This is my first post in the classic papers series. I have a passion for volcanogenic massive sulfide (VMS) deposits, so I thought it would be fun to write a short blog on a classic paper that described and documented the first seafloor massive sulfides – Hekinian et al. (1980)(Figure 1).
Figure 1. Cover of the May 28, 1980 issue of Science with the venting of sulfide-rich black smoke from hydrothermal vents near 21oN on the East Pacific Rise (from Science Magazine – see associated paper by Spiess et al., 1980).
Prior to this paper many people had surmised that hydrothermal exhalation had occurred on the seafloor, including inferences from the presence of metalliferous sediments (e.g., Bostrom and Peterson, 1966) and predictions from VMS deposits on land (e.g., Solomon and Walshe, 1979). Additionally, while there had been the discovery of hydrothermal venting in the 1970s (e.g., Edmond et al., 1979 and Spiess et al., 1980), up to that point no sulfide mineralization had been found nor documented on the seafloor.
The paper documented the sulfide occurrences on the seafloor, illustrating their mode of occurrence; their sulfide and silicate mineralogy, textures, sulfide mineral chemistry and paragenesis; bulk sulfide chemistry; and sulfur isotope geochemistry. They provided key arguments as to how the deposits formed. They argued that the metals present in the deposits were likely leached from basaltic oceanic crust by convecting hydrothermal fluids. They illustrated the importance of both leaching of wall rock (igneous) sulfur and thermochemical sulfate reduction of seawater sulfate to provide the reduced sulfur needed to form the sulfides. They also surmised that magmatism may play a role in the metal budget of the seafloor massive sulfide deposits, but were uncertain as to the exact mechanism of how it contributed to the metal budgets. Ironically, we are still debating the role and mechanisms of magmatism in the metal budgets of VMS deposits (e.g., Dube et al., 2007, and references therein; Wysoczanski et al., 2012). Probably most important with this paper, however, was that the authors made the link between active seafloor venting, seafloor massive sulfide deposits, and on-land Cyprus-type VMS deposits (e.g., Spooner and Fyfe 1972; Solomon and Walshe, 1979).
It was a major breakthrough that not only led to an enhanced understanding of VMS deposits on land, but also resulted in significant research in the area of seafloor hydrothermal vents and massive sulfide deposits that has greatly enhanced our understanding of Earth geological, hydrothermal, and biological processes (see video by Dr. Susan Humphris below). The work has also set the stage for the potential marine mining of seafloor massive sulfide deposits (e.g., Nautilus Minerals).
Vents from the East Pacific Rise
Great overview of the significance of hydrothermal vents by Dr. Susan Humphris (Woods Hole Oceanographic Institution)