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Title: Using eclogite retrogression to track the rapid exhumation of the Pliocene Papua New Guinea UHP Terrane

Journal Article · · Journal of Petrology
 [1];  [1];  [2];  [3];  [4];  [5];  [6]
  1. Univ. of Nevada, Reno, NV (United States). Dept. of Geological Sciences
  2. Victoria Univ. of Wellington (New Zealand). School of Geography, Environment and Earth Sciences
  3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Dept. of Earth, Atmospheric, and Planetary Sciences
  4. Princeton Univ., NJ (United States). Dept. of Geosciences
  5. Princeton Univ., NJ (United States). Dept. of Geosciences; Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Nuclear and Chemical Sciences
  6. Univ. of California, Santa Barbara, CA (United States). Dept. of Earth Science
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The D’Entrecasteaux Islands of eastern Papua New Guinea (PNG) host the youngest known ultrahigh-pressure terrane on Earth and represent the only location where ultrahigh-pressure (UHP) rocks have been exhumed in an active rift. The PNG (U)HP rocks, consisting of Pliocene eclogites, garnet amphibolites and migmatitic gneisses, are exposed in five domal structures across the Islands. Zirconium-in-rutile thermometry records peak temperatures of ~780°C from the eastern Oiatabu and nearby central Mailolo Domes, and hotter temperatures of ~825–865°C within the western Goodenough Dome. Uranium–lead (U–Pb) and trace element zircon compositions from a suite of eclogite, host gneiss, felsic dikes and pegmatite from three domes document the rapid exhumation history of the PNG UHP terrane. High-spatial resolution laser-ablation split-stream inductively coupled plasma-mass spectrometry (LASS ICP-MS) analyses of select eclogite zircons exhibit no resolvable age zoning within single crystals. The same eclogite zircons, combined with separate zircons extracted from additional eclogite, host gneiss and felsic intrusions, were subsequently analysed by high-precision U–Pb chemical-abrasion isotope-dilution thermal ionization mass spectrometry and solution ICP-MS trace element analysis (TIMS-TEA). The results record discrete tectonic events across the three domes at sub-million year timescales: (1) (re)crystallization of host gneiss within the lower crust exposed in the eastern Oiatabu Dome from c.5·7–4·5 Ma; (2) initial retrogression and local decompression melting of eclogites from the Oiatabu and Mailolo Domes at c.4·6–4·3 Ma; (3) melt crystallization of weakly deformed felsic dikes of the Oiatabu Dome at c.3·0–2·9 Ma; and (4) retrogression and melt crystallization within eclogite–amphibolite-facies rocks in the western Goodenough Dome at c.2·9–2·6 Ma. In comparison to Zr-in-rutile peak temperature estimates, Ti-in-zircon temperatures >800°C may reflect increased temperatures during exhumation that resulted in partial melting of the eclogites. Inclusions of crystallized hydrous melt consisting of Na-rich plagioclase ± K-feldspar + quartz within eclogite zircons document this process. The elevated temperatures and the presence of the polyphase inclusions are the first documentation of partial melting of the (U)HP eclogites within PNG during initial retrogression from c.4·6–4·3 Ma. Finally, overall, U–Pb zircon geochronology and geochemistry track both the timing of retrogressive overprinting within the lower-to-middle crust and final upper crustal emplacement over a relatively short span of ~2 Myr during the rapid (≥2·3 cm/yr) exhumation of the youngest known (U)HP eclogites.

Research Organization:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
AC52-07NA27344
OSTI ID:
1488782
Report Number(s):
LLNL-JRNL-752477; 938687
Journal Information:
Journal of Petrology, Vol. vol. 59, Issue no. 10; ISSN 0022-3530
Publisher:
Oxford University PressCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 8 works
Citation information provided by
Web of Science

Cited By (1)

An experimentally calibrated thermobarometric solubility model for titanium in coesite (TitaniC) journal April 2019

Figures / Tables (11)

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Fig. 10(p. 81)figure Fig. 10
Fig. 11(p. 82)figure Fig. 11

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