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GEOLOGY AND GEOCHEMISTRY OF CANLAON VOLCANO,
NEGROS ISLAND, PHILIPPINES

M.L. Martinez-Villegas1, M.A.V. Bornas2,
M.I.T. Abigania1
and E.L. Listanco2
1
Philippine Institute of Volcanology and Seismology (PHIVOLCS)
2U.P. National Institute of Geological Sciences (UPNIGS)
 

 

 

 

ABSTRACT



Canlaon Volcano's history consists of both pyroclastic flow and lava flow eruptions, including at least one major debris avalanche event. The debris avalanche event was followed by rebuilding of the Canlaon edifice by subsequent pyroclastic flow and lava flow eruptions. Three major types of pyroclastic flow deposits have been identified : (a) Canlaon Block-rich Pyroclastic Flow deposit; (b) Canlaon Scoria-rich Pyroclastic Flow deposit; and (c) Canlaon Pumice-rich Pyroclastic Flow deposit. There are at least 4 main types of lava flow units namely: (a) pyroxene andesite; (b) hornblende pyroxene andesite; (c) pyroxene basaltic andesite and (d) olivine-bearing basalt-basaltic andesite.


New set of stratigraphic data in combination with petrochemical data were used to establish the stratigraphic relationship of Canlaon Volcano products and to characterize in detail the chemistry of its eruptive products through time. The interspersed relationship of the various pyroclastic flow and lava flow units suggests shifts in eruptive behavior from explosive to effusive episodes.

The composition of the different products from Canlaon generally fall within dominantly high-K basaltic andesite to andesite to dacitic compositional range (with 52-63 wt% SiO2 and 1.46-3.43 wt% K2O). Mg# of lavas fall within two separable ranges, those with Mg# within 60-67 and 37-48. Canlaonís chemical evolution, in the context of its presently known volcano stratigraphy is not a simple progression from basaltic to silicic trend. The chemical composition of magmas through time has varied back and forth from basaltic-basaltic andesite to andesite to dacitic which suggests possibly several episodes of magma re-supply from depth.


Understanding the wide variety of eruptive products and temporal variation of compositions based on stratigraphic relationships is crucial to the hazards assessment of Canlaonís future activities.
 

 

 

 

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