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  • 2020-2024  (21)
Publikationsart
Schlagwörter
Verlag/Herausgeber
Erscheinungszeitraum
Jahr
  • 1
    facet.materialart.
    Unbekannt
    Shipboard ADCP current measurements (75 kHz) during RV SONNE cruise SO299 (2024)
    PANGAEA
    Details
    Publikationsdatum: 2024-04-03
    Beschreibung: Current velocities of the upper water column along the cruise track of R/V Sonne cruise SO299 were collected by a vessel-mounted 75 kHz RDI Ocean Surveyor ADCP. The ADCP transducer was located at 6.0 m below the water line. The instrument was operated in narrowband mode (WM10) with a bin size of 8.00 m, a blanking distance of 8.00 m, and a total of 100 bins, covering the depth range between 22.0 m and 814.0 m. Heading, pitch and roll data from the ship's motion reference unit and the navigation data from the Global Positioning systems were used by the data acquisition software VmDAS internally to convert ADCP velocities into earth coordinates. Single-ping data were screened for bottom signals and, where appropriate, a bottom mask was manually processed. The ship's velocity was calculated from position fixes obtained by the Global Positioning System (GPS). Accuracy of the ADCP velocities mainly depends on the quality of the position fixes and the ship's heading data. Further errors stem from a misalignment of the transducer with the ship's centerline. Data post-processing included water track calibration of the misalignment angle (-0.1438° +/- 0.4600°) and scale factor (1.0005 +/- 0.0086) of the Ocean Surveyor signal. The velocity data were averaged in time using an average interval of 300 s. Velocity quality flagging is based on different threshold criteria: Depth cells with ensemble-averaged percent-good values below 25% are marked as 'bad data'. Depth cells with velocities above 1.5 m/s are flagged as 'bad data'. Depth cells with a root-mean-square deviation between the measured ensemble-average velocity and a cell-wise running-mean velocity above 0.5 m/s are flagged as 'probably bad data'.
    Schlagwort(e): Current velocity, east-west; Current velocity, north-south; DAM_Underway; DAM Underway Research Data; DATE/TIME; DEPTH, water; DynaMet; Echo intensity, relative; LATITUDE; LONGITUDE; Pings, averaged to a double ensemble value; Quality flag, current velocity; Seadatanet flag: Data quality control procedures according to SeaDataNet (2010); SO299; SO299/1_0_Underway-4; Sonne_2; Vessel mounted Acoustic Doppler Current Profiler [75 kHz]; VMADCP-75
    Materialart: Dataset
    Format: text/tab-separated-values, 5107345 data points
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    DATA PANGAEA
  • 2
    facet.materialart.
    Unbekannt
    Shipboard ADCP current measurements (38 kHz) during RV SONNE cruise SO299 (2024)
    PANGAEA
    Details
    Publikationsdatum: 2024-04-03
    Beschreibung: Current velocities of the upper water column along the cruise track of R/V Sonne cruise SO299 were collected by a vessel-mounted 38 kHz RDI Ocean Surveyor ADCP. The ADCP transducer was located at 6.0 m below the water line. The instrument was operated in narrowband mode (WM10) with a bin size of 32.00 m, a blanking distance of 16.00 m, and a total of 50 bins, covering the depth range between 54.0 m and 1622.0 m. Heading, pitch and roll data from the ship's motion reference unit and the navigation data from the Global Positioning systems were used by the data acquisition software VmDAS internally to convert ADCP velocities into earth coordinates. Single-ping data were screened for bottom signals and, where appropriate, a bottom mask was manually processed. The ship's velocity was calculated from position fixes obtained by the Global Positioning System (GPS). Accuracy of the ADCP velocities mainly depends on the quality of the position fixes and the ship's heading data. Further errors stem from a misalignment of the transducer with the ship's centerline. Data post-processing included water track calibration of the misalignment angle (-0.2374° +/- 0.5601°) and scale factor (1.0045 +/- 0.0097) of the Ocean Surveyor signal. The velocity data were averaged in time using an average interval of 60 s. Velocity quality flagging is based on different threshold criteria: Depth cells with ensemble-averaged percent-good values below 25% are marked as 'bad data'. Depth cells with velocities above 1.5 m/s are flagged as 'bad data'. Depth cells with a root-mean-square deviation between the measured ensemble-average velocity and a cell-wise running-mean velocity above 0.3 m/s are flagged as 'probably bad data'.
