Novel Forms of Seafloor Fluid Flow: Exploring Pito Deep & Pito Seamount

Chris German, Geology & Geophysics
Jeff Seewald, Marine Chemistry & Geochemistry



Earth’s seafloor undoubtedly plays host to more different forms of fluid flow than have yet been discovered, with hard-to-predict implications for the transfer of mass and chemicals from the lithosphere to the oceans and for the impact of any such fluxes on ocean biogeochemical cycles and life.  As one illustration of how exploration continues to reveal new surprises, three independent studies led by WHOI PIs in the past few years have revealed evidence for new forms of low-temperature fluid flow associated with deep penetrating faults at three separate locations spanning the breadth of the Atlantic: at the Mid Cayman Rise, at the Kane Oceanic Core Complex (OCC) on the Mid-Atlantic Ridge and at the Iberian Margin.  Only one of those sites revealed active flow and the ROV dive that made that discovery, directed from WHOI’s OEI Telepresence Center, was only equipped to determine fluid temperatures (~10°C) withno ability to collect samples.  Here, we seek to extend those investigations to the SE Pacific Ocean and investigate for comparable fluid flow at a new variant of these Atlantic “tectonic windows”.
In January 2017, long-term WHOI colleague, Dr Mike Cheadle (U.Wyoming) will lead a research cruise aboard RV Atlantis, equipped with the ROV Jason and AUV Sentry to investigate the lower ocean crust that is exposed at Pito Deep, SE Pacific, part of the Easter Island tectonic micro-plate.  At his invitation, we seek to add a highly leveraged program of ocean exploration to that cruise, to investigate for seafloor fluid flow at the base of the scarp where deep penetrating faults intersect the seabed.  We will conduct our exploration using the same proven combination of CTD casts, water column analyses and AUV deployments that we have previously used to explore for and discover low-temperature vents at mid-ocean ridges and cold seeps at ocean margins.   Wherever new sites of fluid flow are found, we will seize the opportunity to sample those settings for fluid geochemistry and first “voucher” samples for (micro)biology using the ROV Jason.  Success for this project is guaranteed because, even if no new sites of fluid flow are found at Pito Deep (itself a surprising and publishable result) we will also have the opportunity to collect the first vent-fluid and biological samples from a novel, isolated, black smoker vent located ~50km distant on the summit of the “zero-age” Pito Seamount.  That site was imaged but not sampled during a single dive with the Nautile submersible in 1993 but, because of its remote location, has never been revisited since.