Multiple hydrothermal sources along the south Tonga arc and Valu Fa Ridge

Abstract

Quantifying hydrothermal venting at the boundaries of tectonic plates is an outstanding geoscience problem. Considerable progress has been made by detailed surveys along mid‐ocean ridges (MORs), but until recently little was known about fluid venting along volcanic arcs. We present the first systematic survey for hydrothermal venting along the 425‐km‐long south Tonga arc and new chemistry data for particle and thermal plumes previously reported along an adjacent 88‐km‐long section of the back‐arc Valu Fa Ridge (VFR). Eleven hydrothermal plumes, recognized by their anomalous light backscattering, Eh, temperature, pH, dissolved 3He, CH4, and total dissolvable Fe and Mn, were identified arising from seven volcanic centers along the arc. Five plumes on the VFR were characterized chemically. Vent field density for the south Tonga arc was 2.6 sites/100 km of arc front, comparable to that found by surveys of the Kermadec arc (1.9 to 3.8 sites/100 km) and to MORs in the eastern Pacific (average value for 2280 km of surveyed ridgecrest: 3.2 sites/100 km). A “vent gap” occurs along a 190 km section of the arc closest to the VFR, and a site density twice the average for MORs on the eastern edge of the Pacific plate was found on this part of the VFR (6.6 sites/100 km). We suggest magmas ascending under the adjacent south Tonga arc have been captured by the VFR. While chemical enrichments of plumes on the south Tonga arc were, in general, slightly less than those on the Kermadec arc, several instances of excessive anomalies in pH suggest a similar presence of fluids enriched in magmatic volatiles (CO2‐SO2‐H2S). Locally, venting on the VFR has contributed to accumulations of 3He, Fe, and Mn within the southern Lau basin. On a broader scale, our results provide considerable support for the notion that venting from intraoceanic arcs on the convergent margin of the Pacific plate adds significantly to the total hydrothermal input into the Pacific Ocean.

Volcanic evolution of the South Sandwich volcanic arc, South Atlantic, from multibeam bathymetry

“…Active submarine hydrothermal vents are known from Adventure and Kemp calderas. The apparent concentration of hydrothermal activity within or adjacent to the calderas is consistent with strong association of hydrothermal plumes with submarine calderas in other intra-oceanic arcs (Baker et al, 2003(Baker et al, , 2008Massoth et al, 2007).…”

“…Caldera walls are well-defined and steep, suggesting well-defined ring faults. Caldera diameters range from 1.6 to 6 km, within the somewhat larger range of caldera diameters recorded in the Tonga-Kermadec (Wright et al, 2006;Massoth et al, 2007;I.J. Graham et al, 2008) and Izu-Bonin (Yuasa et al, 1991;Fiske et al, 2001;Tani et al, 2008) intraoceanic arcs.…”

Hydrodynamic modeling of magmatic–hydrothermal activity at submarine arc volcanoes, with implications for ore formation

“…Numerous studies based on research voyages have highlighted the variable characteristics of submarine hydrothermal activity and seafloor metallogenesis along convergent settings (e.g., Wright et al, 1998;de Ronde et al, 2001de Ronde et al, , 2003bde Ronde et al, , 2007Massoth et al, 2007). However, numerical models investigating the sub-seafloor hydrology of modern arc-related hydrothermal systems are largely lacking in the literature.…”

Renewable energy-driven desalination technologies: A comprehensive review on challenges and potential applications of integrated systems

“…those of the Caribbean, the Mediterranean and the Pacific where extensive submarine hydrothermal systems have been described e.g. in the areas of Tonga [125,126], However these geothermal systems have yet been exploited despite the fact that temperatures range from 245-265°C and their easy accessibility at depths of only 385-540 m [127,128] and a distance of only 50 km from Tongatapu [125]. The same is true for the region of the Northern Marianas Islands where high heat flux of submarine systems has been reported along the Mariana arc [125,129].…”