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Edward T. Baker - One of the best experts on this subject based on the ideXlab platform.
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enhanced Hydrothermal Activity on an ultraslow spreading supersegment with a seismically detected melting anomaly
Marine Geology, 2020Co-Authors: Chunhui Tao, Edward T. Baker, Xihe Yue, Xianming Deng, Jianping Zhou, Yuan Wang, Guoyin Zhang, Jie ChenAbstract:Abstract Seafloor Hydrothermal venting fields occur on all ocean spreading ridges (OSRs) regardless of spreading rates. However, the distribution of seafloor Hydrothermal Activity such as frequency and spacing on ultraslow-spreading OSRs are poorly known. Chinese Dayang cruises from 2015 to 2016 conducted detailed water column surveys for seafloor Hydrothermal Activity using a towed system, with an array of turbidity sensors and a near-bottom camera, along the ultraslow-spreading Southwest Indian Ridge. Here we report the discovery of multiple Hydrothermal plumes overlying segments 28, 29, and 30 between the Indomed and Gallieni fracture zones. From these data, and earlier explorations in segments 25–27, we identify nine active venting sites. The spatial density (Fs, sites/100 km) of active sites along the 394 km of ridge axis in our study area is thus 2.8, nearly 3× higher than predicted by the global trend of Fs for ultraslow OSRs in the InterRidge database. Previous studies concluded that an enhanced magma supply to the central Indomed–Gallieni supersegment 11–8 Ma is now limited to segment 27. Our results indicate that although Hydrothermal Activity may be most concentrated in segment 27, the discoveries of active venting in segments 25–30 implies the presence of additional magma bodies across a broad extent of the Indomed–Gallieni supersegment.
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first Hydrothermal discoveries on the australian antarctic ridge discharge sites plume chemistry and vent organisms
Geochemistry Geophysics Geosystems, 2015Co-Authors: Doshik Hahm, Edward T. Baker, Joseph A Resing, Tae Siek Rhee, J E Lupton, Sunghyun ParkAbstract:The Australian-Antarctic Ridge (AAR) is one of the largest unexplored regions of the global mid-ocean ridge system. Here, we report a multiyear effort to locate and characterize Hydrothermal Activity on two first-order segments of the AAR: KR1 and KR2. To locate vent sites on each segment, we used profiles collected by Miniature Autonomous Plume Recorders on rock corers during R/V Araon cruises in March and December of 2011. Optical and oxidation-reduction-potential anomalies indicate multiple active sites on both segments. Seven profiles on KR2 found 3 sites, each separated by ∼25 km. Forty profiles on KR1 identified 17 sites, some within a few kilometer of each other. The spatial density of Hydrothermal Activity along KR1 and KR2 (plume incidence of 0.34) is consistent with the global trend for a spreading rate of ∼70 mm/yr. The densest area of Hydrothermal Activity, named “Mujin,” occurred along the 20 km-long inflated section near the segment center of KR1. Continuous plume surveys conducted in January–February of 2013 on R/V Araon found CH4/3He (1 − 15 × 106) and CH4/Mn (0.01–0.5) ratios in the plume samples, consistent with a basaltic-hosted system and typical of ridges with intermediate spreading rates. Additionally, some of the plume samples exhibited slightly higher ratios of H2/3He and Fe/Mn than others, suggesting that those plumes are supported by a younger Hydrothermal system that may have experienced a recent eruption. The Mujin-field was populated by Kiwa crabs and seven-armed Paulasterias starfish previously recorded on the East Scotia Ridge, raising the possibility of circum-Antarctic biogeographic connections of vent fauna.
