RT Journal Article
T1 Procesos de silicificación y tipos de cuarzos en rocas volcánicas (Área volcánica del Cabo de Gata)
T1 Silicification and quartz types in volcanic rocks (Cabo de Gata volcanic region)
A1 Aparicio, Alfredo
A1 Bustillo Revuelta, María Ángeles
A1 Fernández, P.
A1 García, R.
AB The original mineralogical and geochemical compositions of andesitic volcanic rocks from SE of Spain havebeen modified by different processes, under hydrothermal environment. In particular, silicification processincreases the initial silica concentration of the volcanic rock from 69 % to 97%. One of the characteristicsof this alteration is the breakdown of mafics minerals and feldspars with supply of Al, Fe, Mg…etc to theinterstitial fluids which can be later introduce as traces in the new quartz formed. The silica rocks createdin the process are mainly constituted by quartz with different crystal sizes and textures. The spectralanalysis of the cathodoluminiscence (CL) emission in combination with the Scanning Electron microscopyobservations show that the igneous quartz crystals of the volcanic rock are characterized by a dominantband at 2,95 eV (420 nm) while the quartz crystals formed by silicification have a dominant band at 2,54eV (~ 500 nm). Although it is difficult to identify the causes of these spectral differences, it is consideredthat the 420 nm emission band is due to native defects of the igneous quartz and the ~ 500 nm emissionband is due to the substitutional incorporations of impurity ions in the hydrothermal quartz crystals. TheSEM-CL imagines show a non uniform luminescent emission. This is interpreted in terms of eithermicrosilicifications affecting the quartz crystals and the groundmass of the volcanic rocks or as consequenceof the pseudomorphic replacements by quartz of the primary minerals. The hydrothermal silicification isan early process that increase the amount of silica of the initial andesitic rock making other petrologicaland geochemical types of volcanic rocks
PB Sociedad Geológica de España
YR 2005
FD 2005
LK http://hdl.handle.net/10272/8679
UL http://hdl.handle.net/10272/8679
LA spa
DS Repositorio Institucional de la Universidad de Huelva
RD 31 may 2026