    Schlagwort(e): Current velocity, east-west; Current velocity, north-south; DAM_Underway; DAM Underway Research Data; DATE/TIME; DEPTH, water; DynaMet; Echo intensity, relative; LATITUDE; LONGITUDE; Pings, averaged to a double ensemble value; Quality flag, current velocity; Seadatanet flag: Data quality control procedures according to SeaDataNet (2010); SO299; SO299/1_0_Underway-5; Sonne_2; Vessel mounted Acoustic Doppler Current Profiler [38 kHz]; VMADCP-38
    Materialart: Dataset
    Format: text/tab-separated-values, 11025015 data points
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    DATA PANGAEA
  • 3
    facet.materialart.
    Unbekannt
    Master track of SONNE cruise SO299/1 in 1 sec resolution (zipped, 190.7 MB) (2023)
    PANGAEA
    In:  GEOMAR - Helmholtz Centre for Ocean Research Kiel
    Details
    Publikationsdatum: 2024-04-20
    Beschreibung: Raw data acquired by position sensors on board RV SONNE during expedition SO299/1 were processed to receive a validated master track which can be used as reference of further expedition data. During SO299/1 the motion reference unit Kongsberg SeaTex AS MRU-5 combined with Kongsberg SeaTex AS Seapath 320 and two GPS receivers SAAB MGL-4 were used as navigation sensors. Data were downloaded from DAVIS SHIP data base (https://dship.bsh.de) with a resolution of 1 sec. Processing and evaluation of the data is outlined in the data processing report. Processed data are provided as a master track with 1 sec resolution derived from the position sensors' data selected by priority and a generalized track with a reduced set of the most significant positions of the master track.
    Schlagwort(e): 1 sec resolution; CT; DAM_Underway; DAM Underway Research Data; DynaMet; SO299; SO299/1-track; Sonne_2; Underway cruise track measurements
    Materialart: Dataset
    Format: application/zip, 190.7 MBytes
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    DATA PANGAEA
  • 4
    facet.materialart.
    Unbekannt
    Master tracks in different resolutions of SONNE cruise SO299/1, Townsville - Singapore, 2023-06-07 - 2023-07-29 (2023)
    PANGAEA
    In:  GEOMAR - Helmholtz Centre for Ocean Research Kiel
    Details
    Publikationsdatum: 2024-04-20
    Beschreibung: Raw data acquired by position sensors on board RV SONNE during expedition SO299/1 were processed to receive a validated master track which can be used as reference of further expedition data. During SO299/1 the motion reference unit Kongsberg SeaTex AS MRU-5 combined with Kongsberg SeaTex AS Seapath 320 and two GPS receivers SAAB MGL-4 were used as navigation sensors. Data were downloaded from DAVIS SHIP data base (https://dship.bsh.de) with a resolution of 1 sec. Processing and evaluation of the data is outlined in the data processing report. Processed data are provided as a master track with 1 sec resolution derived from the position sensors' data selected by priority and a generalized track with a reduced set of the most significant positions of the master track.
    Schlagwort(e): Calculated; Course; CT; DAM_Underway; DAM Underway Research Data; DATE/TIME; DynaMet; LATITUDE; LONGITUDE; SO299; SO299/1-track; Sonne_2; Speed; Underway cruise track measurements
    Materialart: Dataset
    Format: text/tab-separated-values, 14894 data points
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    DATA PANGAEA
  • 5
    facet.materialart.
