Site 105: Lower Continental Rise Hills

Hollister, C.D.; Ewing, John; Habib, Daniel; Hathaway, John C.; Lancelot, Y.; Luterbacher, Hanspeter; Paulus, F.J.; Poag, C. Wylie; Wilcoxon, J.A.; Worstell, P.

doi:10.2973/dsdp.proc.11.106.1972

Cited by 8 publications

(4 citation statements)

References 4 publications

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“…1C; Martínez-Loriente et al, 2013). Evidence from DSDP Site 105 (Hollister et al, 1972), the western Atlantic counterpart to Site 135, suggests that Upper Jurassic sediments in the study area are indeed pelagic limestones.…”

Section: Fluid Sources and Implicationsmentioning

confidence: 85%

Strike-slip faults mediate the rise of crustal-derived fluids and mud volcanism in the deep sea

Hensen¹,

Scholz²,

Nuzzo³

et al. 2015

Geology

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We report on newly discovered mud volcanoes located at ~4500 m water depth ~90 km west of the deformation front of the accretionary wedge of the Gulf of Cadiz, and thus outside of their typical geotectonic environment. Seismic data suggest that fluid flow is mediated by a >400-km-long strike-slip fault marking the transcurrent plate boundary between Africa and Eurasia. Geochemical data (Cl, B, Sr, 87 Sr/ 86 Sr, d 18 O, dD) reveal that fluids originate in oceanic crust older than 140 Ma. On their rise to the surface, these fluids receive strong geochemical signals from recrystallization of Upper Jurassic carbonates and clay-mineral dehydration in younger terrigeneous units. At present, reports of mud volcanoes in similar deep-sea settings are rare, but given that the large area of transform-type plate boundaries has been barely investigated, such pathways of fluid discharge may provide an important, yet unappreciated link between the deeply buried oceanic crust and the deep ocean.

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Section: Fluid Sources and Implicationsmentioning

confidence: 85%

Strike-slip faults mediate the rise of crustal-derived fluids and mud volcanism in the deep sea

Hensen¹,

Scholz²,

Nuzzo³

et al. 2015

Geology

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“…M A N U S C R I P T ACCEPTED MANUSCRIPT 5 ( Fig. 1; Hollister et al, 1972). A vein of tiny Cu 0 crystals occurs in the pale red, reddish-brown and greenish intercalations of clayey limestone ~10 m above the basalt unit ( Fig.…”

Section: A C C E P T E Dmentioning

confidence: 99%

Native Cu from the oceanic crust: Isotopic insights into native metal origin

et al. 2013

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Ocean drilling has revealed that, although a minor mineral phase, native Cu ubiquitously occurs in the oceanic crust. Cu isotope systematics for native Cu from a set of occurrences from volcanic basement and sediment cover of the oceanic crust drilled at several sites in the Pacific, Atlantic and Indian oceans constrains the sources of Cu and processes that produced Cu 0. We propose that both hydrothermallyreleased Cu and seawater were the sources of Cu at these sites. Phase stability diagrams suggest that Cu 0 precipitation is favored only under strictly anoxic, but not sulfidic conditions at circum-neutral pH even at low temperature. In the basaltic basement, dissolution of primary igneous and potentially hydrothermal Cusulfides leads to Cu 0 precipitation along veins. The restricted Cu-isotope variations (δ 65 Cu = 0.02-0.19‰) similar to host volcanic rocks suggest that Cu 0 precipitation occurred under conditions where Cu +-species were dominant, precluding Cu redox fractionation. In contrast, the Cu-isotope variations observed in the Cu 0 from sedimentary layers yield larger Cu-isotope fractionation (δ 65 Cu = 0.41-0.95‰) suggesting that Cu 0 precipitation involved redox processes during the diagenesis, with potentially seawater as the primary Cu source. We interpret that native Cu precipitation in the basaltic basement is a result of low temperature (20°-65 °C) hydrothermal processes under anoxic, but not H 2 S-rich conditions. Consistent with positive δ 65 Cu signatures, the sediment cover receives major Cu contribution from hydrogenous (i.e., seawater) sources, although hydrothermal contribution from plume fallout cannot be entirely discarded. In this case, disseminated hydrogenous and/or hydrothermal Cu might be diagenetically remobilized and reprecipitated as Cu 0 in reducing microenvironment. Highlights ► native Cu is a minor mineral phase in the oceanic crust ► Cu 0 precipitation is favored under anoxic, but not sulfidic conditions at pH ~ 7 ► Cu +-species are dominant in the basaltic basement ► Cu 2 +-species dominate in the solutions in the sedimentary layer ► Cu 0 precipitation in the basaltic basement is related to seawater-rock interaction ► sediment cover receives major Cu contribution from hydrogenous (seawater) source.

