Publication Date:
2022-09-15
Description:
The abundance of mantle-derived rocks and lavas, in combination with its
tectonic evolution, render Mexico a perfect laboratory to investigate the
chemical and the isotopic heterogeneity of the lithospheric mantle. New
data on the composition of noble gases and CO2 in Mexican mantle
xenoliths and lavas is reported. Our samples consist of six ultramafic nodules
from the Durango Volcanic Field (DVF) and the San Quintin Volcanic Field
(SQVF), monogenetic complexes belonging to the Mexican Basin and Range
province; and four lavas from the Sierra Chichinautzin (SCN), a Quaternary
monogenetic volcanic field located in the Mexican volcanic arc. Ne and Ar
isotopes in fluid inclusions reveal mixing between atmospheric and MORB-like
fluids (e.g., 40Ar/36Ar 〈 1,200). DVF and SQVF nodules record low 40Ar/36Ar and
4He/20Ne that confirm the existence of recycled atmospheric-derived noble
gases in the local mantle. The averages of the Rc/Ra ratios (3He/4He corrected
for atmospheric contamination) measured in Mexican localities are within the
MORB-like range: DVF= 8.39 ± 0.24 Ra, SQVF = 7.43 ± 0.19 Ra and SCN lavas =
7.15 ± 0.33 Ra (1σ). With the aim of assessing the isotopic variability of the
Mexican lithospheric mantle, the above results were compared with similar data
previously obtained from ultramafic nodules found in the Ventura Espiritu Santo
Volcanic Field (VESVF), another Quaternary monogenetic volcanic complex
belonging the Basin and Range. The higher 3He/4He ratios in DVF relative to
those reported for the VESVF and the SQVF are explained as reflecting different
ages of mantle refertilization, triggered by the retreating of the Farallon slab
(~40 Ma ago) and associated delamination slab processes. We propose that the
DVF mantle was refertilized more recently (〈10 Ma ago) than the mantle
beneath the SQVF and VESVF (~40–20 Ma ago). On the other hand, He-Ne-
Ar compositions of SCN olivines share similarities with VESVF xenoliths,suggesting a relatively homogeneous lithospheric mantle in central Mexico.
Finally, DVF and the SCN samples exhibit δ13C values within the MORB range
(comparable to other values previously reported in fluid inclusions and
fumaroles from Popocatépetl, Colima—Ceboruco volcanoes). While we
explain the MORB-like carbon signatures of the DVF samples as the result of
the above-mentioned refertilization process, the SCN signatures likely reflect
either (i) trapping of isotopically fractionated CO2 derived from magmatic
degassing or (ii) a mantle source unaffected by subduction-related crustal
carbon recycling.
Description:
Published
Description:
973645
Description:
2V. Struttura e sistema di alimentazione dei vulcani
Description:
3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
Description:
4V. Processi pre-eruttivi
Description:
JCR Journal
Keywords:
Basin and Range province
;
Trans-mexican Volcanic Belt
;
Mexican mantle xenoliths
;
arc lavas
;
fluid inclusions
;
noble gas isotopes
;
CO2 isotopes
;
carbon recycling
;
04.08. Volcanology
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
