A detailed mineralogical study was carried out on potassium feldspars contained in some ''paleosoil'' samples from the Alban Hills volcanic region (Latium, Italy). Chemical and structural correlation of the data allowed a comparison with data on sanidinite feldspars from the same area and with data on other nearby volcanic complexes. The chemistry (N-Or = 72.6 divided by 88.3 % Or) and lattice parameters [a(o) = 8.492 divided by 8.574(Angstrom), b(o) = 12.996 divided by 13.034(Angstrom), c(o) = 7.163 divided by 7.190(Angstrom)] indicate a prevalently more sanidinitic character for the paleosoil feldspars compared with those in Alban ''sanidinites''. The particular structural state (HT disorder) of some paleosoil K-feldspars would suggest different crystallization temperatures and, for some samples, also a possible pressure influence during their formation. The abundance of K-feldspars in the samples examined and their less orthoclasic features compared with feldspars found in sanidinitic Alban ejecta would highlight a rather different genetic process for these paleosoils compared with that of the more typical Alban volcanic products, mainly of leucititic composition. The studied K-feldspars may be considered as good volcanic paleosoil indicators and a probable allochthonous origin of the Alban paleosoils is hypothesized.
K-FELDSPARS AS VOLCANIC PALEOSOIL INDICATORS - FIRST INVESTIGATION IN THE ALBAN HILLS VOLCANIC AREA, LATIUM, ITALY / Gianfagna, Antonio; F., Burragato; A., Marcotulli. - In: NEUES JAHRBUCH FUR MINERALOGIE MONATSHEFTE. - ISSN 0028-3649. - STAMPA. - 9:(1995), pp. 408-420.
K-FELDSPARS AS VOLCANIC PALEOSOIL INDICATORS - FIRST INVESTIGATION IN THE ALBAN HILLS VOLCANIC AREA, LATIUM, ITALY
GIANFAGNA, Antonio;
1995
Abstract
A detailed mineralogical study was carried out on potassium feldspars contained in some ''paleosoil'' samples from the Alban Hills volcanic region (Latium, Italy). Chemical and structural correlation of the data allowed a comparison with data on sanidinite feldspars from the same area and with data on other nearby volcanic complexes. The chemistry (N-Or = 72.6 divided by 88.3 % Or) and lattice parameters [a(o) = 8.492 divided by 8.574(Angstrom), b(o) = 12.996 divided by 13.034(Angstrom), c(o) = 7.163 divided by 7.190(Angstrom)] indicate a prevalently more sanidinitic character for the paleosoil feldspars compared with those in Alban ''sanidinites''. The particular structural state (HT disorder) of some paleosoil K-feldspars would suggest different crystallization temperatures and, for some samples, also a possible pressure influence during their formation. The abundance of K-feldspars in the samples examined and their less orthoclasic features compared with feldspars found in sanidinitic Alban ejecta would highlight a rather different genetic process for these paleosoils compared with that of the more typical Alban volcanic products, mainly of leucititic composition. The studied K-feldspars may be considered as good volcanic paleosoil indicators and a probable allochthonous origin of the Alban paleosoils is hypothesized.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.