{"id":7779,"date":"2016-06-14T23:07:13","date_gmt":"2016-06-14T23:07:13","guid":{"rendered":"https:\/\/www.darkenergybiosphere.org\/?post_type=publication&#038;p=7768"},"modified":"2016-10-14T19:06:50","modified_gmt":"2016-10-14T19:06:50","slug":"stealth-export-of-hydrogen-and-methane-from-a-low-temperature-serpentinization-system","status":"publish","type":"publication","link":"https:\/\/www.darkenergybiosphere.org\/publication\/stealth-export-of-hydrogen-and-methane-from-a-low-temperature-serpentinization-system\/","title":{"rendered":"Stealth export of hydrogen and methane from a low temperature serpentinization system"},"content":{"rendered":"<p>Chemical input to the deep sea from hydrothermal systems is a globally distributed phenomenon. Hydrothermal discharge is one of the primary mechanisms by which the Earth\u2019s interior processes manifest themselves at the Earth\u2019s surface, and it provides a source of energy for autotrophic processes by microbes that are too deep to capitalize on sunlight. Much is known about the water-column signature of this discharge from high-temperature mid-ocean Ridge (MOR) environments and their neighboring low-temperature counterparts. Hydrothermal discharge farther away from the ridge, however, has garnered less attention, owing in part to the difficulty in finding this style of venting, which eludes methods of detection that work well for high-temperature \u2018black smoker\u2019-type venting. Here we present a case study of the plume from one such \u2018invisible\u2019 off-axis environment, The Lost City, with an emphasis on the dissolved volatile content of the hydrothermal plume. Serpentinization and abiotic organic synthesis generate significant concentrations of H<sub>2<\/sub> and CH<sub>4<\/sub> in vent fluid, but these species are unevenly transported to the overlying plume, which itself appears to be a composite of two different sources. A concentrated vent cluster on the talus slope channels fluid through at least eight chimneys, producing a water-column plume with the highest observed concentrations of CH<sub>4<\/sub> in the field. In contrast, a saddle in the topography leading up to a carbonate cap hosts broadly distributed, nearly invisible venting apparent only in its water-column signals of redox potential and dissolved gas content, including the highest observed plume H<sub>2<\/sub>. After normalizing H<sub>2<\/sub> and CH<sub>4<\/sub> to the <sup>3<\/sup>He background-corrected anomaly (<sup>3<\/sup>He<sup><strong class=\"boldFont\">\u0394<\/strong><\/sup>) to account for mixing and relative amount of mantle input, it appears that, while a minimum of 60% of CH<sub>4<\/sub> is transported out of the system, greater than 90% of the H<sub>2<\/sub> is consumed in the subsurface prior to venting. The exception to this pattern occurs in the plume originating from the area dubbed Chaff Beach, in which somewhat more than 10% of the original H<sub>2<\/sub> remains, indicating that this otherwise unremarkable plume, and others like it, may represent a significant source of H<sub>2<\/sub> to the deep sea.<\/p>\n","protected":false},"template":"","tags":[],"publication_type":[19],"_links":{"self":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication\/7779"}],"collection":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication"}],"about":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/types\/publication"}],"wp:attachment":[{"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/media?parent=7779"}],"wp:term":[{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/tags?post=7779"},{"taxonomy":"publication_type","embeddable":true,"href":"https:\/\/www.darkenergybiosphere.org\/wp-json\/wp\/v2\/publication_type?post=7779"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}