Deconvolving Ocean Drilling Program Temperature Logging Tool Data to Improve Borehole Temperature Estimates - Chile Triple Junction

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Journal of Geophysical Research-Solid Earth
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Jun 10
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We present a technique for correcting borehole fluid temperature observations made by the Ocean Drilling Program (ODP) with the Lamont temperature logging tool (TLT), for the effects of the slow temperature response of one of its sensors. TLT data have been recorded in many ODP boreholes, but, perhaps partly because of tool response effects, the data have only rarely been used. It has been shown that a continuous temperature log is the convolution of a tool response function and the temperature history experienced by the tool. We use temperature data from ODP Leg 141 to estimate the tool response function of the TLT. We then use Wiener filter theory to design a deconvolution operator to remove the effect of the tool response from the recorded data. We apply. the deconvolution operator to the data from Leg 141, assess the effectiveness of the deconvolution technique, and extrapolate the resulting borehole fluid temperatures to estimate the equilibrium geotherm at the two sites considered. The geothermal gradient in the accretionary wedge near the Chile Triple Junction increases with depth. This suggests that the thermal environment is not steady state, that fluid flow is transporting heat, or, most likely, both. The average heat flow in the accretionary wedge near the Chile Triple Junction is higher over the subducting Chile Ridge axis than over subducting young oceanic crust near the ridge axis.


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