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“…Most of the samples used for this study were obtained from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) sample archives. Our existing sample collections (DSDP sites 105, 144, 367 and 603B and ODP site 1258 [ Berger and von Rad , 1972; Hayes et al , 1972; Hollister et al , 1972; van Hinte et al , 1987; Thurow , 1988; Shipboard Scientific Party , 2004]) were complemented with additional samples obtained from the core repository in Bremen, Germany, in 2008. Samples from Tarfaya core S75 were collected as part of the oil shale campaign undertaken by Shell International Exploration and Production [ Kuhnt et al , 1997], and the Eastbourne outcrop section was logged and sampled at the Gun Gardens locality in East Sussex, England.…”

Section: Sampling: Sites and Collection Protocolsmentioning

confidence: 99%

Iron isotope and trace metal records of iron cycling in the proto‐North Atlantic during the Cenomanian‐Turonian oceanic anoxic event (OAE‐2)

Owens¹,

Lyons²,

Li³

et al. 2012

Paleoceanography

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[1] The global carbon cycle during the mid-Cretaceous ($125-88 million years ago, Ma) experienced numerous major perturbations linked to increased organic carbon burial under widespread, possibly basin-scale oxygen deficiency and episodes of euxinia (anoxic and H 2 S-containing). The largest of these episodes, the Cenomanian-Turonian boundary event (ca. 93.5 Ma), or oceanic anoxic event (OAE) 2, was marked by pervasive deposition of organic-rich, laminated black shales in deep waters and in some cases across continental shelves. This deposition is recorded in a pronounced positive carbon isotope excursion seen ubiquitously in carbonates and organic matter. Enrichments of redox-sensitive, often bioessential trace metals, including Fe and Mo, indicate major shifts in their biogeochemical cycles under reducing conditions that may be linked to changes in primary production. Iron enrichments and bulk Fe isotope compositions track the sources and sinks of Fe in the proto-North Atlantic at seven localities marked by diverse depositional conditions. Included are an ancestral mid-ocean ridge and euxinic, intermittently euxinic, and oxic settings across varying paleodepths throughout the basin. These data yield evidence for a reactive Fe shuttle that likely delivered Fe from the shallow shelf to the deep ocean basin, as well as (1) hydrothermal sources enhanced by accelerated seafloor spreading or emplacement of large igneous province(s) and (2) local-scale Fe remobilization within the sediment column. This study, the first to explore Fe cycling and enrichment patterns on an ocean scale using iron isotope data, demonstrates the complex processes operating on this scale that can mask simple source-sink relationships. The data imply that the proto-North Atlantic received elevated Fe inputs from several sources (e.g., hydrothermal, shuttle and detrital inputs) and that the redox state of the basin was not exclusively euxinic, suggesting previously unknown heterogeneity in depositional conditions and biogeochemical cycling within those settings during OAE-2.

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Site 105: Lower Continental Rise Hills

Cited by 8 publications

References 4 publications

Strike-slip faults mediate the rise of crustal-derived fluids and mud volcanism in the deep sea

Strike-slip faults mediate the rise of crustal-derived fluids and mud volcanism in the deep sea

Native Cu from the oceanic crust: Isotopic insights into native metal origin

Iron isotope and trace metal records of iron cycling in the proto‐North Atlantic during the Cenomanian‐Turonian oceanic anoxic event (OAE‐2)

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