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relationships between Hydrothermal Activity and axial magma chamber distribution depth and melt content
Geochemistry Geophysics Geosystems, 2009Co-Authors: Edward T. BakerAbstract:[1] Hydrothermal Activity, especially high-temperature discharge, is commonly thought to require the presence of an axial magma chamber (AMC), but this association has not been examined systematically. The availability of six lengthy (170–560 km) ridge sections with continuous surveys of both AMCs and Hydrothermal plumes now makes it possible to quantitatively compare the distribution and intensity of Hydrothermal Activity to AMC extent, depth, and, at a few locations, melt content. These six ridge sections span spreading rates from 55 to 145 mm/a and total 20 second-order segments. At the section (multisegment) scale the linear incidence of Hydrothermal plumes increases with AMC incidence (AMCI, r2 = 0.64), excluding the hot spot–affected Galapagos spreading center. For all six sections, plume incidence increases as AMC depth below the seafloor decreases (AMCZ, r2 = 0.66). At the second-order segment scale, plume incidence is poorly correlated with both AMCI (r2 = 0.12) and AMCZ (r2 = 0.25). Finally, at the subsegment, or local, scale (0.75-km-long bins), plume intensity increases as AMCZ shallows (r2 = 0.85). Of bins where plumes are most intense and thus closest to their seafloor sources, 68 ± 13% lie directly over an AMC, as do at least 37 of the 40 known high-temperature vent fields. The data also allow tests of other hypotheses linking AMC properties and Hydrothermal Activity. Existing data, though still sparse, do not support the hypothesis that lenses of melt-rich magma preferentially support vigorous, long-lasting venting. Also, the suggestion that increased Hydrothermal cooling within a segment locally depresses AMCZ finds no support within any ridge section. Evidence for magma bodies is much scarcer on slow spreading ridges, but the data are nevertheless consistent with those from faster ridges. Observations from all spreading rates thus demonstrate that high-temperature vent fields are almost universally associated with the presence or inference of magma; “hot rock” or other nonmagmatic heat sources are insufficient.
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high resolution surveys along the hot spot affected galapagos spreading center 3 black smoker discoveries and the implications for geological controls on Hydrothermal Activity
Geochemistry Geophysics Geosystems, 2008Co-Authors: Rachel M Haymon, Edward T. Baker, Scott M White, Ken C Macdonald, Peter G Anderson, Joseph A ResingAbstract:[1] To explore effects of hot spots on mid-ocean ridge Hydrothermal systems, we conducted nested sonar, Hydrothermal plume, and near-bottom photographic surveys along the portion of the Galapagos Spreading Center (GSC) influenced by the Galapagos hot spot, from longitude 95°–89.5°W. We report the first active high-temperature black smokers to be found on the GSC, at longitudes 94°4.5′W and 91°56.2′–54.3′W; describe two areas of recently inactive smokers, at longitudes 91°23.4′–23.7′W and 91°13.8′W; and document an older inactive site, at longitude 90°33.4′W. All imaged vents issue either from dike-induced fissures along linear axial volcanic ridges and collapses or from a caldera. Magmatic control of Hydrothermal systems also is revealed by spatial clustering of plumes within the topographically elevated middles of volcanic ridge segments with inferred centralized melt supply. In searched areas, smokers are more typical than diffuse flow vents, but total GSC plume incidence is half of that expected from the spreading rate. Why? Dike-fed fissures provide permeable pathways for efficient Hydrothermal extraction of magmatic heat, but cones without calderas do not. Among many point-source cones surveyed, only the two with calderas had detectable plumes. Possibly, dominance of point-source over linear-source melt delivery on the GSC decreases plume incidence. Also, similar maturities of observed vents and their host lava flows indicate that Hydrothermally active volcanic segments along the western GSC are contemporaneously in a waning phase of volcanic-Hydrothermal Activity. Perhaps ridge/hot spot interaction produces melt pulses that drive near-synchronous volcanic-Hydrothermal Activity on the volcanic segments spanning the hot spot. During active periods, Hydrothermally active dike-fed fissures and calderas may be more abundant than we currently observe.
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high resolution surveys along the hot spot affected galapagos spreading center 1 distribution of Hydrothermal Activity
Geochemistry Geophysics Geosystems, 2008Co-Authors: Edward T. Baker, Rachel M Haymon, Joseph A Resing, Scott M White, S L Walker, Ken C Macdonald, Koichi NakamuraAbstract:The spatial density of Hydrothermal Activity along most mid-ocean ridges is a robust linear function of spreading rate (or magmatic budget), but extreme crustal properties may alter this relationship. In 2005–2006 we tested the effect of thickened crust on Hydrothermal Activity using high-resolution mapping of plumes overlying the hot spot–affected Galapagos Spreading Center from 95° to 89°42′W (∼560 km of ridge crest). Plume mapping discovered only two active, high-temperature vent fields, subsequently confirmed by camera tows, though strong plume evidence indicated minor venting from at least six other locations. Total plume incidence (ph), the fraction of ridge crest overlain by significant plumes, was 0.11 ± 0.014, about half that expected for a non–hot spot mid-ocean ridge with a similar magmatic budget. Plume distributions on the Galapagos Spreading Center were uncorrelated with abrupt variations in the depth of the along-axis melt lens, so these variations are apparently not controlled by Hydrothermal cooling differences. We also found no statistical difference (for a significance level of 0.05) in plume incidence between where the seismically imaged melt lens is shallow (2 ± 0.56 km, ph = 0.108 ± 0.045) and where it is deep (3.4 ± 0.7 km, ph = 0.121 ± 0.015). The Galapagos Spreading Center thus joins mid-ocean ridges near the Iceland (Reykjanes Ridge), St. Paul-Amsterdam (South East Indian Ridge), and Ascension (Mid-Atlantic Ridge) hot spots as locations of anomalously scarce high-temperature venting. This scarcity implies that convective cooling along hot spot–affected ridge sections occurs primarily by undetected diffuse flow or is permanently or episodically reduced compared to normal mid-ocean ridges.