    Unbekannt
    Effects of the hydrous domain in the mantle wedge on magma formation and mixing at the Northeast Lau Spreading Centre, SW Pacific (2022)
    PANGAEA
    Details
    Publikationsdatum: 2024-04-17
    Beschreibung: Major and trace element concentrations of young volcanic rocks from the Northeast Lau Basin in the SW Pacific Ocean, as well as Sr-Nd-Hf-Pb isotope compositions. Analyses were mainly carried out at the GeoZentrum Nordbayern, University of Erlangen, Germany, where major elements were determined by electrons microprobe on volcanic glasses and by XRF on whole rocks. Trace elements were analyzed by LA ICPMS on glass at the Macquarie University, Sydney, Australia, and by dissolution ICPMS at the GeoZentrum Nordbayern. Water concentrations on glasses were analyzed by SIMS at the Australian National University, Canberra, Australia. Isotope ratios were determined by TIMS and MC ICPMS at the GeoZentrum Nordbayern.
    Schlagwort(e): #442; #443; Aluminium oxide; Analysis; Antimony; Arsenic; back-arc spreading; Barium; Bismuth; Cadmium; Caesium; Calcium oxide; Cerium; Chlorine; Chromium; Cobalt; Copper; DATE/TIME; DEPTH, water; Dysprosium; Electron microprobe (EMP); Erbium; Europium; Event label; Gadolinium; Gallium; Gold; Hafnium; Hafnium-176/Hafnium-177; Holmium; Inductively Coupled Plasma Mass Spectrometer (ICPMS); Iron oxide, Fe2O3; Iron oxide, FeO; Lanthanum; LATITUDE; Lau Basin; Lead; Lead-206/Lead-204 ratio; Lead-207/Lead-204 ratio; Lead-208/Lead-204 ratio; Lithium; lithosphere rifting; Location; LONGITUDE; Loss on ignition; Lutetium; Magnesium oxide; Manganese; Manganese oxide; Molybdenum; Neodymium; Neodymium-143/Neodymium-144 ratio; Nickel; Niobium; Palladium; Phosphorus pentoxide; Platinum; Potassium oxide; Praseodymium; Remote operated vehicle; Rhodium; Rock type; ROV; Rubidium; Samarium; Sample comment; Sample ID; Sample method; Scandium; Selenium; Silicon dioxide; Silver; slab component; SO263; SO263_074; SO263_075; SO263_076; SO263_077; SO263_078; SO263_079; SO263_080; SO263_098; SO263_099; SO263_100; SO263_101; SO263_102; SO263_104; SO263_105; SO263_106; SO263_107; SO263_108; SO263_109; SO263_111; SO263_112; SO263_113; SO263_116; SO263_117; SO263_118; SO263_119; SO263_120; SO263_122; SO263_124; SO263_125; SO263_126; SO263_129; SO263_130; Sodium oxide; Sonne_2; Strontium; Strontium-87/Strontium-86 ratio; Sulfite; Sum; Tantalum; Television-Grab; Tellurium; Terbium; Thallium; Thermal Ionization Mass Spectrometry (TIMS) and Inductively Coupled Plasma Mass Spectrometer (ICPMS); Thorium; Thulium; Tin; Titanium dioxide; Tofua island arc; Tonga Rift; Tungsten; TVG; Uranium; Vanadium; Volcanic wax corer; VSR; Water in rock; Water in rock, standard deviation; X-ray fluorescence (XRF); X-ray fluorescence (XRF)/Electron microprobe (EMP); Ytterbium; Yttrium; Zinc; Zirconium
    Materialart: Dataset
    Format: text/tab-separated-values, 3245 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
  • 6
    facet.materialart.
