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Title: Carbon dioxide and helium in hydrothermal fluids from Loihi Seamount, Hawaii, USA: Temporal variability and implications for the release of mantle volatiles

Abstract

Dissolved CO[sub 2], [delta][sup 13]C, He, and [sup 3]He/[sup 4]He were determined in warm (<30[degrees]C) hydrothermal fluids from Pele's Vents on the summit of Lihi Seamount, Hawaii, collected during DSRV Pisces V dives in August and September 1992. Total dissolved CO[sub 2] and He are highly enriched over ambient seawater, with maximum measured concentrations of 190 mmol/kg C[sub T] and 0.193 [mu]mol/kg He, and correlate linearly with dissolved Si concentration and sample temperature. Carbon dioxide [delta][sup 13]C values range from [minus]5.5 to 1.7% (PDB) and corrected [sup 3]He/[sup 4]He ratios from 21.7 to 27.0 R[sub a], indicating a primary magmatic source for both gases. The high concentrations of these volatiles in the vent waters relative to reported bulk concentrations in Lihi basalts suggest that both gases are most likely introduced into the fluids by direct degassing from a magma body, rather than hydrothermal extraction from the summit laves. Comparison of the [sup 3]He/[sup 4]He ratios of the vent waters with reported values for Loihi basalts suggests that the mantle-derived volatiles in the fluids are variably contaminated by radiogenic He, probably due to assimilation of basement rock by the source magma. Such a mechanism could also be responsible for the rangemore » of [sup 3]He/[sup 4]He ratios observed in lavas from Loihi. The data demonstrate remarkable temporal variation in the volatile content of the vent fluids. The authors suggest that these temporal changes reflect progressive degassing from a magmatic intrusion with significant fractionation of CO[sub 2] and He, a process which may also account for the range in C/He ratios of Lihi lavas.« less

Authors:
;  [1];  [2];  [3]
  1. Univ. of Hawaii, Honolulu, HI (United States)
  2. Freie Universitaet Berlin (Germany)
  3. Los Alamos National Laboratory, NM (United States)
Publication Date:
OSTI Identifier:
7158894
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta; (United States)
Additional Journal Information:
Journal Volume: 58:3; Journal ID: ISSN 0016-7037
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CARBON DIOXIDE; ABUNDANCE; FLUIDS; CHEMICAL COMPOSITION; HELIUM; HYDROTHERMAL SYSTEMS; CARBON COMPOUNDS; CARBON OXIDES; CHALCOGENIDES; ELEMENTS; ENERGY SYSTEMS; GASES; GEOTHERMAL SYSTEMS; NONMETALS; OXIDES; OXYGEN COMPOUNDS; RARE GASES; 580000* - Geosciences

Citation Formats

Sedwick, P N, McMurtry, G M, Hilton, D R, and Goff, F. Carbon dioxide and helium in hydrothermal fluids from Loihi Seamount, Hawaii, USA: Temporal variability and implications for the release of mantle volatiles. United States: N. p., 1994. Web. doi:10.1016/0016-7037(94)90587-8.
Sedwick, P N, McMurtry, G M, Hilton, D R, & Goff, F. Carbon dioxide and helium in hydrothermal fluids from Loihi Seamount, Hawaii, USA: Temporal variability and implications for the release of mantle volatiles. United States. https://doi.org/10.1016/0016-7037(94)90587-8
Sedwick, P N, McMurtry, G M, Hilton, D R, and Goff, F. 1994. "Carbon dioxide and helium in hydrothermal fluids from Loihi Seamount, Hawaii, USA: Temporal variability and implications for the release of mantle volatiles". United States. https://doi.org/10.1016/0016-7037(94)90587-8.
@article{osti_7158894,
title = {Carbon dioxide and helium in hydrothermal fluids from Loihi Seamount, Hawaii, USA: Temporal variability and implications for the release of mantle volatiles},
author = {Sedwick, P N and McMurtry, G M and Hilton, D R and Goff, F},
abstractNote = {Dissolved CO[sub 2], [delta][sup 13]C, He, and [sup 3]He/[sup 4]He were determined in warm (<30[degrees]C) hydrothermal fluids from Pele's Vents on the summit of Lihi Seamount, Hawaii, collected during DSRV Pisces V dives in August and September 1992. Total dissolved CO[sub 2] and He are highly enriched over ambient seawater, with maximum measured concentrations of 190 mmol/kg C[sub T] and 0.193 [mu]mol/kg He, and correlate linearly with dissolved Si concentration and sample temperature. Carbon dioxide [delta][sup 13]C values range from [minus]5.5 to 1.7% (PDB) and corrected [sup 3]He/[sup 4]He ratios from 21.7 to 27.0 R[sub a], indicating a primary magmatic source for both gases. The high concentrations of these volatiles in the vent waters relative to reported bulk concentrations in Lihi basalts suggest that both gases are most likely introduced into the fluids by direct degassing from a magma body, rather than hydrothermal extraction from the summit laves. Comparison of the [sup 3]He/[sup 4]He ratios of the vent waters with reported values for Loihi basalts suggests that the mantle-derived volatiles in the fluids are variably contaminated by radiogenic He, probably due to assimilation of basement rock by the source magma. Such a mechanism could also be responsible for the range of [sup 3]He/[sup 4]He ratios observed in lavas from Loihi. The data demonstrate remarkable temporal variation in the volatile content of the vent fluids. The authors suggest that these temporal changes reflect progressive degassing from a magmatic intrusion with significant fractionation of CO[sub 2] and He, a process which may also account for the range in C/He ratios of Lihi lavas.},
doi = {10.1016/0016-7037(94)90587-8},
url = {https://www.osti.gov/biblio/7158894}, journal = {Geochimica et Cosmochimica Acta; (United States)},
issn = {0016-7037},
number = ,
volume = 58:3,
place = {United States},
year = {Tue Feb 01 00:00:00 EST 1994},
month = {Tue Feb 01 00:00:00 EST 1994}
}