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  • 1
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    Argon, uranium, thorium and lead composition and ages of ODP Leg 180 sites (2001)
    PANGAEA
    In:  Supplement to: Monteleone, Brian D; Baldwin, Suzanne L; Ireland, Trevor R; Fitzgerald, Paul G (2001): Thermochronologic constraints for the tectonic evolution of the Moresby Seamount, Woodlark Basin, Papua New Guinea. In: Huchon, P; Taylor, B; Klaus, A (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 180, 1-35, https://doi.org/10.2973/odp.proc.sr.180.173.2001
    Details
    Publication Date: 2024-01-09
    Description: During Ocean Drilling Program (ODP) Leg 180, 11 sites were drilled in the vicinity of the Moresby Seamount to study processes associated with the transition from continental rifting to seafloor spreading in the Woodlark Basin. This paper presents thermochronologic (40Ar/39Ar, 238U/206Pb, and fission track) results from igneous rocks recovered during ODP Leg 180 that help constrain the latest Cretaceous to present-day tectonic development of the Woodlark Basin. Igneous rocks recovered (primarily from Sites 1109, 1114, 1117, and 1118) consist of predominantly diabase and metadiabase, with minor basalt and gabbro. Zircon ion microprobe analyses gave a 238U/206Pb age of 66.4 ± 1.5 Ma, interpreted to date crystallization of the diabase. 40Ar/39Ar plagioclase apparent ages vary considerably according to the degree to which the diabase was altered subsequent to crystallization. The least altered sample (from Site 1109) yielded a plagioclase isochron age of 58.9 ± 5.8 Ma, interpreted to represent cooling following intrusion. The most altered sample (from Site 1117) yielded an isochron age of 31.0 ± 0.9 Ma, interpreted to represent a maximum age for the timing of subsequent hydrothermal alteration. The diabase has not been thermally affected by Miocene-Pliocene rift-related events, supporting our inference that these rocks have remained at shallow and cool levels in the crust (i.e., upper plate) since they were partially reset as a result of middle Oligocene hydrothermal alteration. These results suggest that crustal extension in the vicinity of the Moresby Seamount, immediately west of the active seafloor spreading tip, is being accommodated by normal faulting within latest Cretaceous to early Paleocene oceanic crust. Felsic clasts provide additional evidence for middle Miocene and Pliocene magmatic events in the region. Two rhyolitic clasts (from Sites 1110 and 1111) gave zircon 238U/206Pb ages of 15.7 ± 0.4 Ma and provide evidence for Miocene volcanism in the region. 40Ar/39Ar total fusion ages on single grains of K-feldspar from these clasts yielded younger apparent ages of 12.5 ± 0.2 and 14.4 ± 0.6 Ma due to variable sericitization of K-feldspar phenocrysts. 238U/206Pb zircon, 40Ar/39Ar K-feldspar and biotite total fusion, and apatite fission track analysis of a microgranite clast (from Site 1108) provide evidence for the existence of a rapidly cooled 3.0 to 1.8 Ma granitic protolith. The clast may have been transported longitudinally from the west (e.g., from the D'Entrecasteaux Islands). Alternatively, it may have been derived from a more proximal, but presently unknown, source in the vicinity of the Moresby Seamount.