Joseph A Resing - One of the best experts on this subject based on the ideXlab platform.
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first Hydrothermal discoveries on the australian antarctic ridge discharge sites plume chemistry and vent organisms
Geochemistry Geophysics Geosystems, 2015Co-Authors: Doshik Hahm, Edward T. Baker, Joseph A Resing, Tae Siek Rhee, J E Lupton, Sunghyun ParkAbstract:The Australian-Antarctic Ridge (AAR) is one of the largest unexplored regions of the global mid-ocean ridge system. Here, we report a multiyear effort to locate and characterize Hydrothermal Activity on two first-order segments of the AAR: KR1 and KR2. To locate vent sites on each segment, we used profiles collected by Miniature Autonomous Plume Recorders on rock corers during R/V Araon cruises in March and December of 2011. Optical and oxidation-reduction-potential anomalies indicate multiple active sites on both segments. Seven profiles on KR2 found 3 sites, each separated by ∼25 km. Forty profiles on KR1 identified 17 sites, some within a few kilometer of each other. The spatial density of Hydrothermal Activity along KR1 and KR2 (plume incidence of 0.34) is consistent with the global trend for a spreading rate of ∼70 mm/yr. The densest area of Hydrothermal Activity, named “Mujin,” occurred along the 20 km-long inflated section near the segment center of KR1. Continuous plume surveys conducted in January–February of 2013 on R/V Araon found CH4/3He (1 − 15 × 106) and CH4/Mn (0.01–0.5) ratios in the plume samples, consistent with a basaltic-hosted system and typical of ridges with intermediate spreading rates. Additionally, some of the plume samples exhibited slightly higher ratios of H2/3He and Fe/Mn than others, suggesting that those plumes are supported by a younger Hydrothermal system that may have experienced a recent eruption. The Mujin-field was populated by Kiwa crabs and seven-armed Paulasterias starfish previously recorded on the East Scotia Ridge, raising the possibility of circum-Antarctic biogeographic connections of vent fauna.
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high resolution surveys along the hot spot affected galapagos spreading center 3 black smoker discoveries and the implications for geological controls on Hydrothermal Activity
Geochemistry Geophysics Geosystems, 2008Co-Authors: Rachel M Haymon, Edward T. Baker, Scott M White, Ken C Macdonald, Peter G Anderson, Joseph A ResingAbstract:[1] To explore effects of hot spots on mid-ocean ridge Hydrothermal systems, we conducted nested sonar, Hydrothermal plume, and near-bottom photographic surveys along the portion of the Galapagos Spreading Center (GSC) influenced by the Galapagos hot spot, from longitude 95°–89.5°W. We report the first active high-temperature black smokers to be found on the GSC, at longitudes 94°4.5′W and 91°56.2′–54.3′W; describe two areas of recently inactive smokers, at longitudes 91°23.4′–23.7′W and 91°13.8′W; and document an older inactive site, at longitude 90°33.4′W. All imaged vents issue either from dike-induced fissures along linear axial volcanic ridges and collapses or from a caldera. Magmatic control of Hydrothermal systems also is revealed by spatial clustering of plumes within the topographically elevated middles of volcanic ridge segments with inferred centralized melt supply. In searched areas, smokers are more typical than diffuse flow vents, but total GSC plume incidence is half of that expected from the spreading rate. Why? Dike-fed fissures provide permeable pathways for efficient Hydrothermal extraction of magmatic heat, but cones without calderas do not. Among many point-source cones surveyed, only the two with calderas had detectable plumes. Possibly, dominance of point-source over linear-source melt delivery on the GSC decreases plume incidence. Also, similar maturities of observed vents and their host lava flows indicate that Hydrothermally active volcanic segments along the western GSC are contemporaneously in a waning phase of volcanic-Hydrothermal Activity. Perhaps ridge/hot spot interaction produces melt pulses that drive near-synchronous volcanic-Hydrothermal Activity on the volcanic segments spanning the hot spot. During active periods, Hydrothermally active dike-fed fissures and calderas may be more abundant than we currently observe.
