Radiometric age data from Western Colombia, combined with geological evidence, allow five main plutonic episodes, ranging in age from Triassic to Tertiary, to be recognized. It is suggested that variation in the convergence angle of the oceanic plate relative to the continental edge was an important factor affecting the timing and spatial distribution of plutonic activity. On a regional scale, major breaks in activity are probably best attributed to either low-angle/parallel convergence or periods of accretion along the convergent margin.

The regional geology of Colombia consists of a composite Palaeozoic to Cenozoic sedimentary basin overlying Precambrian shield rocks, which are exposed in the Eastern Cordillera, Magdalena Valley and at least part of the extensive Llanos Plains. A Palaeozoic metamorphic schist belt with abundant post-metamorphic igneous rocks comprises the Central Cordillera. A Mesozoic volcanic suite extends from the western flank of the Central Cordillera and accounts for the bulk of the Western Cordillera. A Cenozoic sedimentary sequence, probably overlying a Late Cretaceous oceanic crust and fore-arc complex, forms the Pacific Coastal Plain. The continental edge of central and southern Colombia is interpreted as a composite margin made up of successively-accreted oceanic island arc related sequences of Palaeozoic, Early Mesozoic and Late Cretaceous ages. The present-day cycle, which began in the Miocene, is not associated with island arc volcanism.

New K/Ar mineral ages from the Barisan Mountains of southern Sumatra suggest four main periods of plutonic activity: Miocene-Pliocene (20–5 Ma), Early Eocene (60–50 Ma), Mid-Late Cretaceous (117–80 Ma) and Jurassic-Early Cretaceous (203–130 Ma). These and all other published ages from exposed plutons in western Sumatra indicate a further period of plutonic activity in the Permian (287–256 Ma). They also suggest either that Early Mesozoic activity began in the Late Triassic, or that there were two distinct magmatic cycles, one in the Late Triassic to Early Jurassic (220–190 Ma) and one extending from the Mid-Jurassic to Early Cretaceous (170–130 Ma). In addition, poorly controlled ages from eastern Sumatra indicate that the important Triassic to Early Jurassic (240–195 Ma) tin-belt magmatism of the peninsular Malaysia Main Range Province extends into that area. Preliminary geochemical studies on the Mesozoic granitoids of the Barisan Range of southern Sumatra confirm that they are calc-alkaline, I-type, metaluminous, subduction-related volcanic arc granites (VAG). They broadly correspond to the southerly extension of a combination of the Central Valley and Western Granite Provinces of Thailand and Burma, and underline the fact that there has been a history of subduction-related magmatism along the southwestern edge of Sundaland since earliest Mesozoic times. The plutonic suites are crudely arranged in subparallel, locally overlapping, NW-SE trending belts, focused along deep-seated faults that have acted as magmatic conduits. It is proposed as a preliminary model that breaks in plutonic activity broadly correspond to changes in approach angle and/or rate of subduction, and that in some instances at least they relate to periods of collision and accretion of allochthonous material (terranes, slivers or blocks) of both oceanic and continental character. At least two such events seem to have occurred during the Mesozoic-Cenozoic tectono-plutonic evolution of Sumatra. One in the early Middle Cretaceous reflects collision and accretion of the oceanic Woyla terranes, and one in the latest Cretaceous is possibly related to collision of a continental sliver/block, the West Sumatra terrane, to the Sundaland margin.

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