ISSN:
1432-0819
Keywords:
Key words K
;
Ar geochronology
;
Unspiked method
;
Quaternary
;
Monogenetic volcanoes
;
Magma
;
Alkalic basalts
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Notes:
Abstract An unspiked K–Ar dating method using a mass-fractionation correction procedure was applied to a Quaternary independent group of monogenetic volcanoes, Ojikajima Volcano Group, located in northwestern Kyushu in Southwest Japan, in order to clarify in detail secular variations in eruptive volume, locations of eruptive vents, and magma compositions in a single monogenetic volcano group. The major results were as follows: (a) K–Ar ages of monogenetic volcanoes distribute from 1.08 to 0.30 Ma, with voluminous peaks at approximately 1.0 and 0.6 Ma. (b) The volcanic activity commenced in the central part of the field, expanded to the whole field at approximately 0.6 Ma, and then shrank to the central area. (3) Concentrations of incompatible elements, such as Ba, K, and Nb, increase with decreasing age, whereas P, Y, and Zr concentrations remain constant. These concentrations suggest gradual decrease in the degree of partial melting from an identical mantle source with residual garnet.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004450050225
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