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Title: Carbon geochemistry of marine-derived brines: I. sup 13 C depletions due to intense photosynthesis

Abstract

The study was conducted in the evaporation pans of a solar salt production plant (simulated sabkha environment) in which ca. 50% of the evaporation area is dominated by microbial mat communities (MMC). MMC are the modern equivalents of fossil stromatolites as old as Early Archean; hence, investigation is relevant to the research of the ancient carbon cycle. Total dissolved CO{sub 2} (C(T)) decreases by ca. 50% of its original value as brine concentration increases from 1.5 to 4 times mean seawater. Roughly 70% of the original total alkalinity is precipitated as calcium carbonate at this salinity range. The relations between total alkalinity A(T) and C(T) (both normalized to salinity) suggest that the brines are depleted in C(T) by up to 50% with respect to equilibrium with atmospheric CO{sub 2}. This large C(T) deficit is driven by the intense photosynthetic activity of the MMC. Considerable depletion in {sup 13}C was observed despite the photosynthetic activity which normally causes a {sup 13}C enrichment of C(T). {delta}{sup 13}C(T) values down to {minus}9{per thousand} were observed in brine concentration range of 2 to 6 times mean seawater. Mass balance calculation is compatible with the suggested mechanism of chemically enhanced atmospheric invasion of {sup 12}Cmore » enriched CO{sub 2}. This kinetic isotope fractionation may serve as an alternative explanation to that of fresh water runoff for some negative {delta}{sup 13}C values of laminated carbonates from evaporitic sections found in the geological record. In addition, at least part of the large scatter observed in the {delta}{sup 13}C vs. age curve for carbonates and organic matter from Precambrian stromatolitic environments may be explained by this mechanism rather than by late metamorphism and maturation processes.« less

Authors:
 [1];  [2]
  1. Hebrew Univ., Elat (Israel)
  2. Hebrew Univ., Jerusalem (Israel)
Publication Date:
OSTI Identifier:
7235654
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta; (United States)
Additional Journal Information:
Journal Volume: 56:1; Journal ID: ISSN 0016-7037
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; CARBON; GEOCHEMISTRY; ATMOSPHERIC CHEMISTRY; BRINES; CALCIUM CARBONATES; CARBON 12; CARBON 13; CARBON CYCLE; CARBON DIOXIDE; DENSITY; ENRICHMENT; EXPERIMENTAL DATA; GEOLOGIC HISTORY; GEOLOGIC MODELS; MASS BALANCE; METHANE; MICROORGANISMS; OXIDATION; PH VALUE; PHOTOSYNTHESIS; PRECIPITATION; SALINITY; SULFATE-REDUCING BACTERIA; ALKALINE EARTH METAL COMPOUNDS; ALKANES; BACTERIA; CALCIUM COMPOUNDS; CARBON COMPOUNDS; CARBON ISOTOPES; CARBON OXIDES; CARBONATES; CHALCOGENIDES; CHEMICAL REACTIONS; CHEMISTRY; DATA; ELEMENTS; EVEN-EVEN NUCLEI; EVEN-ODD NUCLEI; HYDROCARBONS; INFORMATION; ISOTOPES; LIGHT NUCLEI; NONMETALS; NUCLEI; NUMERICAL DATA; ORGANIC COMPOUNDS; OXIDES; OXYGEN COMPOUNDS; PHOTOCHEMICAL REACTIONS; PHYSICAL PROPERTIES; SEPARATION PROCESSES; STABLE ISOTOPES; SYNTHESIS; 580000* - Geosciences

Citation Formats

Lazar, B, and Erez, J. Carbon geochemistry of marine-derived brines: I. sup 13 C depletions due to intense photosynthesis. United States: N. p., 1992. Web. doi:10.1016/0016-7037(92)90137-8.
Lazar, B, & Erez, J. Carbon geochemistry of marine-derived brines: I. sup 13 C depletions due to intense photosynthesis. United States. https://doi.org/10.1016/0016-7037(92)90137-8
Lazar, B, and Erez, J. 1992. "Carbon geochemistry of marine-derived brines: I. sup 13 C depletions due to intense photosynthesis". United States. https://doi.org/10.1016/0016-7037(92)90137-8.
@article{osti_7235654,
title = {Carbon geochemistry of marine-derived brines: I. sup 13 C depletions due to intense photosynthesis},
author = {Lazar, B and Erez, J},
abstractNote = {The study was conducted in the evaporation pans of a solar salt production plant (simulated sabkha environment) in which ca. 50% of the evaporation area is dominated by microbial mat communities (MMC). MMC are the modern equivalents of fossil stromatolites as old as Early Archean; hence, investigation is relevant to the research of the ancient carbon cycle. Total dissolved CO{sub 2} (C(T)) decreases by ca. 50% of its original value as brine concentration increases from 1.5 to 4 times mean seawater. Roughly 70% of the original total alkalinity is precipitated as calcium carbonate at this salinity range. The relations between total alkalinity A(T) and C(T) (both normalized to salinity) suggest that the brines are depleted in C(T) by up to 50% with respect to equilibrium with atmospheric CO{sub 2}. This large C(T) deficit is driven by the intense photosynthetic activity of the MMC. Considerable depletion in {sup 13}C was observed despite the photosynthetic activity which normally causes a {sup 13}C enrichment of C(T). {delta}{sup 13}C(T) values down to {minus}9{per thousand} were observed in brine concentration range of 2 to 6 times mean seawater. Mass balance calculation is compatible with the suggested mechanism of chemically enhanced atmospheric invasion of {sup 12}C enriched CO{sub 2}. This kinetic isotope fractionation may serve as an alternative explanation to that of fresh water runoff for some negative {delta}{sup 13}C values of laminated carbonates from evaporitic sections found in the geological record. In addition, at least part of the large scatter observed in the {delta}{sup 13}C vs. age curve for carbonates and organic matter from Precambrian stromatolitic environments may be explained by this mechanism rather than by late metamorphism and maturation processes.},
doi = {10.1016/0016-7037(92)90137-8},
url = {https://www.osti.gov/biblio/7235654}, journal = {Geochimica et Cosmochimica Acta; (United States)},
issn = {0016-7037},
number = ,
volume = 56:1,
place = {United States},
year = {Wed Jan 01 00:00:00 EST 1992},
month = {Wed Jan 01 00:00:00 EST 1992}
}