Editing Noble gas (section)

====Helium====
[[Helium]] has two abundant isotopes: [[helium-3]], which is [[Primordial nuclide|primordial]] with high abundance in [[Internal structure of Earth|earth's core]] and [[Mantle (geology)|mantle]], and [[helium-4]], which originates from decay of [[radionuclide]]s (<sup>232</sup>Th, <sup>235,238</sup>U) abundant in the [[earth's crust]]. Isotopic ratios of helium are represented by R<sub>A</sub> value, a value relative to air measurement (<sup>3</sup>He/<sup>4</sup>He = 1.39*10<sup>−6</sup>).<ref name="Ozima-2002">{{Cite book |last1=Ozima |first1=Minoru |url=https://books.google.com/books?id=TMIAfSIe428C&pg=PP1 |title=Noble Gas Geochemistry |last2=Podosek |first2=Frank A. |date=2002 |publisher=Cambridge University Press |isbn=978-0-521-80366-3 |language=en}}</ref> [[Volatile (astrogeology)|Volatiles]] that originate from the earth's crust have a 0.02-0.05 R<sub>A</sub>, which indicate an enrichment of helium-4.<ref>{{Cite journal |last1=Ballentine |first1=Chris J. |last2=Sherwood Lollar |first2=Barbara |date=July 2002 |title=Regional groundwater focusing of nitrogen and noble gases into the Hugoton-Panhandle giant gas field, USA |url=https://linkinghub.elsevier.com/retrieve/pii/S0016703702008505 |journal=Geochimica et Cosmochimica Acta |language=en |volume=66 |issue=14 |pages=2483–2497 |doi=10.1016/S0016-7037(02)00850-5|bibcode=2002GeCoA..66.2483B }}</ref> Volatiles that originate from deeper sources such as [[subcontinental lithospheric mantle]] (SCLM), have a 6.1± 0.9 R<sub>A</sub><ref name="Gautheron-2002">{{Cite journal |last1=Gautheron |first1=Cécile |last2=Moreira |first2=Manuel |date=2002-05-30 |title=Helium signature of the subcontinental lithospheric mantle |url=https://linkinghub.elsevier.com/retrieve/pii/S0012821X02005630 |journal=Earth and Planetary Science Letters |volume=199 |issue=1 |pages=39–47 |doi=10.1016/S0012-821X(02)00563-0 |bibcode=2002E&PSL.199...39G |issn=0012-821X}}</ref> and mid-oceanic ridge basalts (MORB) display higher values (8 ± 1 R<sub>A</sub>).  [[Mantle plume]] samples have even higher values than > 8 R<sub>A</sub>.<ref name="Gautheron-2002" /><ref>{{Cite journal |last=Graham |first=D. W. |date=2002-01-01 |title=Noble Gas Isotope Geochemistry of Mid-Ocean Ridge and Ocean Island Basalts: Characterization of Mantle Source Reservoirs |url=https://pubs.geoscienceworld.org/rimg/article/47/1/247-317/235393 |journal=Reviews in Mineralogy and Geochemistry |language=en |volume=47 |issue=1 |pages=247–317 |doi=10.2138/rmg.2002.47.8 |bibcode=2002RvMG...47..247G |issn=1529-6466}}</ref>  [[Solar wind]], which represent an unmodified [[Primordial nuclide|primordial]] signature is reported to have ~ 330 R<sub>A</sub>.<ref>{{Cite journal |last1=Benkert |first1=Jean-Paul |last2=Baur |first2=Heinrich |last3=Signer |first3=Peter |last4=Wieler |first4=Rainer |date=1993-07-25 |title=He, Ne, and Ar from the solar wind and solar energetic particles in lunar ilmenites and pyroxenes |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/93JE01460 |journal=Journal of Geophysical Research: Planets |language=en |volume=98 |issue=E7 |pages=13147–13162 |doi=10.1029/93JE01460 |bibcode=1993JGR....9813147B |issn=0148-0227}}</ref>