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When multiple maturation populations are observed in organic materials derived from core and/or outcrop samples, the common assumption is that the more mature organic constituents have been reworked from older sediments. Uranium roll-front deposits are exceptions to this rule. In core samples that pass through roll-front deposits, the extractable organic matter frequently exhibits various aspects of radiation damage (selective oxidation and/or thermal alteration). Core samples taken above the roll-front contain spores, pollen, and associated plant debris which have a uniform level of alteration (thermal maturity). However, once the roll-front deposit is penetrated, a dual mode of thermal maturity is observed. Lower levels of maturation gradually give way to much higher al eration values as one approaches the zone where the uranium ore is most concentrated. This process reverses itself once the core hole passes through the roll-front into nonmineralized rocks.
Because the alteration of the spores, pollen, plant tissue, and associated vitrinite particles is irreversible, the organic petrographer can use this data to assist the explorationist in regional mapping of uranium roll-front deposits, even when radioactivity in a given location has decreased below measurable levels.
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