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Title: Fluid regimes during late stages of a continental collision: Physical, chemical, and stable isotope measurements of fluid inclusions in fissure quartz from a geotraverse through the Central Alps, Switzerland

Abstract

Fluid evolution during neo-alpine metamorphism during late stages of the continental collision between Europe and Africa was studied by analyzing fluid inclusions in alpine fissure quartz collected in forty-nine localities along a geotraverse through the Central Alps, Switzerland. The methods employed include microthermometry, micro-Raman spectroscopy, K/Na thermometry, and stable isotope analysis. Early fluid inclusions provide evidence of close to peak metamorphic temperatures of the late Tertiary or neo-alpine metamorphic event. Fluid composition evolved along the geotraverse from north to south as follows: higher hydrocarbons were dominant in the low- and medium-grade diagenetic zones, methane was the main volatile in the high-grade diagenetic and low-grade anchizone, water dominated in the high-grade anchizone and low-grade epizone, with CO[sub 2] > 10 mol% in the high-grade epizone and in the mesozone. Higher hydrocarbons and CH[sub 4] were the products of kerogen maturation and cracking of preexisting petroleum. Large water supplies originated from the dehydration of cooler metasedimentary rocks that were overthrust by crystalline basements of the Lepontines, Aar, and Gotthard massifs. Carbon isotope analyses suggest that the CO[sub 2] component was derived from oxidation of graphitic matter, especially in the vicinity of sulfate-bearing metasediments and from decarbonation reactions. In the Aar and Gotthardmore » massifs as well as in the Helvetic Axen nappe and its underlying North Helvetic flysch, high fluid pressures prevailed and favored nappe transport. By contrast, in the southern Lepontine area, very low early fluid pressures were probably related to dry rocks and scarce metasediments, and to high geothermal gradients that resulted from intense uplift and erosion between 26 and 18 Ma.« less

Authors:
 [1]; ;  [2];  [3]
  1. Mineralogisch-Petrographisches Institut, Basel (Switzerland)
  2. CREGU-BP, Vandoeuvre-Les-Nancy (France)
  3. Univ. of Michigan, Ann Arbor, MI (United States)
Publication Date:
OSTI Identifier:
6819108
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta; (United States)
Additional Journal Information:
Journal Volume: 58:10; Journal ID: ISSN 0016-7037
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 02 PETROLEUM; 03 NATURAL GAS; CONTINENTAL CRUST; COLLISIONS; FLUIDS; CHEMICAL COMPOSITION; EARTH CRUST; 580000* - Geosciences; 020200 - Petroleum- Reserves, Geology, & Exploration; 030200 - Natural Gas- Reserves, Geology, & Exploration

Citation Formats

Mullis, J, Dubessy, J, Poty, B, and O'Neil, J. Fluid regimes during late stages of a continental collision: Physical, chemical, and stable isotope measurements of fluid inclusions in fissure quartz from a geotraverse through the Central Alps, Switzerland. United States: N. p., 1994. Web. doi:10.1016/0016-7037(94)90008-6.
Mullis, J, Dubessy, J, Poty, B, & O'Neil, J. Fluid regimes during late stages of a continental collision: Physical, chemical, and stable isotope measurements of fluid inclusions in fissure quartz from a geotraverse through the Central Alps, Switzerland. United States. https://doi.org/10.1016/0016-7037(94)90008-6
Mullis, J, Dubessy, J, Poty, B, and O'Neil, J. 1994. "Fluid regimes during late stages of a continental collision: Physical, chemical, and stable isotope measurements of fluid inclusions in fissure quartz from a geotraverse through the Central Alps, Switzerland". United States. https://doi.org/10.1016/0016-7037(94)90008-6.
@article{osti_6819108,
title = {Fluid regimes during late stages of a continental collision: Physical, chemical, and stable isotope measurements of fluid inclusions in fissure quartz from a geotraverse through the Central Alps, Switzerland},
author = {Mullis, J and Dubessy, J and Poty, B and O'Neil, J},
abstractNote = {Fluid evolution during neo-alpine metamorphism during late stages of the continental collision between Europe and Africa was studied by analyzing fluid inclusions in alpine fissure quartz collected in forty-nine localities along a geotraverse through the Central Alps, Switzerland. The methods employed include microthermometry, micro-Raman spectroscopy, K/Na thermometry, and stable isotope analysis. Early fluid inclusions provide evidence of close to peak metamorphic temperatures of the late Tertiary or neo-alpine metamorphic event. Fluid composition evolved along the geotraverse from north to south as follows: higher hydrocarbons were dominant in the low- and medium-grade diagenetic zones, methane was the main volatile in the high-grade diagenetic and low-grade anchizone, water dominated in the high-grade anchizone and low-grade epizone, with CO[sub 2] > 10 mol% in the high-grade epizone and in the mesozone. Higher hydrocarbons and CH[sub 4] were the products of kerogen maturation and cracking of preexisting petroleum. Large water supplies originated from the dehydration of cooler metasedimentary rocks that were overthrust by crystalline basements of the Lepontines, Aar, and Gotthard massifs. Carbon isotope analyses suggest that the CO[sub 2] component was derived from oxidation of graphitic matter, especially in the vicinity of sulfate-bearing metasediments and from decarbonation reactions. In the Aar and Gotthard massifs as well as in the Helvetic Axen nappe and its underlying North Helvetic flysch, high fluid pressures prevailed and favored nappe transport. By contrast, in the southern Lepontine area, very low early fluid pressures were probably related to dry rocks and scarce metasediments, and to high geothermal gradients that resulted from intense uplift and erosion between 26 and 18 Ma.},
doi = {10.1016/0016-7037(94)90008-6},
url = {https://www.osti.gov/biblio/6819108}, journal = {Geochimica et Cosmochimica Acta; (United States)},
issn = {0016-7037},
number = ,
volume = 58:10,
place = {United States},
year = {Sun May 01 00:00:00 EDT 1994},
month = {Sun May 01 00:00:00 EDT 1994}
}