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Koleksi Tamadun Pahang
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| Abstract : Geological Society of Malaysia |
| Late Cainozoic basaltic rocks of the Kuantan area were first described by Fitch (1952, p. 38) as olivine basalts with or without nepheline. Recently, Hanif (1975), who made a somewhat detailed petrographic and chemical study of these rocks, distinguished two rock types - alkali olivine basalt and basanite (doleritic dykes in Triassic 'granite' in the area arc not considered here). The writer is currently examining these basaltic rocks for petrogenetic considerations. From thin section studies of about 50 specimens, supplemented by a few chemical analyses, several other important rock types have been identified. But what seems to be more significant is that the basaltic rocks of Kuantan belong to two distinct and perhaps independent magma types, alkali olivine basalt magma and olivine nephelinite magma. The former, areally more widespread, is relatively undifferentiated and represented almost exclusively by olivine basalts and rare differentiates like olivine mugearite (?) and possibly basanite. The rock types belonging to the latter, on the other hand, are varied and include olivine nephelinite (dominant), nephelinite, limburgite (only two specimens), basanite, etc. The spatial distribution of these rock types have not yet been fully delineated. However, it appears that olivine basalts by and large occur in the western part whereas olivine nephelinites, etc., are restricted to the eastern side (Fig. 1). The sequence of eruptions of the different types of lavas is not known. But from Hanif's report it appears that olivine nephelinite is, at least in part, later than olivine basalt (incidentally, the basanites described by Hanif are mostly olivine nephelinites). |
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