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KUANTAN BASALT Largest body of mafic intrusives in the Malay Peninsula

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KUANTAN BASALT Largest body of mafic intrusives in the Malay Peninsula

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  1. New Trace, Major and Rare Earth Element data for the Early Pleistocene Alkali Olivine Basalts and Olivine Nephelinites from Kuantan, Pahang: Plume-related Rift Volcanics or Wrench-related Crustal Extension?Azman A Ghani and Nur Iskandar TaibDepartment of Geology University of Malaya 50603 Kuala Lumpur, MALAYSIA

  2. KUANTAN BASALT Largest body of mafic intrusives in the Malay Peninsula Generally not well exposed, forms a distinctive deep red/chocolate colored soil. Also Pantai Batu Hitam 2 units – Alkali olivine basalt Olivine nephelinite Age: 1.6 Ma (Pleistocene)

  3. Tectonic Setting • Alkali basalts – • Early stages of Oceanic Island magmatism • Continental Rifting • Backarc Spreading

  4. Regional tectonics – Evidence for crustal extension on the East Coast • Dolerite dikes in granites • 110 Ma • Sedimentary basins • Began as rifts, continued subsidence due to wrench tectonics as a result of the Indian subcontinent colliding with Asia

  5. Kuantan Basalt Tjia, 1999 fig. 7.16

  6. South Indochina Basalt Province Axial Malay Fault Zone Triple Junction High heat flow Tjia, 1999 fig. 7.11 Midai Island Kuantan Basalt Penyu Basin Occurrences of Alkali Basalt

  7. Regional tectonics – Timing • 110 Ma(Albian)– onset of rifting due to mantle plume • Initial opening of Malay, Penyu and West Natuna basins, high heat flow in basins. Dolerite dikes in granite • 40 Ma – 25 Ma (Late Oligocene) – Wrench-based extension in Malay and Penyu (most likely also West Natuna) basins. • Synrift sediments, structures • 14 Ma (Mid-Miocene)– Present (but mostly before 11Ma) – Compression and inversion • Reversal of strike slip faults and normal faults, compression-like structures • 1.6 Ma (Pleistocene) – Eruption of Kuantan Basalt

  8. Origin of Kuantan Basalt • Mantle plume • As a result of wrench-induced extension (i.e. “pull apart” rifting) • As a result of compression (localized pull-apartism?) • Old block of rift/backarc basalt, remobilized

  9. Origin of Kuantan Basalt the devil is in the details • Mantle plume • No evidence of one under Kuantan at this time • Much younger than dolerites (110 Ma) • As a result of wrench-induced extension (i.e. “pull apart” rifting) • To late, region is under compression, has been for 14 Ma • As a result of compression (localized pull-apartism?) • Again, too late (major compression was 12.5-11 Ma) • Old block of rift/backarc basalt, remobilized • Remobilizing basalt is impractical (high T needed)

  10. QUACK! • Kuantan Basalt trace/REE signature looks like OIB/Rift • Caveat: What would a wrench-extension produced basalt look like? • Don’t know yet, will have to look at early pull-apart basin magmatism • Probably very different (shallow melting, probably greater degree of partial melting, so LREE/Incompatible Element enrichment will be less, or even negative compared to E-Morb)

  11. Origin of Kuantan Basalt the devil is in the details • Mantle plume • No evidence of one under Kuantan at this time • Much younger than dolerites (110 Ma) • As a result of wrench-induced extension (i.e. “pull apart” rifting) • To late, region is under compression, has been for 14 Ma • As a result of compression (localized pull-apartism?) • Again, too late (major compression was 12.5-11 Ma) • Old block of rift/backarc basalt, remobilized • Remobilizing basalt is impractical (high T needed) • Origin of Kuantan Basalt the devil is in the details • Mantle plume • No evidence of one under Kuantan at this time • Much younger than dolerites (110 Ma) • As a result of wrench-induced extension (i.e. “pull apart” rifting) • To late, region is under compression, has been for 14 Ma • As a result of compression (localized pull-apartism?) • Again, too late (major compression was 12.5-11 Ma) • Old block of rift/backarc basalt, remobilized • Remobilizing basalt is impractical (high T needed) • Continued activity of the Malay Dome mantle plume

  12. Continued activity of the Malay Dome mantle plume? • Heat flow in the Malay and Penyu basins, close to the triple point, are quite high, even to this day • Wrench and inversion tectonics has resulted in numerous major faults in the region, and might provide a weak zone facilitating the movement of magma • Alkali basalt province in Indochina shows ages from Miocene to Recent – long lived magmatism over a plume is possible • Plume is under Sundaland, overlying plate movement is slow/nonexistent with respect to hot spot frame of reference

  13. Future work? • Find samples of Penyu Basin basalts • Geochemistry of Vietnam and Natuna basalts

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