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Rapid cooling and exhumation as a consequence of extension and crustal thinning: Inferences from the Late Miocene to Pliocene Palu Metamorphic Complex, Sulawesi, Indonesia

Hennig, Juliane; Hall, Robert; Forster, Marnie; Kohn, B P; Lister, Gordon

Description

Metamorphic complexes forming high mountains of 1.5–2 km in Western Sulawesi were previously considered to be Mesozoic or older basement of Gondwana crust. However, many of the metamorphic rocks are much younger than previously thought. Some have Eocene sedimentary protoliths. New geothermobarometric and geochronological data from metamorphic rocks of the Palu Metamorphic Complex (PMC) and associated granitoids provide information on the timing and mechanisms of Neogene metamorphism and...[Show more]

dc.contributor.authorHennig, Juliane
dc.contributor.authorHall, Robert
dc.contributor.authorForster, Marnie
dc.contributor.authorKohn, B P
dc.contributor.authorLister, Gordon
dc.date.accessioned2021-09-08T22:51:01Z
dc.identifier.issn0040-1951
dc.identifier.urihttp://hdl.handle.net/1885/247701
dc.description.abstractMetamorphic complexes forming high mountains of 1.5–2 km in Western Sulawesi were previously considered to be Mesozoic or older basement of Gondwana crust. However, many of the metamorphic rocks are much younger than previously thought. Some have Eocene sedimentary protoliths. New geothermobarometric and geochronological data from metamorphic rocks of the Palu Metamorphic Complex (PMC) and associated granitoids provide information on the timing and mechanisms of Neogene metamorphism and contemporaneous rapid exhumation. The metamorphic rocks are strongly deformed and some were partially melted to form migmatites. Schists contain relict andalusite, cordierite, staurolite and Mn-rich garnet which are wrapped by a pervasive fabric. 40Ar/39Ar dating of biotite, white mica and amphibole from strongly deformed, mylonitic schists and recrystallised amphibolites reveals cooling occurred in the Early Pliocene (c. 5.3–4.8 Ma) in the northern part and during the Late Pliocene (c. 3.1–2.7 Ma) in the southern part of the PMC. U-Pb, 40Ar/39Ar and (U-Th)/He analyses of various minerals from PMC metamorphic and S-type magmatic rocks give very similar mid to Late Pliocene ages, indicating very fast cooling and rapid exhumation, and show the high speed at which tectonic processes, including magmatism, exhumation, and reworking into a sediment, must have occurred. The high rates could be unique to this area but we suggest they record the true speed of metamorphic complex exhumation in a very young orogenic belt. Rates in older orogens appear lower because they are averages measured over longer periods of time. Contemporaneous magmatism and deformation are interpreted as a consequence of decompressional melting due to extension and thinning of the crust, promoted by possible detachment faults and normal faulting at the major NW-trending Palu-Koro and Tambarana Faults. In contrast, I-type magmatic rocks, separated from the PMC by the Palu-Koro Fault, were exhumed from upper crustal levels by erosion at moderate rates.
dc.description.sponsorshipThis study was supported by the SE Asia Research Group which is funded by a consortium of oil companies.
dc.format.mimetypeapplication/pdf
dc.language.isoen_AU
dc.publisherElsevier
dc.rights© 2016 Elsevier B.V
dc.sourceTectonophysics
dc.subjectSE Asia
dc.subjectPalu Metamorphic Complex
dc.subjectRapid exhumation
dc.subjectCooling histories
dc.subject40Ar/39Ar
dc.subject(U-Th)/He
dc.titleRapid cooling and exhumation as a consequence of extension and crustal thinning: Inferences from the Late Miocene to Pliocene Palu Metamorphic Complex, Sulawesi, Indonesia
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume712
dc.date.issued2017
local.identifier.absfor040312 - Structural Geology
local.identifier.ariespublicationu4027924xPUB600
local.type.statusPublished Version
local.contributor.affiliationHennig, Juliane, Royal Holloway University of London
local.contributor.affiliationHall, Robert , Southeast Asia Research Group, Department of Earth Sciences, Royal Holloway University of London
local.contributor.affiliationForster, Margaret, College of Science, ANU
local.contributor.affiliationKohn, B P, University of Melbourne
local.contributor.affiliationLister, Gordon, College of Science, ANU
local.description.embargo2099-12-31
local.identifier.doi10.1016/j.tecto.2017.06.025
local.identifier.absseo970104 - Expanding Knowledge in the Earth Sciences
dc.date.updated2020-11-23T11:00:46Z
local.identifier.scopusID2-s2.0-85032947148
local.identifier.thomsonID000409284500044
CollectionsANU Research Publications

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