Polonium halos

@article{crossref1964polonium,
    title = "POLONIUM",
    year = "1964",
    journal = "The Lancet",
    url = "https://doi.org/10.1016/s0140-6736(64)90637-3",
    doi = "10.1016/s0140-6736(64)90637-3",
    number = "7359",
    pages = "574-575",
    volume = "284"
}

Pleochroic halos had been known for about a quarter of a century before the geologist, J. Joly, explained that they owed their origin to the newly discovered phenomenon of radioactivity [Joly, 1907]. With the aid of a microscope, such halos are usually seen as small darkened circular spots surrounded by dark or colored rings. Joly proposed that the tiny mineral inclusions frequently seen at the centers of the halos were radioactive and that the passage of a particles from the inclusion through the host crystal produced the discoloration seen. Uranium was known to decay through a whole series of radioactive daughters, a number of which also ejected α particles. The energies of these α particles were characteristic of each emitter, and so each α‐emitting radioactive element in the decay chain ejected α's with a characteristic range in a given medium. Thus, said Joly, the various rings in a halo corresponded to the ranges in the mineral of the α particles from particular members of the uranium decay chain. Herein was a beautiful, almost photographic, record of the radioactive process, as it had gone on for hundreds of millions of years. Joly's explanation was soon accepted, and during the next 30 or so years, a number of investigators, including Joly, examined halos in some detail [Holmes, 1931]. The hope that they might be useful for the measurement of the ages of rocks was a strong motivation. The idea was that laboratory‐induced discoloration of minerals by known a doses could be compared with the natural discoloration in halos, thereby indicating the natural dose involved in the generation of the halos. This natural dose could then easily be converted into an age, if the uranium content of the radioactive inclusion at the center of the halo were known. The hopes of using pleochroic halos foundered, however, on the great difficulty of quantitatively measuring the degree of discoloration of a mineral. As a time piece, the pleochroic halo was an even bigger disappointment than its contemporary, U‐He dating. The classical era for the study of halos came to an end with the outbreak of the Second World War. It was also marked by the appearance in the Proceedings of the Royal Society of London of two striking papers [Henderson, 1939; Henderson and Sparks, 1939] by G. H. Henderson of Dalhousie University, Nova Scotia. These papers form the basis of the remainder of our discussion.

@article{york1979polonium,
    author = "York, Derek",
    title = "Polonium halos and geochronology",
    year = "1979",
    journal = "Eos, Transactions American Geophysical Union",
    abstract = "Pleochroic halos had been known for about a quarter of a century before the geologist, J. Joly, explained that they owed their origin to the newly discovered phenomenon of radioactivity [Joly, 1907]. With the aid of a microscope, such halos are usually seen as small darkened circular spots surrounded by dark or colored rings. Joly proposed that the tiny mineral inclusions frequently seen at the centers of the halos were radioactive and that the passage of a particles from the inclusion through the host crystal produced the discoloration seen. Uranium was known to decay through a whole series of radioactive daughters, a number of which also ejected α particles. The energies of these α particles were characteristic of each emitter, and so each α‐emitting radioactive element in the decay chain ejected α's with a characteristic range in a given medium. Thus, said Joly, the various rings in a halo corresponded to the ranges in the mineral of the α particles from particular members of the uranium decay chain. Herein was a beautiful, almost photographic, record of the radioactive process, as it had gone on for hundreds of millions of years. Joly's explanation was soon accepted, and during the next 30 or so years, a number of investigators, including Joly, examined halos in some detail [Holmes, 1931]. The hope that they might be useful for the measurement of the ages of rocks was a strong motivation. The idea was that laboratory‐induced discoloration of minerals by known a doses could be compared with the natural discoloration in halos, thereby indicating the natural dose involved in the generation of the halos. This natural dose could then easily be converted into an age, if the uranium content of the radioactive inclusion at the center of the halo were known. The hopes of using pleochroic halos foundered, however, on the great difficulty of quantitatively measuring the degree of discoloration of a mineral. As a time piece, the pleochroic halo was an even bigger disappointment than its contemporary, U‐He dating. The classical era for the study of halos came to an end with the outbreak of the Second World War. It was also marked by the appearance in the Proceedings of the Royal Society of London of two striking papers [Henderson, 1939; Henderson and Sparks, 1939] by G. H. Henderson of Dalhousie University, Nova Scotia. These papers form the basis of the remainder of our discussion.",
    url = "https://doi.org/10.1029/eo060i033p00617",
    doi = "10.1029/eo060i033p00617",
    number = "33",
    pages = "617-618",
    volume = "60"
}

I welcome York's contribution [York, 1979] to the exchange of views concerning the possible existence and potential cosmological implications of polonium halos in Precambrian granites [Damon, 1979; Gentry, 1979], but I must take exception to some omissions from his comments about my results on Po halos. York seems to regard even the existence of Po halos as only tentative. But notwithstanding the uncertainties, his article leans heavily toward the proposition that Po halos do exist, at least in micas. York's thesis is that Po halos are most probably explainable within the accepted framework because the interlocking nature of various radiometric dating techniques provides powerful evidence that conventional geochronology is correct. York faults me for ignoring this internal consistency. Contrary to his understanding, I do not ignore these data. But neither do I accept the idea that the presumed agreement between techniques is really coercive evidence for the correctness of the uniformitarian assumption which undergirds the present model. There was no discussion of the 238 U 206 Pb ratios [Gentry et al., 1976], which raise significant questions about the accepted geochronological scheme.

