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| Titel |
Detrital Zircon U-Pb and Hf-isotope Constrains on Basement Ages, Granitic Magmatism, and Sediment Provenance in the Malay Peninsula |
| VerfasserIn |
Inga Sevastjanova, Benjamin Clements, Robert Hall, Elena Belousova, Norman Pearson, William Griffin |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250041523
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| Zusammenfassung |
| The Malay Peninsula forms the western part of central Sundaland in SE Asia. Sundaland
comprises Indochina, the Thai-Malay Peninsula, Sumatra, Java, Borneo, and the shallow
shelf between these landmasses. It is a composite region of continental crustal fragments that
are separated by sutures that represent remnant ocean basins and volcanic arcs. The Malay
Peninsula includes two of these fragments – East Malaya and Sibumasu – separated by the
Bentong-Raub Suture Zone. The latter is a Palaeo-Tethyan ocean remnant. Granitoids of the
Malay Peninsula are the major sources of detrital zircon in Sundaland. East Malaya is
intruded by Permian-Triassic Eastern Province granitoids interpreted as products of
Palaeozoic subduction of oceanic crust beneath the East Malaya Volcanic Arc. Sibumasu is
intruded by Triassic Main Range Province granitoids interpreted as syn- to post-collisional
magmatism following suturing to East Malaya. Locally, there are minor Late Cretaceous
plutons.
Basements of Sibumasu and East Malaya are not exposed and their ages are poorly
constrained. The exact timing of the collision between these fragments is also contentious. In
order to resolve these uncertainties, 752 U-Pb analyses from 9 samples were carried out on
detrital zircons from modern rivers draining the Malay Peninsula and, of these, 243 grains
from 6 samples were selected for Hf-isotope analyses.
U-Pb zircon ages show that small numbers of Neoarchean-Proterozoic grains are consistently
present in all samples, but do not form prominent populations. Permian-Triassic populations
are dominant. Only one sample contains a small Jurassic population probably sourced from
the area of Thailand and most likely recycled from fluvial-alluvial Mesozoic ‘red-beds’. Late
Cretaceous populations are locally abundant.
Hf-isotope crustal model ages suggest that basement beneath the Malay Peninsula is
heterogeneous. Some basement may be Neoarchean but there is no evidence for basement
older than 2.8 Ga beneath the Malay Peninsula. Both Sibumasu and East Malaya basements
are Paleoproterozoic, but of different ages.
176Hf/177Hfi ratios suggest that Permian-Triassic zircons were sourced from three major
magmatic suites: (a) Permian crust-derived granitoids, (b) Early-Middle Triassic granitoids
with a mixed mantle- and crust-derived source, and (c) Late Triassic crust-derived granitoids.
This suggests three major Permian-Triassic episodes of magmatism in the Malay Peninsula.
Two of these episodes (a and b) occurred in the Eastern Province. This suggests
a multi-phase evolution of the East Malaya Volcanic Arc. Crust-derived zircon
Hf-isotope signatures are unusual for a continental margin arc and may indicate
contamination from older crust beneath the East Malaya fragment. A Late Permian-Early
Triassic gap in magmatism and subsequent change of zircon source may indicate
a micro-collision around 260-270 Ma (e.g. with an island arc or a seamount on
the Paleo-Tethys oceanic crust). U-Pb ages and Hf-isotope composition of zircons
sourced from the Main Range Province granitoids suggest that Sibumasu-East Malaya
collision occurred by Late Triassic, but it is not clear when exactly this collision
initiated.
Different Hf-isotope signatures of Triassic zircons can be used as indicators of sediment
provenance from the Malay Peninsula. Crust-derived signatures are diagnostic of
Triassic zircons from the Main Range Province source, whereas mixed crust- and
mantle-derived signatures of similar age zircons indicate Eastern Province source. |
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