Radiohalos are a physical record of radioactive decay that occurred in granites and metamorphic rocks through earth history. They result from damage to the host crystals, primarily biotite, by α-particles produced in the 238U decay chain within tiny zircon inclusions. However, radiohalos are annealed at 150°C, so those observed today even in Precambrian rocks are likely only due to accelerated 238U decay and associated hydrothermal fluid activity during the Flood. There may not have been any major magmatic events producing hydrothermal fluids capable of forming radiohalos between the unique conditions during the Creation Week and the upheavals of the Flood cataclysm. Therefore, Precambrian granites and metamorphic rocks then affected by the Flood would have generated new radiohalos as they cooled below that temperature. The radiohalos data was selected for 147 granites and regional metamorphic rocks spanning the conventional geologic timescale from 33-3200 Ma whose samples had followed a protocol of similar numbers of slides scanned for radiohalos per sample averaged accordingly to provide statistically robust comparisons between rock units. The plotted radiohalos frequency data were interpreted as consistent with the pre-Flood/Flood boundary being approximately at the Precambrian/Cambrian boundary in the rock record. However, they are unable to distinguish the location of the Flood/post-Flood boundary, as 100 million years’ worth of accelerated 238U decay (at today’s measured rate) are needed to generate good visible radiohalos. Three small peaks in the radiohalos frequencies in Precambrian granites and metamorphic rocks may coincide with accelerated tectonic activity of God’s supernatural creative work on Days 1, 2 and 3 of the Creation Week. The highest peak in the radiohalos frequency data in the first half of the Phanerozoic coincides with the formation of granites and metamorphic rocks during the catastrophic plate tectonics of the Flood. Some of the highest radiohalos numbers are in granites associated with hydrothermal metallic ore veins consistent with the highest radiohalos numbers being indicative of hydrothermal fluid activity. The reason that there are relatively higher radiohalos numbers in some Precambrian metamorphic rocks compared to the Precambrian granites may be due to more biotite grains being in those rocks facilitating the generation of many new radiohalos during the Flood as heat from accelerated 238U decay activated water more easily permeating those biotite flakes. Further data may enhance and/or add to these conclusions, although it is unlikely that they will be significantly changed. ABSTRACT I. INTRODUCTION Radiohalos (abbreviated from radioactive halos) are minute circular zones of darkening (39-70 μm in diameter) surrounding tiny central mineral inclusions or crystals within some minerals. Often concentric darkened rings are distinguishable within the darkened circular areas. While radiohalos appear in fluorite, cordierite, quartz, and to a lesser extent K-feldspars, they are best observed in thin microscope sections of the black mica, biotite, where the tiny inclusions (or radiocenters) are usually zircon crystals. The significance of radiohalos is due to them being a physical, integral historical record of the decay of radioisotopes in the radiocenters over a period of time. First reported between 1880 and 1890, their origin was a mystery until the discovery of radioactivity. Then in 1907 Joly (1907) and Mügge (1907) independently suggested that the darkening of the minerals around the central inclusions is due to the alpha (α) particles produced by α-decays in the radiocenters. These α-particles are “fired” in all directions like “bullets” and thus damage the crystal structure of the surrounding minerals. It is known as Frenkel defect (a type of point defect) accumulation in which smaller atoms are dislodged from their places in the crystal lattice creating vacancies while they accumulate interstitially. This process produces concentric shells of darkening of discoloration (Fig. 1). When observed in thin sections these shells are concentric circles with diameters between 10 and 40 μm, simply representing planar sections through the concentric spheres centered around the inclusions (Gentry 1973). Many years of subsequent investigations have established that the radii of the concentric circles of the radiohalos as observed in thin sections are related to the α-decay energies. This enables the radioisotopes responsible for the α-decays to be identified (Gentry 1974, 1984, 1986, 1988; Snelling 2000b). Most importantly, when the central inclusions, or radiocenters, are very small (about 1 μm) Andrew A. Snelling, Answers in Genesis, PO Box 510, Hebron, KY 41048, asnelling@answersingenesis.org. © Cedarville University International Conference on Creationism. The views expressed in this publication are those of the author(s) and do not necessarily represent those of Cedarville University. 9th 2023 Snelling, A.A. 2023. Radiohalos through earth history–What clues can they provide us? In J.H. Whitmore (editor), Proceedings of the Ninth International Conference on Creationism, pp. 540560. Cedarville, Ohio: Cedarville University International Conference on Creationism. RADIOHALOS THROUGH EARTH HISTORY– WHAT CLUES CAN THEY PROVIDE US? KEYWORDS radiohalos, granites, metamorphic rocks, accelerated decay, annealing, pre-Flood, Flood, post-Flood
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