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high resolution surveys along the hot spot affected galapagos spreading center 1 distribution of Hydrothermal Activity
Geochemistry Geophysics Geosystems, 2008Co-Authors: Edward T. Baker, Rachel M Haymon, Joseph A Resing, Scott M White, S L Walker, Ken C Macdonald, Koichi NakamuraAbstract:The spatial density of Hydrothermal Activity along most mid-ocean ridges is a robust linear function of spreading rate (or magmatic budget), but extreme crustal properties may alter this relationship. In 2005–2006 we tested the effect of thickened crust on Hydrothermal Activity using high-resolution mapping of plumes overlying the hot spot–affected Galapagos Spreading Center from 95° to 89°42′W (∼560 km of ridge crest). Plume mapping discovered only two active, high-temperature vent fields, subsequently confirmed by camera tows, though strong plume evidence indicated minor venting from at least six other locations. Total plume incidence (ph), the fraction of ridge crest overlain by significant plumes, was 0.11 ± 0.014, about half that expected for a non–hot spot mid-ocean ridge with a similar magmatic budget. Plume distributions on the Galapagos Spreading Center were uncorrelated with abrupt variations in the depth of the along-axis melt lens, so these variations are apparently not controlled by Hydrothermal cooling differences. We also found no statistical difference (for a significance level of 0.05) in plume incidence between where the seismically imaged melt lens is shallow (2 ± 0.56 km, ph = 0.108 ± 0.045) and where it is deep (3.4 ± 0.7 km, ph = 0.121 ± 0.015). The Galapagos Spreading Center thus joins mid-ocean ridges near the Iceland (Reykjanes Ridge), St. Paul-Amsterdam (South East Indian Ridge), and Ascension (Mid-Atlantic Ridge) hot spots as locations of anomalously scarce high-temperature venting. This scarcity implies that convective cooling along hot spot–affected ridge sections occurs primarily by undetected diffuse flow or is permanently or episodically reduced compared to normal mid-ocean ridges.
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opposing trends in crustal thickness and spreading rate along the back arc eastern lau spreading center implications for controls on ridge morphology faulting and Hydrothermal Activity
Earth and Planetary Science Letters, 2006Co-Authors: Fernando Martinez, Edward T. Baker, Joseph A Resing, Brian Taylor, S L WalkerAbstract:Abstract Along back-arc ridges located near the arc volcanic front, crustal thickness is observed to vary systematically with arc proximity independent of spreading rate. This effect is especially well expressed by the ∼ 400-km-long Eastern Lau Spreading Center (ELSC) where, approaching the arc volcanic front (from ∼ 100 to 40 km), crustal thickness nearly doubles (∼ 5.5–9 km) as spreading rates decrease by more than half (97–39 mm/yr). The crustal thickness variations at the ELSC appear to result primarily from changes in mantle wedge composition caused by subduction. We investigated the effects of these large and opposed crustal thickness and spreading rate variations on ridge morphology, faulting, and Hydrothermal Activity as part of the first phase of RIDGE2000 Integrated Studies in the Lau back-arc basin. We used deep-towed side-scan sonar instruments (DSL120A and IMI30) to continuously map the near-axis region within broader-coverage ship multibeam bathymetry and acoustic imagery swaths. An array of optical sensors (MAPRs) concurrently surveyed the near-bottom water for Hydrothermal plume anomalies. Hydrocasts made at identified plume sites confirmed their Hydrothermal origin. The data show that as spreading rates increase and crustal thicknesses decrease along the ELSC: (1) morphology transitions from shallow peaked volcanic highs to a deeper flat axis; (2) faults become larger and more widely spaced; (3) Hydrothermal Activity, as measured by plume incidence, increases and appears to reach levels higher than the global mid-ocean ridge trend with spreading rate. The observations indicate that crustal thickness (magma supply) has a greater control on ridge morphology and faulting than spreading rate, even at fast rates where the thermal lithosphere should be thin. However, heat input from mantle advection proportional to spreading rate, perhaps in combination with increased fault permeability, appears to have a greater control on Hydrothermal Activity than crustal thickness and the magmatic robustness of the ridge. Although subduction effects give rise to the opposed trends in crustal thickness and spreading rate at the ELSC, the observed effects may have generic implications for controls of seafloor spreading characteristics at mid-ocean ridges.
