The Von Damm Vent Field (VDVF) is located on the flanks of the Mid-Cayman Spreading Centre, 13 km west of the axial rift, within a gabbro and peridotite basement. Unlike any other active vent field, hydrothermal precipitates at the VDVF comprise 85–90% by volume of the magnesium silicate mineral, talc. Hydrothermal fluids vent from a 3-m high, 1-m diameter chimney and other orifices at up to 215 °C with low metal concentrations, intermediate pH (5.8) and high concentrations (667 mmol kg−1) of chloride relative to seawater. Here we show that the VDVF vent fluid is generated by interaction of seawater with a mafic and ultramafic basement which precipitates talc on mixing with seawater. The heat flux at the VDVF is measured at 487±101 MW, comparable to the most powerful magma-driven hydrothermal systems known, and may represent a significant mode of off-axis oceanic crustal cooling not previously recognized or accounted for in global models.

The Beebe Vent Field (BVF) is the world's deepest known hydrothermal system, at 4960 m below sea level. Located on the Mid-Cayman Spreading Centre, Caribbean, the BVF hosts high temperature ( 4018C) ''black smoker'' vents that build Cu, Zn and Au-rich sulfide mounds and chimneys. The BVF is highly gold-rich, with Au values up to 93 ppm and an average Au:Ag ratio of 0.15. Gold precipitation is directly associated with diffuse flow through ''beehive'' chimneys. Significant mass-wasting of sulfide material at the BVF, accompanied by changes in metal content, results in metaliferous talus and sediment deposits. Situated on very thin (2-3 km thick) oceanic crust, at an ultraslow spreading centre, the hydrothermal system circulates fluids to a depth of 1.8 km in a basement that is likely to include a mixture of both mafic and ultramafic lithologies. We suggest hydrothermal interaction with chalcophile-bearing sulfides in the mantle rocks, together with precipitation of Au in beehive chimney structures, has resulted in the formation of a Au-rich volcanogenic massive sulfide (VMS) deposit. With its spatial distribution of deposit materials and metal contents, the BVF represents a modern day analogue for basalt hosted, Au-rich VMS systems.

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The Beebe vent field (BVF) in the Cayman Trough has built an auriferous massive sulfide deposit on the ultraslow spreading mid‐Cayman spreading center. The genesis of auriferous sulfide deposits at mid‐ocean ridges is not fully understood, although there is a growing recognition that slow and ultraslow spreading centers are conducive to gold mineralization. Analysis of hydrothermal precipitates from the BVF indicates that the highest gold contents are present within “beehive diffusers,” which have developed a highly porous pyrrhotite framework. The beehive structure allows vent fluids to effuse slowly while allowing ingress of seawater to cool the fluid. The prevalence of pyrrhotite in the beehive samples, lack of sulfates, association between pyrrhotite and gold grains, and results of thermodynamic modeling suggest gold precipitation occurred under highly reduced conditions even during mixing with seawater. In contrast, high‐temperature chimneys, with a single orifice, maintain high temperatures to the primary vent orifice and much of the gold is lost to seawater. Despite this, both chimney types are relatively gold‐enriched, which points to a further underlying cause for high gold at the BVF such as interaction of hydrothermal fluids with ultramafic lithologies in the basement. The final gold composition of the deposit is partially controlled by loss of gold during mass‐wasting of the material, with gold depletion most prevalent in blocks formed at beehive‐type chimneys. The BVF demonstrates that the overall gold content of a massive sulfide deposit is the sum of basement, precipitation, and surface processes.

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the source for the world-class placer gold deposits made famous in the Klondike Gold Rush. However, the recent discovery of gold within a unit of felsic schist led to a new model for mineralisation that included an understanding of host rock rheology and composition. The mapping project aimed to provide a refined structural framework and subdivide the complex schist units that were previously classified as 'undifferentiated'.The increasing capability of portable mapping devices has led to paperless mapping and workflows that allow capture, integration and interpretation of data in the field. SRK ES used ESRI's ArcGIS mapping and analytic software to share base maps, collect data, and generate map interpretations. The workflow involved ArcOnline ™ and Collector ™ to collect data which was then inspected by teams based on site and in the head office.The integrated approach to lithological and structural mapping worked efficiently and effectively for the Klondike Gold District. Additional technologies are being actively developed at SRK ES to improve the efficiency of planning and completing field mapping. The increasing application of machine learning is also providing opportunities to generate preliminary map-based prospectivity interpretations from remote sensing and geological data.The fundamental skills involved in lithological and structural mapping remain broadly the same, but technological advancements and improvements to data quality make the process much more effective and efficient.