Abundance of low-temperature axial venting at the equatorial East Pacific Rise.

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Date: Jan. 2021
Publisher: Elsevier B.V.
Document Type: Report
Length: 418 words

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Keywords Hydrothermal venting; Low temperature flow; East pacific ridge; ORP Highlights * We investigated the fast-spreading EPR for the abundance of low-T submarine venting. * Including low-T flow increases the incidence of venting by 3-fold. * Such low-T flow may play an important role in global-scale ocean biogeochemistry. Abstract Since their first discovery, predictions of the incidence of high temperature submarine vents has been made from along-axis surveys for the presence or absence of particle-rich "black smoker" hydrothermal plumes in the overlying water column. Recent work along intermediate and fast spreading ridges, however, has shown that abundant lower-temperature forms of seafloor fluid flow might be overlooked by this approach. Here, we report new data that allow us to test for both high- and low-temperature venting along the fast-spreading (110--132 mm/yr) equatorial East Pacific Rise (EPR), between 1.9°N and 4.9°S. We identify at least 32 discrete sites of hydrothermal activity, of which just 11 would have been resolved by particle-plume only survey methods. Such an approach would lead to a predicted frequency of high-temperature venting (F.sub.s) along this section of the EPR of 4.2 sites/100 km, consistent with other particle-plume only surveys conducted under the auspices of InterRidge. When we include ORP sensor data to prospect for near-seafloor evidence of low-temperature venting, however, the calculated spatial frequency (Fs) for all styles of seafloor fluid flow increases by more than 3-fold, to Fs [greater than or equal to] 15.5 sites/100 km. Hence, this study provides confirmation that low-temperature venting should be widespread along all fast-spreading mid-ocean ridges. While an appreciation of the importance of low-temperature axial venting to geophysical fluxes (heat, mass) is well established, our results reveal evidence for low-temperature fluid flow that is out of geochemical (redox) equilibrium with the overlying water column. Consequently, these fluxes may also play an important but previously overlooked role in global-scale ocean biogeochemical cycles. Author Affiliation: (a) Ocean Technology and Equipment Research Center, School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou, 310018, China (b) Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, 02543, USA (c) Key Laboratory of Submarine Geosciences, SOA & Second Institute of Oceanography, MNR, Hangzhou, 310012, China (d) School of Oceanography, Shanghai Jiao Tong University, Shanghai, 200240, China * Corresponding author. Ocean Technology and Equipment Research Center, School of Mechanical Engineering, Hangzhou Dianzi University, Hangzhou, 310018. China. Article History: Received 14 June 2020; Revised 23 October 2020; Accepted 23 October 2020 Byline: Sheng Chen [chensh@hdu.edu.cn] (a,b,*), Chunhui Tao [taochunhuimail@163.com] (c,d,**), Christopher R. German (b)

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Gale Document Number: GALE|A648410970