Gisela Winckler - One of the best experts on this subject based on the ideXlab platform.
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Hydrothermal deposition on the juan de fuca ridge over multiple glacial interglacial cycles
Earth and Planetary Science Letters, 2017Co-Authors: Charles H Langmuir, Kassandra M Costa, Jerry F Mcmanus, Jennifer L Middleton, Peter John Huybers, Gisela WincklerAbstract:Abstract Hydrothermal systems play an important role in modern marine chemistry, but little is known about how they may have varied on 100,000 year timescales. Here we present high-resolution records of non-lithogenic metal fluxes within sediment cores covering the last 500,000 years of Hydrothermal deposition on the flanks of the Juan de Fuca Ridge. Six adjacent, gridded cores were analyzed by x-ray fluorescence for Fe, Mn, and Cu concentrations, corrected for lithogenic inputs with Ti, and normalized to excess initial 230 Th to generate non-lithogenic metal flux records that provide the longest orbitally resolved reconstructions of Hydrothermal Activity currently available. Fe fluxes vary with global sea level over the last two glacial cycles, suggesting higher Hydrothermal deposition during interglacial periods. The observed negative relationship between Fe and Mn indicates variable sediment redox conditions and diagenetic remobilization of sedimentary Mn over time. Thus, Mn fluxes may not be a reliable indicator for Hydrothermal Activity in the Juan de Fuca Ridge sediment cores. Cu fluxes show substantial high-frequency variability that may be linked to changes in vent temperature related to increased magmatic production during glacial periods. Deglacial Hydrothermal peaks on the Juan de Fuca Ridge are consistent with previously published records from the Mid-Atlantic Ridge and the East Pacific Rise. Moreover, on the Juan de Fuca Ridge, the deglacial peaks in Hydrothermal Activity are followed by relatively high Hydrothermal fluxes throughout the ensuing interglacial periods relative to the previous glacial period.
Koichi Nakamura - One of the best experts on this subject based on the ideXlab platform.
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high resolution surveys along the hot spot affected galapagos spreading center 1 distribution of Hydrothermal Activity
Geochemistry Geophysics Geosystems, 2008Co-Authors: Edward T. Baker, Rachel M Haymon, Joseph A Resing, Scott M White, S L Walker, Ken C Macdonald, Koichi NakamuraAbstract:The spatial density of Hydrothermal Activity along most mid-ocean ridges is a robust linear function of spreading rate (or magmatic budget), but extreme crustal properties may alter this relationship. In 2005–2006 we tested the effect of thickened crust on Hydrothermal Activity using high-resolution mapping of plumes overlying the hot spot–affected Galapagos Spreading Center from 95° to 89°42′W (∼560 km of ridge crest). Plume mapping discovered only two active, high-temperature vent fields, subsequently confirmed by camera tows, though strong plume evidence indicated minor venting from at least six other locations. Total plume incidence (ph), the fraction of ridge crest overlain by significant plumes, was 0.11 ± 0.014, about half that expected for a non–hot spot mid-ocean ridge with a similar magmatic budget. Plume distributions on the Galapagos Spreading Center were uncorrelated with abrupt variations in the depth of the along-axis melt lens, so these variations are apparently not controlled by Hydrothermal cooling differences. We also found no statistical difference (for a significance level of 0.05) in plume incidence between where the seismically imaged melt lens is shallow (2 ± 0.56 km, ph = 0.108 ± 0.045) and where it is deep (3.4 ± 0.7 km, ph = 0.121 ± 0.015). The Galapagos Spreading Center thus joins mid-ocean ridges near the Iceland (Reykjanes Ridge), St. Paul-Amsterdam (South East Indian Ridge), and Ascension (Mid-Atlantic Ridge) hot spots as locations of anomalously scarce high-temperature venting. This scarcity implies that convective cooling along hot spot–affected ridge sections occurs primarily by undetected diffuse flow or is permanently or episodically reduced compared to normal mid-ocean ridges.
