Iron reduction is considered one of the most ancient forms of microbial respiration. This and the observation that iron reducers can grow under high temperature and pressure conditions suggest that Fe(III)-reducing microbes may represent a significant part of the deep biosphere. We give an overview of the RESPIRE project, in which we aim at using stable Fe isotopes of dissolved and reactive solid Fe to discriminate microbial and abiotic drivers of Fe(III) reduction in deep subseafloor sediments of site C0023A. As a first step of the project, the total element composition (e.g., Al, Ba, Ca, Fe, Mn, S, Ti) of solid phase samples was determined via acid digestion. The Fe content fluctuates between 3.9 and 4.6 wt% from 400 down to 670 mbsf, coinciding with the occurrence of volcanic ash layers in Subunit IIC and the Upper Shikoku Basin facies. Further below, total Fe is relatively constant at around 4.4 wt%. An increase in total Fe up to 5.1 wt% occurs between 1033 and 1090 mbsf in the Lower Shikoku Basin facies. The Mn content generally increases downcore, which is in agreement with the progressive occurrence of Mn carbonates at depth. The Ca content strongly varies between 0.7 and 7 wt% with highest contents in the Upper Shikoku Basin and the top of the Lower Shikoku Basin facies. Trace element data were gained for interstitial water by mass spectrometry and will be presented.