This report of the GH77-1 cruise includes mainly the results of the on-board surveys and observations in the survey area of the medial-western part of Central Pacific Basin (6N-11N, 175 30'W-179W), and partly the results of the on-shore analytical works on the obtained samples. In addition, some results of the geophysical works along the tracks from off Japan through southwest of Kwajalein and Majuro of Marshall Islands to the survey area are described in Appendixes 1-3. The GH77-1 cruise of the R/V Hakurei-maru (1,821.6T) was carried out from the 12 January to the 12 March, 1977, as the third phase field work of the GSJ five year research program of 'Study on the manganese nodule deposits of the Central Pacific Basin' and also as part of NRIPR research program of 'Technological study on the exploitation of deep sea mineral resources'. The GSJ research program (F.Y. 1974-F.Y. 1978) aims at providing information on the manganese nodule distribution and their origin on the deep sea floor of the Central Pacific Basin bounded by the Marshall Ridge to the west, the Christmas Ridge to the east, and the Mid-Pacific Mountains to the north. The first phase of the investigation was carried out during the GH74-5 cruise in the eastern part of the Basin (6-1030'N, 16430'-17130'W), the second phase was done during the GH76-1 cruise in the central-eastern part (5-10N, 170-175W), and the present third phase covered an area of about 5 square, in the central-western part of the Basin, just west of the GH76-1 area.From 1983 until 1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions. At the time it was the most extended data compilation on ferromanganese deposits world wide. Initially published in a proprietary format incompatible with present day standards it was jointly decided by AWI and NOAA to transcribe this legacy data into PANGAEA. This transfer is augmented by a careful checking of the original sources when available and the encoding of ancillary information (sample description, method of analysis...) not present in the NOAA-MMS database.