Metamorphic episodes of the western foothills of Gunung Ledang (Mt. Ophir), Johore-Malacca, with a background account on the geology

Khoo, T. T. (1983) Metamorphic episodes of the western foothills of Gunung Ledang (Mt. Ophir), Johore-Malacca, with a background account on the geology. Bulletin of the Geological Society of Malaysia, 16. pp. 117-138. ISSN 2637-109X

Abstract

The western foothills area of Gunung Ledang is underlain by a predominantly pelitic group and a calc-silicate group of rocks. The former is made up of both spotted and non-spotted pelitic hornfelses with minor metavolcanics and calc-silicate hornfels. The latter is predominantly calc-silicate hornfels, metavolcanics and thin-banded calc-silicate hornfels and amphibolite. Minor rock types in the calc-silicate group are marble, amphibolite and pelitic hornfelses. These layered rocks are invaded by the Late Cretaceous Ledang granite on the east and the Belading granite on the west. There is evidence of an early regional metamorphism registered in the rocks as relict schistosities and preferred mineral orientation. This episode is believed to be low grade. A second episode of contact metamorphism gave rise to the formation of minerals such as cordierite, sillimanite, andalusite, diopside, forsterite and wollastonite. This is followed by polymetasomatism giving rise to development of axinite, vesuvianite, lime garnet, scapolite, chondrodite and prehnite. Metamorphic zonations are shown by the contact metamorphism and polymetasomatism. It is speculated that the regional metamorphism is a Middle-Late Triassic event if the layered rocks are extensions of the Middle-Late Triassic Gemas beds. The other metamorphic episodes are coeval with the Ledang intrusion of Late Cretaceous age.

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