Rachel M Haymon - One of the best experts on this subject based on the ideXlab platform.
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high resolution surveys along the hot spot affected galapagos spreading center 3 black smoker discoveries and the implications for geological controls on Hydrothermal Activity
Geochemistry Geophysics Geosystems, 2008Co-Authors: Rachel M Haymon, Edward T. Baker, Scott M White, Ken C Macdonald, Peter G Anderson, Joseph A ResingAbstract:[1] To explore effects of hot spots on mid-ocean ridge Hydrothermal systems, we conducted nested sonar, Hydrothermal plume, and near-bottom photographic surveys along the portion of the Galapagos Spreading Center (GSC) influenced by the Galapagos hot spot, from longitude 95°–89.5°W. We report the first active high-temperature black smokers to be found on the GSC, at longitudes 94°4.5′W and 91°56.2′–54.3′W; describe two areas of recently inactive smokers, at longitudes 91°23.4′–23.7′W and 91°13.8′W; and document an older inactive site, at longitude 90°33.4′W. All imaged vents issue either from dike-induced fissures along linear axial volcanic ridges and collapses or from a caldera. Magmatic control of Hydrothermal systems also is revealed by spatial clustering of plumes within the topographically elevated middles of volcanic ridge segments with inferred centralized melt supply. In searched areas, smokers are more typical than diffuse flow vents, but total GSC plume incidence is half of that expected from the spreading rate. Why? Dike-fed fissures provide permeable pathways for efficient Hydrothermal extraction of magmatic heat, but cones without calderas do not. Among many point-source cones surveyed, only the two with calderas had detectable plumes. Possibly, dominance of point-source over linear-source melt delivery on the GSC decreases plume incidence. Also, similar maturities of observed vents and their host lava flows indicate that Hydrothermally active volcanic segments along the western GSC are contemporaneously in a waning phase of volcanic-Hydrothermal Activity. Perhaps ridge/hot spot interaction produces melt pulses that drive near-synchronous volcanic-Hydrothermal Activity on the volcanic segments spanning the hot spot. During active periods, Hydrothermally active dike-fed fissures and calderas may be more abundant than we currently observe.
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high resolution surveys along the hot spot affected galapagos spreading center 1 distribution of Hydrothermal Activity
Geochemistry Geophysics Geosystems, 2008Co-Authors: Edward T. Baker, Rachel M Haymon, Joseph A Resing, Scott M White, S L Walker, Ken C Macdonald, Koichi NakamuraAbstract:The spatial density of Hydrothermal Activity along most mid-ocean ridges is a robust linear function of spreading rate (or magmatic budget), but extreme crustal properties may alter this relationship. In 2005–2006 we tested the effect of thickened crust on Hydrothermal Activity using high-resolution mapping of plumes overlying the hot spot–affected Galapagos Spreading Center from 95° to 89°42′W (∼560 km of ridge crest). Plume mapping discovered only two active, high-temperature vent fields, subsequently confirmed by camera tows, though strong plume evidence indicated minor venting from at least six other locations. Total plume incidence (ph), the fraction of ridge crest overlain by significant plumes, was 0.11 ± 0.014, about half that expected for a non–hot spot mid-ocean ridge with a similar magmatic budget. Plume distributions on the Galapagos Spreading Center were uncorrelated with abrupt variations in the depth of the along-axis melt lens, so these variations are apparently not controlled by Hydrothermal cooling differences. We also found no statistical difference (for a significance level of 0.05) in plume incidence between where the seismically imaged melt lens is shallow (2 ± 0.56 km, ph = 0.108 ± 0.045) and where it is deep (3.4 ± 0.7 km, ph = 0.121 ± 0.015). The Galapagos Spreading Center thus joins mid-ocean ridges near the Iceland (Reykjanes Ridge), St. Paul-Amsterdam (South East Indian Ridge), and Ascension (Mid-Atlantic Ridge) hot spots as locations of anomalously scarce high-temperature venting. This scarcity implies that convective cooling along hot spot–affected ridge sections occurs primarily by undetected diffuse flow or is permanently or episodically reduced compared to normal mid-ocean ridges.