    Unbekannt
    Shallow seismicity and the classification of structures in the Lau back-arc basin (2020)
    PANGAEA
    Details
    Publikationsdatum: 2024-05-02
    Beschreibung: We compared Centroid Moment Tensors (CMTs), calculated for large (Mw 〉5), shallow (〈30 km) seismic events to the orientations of seafloor lineaments (n = 4000) mapped throughout the Lau Basin, in the SW Pacific. Ship-based multibeam was combined with vertical gravity gradient data to provide comprehensive coverage to create the lineament map. By comparing the possible focal planes of the CMTs to the orientations of the lineaments, the most likely fault plane solutions were selected, thus classifying the faults and establishing the nature of the highly variable stress regimes in the basin. We resolved the strike, dip and dip direction of 308 faults, and classified 258 additional structures by fault type. The majority of the table was data downloaded from the Global Centroid Moment Tensor (GCMT) database (www.globalcmt.org: accessed October 2018). For more details about the column headers consult the GCMT database website. New data from this study include the latitude and longitude error estimates (in meters), the classified faults (column: 'fault_type'), and the stress domain (column: 'stress_domain'), allocated to each of the classified faults.
    Schlagwort(e): Area/locality; B010186B; B010285E; B010484C; B010783C; B010783E; B010903A; B011101E; B011398E; B011498H; B011683A; B011694B; B011694F; B011700C; B011700E; B011777B; B011800B; B012099A; B012300F; B012300I; B012385B; B012598A; B012699D; B012999A; B020201E; B020487B; B020494A; B020796B; B020901A; B021298F; B021581B; B021587A; B021696B; B022093C; B022102F; B022387C; B022491B; B022503C; B022689B; B022787B; B030395E; B030601B; B030880A; B030894B; B031198D; B031293F; B031387A; B031387B; B031387E; B031393C; B031481A; B031487C; B031692A; B031992C; B031998A; B032003A; B032103D; B032377B; B032377C; B032377D; B032596A; B032682D; B032780A; B032780B; B032786A; B032882D; B032893B; B032982B; B032986B; B033002A; B033091A; B040691B; B040980A; B040991B; B041083C; B041201E; B041586A; B041780A; B041991C; B042088C; B042186A; B042294B; B042585D; B042700A; B042800B; B042879B; B042890B; B042979A; B050186A; B050198A; B050280D; B050392A; B050601C; B051486G; B051802C; B051981B; B052102D; B053179B; B060583A; B060598C; B060790C; B061186B; B061382A; B061479B; B061481A; B061492F; B061699D; B061797B; B061895B; B061895C; B062392E; B062502B; B062601M; B070188A; B070188B; B070689A; B070900A; B071684B; B071789A; B071997B; B072202A; B072602B; B072603D; B073101E; B080178A; B080497D; B080586A; B080586B; B080799A; B081087A; B081095B; B081286A; B081295A; B081299A; B081388C; B081694H; B081696C; B081696F; B082185A; B082290B; B082486A; B082486C; B082500A; B082577A; B082603B; B082686B; B082788B; B082790A; B082903B; B082995B; B083195C; B090684A; B090695A; B090882C; B091081A; B091377A; B091395C; B091799C; B091899D; B092097G; B092390A; B092492E; B092497C; B092688E; B092695A; B092995A; B093082A; B100179B; B100285B; B100295B; B100482B; B100684A; B100696A; B101303E; B101384A; B101501A; B101802D; B101802E; B101982A; B102287E; B102290A; B102677A; B102677B; B102885C; B103093C; B103100E; B110187C; B110499B; B110598F; B110796A; B111082A; B111382A; B111494B; B111596B; B111696C; B111696F; B111784G; B111796C; B111796E; B111797A; B111997B; B112090C; B112479A; B113087B; B113088B; B120386A; B120491A; B120696E; B120796A; B120888A; B120888B; B121286A; B121286C; B121386A; B121985A; B122190A; B122285A; B122285B; B122383A; B122387A; B122791B; B122998A; back-arc basins; Body wave magnitude; Body waves, components; Body waves, shortest period; Body