    Keywords: Ocean Drilling Program; ODP
    Type: Dataset
    Format: application/zip, 3 datasets
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    DATA PANGAEA
  • 2
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    (Table T1) Thermochronology of ODP Leg 180 sites (2001)
    PANGAEA
    Details
    Publication Date: 2024-01-09
    Keywords: 180-1108B; 180-1109D; 180-1110B; 180-1111A; 180-1117A; 180-1118A; Age, dated; Age, dated standard deviation; DRILL; Drilling/drill rig; Elevation of event; Event label; Joides Resolution; Latitude of event; Leg180; Longitude of event; Method comment; Minerals; Ocean Drilling Program; ODP; Rock type; Sample code/label; Sample comment; Solomon Sea
    Type: Dataset
    Format: text/tab-separated-values, 140 data points
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  • 3
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    (Table T2) Argon composition and 40Ar/39Ar ages of ODP Leg 180 sites (2001)
    PANGAEA
    Details
    Publication Date: 2024-01-09
    Keywords: 180-1108B; 180-1109D; 180-1110B; 180-1111A; 180-1117; 180-1117A; 180-1118A; Age, 40Ar/39Ar Argon-Argon; Age, dated; Age, dated standard deviation; Argon-36/Argon-39; Argon-37/Argon-39; Argon-39; Argon-40; Argon-40/Argon-39; COMPCORE; Composite Core; DRILL; Drilling/drill rig; Elevation of event; Event label; Grain size description; Joides Resolution; Latitude of event; Leg180; Longitude of event; Method comment; Minerals; Ocean Drilling Program; ODP; Parameter; Sample code/label; Sample mass; Solomon Sea; Temperature, technical
    Type: Dataset
    Format: text/tab-separated-values, 1266 data points
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  • 4
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    (Table T3) Uranium, thorium and lead composition, and U/Pb ages of ODP Leg 180 sites (2001)
    PANGAEA
    Details
    Publication Date: 2024-01-09
    Keywords: 180-1108; 180-1110; 180-1111; 180-1117A; Age, dated; Age, dated standard deviation; Age, Uranium-Lead; COMPCORE; Composite Core; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Elevation of event; Event label; Joides Resolution; Latitude of event; Lead-204/Lead-206, error; Lead-204/Lead-206 ratio; Lead-207/Lead-206, standard error; Lead-207/Lead-206 ratio; Leg180; Longitude of event; Ocean Drilling Program; ODP; Rock type; Sample code/label; Sample ID; Solomon Sea; Thorium; Thorium/Uranium ratio; Uranium; Uranium-238/Lead-206, standard error; Uranium-238/Lead-206 ratio
    Type: Dataset
    Format: text/tab-separated-values, 332 data points
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  • 5
    Electronic Resource
    Electronic Resource
    Pliocene eclogite exhumation at plate tectonic rates in eastern Papua New Guinea (2004)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 431 (2004), S. 263-267 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] As lithospheric plates are subducted, rocks are metamorphosed under high-pressure and ultrahigh-pressure conditions to produce eclogites and eclogite facies metamorphic rocks. Because chemical equilibrium is rarely fully achieved, eclogites may preserve in their distinctive mineral assemblages and ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature02846
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Diffusion of 40Ar in metamorphic hornblende (1990)
    Springer
    Contributions to mineralogy and petrology 105 (1990), S. 691-703 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Isothermal, hydrothermal experiments were performed on two compositionally contrasting hornblendes from amphibolites in order to examine Ar diffusion behavior in metamorphic hornblendes. Ten experiments on sample RF were performed at temperatures of 750°C, 800°C, and 850°C and pressures of 1 kbar using measured grain radii of 158, 101, and 34 μm. Eight experiments on sample 118576 were performed under the same conditions using measured grain radii of 145, 77, and 25 μm. Minor (〈5%) alteration was observed in high temperature runs. Diffusion coefficients were calculated from measured radiogenic 40Ar loss following treatment assuming a spherical geometry for the mineral aggregate. Diffusivities calculated for different grain sizes vary by up to an order of magnitude for a given temperature indicating that the effective diffusion radius was less than the measured grain radius. Diffusivities for RF and 118576 calculated for grain radii of 101 and 145 μm, respectively, form a linear array on an Arrhenius diagram with slopes indicating activation energies of ∼ 60 kcal/mol. No correlation between Mg number (100 Mg/(Mg+Fe)) and activation energy was observed. Diffusivities calculated for these experiments are higher than previously reported results from similar experiments performed on hornblendes. A comparison of results for 34 μm splits from these two studies indicates higher apparent diffusivities (by a factor of 5), which probably result from observed phyllosilicate inter-growths (chlorite) and/or exsolution lamellae that partition the metamorphic hornblendes into smaller subdomains. Diffusivities calculated for experiments performed on 65 μm and 34 μm splits of 40Ar/39Ar standard MMhb-1 at 800°C and 1 kbar are consistent with a previously reported activation energy of 65 kcal/mol. Arrhenius parameters which emerge from the empirical model of Fortier and Giletti (1989) agree with experimental results to within analytical uncertainty. Although results of these experiments support previously reported estimates of the activation energy of 40Ar in hornblende (∼60 kcal/mol), phyllosilicate intergrowths and/or microstructures such as exsolution lamellae within the two metamorphic hornblendes result in extremely small diffusion domains, which may lead to lower Ar retentivities and lower closure temperatures. The effective diffusion dimension for 40Ar in hornblende is not likely to be defined by dislocations but rather by some larger structure within the crystal. TEM and SEM studies may provide some insight into the effective diffusion dimension for 40Ar in amphiboles, thereby enabling better estimates of closure temperatures and more precise temperature-time reconstructions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00306534
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  • 7
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    Contrasting styles of (U)HP rock exhumation along the Cenozoic Adria-Europe plate boundary (Western Alps, Calabria, Corsica) (2019)
    Details
    Publication Date: 2019-10-17
    Description: Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary.
