Back-arc spreading and mantle flow in the East Scotia Sea

Livermore, Roy

doi:10.1144/gsl.sp.2003.219.01.15

Cited by 38 publications

(50 citation statements)

References 70 publications

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“…The Na8^Fe8 BAB variations are about two-thirds of the global MOR ones, implying temperature di¡erences of about 200 ‡C if all the global variations are ascribed to temperature di¡erences of a compositionally homogeneous mantle [1,2]. Given that subduction rates are fast beneath Lau and Manus ( s 140 mm/yr [57,58] but slow to intermediate beneath Mariana and Scotia (40^70 and 67^79 mm/yr [48,51]), this is consistent with the correlation between subduction rate and mantle wedge temperature predicted by numerical models [59,60]. In these models fast subduction induces fast mantle wedge advection and isotherms compressed against the slab, whereas slow subduction and advection allow signi¢-cant cooling of the mantle wedge.…”

Section: Inter-basin Comparisonmentioning

confidence: 99%

“…8) [48]. The morphological variation cannot be ascribed to spreading rates, which vary little along strike (60^70 mm/yr).…”

Section: East Scotia Basinmentioning

confidence: 99%

“…Overviews of the tectonic setting and evolution of each of the BABs (Fig. 1) are provided in the following papers: Lau [45], Manus [46], Mariana [47], and east Scotia [48]; as well as in [27].…”

Section: Data and Fractionation Correctionsmentioning

confidence: 99%

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Back-arc basin basalt systematics

Taylor

Martínez

2003

Earth and Planetary Science Letters

402

253

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The Mariana, east Scotia, Lau, and Manus back-arc basins (BABs) have spreading rates that vary from slow ( 6 50 mm/yr) to fast ( s 100 mm/yr) and extension axes located from 10 to 400 km behind their island arcs. Axial lava compositions from these BABs indicate melting of mid-ocean ridge basalt (MORB)-like sources in proportion to the amount added of previously depleted, water-rich, arc-like components. The arc-like end-members are characterized by low Na, Ti and Fe, and by high H 2 O and Ba/La; the MORB-like end-members have the opposite traits. Comparisons between basins show that the least hydrous compositions follow global MORB systematics and an inverse correlation between Na8 and Fe8. This is interpreted as a positive correlation between the average degree and pressure of mantle melting that reflects regional variations in mantle potential temperatures (Lau/Manus hotter than Mariana/Scotia). This interpretation accords with numerical model predictions that faster subduction-induced advection will maintain a hotter mantle wedge. The primary compositional trends within each BAB (a positive correlation between Fe8, Na8 and Ti8, and their inverse correlation with H 2 O(8) and Ba/La) are controlled by variations in water content, melt extraction, and enrichments imposed by slab and mantle wedge processes. Systematic axial depth (as a proxy for crustal production) variations with distance from the island arc indicate that compositional controls on melting dominate over spreading rate. Hydrous fluxing enhances decompression melting, allowing depleted mantle sources just behind the island arc to melt extensively, producing shallow spreading axes. Flow of enriched mantle components around the ends of slabs may augment this process in transform-bounded back-arcs such as the east Scotia Basin. The re-circulation (by mantle wedge corner flow) to the spreading axes of mantle previously depleted by both arc and spreading melt extraction can explain the greater depths and thinner crust of the East Lau Spreading Center, Manus Southern Rifts, and Mariana Trough and the very depleted lavas of east Scotia segments E8/E9. The crust becomes mid-ocean ridge (MOR)-like where the spreading axes, further away from the island arc and subducted slab, entrain dominantly fertile mantle. ß

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Section: Inter-basin Comparisonmentioning

confidence: 99%

“…8) [48]. The morphological variation cannot be ascribed to spreading rates, which vary little along strike (60^70 mm/yr).…”

Section: East Scotia Basinmentioning

confidence: 99%

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Back-arc basin basalt systematics

Taylor

Martínez

2003

Earth and Planetary Science Letters

402

253

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“…Multibeam data have also been obtained for the submerged Douglas Strait Caldera on Southern Thule (Allen and Smellie, 2008), and Kemp seamount and the adjacent Kemp caldera (Supplementary Material S1). The East Scotia Ridge back-arc spreading centre and a section of the fore-arc have been mapped using the lower resolution towed Hawaii MR1 sonar (Livermore et al, 1997;Vanneste and Larter, 2002;Livermore, 2003). Previous soundings data are shown on the UK Admiralty Chart (Hydrographic Office, 2003), which was an invaluable route-finder during the survey work.…”

mentioning

confidence: 99%

Volcanic evolution of the South Sandwich volcanic arc, South Atlantic, from multibeam bathymetry