waves, stations; C010987B; C011298J; C011498E; C012204A; C020399A; C020991A; C021393D; C022304C; C022304E; C022490A; C030693G; C030799E; C031293D; C031387F; C032004G; C032504E; C041704C; C041793C; C051504D; C051583A; C061404A; C070278A; C080497C; C080897C; C082997B; C090382E; C091400B; C091783C; C092304C; C100480A; C101104F; C101302A; C101804A; C103100F; C110892B; C111004D; C112304C; C120301A; C121804G; C200502181525A; C200503132233A; C200504261133A; C200504261856A; C200505051011A; C200505111540A; C200507310419A; C200508071135A; C200508071354A; C200508071441A; C200508221648A; C200509041213A; C200510191410A; C200510291633A; C200512071934A; C200512130316A; C200512130732A; C200512161433A; C200512201148A; C200601290826A; C200602061134A; C200602260418A; C200603020747A; C200603051712A; C200603140529A; C200603171946A; C200603191254A; C200604031604A; C200604032027A; C200604251512A; C200604300703A; C200605211757A; C200606031326B; C200606131540A; C200606151715A; C200606151810A; C200606232150A; C200606270836A; C200606281322A; C200607020257A; C200607031949A; C200607041259A; C200608111807A; C200608111841A; C200608112020A; C200611061053A; C200611061124A; C200611210112A; C200611241711A; C200701160153A; C200702031647A; C200702050956A; C200702051016A; C200702051019A; C200703270803B; C200704050246A; C200704050325A; C200704130150A; C200705030630A; C200706140529A; C200706192036A; C200706231914A; C200706231920A; C200706231935A; C200706232102A; C200706232152A; C200706241015A; C200706260801A; C200707020054A; C200707090650A; C200707170939A; C200707180007A; C200707182351A; C200707191933A; C200707270351A; C200708222224A; C200709101004A; C200709140546A; C200709160010A; C200709180610A; C200709302011A; C200710050352A; C200710050417A; C200710300458A; C200711231222A; C200711231237A; C200712150246A; C200801201630A; C200801220009A; C200801220628A; C200801220755A; C200801221049A; C200801231220A; C200801240250A; C200801271528A; C200801302347A; C200801310152A; C200802011026A; C200802112320A; C200802141905A; C200803161956A; C200804151724A; C200804160035A; C200804251844A; C200806200424A; C200807221851A; C200807231255A; C200807231324A; C200807231354A; C200808141242A; C200808141510A; C200808240100A; C200809010531A; C200809010706A; C200809011032A; C200810030834A; C200810092308A; C200810232336A; C200810240058A; C200811201758A; C200901300347A; C200902080724A; C200902110931A; C200903070941A; C200903241813A; C200904142237A; C200904142329A; C200905110526A; C200905260049A; C200907020806A; C200907101604A; C200907211507A; C200908070242A; C200908070334A; C200908071734A; C200909210606A; C200910011739A; C200910011821A; C200910011840A; C200910031402A; C200910031410A; C200910051852A; C200910071310A; C200910141800A; C200910271201A; C200910281955A; C200911050600A; C200911050604A; C200911050611A; C200911291033A; C200912262123A; C200912291202A; C201001131621A; C201001131649A; C201001131651A; C201001171046A; C201002071312A; C201002071359A; C201002150529A; C201003280207A; C201003280251A; C201004042028A; C201007041338A; C201007041613A; C201007171620A; C201008300444A; C201009071249A; C201009071613A; C201009291225A; C201012011601A; C201012182224A; C201012201743A; C201012210736A; C201101211711A; C201101241331A; C201102031113A; C201102280224A; C201103262249A; C201103280847A; C201103310011A; C201103310259A; C201103310744A; C201103311631A; C201103311709A; C201104240601A; C201105021321A; C201105021922A; C201105171035A; C201105180810A; C201105240853A; C201105241630A; C201105300006A; C201106051635A; C201106051656A; C201106192126A; C201106280707A; C201107051902A; C201107061011A; C201107061344A; C201107061446A; C201107101847A; C201107102029A; C201107110054A; C201108030320A; C201108201027A; C201109222307A; C201109230901A; C201110280447A; C201110280913A; C201111130624A; C201111190541A; C201111190706A; C201112140048A; C201201041345A; C201201041804A; C201201041854A; C201201081951A; C201201082004A; C201201090006A; C201202220426A; C201202220804A; C201202221003A; C201202240202A; C201202260246A; C201202260508A; C201202260521A; C201202261117A; C201202261212A; C201202261349A; C201202261613A; C201202261628A; C201202261919A; C201202261937A; C201202270135A; C201202270301A; C201202270711A; C201202271434A; C