@article{gentry1980polonium,
    author = "Gentry, Robert V.",
    title = "Polonium halos",
    year = "1980",
    journal = "Eos, Transactions American Geophysical Union",
    abstract = "I welcome York's contribution [York, 1979] to the exchange of views concerning the possible existence and potential cosmological implications of polonium halos in Precambrian granites [Damon, 1979; Gentry, 1979], but I must take exception to some omissions from his comments about my results on Po halos. York seems to regard even the existence of Po halos as only tentative. But notwithstanding the uncertainties, his article leans heavily toward the proposition that Po halos do exist, at least in micas. York's thesis is that Po halos are most probably explainable within the accepted framework because the interlocking nature of various radiometric dating techniques provides powerful evidence that conventional geochronology is correct. York faults me for ignoring this internal consistency. Contrary to his understanding, I do not ignore these data. But neither do I accept the idea that the presumed agreement between techniques is really coercive evidence for the correctness of the uniformitarian assumption which undergirds the present model. There was no discussion of the 238 U 206 Pb ratios [Gentry et al., 1976], which raise significant questions about the accepted geochronological scheme.",
    url = "https://doi.org/10.1029/eo061i027p00514-01",
    doi = "10.1029/eo061i027p00514-01",
    number = "27",
    pages = "514-514",
    volume = "61"
}

@article{ellenberger1984polonium,
    author = "Ellenberger, C. Leroy and Gentry, Robert V.",
    title = "Polonium halos redux",
    year = "1984",
    journal = "Physics Today",
    url = "https://doi.org/10.1063/1.2916022",
    doi = "10.1063/1.2916022",
    number = "12",
    pages = "91-92",
    volume = "37"
}

@article{wyckoff1984polonium,
    author = "Wyckoff, Robert C. and Gentry, Robert V.",
    title = "Polonium halos",
    year = "1984",
    journal = "Physics Today",
    url = "https://doi.org/10.1063/1.2916180",
    doi = "10.1063/1.2916180",
    number = "4",
    pages = "106-109",
    volume = "37"
}

@misc{wakefield1987gentrys1,
    author = "Wakefield, J. R",
    title = "Gentry's Tiny Mystery",
    year = "1987",
    howpublished = "Unsupported by Geology: Creation/ Evolution, v. 22, p. 13-33",
    note = "talkorigins\_source = {true}; raw\_reference = {Wakefield, J. R., 1987, Gentry's Tiny Mystery: Unsupported by Geology: Creation/ Evolution, v. 22, p. 13-33.}"
}

@article{wakefield1988the,
    author = "Wakefield, Jeffery Richard",
    title = "The Geology of Gentry's “Tiny Mystery”",
    year = "1988",
    journal = "Journal of Geological Education",
    url = "https://doi.org/10.5408/0022-1368-36.3.161",
    doi = "10.5408/0022-1368-36.3.161",
    number = "3",
    pages = "161-175",
    volume = "36"
}

@misc{crossref2006gentry,
    title = "Gentry",
    year = "2006",
    booktitle = "The SAGE Dictionary of Sociology",
    url = "https://doi.org/10.4135/9781446279137.n393",
    doi = "10.4135/9781446279137.n393"
}

@article{gaite2015one,
    author = "Gaite, Jose",
    title = "One dark matter mystery: halos in the cosmic web",
    year = "2015",
    journal = "Journal of Physics: Conference Series",
    url = "https://doi.org/10.1088/1742-6596/574/1/012040",
    doi = "10.1088/1742-6596/574/1/012040",
    pages = "012040",
    volume = "574"
}

@incollection{georgewarren20207,
    author = "George-Warren, Holly",
    title = "7. Mystery Girl: The Forgotten Artistry of Bobbie Gentry",
    year = "2020",
    booktitle = "Listen Again",
    url = "https://doi.org/10.1515/9780822390558-008",
    doi = "10.1515/9780822390558-008",
    pages = "120-136"
}

@article{barras2025fossil,
    author = "Barras, Colin",
    title = "Fossil leg deepens mystery of our tiny cousin Paranthropus",
    year = "2025",
    journal = "New Scientist",
    url = "https://doi.org/10.1016/s0262-4079(25)00530-5",
    doi = "10.1016/s0262-4079(25)00530-5",
    number = "3537",
    pages = "11",
    volume = "266"
}