Imperial College London
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Dr Cédric M. John

Faculty of Engineering, Department of Earth Science & Engineering

Visiting Reader
 
 
 
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Contact

 

cedric.john Website

 
 
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Location

 

N/ARoyal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Kluge:2018:10.1029/2017GC006969,
author = {Kluge, T and John, CM and Boch, R and Kele, S},
doi = {10.1029/2017GC006969},
journal = {Geochemistry, Geophysics, Geosystems},
pages = {1844--1858},
title = {Assessment of factors controlling clumped isotopes and delta O-18 values of hydrothermal vent calcites},
url = {http://dx.doi.org/10.1029/2017GC006969},
volume = {19},
year = {2018}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - The clumped isotope composition of CaCO3 (Δ47) is a geochemical proxy that can provide mineral formation temperatures and, together with measured carbonate δ18O, inferred fluid δ18O values. Under natural conditions, carbonates form within a relatively wide pH range and varying growth rates which are typically not reflected in laboratorybased calibrations (mostly ∼pH 8, moderate growth rates). A pH and growthrate dependence is known for oxygen isotopes and was also postulated for clumped isotopes. Theoretical predictions suggest that Δ47 values could lie between the carbonate equilibrium value and the value inherited from the dissolved inorganic carbon (predicted offset: +0.04‰ pH < 4 and −0.025‰ at high pH > 12). Here we test whether pH (in addition to temperature) is recorded in the carbonate clumped isotope composition using modern calcites from natural travertineforming streams and scales precipitated in pipes of deep geothermal wells from Italy, Hungary, and Turkey (pH: 6.1–7.5, T: 33–100°C). Although a comparison of all samples with expected equilibrium values in this pH range and known formation temperatures reveals only an insignificant Δ47 offset (0.006 ± 0.004‰, 1SE, n = 9), the clumped isotope values of samples with the highest growth rates (0.014 ± 0.007‰, 1SE, n = 5) are consistent with the theoretical prediction attributable to pH of 0.01‰. Similarly, deviations in δ18O of up to −2‰ follow a growthrate dependence. This fieldbased study shows that pHrelated effects are mostly small for Δ47 in the subsurface environment at lower pH and that high mineral growth rates control the magnitude of this disequilibrium.
AU  - Kluge,T
AU  - John,CM
AU  - Boch,R
AU  - Kele,S
DO  - 10.1029/2017GC006969
EP  - 1858
PY  - 2018///
SN  - 1525-2027
SP  - 1844
TI  - Assessment of factors controlling clumped isotopes and delta O-18 values of hydrothermal vent calcites
T2  - Geochemistry, Geophysics, Geosystems
UR  - http://dx.doi.org/10.1029/2017GC006969
UR  - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000445194000009&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
UR  - http://hdl.handle.net/10044/1/63564
VL  - 19
ER  -
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