201202271454A; C201203122148A; C201203192346A; C201203300618A; C201203312252A; C201205041758A; C201205051118A; C201205132246A; C201206041418A; C201206070023A; C201206170638A; C201206190036A; C201207060040A; C201207110357A; C201207230328A; C201208030508A; C201208030722A; C201208031945A; C201208100642A; C201208192054A; C201208200048A; C201208200215A; C201209271131A; C201209271139A; C201210121510A; C201210132236A; C201210220032A; C201210301059A; C201211032259A; C201211132323A; C201211220619A; C201211281016A; C201212120144A; C201212141652A; C201212271531A; C201301020819A; C201301031649A; C201301291329A; C201302152120A; C201302250259A; C201302250356A; C201304120048A; C201304262010A; C201305060733A; C201305310334A; C201306181313A; C201306301513A; C201307090124A; C201307290812A; C201309081000A; C201311141415A; C201312111809A; C201312151451A; C201401210129A; C201401220341A; C201401231209A; C201401261039A; C201401300446A; C201402230216A; C201402231654A; C201402231700A; C201402240119A; C201403070557A; C201403161115A; C201403281437A; C201403281454A; C201404250841A; C201405020746A; C201405131005A; C201405180058A; C201405180246A; C201405180638A; C201406062306A; C201406081108A; C201406091119A; C201406291552A; C201406291715A; C201406291824A; C201407041130A; C201407101732A; C201407212144A; C201408141846A; C201408271631A; C201409280623A; C201410051716A; C201410192047A; C201410201315A; C201410240452A; C201410280044A; C201410280315A; C201411051813A; C201411240417A;
    Materialart: Dataset
    Format: text/tab-separated-values, 42372 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
  • 7
    facet.materialart.
    Unbekannt
    Temporal evolution of proto-Izu–Bonin–Mariana arc volcanism over 10 Ma: Constraints from statistical analysis of melt inclusion compositions (2020)
    Oxford University Press
    Details
    Publikationsdatum: 2023-02-08
    Beschreibung: International Ocean Discovery Program (IODP) Expedition 351 “Izu–Bonin–Mariana (IBM) Arc Origins” drilled Site U1438, situated in the north-western region of the Philippine Sea. Here volcaniclastic sediments and the igneous basement of the proto-IBM volcanic arc were recovered. To gain a better understanding of the magmatic processes and evolution of the proto-IBM arc, we studied melt inclusions hosted in fresh igneous minerals and sampled from 30- to 40-Ma-old deposits, reflecting the maturation of arc volcanism following subduction initiation at 52 Ma. We performed a novel statistical analysis on the major element composition of 237 representative melt inclusions selected from a previously published dataset, covering the full age range between 30 and 40 Ma. In addition, we analysed volatiles (H2O, S, F and Cl) and P2O5 by Secondary Ion Mass Spectrometry (SIMS) for a subset of 47 melt inclusions selected from the dataset. Based on statistical analysis of the major element composition of melt inclusions and by considering their trace and volatile element compositions, we distinguished five main clusters of melt inclusions, which can be further separated into a total of eight subclusters. Among the eight subclusters, we identified three major magma types: (1) enriched medium-K magmas, which form a tholeiitic trend (30–38 Ma); (2) enriched medium-K magmas, which form a calc-alkaline trend (30–39 Ma); and (3) depleted low-K magmas, which form a calc-alkaline trend (35–40 Ma). We demonstrate that (1) the eruption of depleted low-K calc-alkaline magmas occurred prior to 40 Ma and ceased sharply at 35 Ma; (2) the eruption of depleted low-K calc-alkaline magmas, enriched medium-K calc-alkaline magmas and enriched medium-K tholeiitic magmas overlapped between 35 and 38 − 39 Ma; and (3) the eruption of enriched medium-K tholeiitic and enriched medium-K calc-alkaline magmas became predominant thereafter at the proto-IBM arc. Identification of three major magma types are distinct from the previous work, in which enriched medium-K