Publication Date:
2017-04-04
Description:
The Jalisco Block (JB) is a geologically and tectonically complex part of northwestern Mexico
characterized by active subduction-type volcanism, rifting, and old stable structures. Thermal springs and groups of springs are widely distributed over JB. Bubbling gas from seven thermal springs located within different tectonic environments of the JB was analyzed for He, 20Ne, and N2 concentrations and d15N ratios. All gases are N2-dominant (〉84%) with the exception of one sample (Rio´ Purificacio´n), which has a
significant CH4 content (about 50%). All collected gas samples are relatively high in He, up to 1500 ppm vol and with 3He/4He values ranging from 0.6 to 4.5 Ra. All measured nitrogen isotope ratios are heavier than air with d15N values ranging from 0.5 to 5.0%. The relative N2 excess with respect to air-saturated water computed on the basis of N2 and 20Ne contents indicates the contribution of a nonatmospheric N2
source. All the samples show a good correlation between d15N and the relative excess of N2 with d15N +5.3% for the maximum N2 excess of 100%. Due to a presumed lack of seafloor sediment involved in the subduction process, such a d15N positive value seems to reflect the addition to the fluids of a heavy nitrogen originating from metamorphism processes of rocks occurring within the overlying continental crust.
Description:
Published
Description:
1-9
Description:
partially_open
Keywords:
bubbling gases
;
forearc region
;
Jalisco Block-Mexico
;
nitrogen isotopes
;
subduction-related volcanism
;
03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
;
03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems
;
04. Solid Earth::04.07. Tectonophysics::04.07.06. Subduction related processes
;
04. Solid Earth::04.08. Volcanology::04.08.01. Gases
;
05. General::05.02. Data dissemination::05.02.01. Geochemical data
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Format:
532399 bytes
Format:
503 bytes
Format:
application/pdf
Format:
text/html
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