Leat

Day

Tate

et al. 2013

Journal of Volcanology and Geothermal Research

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New multibeam bathymetry data are presented for the South Sandwich intra-oceanic arc which occupies the small Sandwich plate in the South Atlantic, and is widely considered to be a simple end-member in the range of intra-oceanic arc types. The images show for the first time the distribution of submarine volcanic, tectonic and erosional-depositional features along the whole length of the 540 km long volcanic arc, allowing systematic investigation of along-arc variations. The data confirm that the volcanic arc has a simple structure composed of large volcanoes which form a well-defined volcanic front, but with three parallel crosscutting seamount chains extending 38-60 km from near the volcanic front into the rear-arc. There is no evidence for intra-arc rifting or extinct volcanic lines. Topographic evidence for faulting is generally absent, except near the northern and southern plate boundaries. Most of the volcanic arc appears to be built on ocean crust formed at the associated back-arc spreading centre, as previously proposed from magnetic data, but the southern part of the arc appears to be underlain by older arc or continental crust whose west-facing rifted margin facing the back-arc basin is defined by the new bathymetry. The new survey shows nine main volcanic edifices along the volcanic front and ca. 20 main seamounts. The main volcanoes form largely glaciated islands with summits 3.0-3.5 km above base levels which are 2500-3000 m deep in the north and shallower at 2000-2500 m deep in the south. Some of the component seamounts are interpreted to have been active since the last glacial maximum, and so are approximately contemporaneous with the volcanic front volcanism. Seven calderas, all either submarine or ice-filled, have been identified: Adventure volcano, a newly discovered submarine volcanic front caldera volcano is described for the first time. All but one of the calderas are situated on summits of large volcanoes in the southern part of the arc, and most are associated with current or historic volcanic or hydrothermal activity. Shallow shelves around the islands are generally 1-10 km wide. Submerged banks up to 1100 m deep are interpreted as subsided erosional surfaces. Seamounts and emergent volcanoes experienced a range of mass wasting processes including by landsliding and smaller mass flows. KeywordsVolcanic arc, subduction zone, caldera, seamount, submarine volcanism The importance of the South Sandwich volcanic arcThe South Sandwich volcanic arc, situated in the South Atlantic ( Fig. 1), is a tectonically simple, active, intra-oceanic arc, and is ideally suited to studies of volcanic arc crustal structure, geochemical investigation of mantle processes above a subduction zone, and sedimentation in an early stage of arc evolution. The active arc is built largely on oceanic crust of the small Sandwich plate which formed about 10 Ma at the back-arc East Scotia ridge spreading centre . The arc is forming in response to steeply inclined subduction of the South American plate beneath the Sand...

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“…Interestingly, one of the gastropod species, the limpet Leptodrilus sp., also occurs in the neighboring Kemp caldera in of the South Sandwich Arc, a region from which V. scotiaensis is also known (Rogers et al 2012). Roterman (2013) Although mean water fluxes in the ESR have an easterly or north-easterly direction, largely influenced by the Antarctic Circumpolar Current (Meredith et al 2008), the local hydrography and flows on the E2, E9 (Livermore 2003), which causes the formation of deep axial valleys with high walls that likely modify local current regimes. Mid-ocean ridges with similar characteristics are known to generate significant flows along and on the flanks of the ridge axes (Thurnherr et al 2008;Thurnherr et al 2011;Lavelle et al 2012), thus potentially facilitating dispersal among spatially separated vent fields.…”

Section: Local Connectivity Patterns In the East Scotia Ridgementioning

confidence: 99%

Evolutionary and ecological genomics in deep-sea organisms

Monroy¹

2015

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Hydrothermal vents and coral ecosystems are conspicuous biological hot spots in the deep-sea. These ecosystems face increasing threats from human activities. Having thorough taxonomic inventories as well as understanding species' relatedness, genetic diversity, connectivity patterns, and adaptive potential is fundamental for the implementation of conservation strategies that help mitigate these threats. This thesis provides fundamental high-priority knowledge in taxonomic, evolutionary, and ecological aspects of deep-sea coral and vent species, by harnessing the power of genomic tools and overcoming long-standing methodological barriers. First, I develop bioinformatic tools that help guide the design of studies aiming to characterize eukaryotic genome diversity using restriction-site associated DNA sequencing. Using these tools I find that the predictability of restriction site frequencies in eukaryotic genomes is chiefly determined by the phylogenetic position of the target species and the recognition sequence of the selected restriction enzyme. These tools are then applied to test global-scale historical biogeographic hypotheses of vent fauna using barnacles as model. Phylogeographic inferences suggest that the western Pacific was the place of origin of the major vent barnacle lineage, followed by circumglobal colonization eastward along the southern hemisphere during the Neogene. I suggest that the geological processes and dispersal mechanisms discussed here can explain distribution patterns of many other marine taxa in addition to barnacles. Regional-scale analyses indicate that vent barnacle populations are well connected within basins and ridge systems, and that their diversity patterns do not conform to the predictions from the hypothesis that seamounts are centers of endemism. I then move on to resolve long-standing questions regarding species definitions in recalcitrant deep-sea coral taxa, by unambiguously resolving evolutionary relationships and objectively inferring species boundaries. Finally, I explore the adaptive potential of deep-sea coral species to environmental changes by examining a case of adaptation to shallow water from the deep sea. Candidate positive-selection markers shared between pairs of shallow and deep populations are identified as likely makers for genomic regions involved in adaptation. Overall, the results from this thesis constitute critical baseline data with which to assess potential effects of anthropogenic disturbances on deep-sea ecosystems. AKNOWLEDGEMENTSThis degree is the fulfillment of a lifelong dream. I am infinitely grateful to Tim Shank, for taking a chance with me, for challenging me constantly, for honest advising, for providing limitless opportunities to pursue my interests and develop my skills, for unconditional support and trust, and for making me feel more like a colleague than a student since the first day. I could not imagine a better place to have done my PhD. I look forward to many more ventures to come. I am extremely grateful to my committee ...

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Back-arc spreading and mantle flow in the East Scotia Sea

Cited by 38 publications

References 70 publications

Back-arc basin basalt systematics

Back-arc basin basalt systematics

Volcanic evolution of the South Sandwich volcanic arc, South Atlantic, from multibeam bathymetry

Evolutionary and ecological genomics in deep-sea organisms

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