calc-alkaline magmas and depleted low-K calc-alkaline magmas were not identified. This indicates the usefulness of our statistical analysis as a powerful tool to partition a mixture of multivariable geochemical datasets, such as the composition of melt inclusions in this case. Our data suggest that a depleted mantle source had been replaced by an enriched mantle source due to convection beneath the proto-IBM arc from >40 to 35 Ma. Finally, thermodynamic modelling indicates that the overall geochemical variation of melt inclusions assigned to each cluster can be broadly reproduced either by crystallisation differentiation assuming P = 50 MPa (∼2-km deep) and ∼2 wt % H2O (almost saturated H2O content at 50 MPa) or P = 300 MPa (∼15-km deep) and ∼6 wt % H2O (almost saturated H2O content at 300 MPa). Assuming oxygen fugacity (fO2) of log fO2 equal to + 1 relative to nickel-nickel oxide (NNO) buffer best reproduces the overall geochemical variation of melt inclusions, but assuming a more oxidising conditions (log fO2 = +1 to + 2 NNO) likely reproduces the geochemical variation of enriched medium-K and calc-alkaline melt inclusions (30 − 39 Ma).
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    The 6–8 Aug 2019 eruption of ‘Volcano F’ in the Tofua Arc, Tonga (2020)
    Elsevier
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    Publikationsdatum: 2023-02-08
    Beschreibung: Highlights • We identify Volcano F as the source of the August 2019 pumice raft in Tonga. • Satellite and seismic data give constraints on the timing of the submarine eruption. • 2.5–12.3*106 m3 estimated eruption volume, corresponding to VEI 2–3. • First report of the morphology and geology of Volcano F. Abstract In August 2019 a large raft of pumice appeared in the territorial waters of Tonga. As in many other cases, this pumice raft was the only surface expression of a major submarine volcanic eruption. Discolored water and reconstruction of the drift path of the pumice raft using satellite imagery points towards ‘Volcano F’ in the Tofua Arc NW of the island of Vava’u as the most likely volcanic source. Here we present imagery from ESA’s Sentinel-2 satellite that captured the start of the submarine eruption on 6 August 2019 and the waning of the eruption on 8 August, followed by observations of the drifting pumice raft until 14 August. This start time is consistent with T-phase records at the seismic stations on Niue Island and Rarotonga and the signal delay time of 733 s between the two stations is consistent with an origin at or at least near Volcano F. On 8 August, a 〉136.7 km2 large raft of pumice appears at the sea surface. The modelled minimum raft volume is 8.2–41.0*106 m3, which is equivalent to 2.5–12.3*106 m3 dense rock. The eruption thus corresponds to a volcanic explosivity index (VEI) 2–3 eruption in the submarine environment. Prior to the volcanic eruption, a series of earthquakes close to Volcano F was recorded. The series started on 5 August with a Mb 4.7 event, followed by at least six shallow earthquakes (Mb 〉3.9) on 6 August. In December 2018 and January 2019, we surveyed the seafloor around Volcano F with multibeam sonar. Combining our data with pre-existing information, we present the first comprehensive bathymetric map of the volcanic edifice and its geologic setting. We show that Volcano F represents a major arc volcanic complex that is situated in an extensional setting. The basal diameter of the volcanic apron is 〉50 km with a large central, 8.7 x 6 km caldera with a floor at ∼700 m water depth. The top of the post-caldera constructional cone complex had a summit depth of 35 m below sea level in 2004. The volcano shows geochemical differences to the adjacent arc volcanoes on Fonualei and Late islands. The volcano’s pristine volcanic morphology and two documented eruptions (2001 and 2019) indicate a highly active volcanic system that warrants further scientific attention.
