230Th-238U data in conflict with 40Ar/39Ar leucite ages for quaternary volcanic rocks of the Alban Hills, Italy
Voltaggio, Mario; Andretta, Dario; Taddeucci, Adriano
European Journal of Mineralogy Volume 6 Number 2 (1994), p. 209 - 216
published: Mar 31, 1994
manuscript accepted: Dec 15, 1993
manuscript received: Nov 30, 1992
ArtNo. ESP147050602005, Price: 29.00 €
Abstract 230Th-238U data on late-Quaternary volcanic rock samples from the Alban Hills (Italy), originally presented at meetings in 1988, have been questioned on the basis of leucite 40Ar/39Ar data which lead to inapplicable ages attributed to the same samples. In order to address the criticism and to clarify the problem, field and laboratory evidence is presented on four of the rocks with 230Th-238U internal isochron ages between 33 and 11 ka. Agreement between both methods exists for one sample. In three cases, we encounter a discordance of results. Evaluation of the 40Ar/39Ar literature shows that the analytical evidence previously given is not irrefutable. Therefore, the arguments for very recent volcanic activity in the Alban Hills still hold.