deletions | additions       diff --git a/discussion_fluids2.tex b/discussion_fluids2.tex  index 392852a..71aa743 100644  --- a/discussion_fluids2.tex  +++ b/discussion_fluids2.tex 
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At a temperature of 100$^{\circ}$C a pore fluid in equilibrium with the shale has a $\delta$^{18}O value of $\approx$5‰_{VSMOW}. $\approx$5‰_{VSMOW} in good agreement with the derived fluid isotope composition determined using T($\Delta$_{47}) and the $\delta$^{18}O value of the vein calcite. None of the assumptions we have made in this calculation are unreasonable. Both the clay mineral content and bulk rock isotope values for shales are close to +20‰_{VSMOW}. Using the excess He content of fluids trapped in fluid inclusions Kendrick et al. (2002) have estimated typical pore water residence times for the Edale Gulf fluids of as much as 50Ma allowing plenty of time for the pore water to come to thermal equilibrium with detrital and authigenic clay minerals.  We are reassured that the derived fluid $\delta$^{18}O values are consistent with our understanding of the isotopic compositions of naturally occurring fluids and suggests that the clumped isotope temperatures are robust. For example were the calcite temperatures to have been as high as the maximum reported fluid inclusion homogenization temperatures of 240$^{\circ}$C then the derived fluid $\delta$^{18}O values would need to have been in excess of 18 - 20‰_{VSMOW}. Such values are in excess of any reported data for modern geothermal and formation waters \citep{Sheppard:1986ta}.