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

Abstract

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 Domemore » 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.« less

Authors:
 [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
Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1488782
Report Number(s):
LLNL-JRNL-752477
Journal ID: ISSN 0022-3530; 938687
Grant/Contract Number:  
AC52-07NA27344
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Petrology
Additional Journal Information:
Journal Volume: vol. 59; Journal Issue: no. 10; Journal ID: ISSN 0022-3530
Publisher:
Oxford University Press
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES

Citation Formats

DesOrmeau, Joel W., Gordon, Stacia M., Little, Timothy A., Bowring, Samuel A., Schoene, Blair, Samperton, Kyle M., and Kylander-Clark, Andrew R. C. Using eclogite retrogression to track the rapid exhumation of the Pliocene Papua New Guinea UHP Terrane. United States: N. p., 2018. Web. doi:10.1093/petrology/egy088.
DesOrmeau, Joel W., Gordon, Stacia M., Little, Timothy A., Bowring, Samuel A., Schoene, Blair, Samperton, Kyle M., & Kylander-Clark, Andrew R. C. Using eclogite retrogression to track the rapid exhumation of the Pliocene Papua New Guinea UHP Terrane. United States. doi:10.1093/petrology/egy088.
DesOrmeau, Joel W., Gordon, Stacia M., Little, Timothy A., Bowring, Samuel A., Schoene, Blair, Samperton, Kyle M., and Kylander-Clark, Andrew R. C. Tue . "Using eclogite retrogression to track the rapid exhumation of the Pliocene Papua New Guinea UHP Terrane". United States. doi:10.1093/petrology/egy088. https://www.osti.gov/servlets/purl/1488782.
@article{osti_1488782,
title = {Using eclogite retrogression to track the rapid exhumation of the Pliocene Papua New Guinea UHP Terrane},
author = {DesOrmeau, Joel W. and Gordon, Stacia M. and Little, Timothy A. and Bowring, Samuel A. and Schoene, Blair and Samperton, Kyle M. and Kylander-Clark, Andrew R. C.},
abstractNote = {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.},
doi = {10.1093/petrology/egy088},
journal = {Journal of Petrology},
number = no. 10,
volume = vol. 59,
place = {United States},
year = {2018},
month = {9}
}

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