The structural evolution of the Bentong-Raub Zone and the Western Belt around Kuala Lumpur, Peninsular Malaysia

Abstract

To determine what deformed the inherited Bentong-Raub suture zone in western Peninsular Malaysia, a detailed field study in the area around Kuala Lumpur was conducted focussing on the various structural, metamorphic and kinematic features of the Bentong-Raub Zone and the surrounding Western- and Central Belts. The in-depth knowledge on large-scale structures and the tectonic origin of the study area was used to develop a tectonic model for the evolution of western Malaysia. Four deformation phases were recognized in the field, of which the most prominent one, D1, is a progressive deformation phase comprising two foliations, two folding geometries and coeval shear, and can be related to NE-SW shortening. Presumably, this deformation corresponds to accretionary wedge formation during northward subduction of the Paleo-Tethys Ocean beneath Indochina. Burial of sediments in this accretionary wedge led to the growth of biotite, muscovite, chlorite, garnet, quartz and feldspar under greenschist facies metamorphic conditions. Sedimentation and subsequent deformation and burial-related sub-greenschist facies metamorphism of a Triassic forearc basin recorded a second deformation event D2. Intrusion of the Triassic S-type Main Range Granites caused contact metamorphism in the surrounding metasediments and was followed by steep normal faulting (D3) and a later, regional strike-slip shearing event (D4). The combined effect of D3 and D4 is thought to have played a major role in the exhumation of western Peninsular Malaysia during Paleogene times. It is also suggested that this shear is related to Eocene formation of offshore sedimentary basins due to Indian-Eurasian collision and subsequent clockwise rotation of south-east Asia.