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Erzinger J Becker K Dick H J B and Stokking L B Eds 1995 Proceedings of the Ocean Drilling Program Scientific Results Vol 137 140 30 DATA REPORT GEOCHEMICAL LOGGING RESULTS FROM THE EASTERN EQUATORIAL PACIFIC HOLE 504B1 Elizabeth Lewis Pratson 2 Cristina Broglia 2 Philippe Pezard 3 and Peter K H Harvey4 ABSTRACT Geochemical well logs were obtained through sediment and basalt at Site 504 of Leg 140 Corrections have been applied to the logs to account for variations in borehole size drilling fluid composition and drill pipe attenuation Concentrations of Th U and Gd as well as oxide weight percentages have been calculated from the logs and compared with available X ray fluorescence XRF core measurements The geochemical processing was performed in the open hole sections of Hole 504B only The comparison of XRF core data to log data is good INTRODUCTION The primary objective of Leg 140 was to deepen the previously existing Hole 504B into the sheeted dike complex Fig 1 Shipboard Scientific Party 1992 The hole was logged with the geochemical logging tool string GLT which measures the major elements of a formation at intervals of 0 1524 m The GLT measurements provide continuous in situ chemical measurements of the rock and are not affected by incomplete core recovery or core expansion a common problem in core based studies This report describes the basic principles of the GLT and outlines the post cruise processing techniques It then briefly compares geochemical log values with lithologic core descriptions and available core measurements GEOCHEMICAL TOOL STRING The geochemical logging tool string GLT consists of four tool components the natural gamma ray tool NGT the compensated neutron tool CNT the aluminum activation clay tool AACT and the gamma ray spectrometry tool GST GLT NGT CNT AACT and GST are trademarks of Schlumberger Fig 2 The combination of the tool components uses three separate modes of gamma ray spectroscopy for a comprehensive elemental analysis of the



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