Silicic arc volcanism in Central Luzon, the Philippines: Characterization of its space, time and geochemical relationship

Abstract

The silicic volcanic rocks in Central Luzon show a temporal and spatial relationship with its geochemistry. Volcanic centers dated to approximately 5 Ma are silicic in geochemical composition whereas those between <5–1 Ma expose basaltic to andesitic rocks. Volcanic centers dated <1 Ma are characterized by a wide range of geochemistry encompassing basaltic through andesitic to dacitic signatures. Aside from changes in geochemistry through time, the areas (i.e. fore‐arc to back‐arc region) where the volcanic centers are formed also vary. The shift in the location of the volcanic centers in Central Luzon is attributed to changes in the dip of subduction of the South China Sea crust along the Manila Trench. Flat subduction resulted from the subduction of the Scarborough Seamount Chain, an oceanic bathymetric high along the Manila Trench west of northern Luzon. However, collision of Luzon with Taiwan in the north and Palawan in the south resulted in steepening of the subduction angle. The silicic volcanic centers in the forearc (Ce/Yb = 20–140) and back‐arc (Ce/Yb = 20–60) regions are generally characterized by higher Ce/Yb compared to the basaltic‐andesitic volcanic rocks in the main volcanic arc (Ce/Yb = 20) and back‐arc (Ce/Yb = 20–30) regions. This across‐arc geochemical variation highlights the contributions from the slab, mantle and crust coupled with the effects of geochemical processes that include partial melting, fractionation, magma mixing and mantle–melt interaction.

Tectonic setting of a composite terrane: A review of the Philippine island arc system

“…In closing, the different volcanic arc rocks in the Philippines manifest geochemical signatures that show the influence of the mantle, crust, subducted slab, sediments, and even mantle plumes, similar to what has been observed in other parts of the world (e.g., Sajona et al, 2000;Yumul et al, 2003c;Macpherson et al, 2006;Currie et al, 2007;Ingle et al, 2007).…”

Characterization of the Pleistocene Volcanic Chain of the Bicol Arc, Philippines: Implications for Geohazard Assessment

“…Geochemical and petrographic analyses of the Pleistocene samples of the Bicol Arc reveal that magma mixing was a dominant factor in their magmatic evolution similar to what has been noted elsewhere (e.g., Yumul et al 2003a, b;De Hoog et al 2004). Major element plots in Harker diagrams define linear trends, which to a first order of approximation, suggest magma mixing.…”

“…The Philippine archipelago, which lies at the junction of two oppositely-dipping subduction zones, is characterized by several volcanic arcs (e.g., Yumul et al 2003a, b). On its western side, subduction along the east-dipping Manila-Negros-Cotabato trench system produced the Taiwan-Luzon, Negros-Masbate and Cotabato arc systems.…”

Adakitic rocks in the Masara gold-silver mine, Compostela Valley, Mindanao, Philippines: Different places, varying mechanisms?

“…This is further complicated by the recognition that not all adakites are formed in the forearc region, as originally envisioned by Defant and Drummond (1990). Adakites are also found in the main volcanic arc region and even in the back-arc side (Yumul et al, 2003a;Chiaradia et al, 2009b;Castillo, 2012), thus suggesting a non-amphibolitic subducted slab source region but an eclogitic one. This is inconsistent with the slab melting origin of adakites.…”

“…Bellon and Yumul, 2001;Yumul et al, 2003a). Adakites have also been encountered in the main volcanic arc, back-arc, or intraplate regions where subduction of young, hot subducted slab was not a necessary component to form these rocks.…”