Physico-chemical properties of newly discovered hydrothermal plumes above the Southern Mid-Atlantic Ridge (13°-33°S)

Schmid, Florian; Peters, Maike V.; Walter, Maren; Devey, Colin W.; Petersen, Sven; Yeo, Isobel; Köhler, Janna; Jamieson, John; Walker, S. L.; Sültenfuß, Jürgen

doi:10.1016/j.dsr.2019.04.010

Cited by 22 publications

(12 citation statements)

References 61 publications

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“…The primary goal of CREST was continuous characterization of slow to intermediate spread oceanic crust from the active spreading center to crust formed ~70 Ma; the study also served as a site survey to plan scientific ocean drilling. The present‐day MAR axis at this location has a well‐defined axial valley, four distinct ridge segments varying in length from ~60 to 100 km (Figure 1), and two inferred active vents (Schmid et al, 2019). Our seismic survey crossed a ridge segment that is ~100 km long and is bounded to the north and south by nontransform offsets ~16–22 km in width.…”

Section: Regional Settingmentioning

confidence: 93%

South Atlantic Transect: Variations in Oceanic Crustal Structure at 31°S

Christeson

Reece

Kardell

et al. 2020

Geochem Geophys Geosyst

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We present an analysis of geophysical data acquired along a transect of 0–62 Ma crust located on the western flank of the Mid‐Atlantic Ridge at 31°S; all crust was formed at the same ridge segment. Crustal thickness, constrained by five wide‐angle profiles, has mean values of 5.6 km at 6.6 and 15.2 Ma, 7.0 km at 30.6 Ma, 5.5 km at 49.2 Ma, and 3.6 km at 61.2 Ma. Crustal thickness is uniform along each ridge‐parallel profile (standard deviations 0.1–0.3 km), indicating uniform along‐axis magmatic accretion over lateral distances of 40–60 km. The crustal structure of 61.2 Ma crust is not only anomalously thin compared to the other profiles but also contains regions with a linear velocity gradient from seafloor to Moho, which suggests that intense fracturing may extend to the base of the thin crust. Abyssal hill root‐mean‐square heights in the study region are 57–142 m and have an inverse correlation with spreading rate. These values are lower than the average root‐mean‐square height of 196 m elsewhere on the southern Mid‐Atlantic Ridge and indicate relatively high mantle temperatures in our study area. Unsedimented or lightly sedimented basement highs are prevalent at all ages; we argue that bottom currents scour the high topography, transporting sediment into adjacent basement lows. All drillsites planned for International Ocean Discovery Program Expeditions 390 and 393 are within 1–10 km of unsedimented or lightly sedimented basement highs, which should facilitate fluid flow and continued geochemical exchange between crust and seafloor.

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Section: Regional Settingmentioning

confidence: 93%

South Atlantic Transect: Variations in Oceanic Crustal Structure at 31°S

Christeson

Reece

Kardell

et al. 2020

Geochem Geophys Geosyst

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“…The present-day MAR axis at 30°-32°S has a well-defined axial valley with two inferred active vents (Schmid et al, 2019). The CREST seismic survey crossed a ridge segment that is ~100 km long and bounded to the north and south by ridge offsets ~16-22 km in width.…”

Section: Seismic Studies/site Survey Datamentioning

confidence: 96%

Expedition 390/393 Scientific Prospectus: The South Atlantic Transect

Coggon¹,

Christeson²,

Sylvan³

et al. 2020

International Ocean Discovery Program Scientific Prospectus

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Portions of this work may have been published in whole or in part in other IODP documents or publications. This IODP Scientific Prospectus is based on precruise JOIDES Resolution Facility advisory panel discussions and scientific input from the designated Co-Chief Scientists on behalf of the drilling proponents. During the course of the cruise, actual site operations may indicate to the Co-Chief Scientists, the Expedition Project Manager/Staff Scientist, and the Operations Superintendent that it would be scientifically or operationally advantageous to amend the plan detailed in this prospectus. It should be understood that any substantial changes to the science deliverables outlined in the plan presented here are contingent upon the approval of the IODP JRSO Director and/or JOIDES Resolution Facility Board.

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“…The present-day MAR axis at 30°-32°S has a well-defined axial valley with two inferred active hydrothermal vents (Schmid et al, 2019). The CREST seismic survey crossed a ridge segment that is ~100 km long and bounded to the north and south by ridge offsets ~16 to ~22 km in width.…”

Section: Seismic Studies/site Survey Datamentioning

confidence: 97%

Expedition 390C Preliminary Report: South Atlantic Transect Reentry Systems

Estes¹,

Scientists²,

Williams³

et al. 2021

International Ocean Discovery Program Preliminary Report

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International Ocean Discovery Program (IODP) Expedition 390C was implemented in response to the global COVID-19 pandemic and occupied sites proposed for the postponed Expeditions 390 and 393. The objectives for Expedition 390C were to core one hole at each site with the advanced piston corer/extended core barrel (APC/XCB) system to basement for gas safety monitoring and to install a reentry system with casing through the sediment to between ~5 m above basement and <5 m into basement in a second hole. These operations will expedite basement drilling during the rescheduled South Atlantic Transect Expeditions 390 and 393. The six primary sites for those expeditions form a transect perpendicular to the Mid-Atlantic Ridge on the South American plate, overlying crust ranging in age from 7 to 61 Ma. Basement coring will increase our understanding of how crustal alteration progresses over time across the flanks of a slow/intermediate spreading ridge and how microorganisms survive in deep subsurface environments. Sediment will be used in paleoceanographic and microbiological studies. Expedition 390C started in Kristiansand, Norway, and ended in Cape Town, South Africa, after 31 days of operations. We cored a single APC/XCB sediment hole to the contact with hard rock material at four of the six sites and successfully installed reentry systems with casing at three. Two failed attempts at drilling in casing and a reentry system into hard rock at Site U1558 indicate that the Dril-Quip reentry cones and running tools are incompatible with use in hard rock because the release mechanism does not work when the casing string weight cannot be fully removed from the running tool. Therefore, at Sites U1558 and U1559, casing was installed to ~10 m above basement. Site U1557 has a thick sediment cover (564 m) and will require multiple casing strings to reach basement; a single 16" casing string was installed to 60 meters below seafloor at this site, and later expeditions will extend casing.

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Physico-chemical properties of newly discovered hydrothermal plumes above the Southern Mid-Atlantic Ridge (13°-33°S)

Cited by 22 publications

References 61 publications

South Atlantic Transect: Variations in Oceanic Crustal Structure at 31°S

South Atlantic Transect: Variations in Oceanic Crustal Structure at 31°S

Expedition 390/393 Scientific Prospectus: The South Atlantic Transect

Expedition 390C Preliminary Report: South Atlantic Transect Reentry Systems

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