Gallego (volcano)

The oldest basement rocks date back to the Cretaceous and are made up of ocean flood basalts from previous Large igneous provinces (LIPs) which makes up the Guadalcanal terrane.^[2]

Initially subduction was north of Gallego. Between 25 and 20 Ma, the Ontong Java Plateau made it to the subduction zone. Due to the thick crust of the Ontong Java Plateau, subduction ceased. Moderen subduction began 5-8 Ma, where subduction underwent a subduction polarity reversal, creating the modern subduction orientation south of Gallego. Subduction continues today which created the southern Solomon Islands, including Guadalcanal and Gallego.^[3]

The central Gallego volcanic ridge has 4 distinct craters; Gallego, Popori (oldest), Talulu, and Komambulu. The caldera structure has been deeply eroded away, with only the volcanic interior visible today. Lava/pyroclastic laharic flows are seen extending from the central crater. It is thought that this volcanic complex was quite wide measuring (12 km/7.5 miles) across.^[4]

Lava composition varies greatly with layers of basalt, basaltic andesite, andesite, dacite, and rhyolite. These are moderate in calc-alkali. Mineralisation occurs as sulphide stockworks of porphyry-copper style, as sulphides in the andesites and volcanic porphyries and as hydrothermal epithermal mineralisation in altered, reworked andesitic pyroclastics (Gold Ridge, Guadalcanal).^[5]

• List of volcanoes in Solomon Islands
• Guadalcanal