deletions | additions       diff --git a/untitled.tex b/untitled.tex  index b9cfc54..fc2076f 100644  --- a/untitled.tex  +++ b/untitled.tex 
...
A characteristic feature of systems with episodic pulsing of warm to hot fluid is the development of a thermal anomaly along the high permeability paths in which flow is focused. An example is the perturbation of the temperature field observed in Mississippi Valley Type (MVT) districts that lie around the upper Mississippi Valley and other major Palaeozoic sediment basins in the continental USA \citep{Sangster:1994ub}. Similar temperature anomalies have been reported for other sedimentary basins, for example to the south east of the Massif Central in France \citep{Charef:1988vt}. The anomaly is seen as a difference between the temperature of precipitation of hydrothermal minerals and that of the of the host rock at the depth of burial and time that the mineralization took place. Using simple thermal modelling Cathles and co-workers show that that the temperature difference is due to heat advection associated with episodic, rapid release of hot fluids from deeper regions of the basins \citep{Cathles:1983tj,CathlesIII:2005uo}. In these example the fluids are thought to originate from overpressured formation water in the compacting sedimentary basins. Importantly, the fluid velocities required to produce the thermal anomaly are more than 1000 times greater than could be produced by the steady subsidence, compaction, and dewatering of the basins \citep{Cathles:1983tj}. This suggests to us that the pulses result from a coupling between the pore fluid pressure and rock failure. We envisage that when pore fluid pressures approach lithostatic either mode I hydraulic fracturing or shear failure and development of dilation jogs along fault surfaces allows rapid dewatering of shales within the sediment pile. The fluid is channelled into high permeability aquifers towards the base of the basins where it flows outwards towards the basin margins.  Mineralization with MVT affinities occurs in the Peak District, located in District area of  the southern Pennines of in  the UK. Here strata bound deposits (flats) of dominantly Pb-Zn and fluorite mineralization are closely associated with near vertical veins (scrins) that lie along strike-slip fault surfaces and fractures of Variscan age \citep{Quirk:1991uq}. As with the upper Mississippi valley sedimentary basins it is widely held that the mineralization results from basin scale migration of sedimentary formation waters \citep{ixer1993lead}. However, the driving force for, and rates of fluid migration are poorly constrained. Opinion ranges from slow  gravity driven flow as a result of tectonic uplift associated with the Variscan inversion \citep{Quirk:1991uq} to a seismic valve type process with rapid dewatering of the over-pressured basin fill triggered by fault activity \citep{Frazer:2014eh}. Evidence for a thermal anomaly associated with rapid advection of fluids is not conclusive. Fluid inclusion homogenisation homogenization  temperatures span a wide range from <70$^{\circ}$ to >240$^{\circ}$C \citep{Atkinson:1983ua, Kendrick:2002vc}. Mineralization is thought to have occurred at depths between 1 and 2km \citep{Colman:1989vf}. Thus, assuming a geothermal gradient of 30$^{\circ}$C.km^{-1}, the fluid inclusion homogenization temperatures are at, or greater than the maximum expected host rock temperature at the time of mineralization. This suggests that fluid movement was rapid. rapid and therefore unlikely to be associated with slow, gravity driven flow or a gradual dewatering of the basin fill.  There are questions, however, as to the reliability of some of the reported temperatures that are derived from fluid inclusion analysis. It is difficult to envisage how the very high temperatures of >240$^{\circ}$C or more are generated in sedimentary basins with maximum depths on the order of four to five km. In addition Kendrick and co-workers report evidence of stretching, necking down and leakage in samples that show anomalously high temperatures \citep{Kendrick:2002vc}. To better understand the possible  coupling between faulting and fluid flow in the Peak DistrictMVT province  we have used clumped isotope thermometry to determine the temperature at which a Variscan  hydrothermalvein  calcite vein  precipitated.The calcite is found as dilation voids of a Variscan strike-slip fault in the southern Pennines of the United Kingdom. The veins are associated with Pb-Zn and fluorite mineralization and in the past the fault, and other areas of the southern Pennines have been extensively worked as an economic deposit. Whilst on a different scale it has been suggested that the Pb-Zn mineralization has close affinities with the classic MVT deposits of North America. The fault, located on the margin of a lower Carboniferous platform on which shelf carbonates were deposited, separates the platform from a half-graben basin filled with deep water facies limestones and shales of lower to upper Carboniferous age. Previous workers have suggested that the faults bordering the platform provided a network of high permeability channels for the mineralizing fluids \citep{Quirk:1991uq, Kendrick:2002vc, Frazer:2014eh}. Our knowledge, however, of both the source of the fluids and rates of fluid flow are limited.  Clumped isotope geothermometry relies thermometry is based  on the fact that the rare,  heavy isotopes ^{13}C of carbon (^{13}C)  and ^{18}O oxygen (^{18}O)  are ordered in the carbonate lattice with the degree of ordering being an inverse function of temperature. lattice.  This is a result of the greater stability of the ^{13}C-^{18}O bond compared to bonds involving either no, or a single isotopic substitution. The degree of ordering is an inverse function of temperature.  As temperature increases the isotopes tend towards a more random or stochastic distribution. distribution \citep{Eiler:2007vua}.  Measurement of the degree of ordering allows us to estimate the temperature at which the distribution of isotopes in the calcite structure are locked in. in \citep{Ghosh:2006cn}.  This is analogous to the concept of a closure temperature for radiogenic isotopes or for  cation ordering in minerals.In this study this temperature is taken as the precipitation temperature of the calcite.  A key advantage of the method is that the temperature estimate is based on the distribution of carbon and oxygen isotopes within a single phase and not on the partitioning of oxygen isotopes between calcite and it’s parent fluid as in the conventional oxygen isotope geothermometer. Thus combining the clumped isotope temperature (T($\Delta$_{47})) with the bulk oxygen isotope composition of the carbonate represented by it's $\delta^{13}$C value  we can use published fractionation factor calibrations to calculate constrain  the isotopic composition of the parent fluid. Using these techniques we find: find:\enumerate  (i) the calcite precipitated at temperatures between 40° and 100°C.  (ii) the parent fluids range in isotopic composition from -4‰_{VSMOW} to +5‰_{VSMOW} and represent mixtures of a cool, meteoric water and a more evolved formation water.  (ii) the temperature at which the calcite precipitated is a conservative tracer for the fluid mixing. This implies that heat is rapidly advected as the hydrothermal fluid flow is focussed along the fault plane.