The iron ore deposits of Ulu Rompin, Malaya

Abstract

The Ulu Rompin iron deposits are located in an area of rugged topography in the State of Pahang, Malaya. There are several high grade primary ore bodies and superficial sheets of lateritic ore. The area is underlain by sheared alkalic rhyolite lavas and tuffs in which there are small lenses of sedimentary rocks, carbonates being the most important. There are several small stocks of hornblende granodiorite which probably merge into one larger parental mass at depth. The Bt Ibam ore body, which is the largest, is a tabular mass of magnetite in a highly magnesian gangue, originally chlorite and actinolite but now largely altered to talc. Underneath the ore there is a thin intermittent layer of calcic skarn, while massive chlorite appears along parts of the hanging wall. A short distance below the footwall there is granodiorite. The Bt. Batu Puteh deposit is magnetite associated with calcite marble, and at Bt. Hitam magnetite is found just above granodiorite. At Bt. Pesagi and BT. Sanlong the primary ore is haematite with very little magnetite. These bodies are located in shear zones in the volcanic rocks, and are not associated with calcic or magnesian minerals. All the ore bodies and country rocks have been pyritized, and other sulphides and sulphosalts have impregnated the Bt. Ibam body. These have produced zones, contaminated by copper and zinc, and to a lesser degree bismuth and lead. Hypogene and supergene alteration have extensively affected the iron ores and rocks and caused some redistribution of the impurity elements. The iron ores probably originated in the cooling granodiorite magma and were transported as chlorides or chloride complexes. The control over the loci of mineralization was partly lithological - magnetite bodies in calcic and magnesian rocks, and partly structural - haematite bodies in shear zones.