This dataset comprises the geochemical and mineralogical analysis of six samples of massive sulphide deposit. Three samples were obtained from seafloor massive sulphide (SMS) systems obtained during RV Celtic Explorer cruise CE11009 (Mid-Atlantic Ridge 45° N, 2011) and RRS James Cook cruises JC082 (Mid-Cayman Spreading Centre, 2013) and JC138 (Mid-Atlantic Ridge at 26° N, 2016). Three samples were obtained from land-based volcanogenic massive sulphide (VMS) deposits on Wetar Island, Indonesia. It is thought these samples were obtained in 2002 at Kali Kuning and Lerokis Zones 4 and 5, but users should be aware there is little to no metadata about the Wetar Island sample origins. The sample analyses includes: (1) bulk geochemical analysis of sulphide samples by inductively coupled plasma mass spectrometry (ICP-MS) for bulk and effluent analysis and inductively coupled plasma orbital emission spectrometry (ICP-OES), (2) petrographic descriptions of samples by reflective microscopy, (3) geochemical analysis of seawater samples during experiments by ICP-MS, (4) mineralogical analyses (X-ray Diffraction) of sulphide samples, (5) mineralogical analyses by Scanning Electron Microscope and energy dispersive X-ray spectroscopy (SEM-EDS) on sulphide grains, (6) SEM backscattered electron (BSE) images of reacted sulphide grains, and (7) surface areas determined by Brunauuer-Emmett-Teller (BET) surface area analysis. All analyses were undertaken as part of a PhD project which aimed to enhance understanding of sulphide oxidation kinetics, the formation of Fe-oxyhydroxide from sulphide oxidation, its capacity to retain metals that would otherwise be lost to seawater in SMS systems, and the implications for potential seafloor mining operations. Analyses took place at the University of Southampton and the National Oceanography Centre Southampton, funded under the Natural Environment Research Council (NERC) project Ultramafic-hosted mineral Resource Assessment (ULTRA) grant, NE/S004068/1. This collection consists only of the data collected under the PhD project and not all data associated with the ULTRA project.