    Description: Published
    Description: 1786–1824
    Description: 1T. Struttura della Terra
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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    Atmospheric Ar and Ne returned from mantle depths to the Earth’s surface by forearc recycling (2015)
    National Academy of Sciences
    Details
    Publication Date: 2015-11-05
    Description: In subduction zones, sediments, hydrothermally altered lithosphere, fluids, and atmospheric gases are transported into the mantle, where ultrahigh-pressure (UHP) metamorphism takes place. However, the extent to which atmospheric noble gases are trapped in minerals crystallized during UHP metamorphism is unknown. We measured Ar and Ne trapped in phengite and omphacite from the youngest known UHP terrane on Earth to determine the composition of Ar and Ne returned from mantle depths to the surface by forearc recycling. An 40Ar/39Ar age [7.93 ± 0.10 My (1σ)] for phengite is interpreted as the timing of crystallization at mantle depths and indicates that 40Ar/39Ar phengite ages reliably record the timing of UHP metamorphism. Both phengite and omphacite yielded atmospheric 38Ar/36Ar and 20Ne/22Ne. Our study provides the first documentation, to our knowledge, of entrapment of atmospheric Ar and Ne in phengite and omphacite. Results indicate that a subduction barrier for atmospheric-derived noble gases does not exist at mantle depths associated with UHP metamorphism. We show that the crystallization age together with the isotopic composition of nonradiogenic noble gases trapped in minerals formed during subsolidus crystallization at mantle depths can be used to unambiguously assess forearc recycling of atmospheric noble gases. The flux of atmospheric noble gas entering the deep Earth through subduction and returning to the surface cannot be fully realized until the abundances of atmospheric noble gases trapped in exhumed UHP rocks are known.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Geochronology of Blueschists from West-Central Baja California and the Timing of Uplift in Subduction Complexes (1989)
    University of Chicago Press
    Details
    Publication Date: 1989-03-01
    Print ISSN: 0022-1376
    Electronic ISSN: 1537-5269
    Topics: Geosciences
    Published by University of Chicago Press
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  • 10
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    Transient fluvial incision and active surface uplift in the Woodlark Rift of eastern Papua New Guinea (2012)
    Geological Society of America (GSA)
    Details
    Publication Date: 2012-04-01
    Description: The Woodlark Rift of southeastern Papua New Guinea is among the fastest evolving plate boundaries on Earth. Rapid extension led to formation of metamorphic core complexes ahead of the westward-propagating Woodlark basin spreading center, but it is unknown whether all core complexes are still active. We assess the spatial pattern and recent history of rock and surface uplift in the subaerial portion of the Woodlark Rift using stream profile analyses on the D'Entrecasteaux Islands and eastern Papuan Peninsula. Most stream profiles are characterized by prominent convexities, or knickpoints, many of which occur at the heads of inner gorges and likely formed from transient stream erosion in the Quaternary due to an increase in rock uplift rate. The amount of transient incision and rock uplift (∼200–800 m) correlates with channel slopes below knickpoints normalized for drainage area. Recent erosion lags behind rock uplift; hence, the region of study has undergone net surface uplift, elevating a relict landscape upstream of knickpoints by an average of 450 m, and increasing basin relief by an average of 60%. On a local scale, stream slopes, transient incision, and uplifted relict stream channels provide independent quantitative evidence for patterns of active uplift in the D'Entrecasteaux Islands and Papuan Peninsula consistent with available geologic and thermochronologic data. Surface uplift increases from east to west on a regional scale, in a region of active lithospheric extension. Rising topography in thinned crust occurs over low-density asthenosphere, indicating that mantle buoyancy and flow contribute to active surface uplift and landscape evolution in the Woodlark Rift.
    Print ISSN: 1941-8264
    Electronic ISSN: 1947-4253
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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