Hydrothermal vent fields located in the gap between known sites in Guaymas Basin and 21°N on the East Pacific Rise were discovered on the Alarcón Rise and in southern Pescadero Basin. The Alarcón Rise spreading segment was mapped at 1‐m resolution by an autonomous underwater vehicle. Individual chimneys were identified using the bathymetric data. Vent fields were interpreted as active from temperature anomalies in water column data and observed and sampled during remotely operated vehicle dives. The Ja Sít, Pericú, and Meyibó active fields are near the eruptive fissure of an extensive young lava flow. Vent fluids up to 360 °C from Meyibó have compositions similar to northern East Pacific Rise vents. The Tzab‐ek field is 850 m west of the volcanic axis, and active chimneys rise up to 33 m above a broad sulfide mound. The inactive field is 10 km north‐northeast along the rift axis, and most sulfide chimneys are enriched in Zn and associated elements that are transported at lower temperature compared to the more Cu‐rich active fields. In southern Pescadero Basin, the Auka field is on the margin of a sediment‐filled graben at 3,670‐m depth. Discharging fluids are clear, contain hydrocarbons, and have neutral pH, elevated salinity, and temperatures up to 291 °C. They have deposited massive mounds of calcite with minor sulfide. The fluids are compositionally similar to those in Guaymas Basin, produced by high‐temperature basalt‐seawater interaction followed by reaction with sediment. The paucity of sulfide minerals suggests subsurface deposition of metals.

Introduction 4 Background 7 Site summaries 40 Preliminary scientific assessment 45 References

The best precaution is to ensure that the operating temperature is constant during measurements, and preferably cool, and that sensor and samples have time to reach an equilibrium temperature. This may be more difficult when operating in the field. Wet ConditionsCaution: These instruments are protected against the ingress of moisture but operation in very wet conditions should be avoided.Note: Some sensors can be operated while submerged in water: see product brochure for further information. Noise and Interference CheckCaution: These instruments should not be operated close to high power radio transmitters, heavy electrical machinery, computers, or other electrical or magnetic equipment. Note:The unit is unlikely to be affected by interference from other equipment in the normal operating environment. However, by their nature the sensors are susceptible to electromagnetic interference and operation close to a radio frequency source with a frequency close to the operating frequency of the sensor should be avoided. It is important to position the sensor to minimise interference and obtain the best performance.Select the normal sensitivity, x1.0 range. With no sample present, first press the 'Z' button and then select continuous measurements on the 'M' toggle switch. If fluctuations of greater than ±1 least significant digit per reading appear on the display then external electrical noise should be suspected. In this case the only solution is to re-site the equipment.Before using the laboratory sensors, first check the selected area for freedom from large ferrous objects by moving the sensor and watching for any changes on the display.

Background and objectives 8 Operations 14 Lithostratigraphy 26 Igneous petrology and alteration 37 Structural geology 39 Biostratigraphy 42 Paleomagnetism 50 Inorganic geochemistry 54 Organic geochemistry 62 Microbiology 65 Petrophysics 77 References

Periodic revisions of the Global Heat Flow Database (GHFD) take place under the auspices of the International Heat Flow Commission (IHFC) of the International Association of Seismology and Physics of the Earth's Interior (IASPEI). A growing number of heat-flow values, advances in scientific methods, digitization, and improvements in database technologies all warrant a revision of the structure of the GHFD that was last amended in 1976. We present a new structure for the GHFD, which will provide a basis for a reassessment and revision of the existing global heat-flow data set. The database fields within the new structure are described in detail to ensure a common understanding of the respective database entries. The new structure of the database takes advantage of today's possibilities for data management. It supports FAIR and open data principles, including interoperability with external data services, and links to DOI and IGSN numbers and other data resources (e.g., world geological map, world stratigraphic system, and International Ocean Drilling Program data). Aligned with this publication, a restructured version of the existing database is published, which provides a starting point for the upcoming collaborative process of data screening, quality control and revision. In parallel, the IHFC will work on criteria for a new quality scheme that will allow future users of the database to evaluate the quality of the collated heat-flow data based on specific criteria.