in extraterrestrial items such as meteorites. By measuring cosmogenic isotopes, scientists are able to gain insight into a range of geological and astronomical processes. There are both radioactive and stable cosmogenic isotopes. This assumes ⁴He released by heating is due to magmatic component with a helium isotopic composition which seems to be a reasonable assumption for a low uranium olivine. Ne concentrations monitor assumption that 4He belongs to the magmatic component. Ne has 3 isotopes: 20Ne, 21Ne, and 22Ne. 22Ne is dominated by the magmatic component. 21Ne has a cosmogenic contribution.