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  • 9
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    Shallow seismicity and the classification of structures in the Lau back-arc basin (2020)
    AGU (American Geophysical Union) | Wiley
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    Publikationsdatum: 2023-02-08
    Beschreibung: Back‐arc basins open in response to subduction processes, which cause extension in the upper plate, usually along trench‐parallel spreading axes. However, global seismic databases reveal that the majority of seismic events in the Lau Basin occur along transcurrent (strike‐slip) rather than extensional faults. To better characterize active deformation in this region we compared Centroid Moment Tensors (CMTs), calculated for large (Mw 〉5), shallow (〈30 km) seismic events to the orientations of seafloor lineaments mapped throughout the Lau Basin. Ship‐based multibeam was combined with vertical gravity gradient data to provide comprehensive coverage to create the lineament map. By comparing the possible focal planes of the CMTs to the orientations of the lineaments, the most likely fault plane solutions were selected, thus classifying the faults and establishing the nature of the highly variable stress regimes in the basin. We resolved the strike, dip and dip direction of 308 faults, and classified 258 additional structures by fault type. The analysis highlights a stress regime that is dominated by a combination of left‐lateral and right‐lateral strike‐slip faults, large‐scale transcurrent motion along rigid crustal‐scale fault zones, and non‐rigid diffuse deformation along pre‐existing seafloor structures, with extension mainly limited to the tips of propagating rifts and spreading centers. By resolving many of the uncertain motions on the mapped lineaments of the Lau Basin, the CMT analysis addresses a number of questions concerning basin‐scale stress regimes and microplate development, complementing GPS measurements and providing a more complete picture of the complexities of back‐arc basin development.
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  • 10
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    Crustal structure of the Niuafo’ou Microplate and Fonualei Rift and Spreading Center in the northeastern Lau Basin, Southwestern Pacific (2020)
    AGU (American Geophysical Union) | Wiley
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    Publikationsdatum: 2023-02-08
    Beschreibung: Key points:  First insights into the crustal structure of the northeastern Lau Basin, along a 290 km transect at 17°20’S.  Crust in southern Fonualei Rift and Spreading Center was created by extension of arc crust and variable amount of magmatism.  Magmatic underplating is present in some parts of the southern Niuafo’ou Microplate The northeastern Lau Basin is one of the fastest opening and magmatically most active back‐arc regions on Earth. Although the current pattern of plate boundaries and motions in this complex mosaic of microplates is reasonably understood, the internal structure and evolution of the back‐arc crust are not. We present new geophysical data from a 290 km long east‐west oriented transect crossing the Niuafo’ou Microplate (back‐arc), the Fonualei Rift and Spreading Centre (FRSC) and the Tofua Volcanic Arc at 17°20’S. Our P‐wave tomography model and density modelling suggests that past crustal accretion inside the southern FRSC was accommodated by a combination of arc crustal extension and magmatic activity. The absence of magnetic reversals inside the FRSC supports this and suggests that focused seafloor spreading has until now not contributed to crustal accretion. The back‐arc crust constituting the southern Niuafo’ou Microplate reveals a heterogeneous structure comprising several crustal blocks. Some regions of the back‐arc show a crustal structure similar to typical oceanic crust, suggesting they originate from seafloor spreading. Other crustal blocks resemble a structure that is similar to volcanic arc crust or a ‘hydrous’ type of oceanic crust that has been created at a spreading center influenced by slab‐derived water at distances 〈 50 km to the arc. Throughout the back‐arc region we observe a high‐velocity (Vp 7.2‐7.5 km s‐1) lower crust, which is an indication for magmatic underplating, which is likely sustained by elevated upper mantle temperatures in this region.
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