Water-rock interactions in the Acoculco geothermal system, eastern Mexico: Insights from paragenesis and elemental mass-balance
Por:
Sanchez-Cordova, Maria M., Canet, Carles, Rodriguez-Diaz, Augusto, Gonzalez-Partida, Eduardo, Linares-Lopez, Carlos
Publicada:
1 abr 2020
Resumen:
Geochemical mass balances, supported by mineral characterization and
whole-rock elemental analyses, were used to decipher the alteration
paragenesis and to understand the elemental mobility related to the
interaction of hydrothermal fluids with volcanic rocks (ignimbrites and
lavas ranging from rhyolite to dacite) from the Acoculco geothermal
system, in the eastern portion of the Trans-Mexican Volcanic Belt. Three
extensive events of hydrothermal alteration were distinguished, from
earliest to latest: (1) selective silicification and argillization, (2)
hydraulic brecciation by silica-rich fluid, and (3) acid-sulfate (vuggy
and argillic advanced) alteration. According to the Gresens-Grant
mass-balance method, the altered volcanic rocks of Acoculco are
generally enriched in Ti and Si and depleted in the rest of major
elements; this chemical behavior is striking in the case of vuggy and
silicic altered rocks. Small changes in some element concentrations
calculated by the Gresens-Grant method may be due to chemical
heterogeneity between the rock chosen to be the reference (''fresh
rocks'') and the protolith of the altered ones. The
chondrite-normalized REE gave different patterns for distinct types of
alteration; vuggy and silicified rocks present low LREE and high HREE in
opposition to the advanced argillic alteration. Boiling, primarily
related to the last alteration event, may have happened at variable
depths (825, 325 and 102 m below present surface); it produced changes
fluid composition, resulting in acidic pH surface alterations.
Filiaciones:
Sanchez-Cordova, Maria M.:
Univ Nacl Autonoma Mexico, Posgrad Ciencias Tierra, Ciudad Univ, Ciudad De Mexico 04510, Mexico
Canet, Carles:
Univ Nacl Autonoma Mexico, Ctr Ciencias Atmosfera, Ciudad Univ, Ciudad De Mexico 04510, Mexico
Univ Nacl Autonoma Mexico, Inst Geofis, Ciudad Univ, Ciudad De Mexico 04510, Mexico
Rodriguez-Diaz, Augusto:
Univ Nacl Autonoma Mexico, Inst Geofis, Ciudad Univ, Ciudad De Mexico 04510, Mexico
Gonzalez-Partida, Eduardo:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Campus Juriquilla, Santiago De Queretaro 76230, Mexico
Linares-Lopez, Carlos:
Univ Nacl Autonoma Mexico, Inst Geofis, Ciudad Univ, Ciudad De Mexico 04510, Mexico
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