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Lam Chau. An altered basalt dyke crops out on the western side of Lam Chau (0847 1801). It intrudes afine-grained, partly epidotized segment of the granite on Chek Lap Kok. The dyke is greenish-grey, with alteredfeldspar phenocrysts up to 2 mm long, set in a chloritized, quartz-sericite groundmass (HK9211). It is 0.3 m wideand trends northnortheast, cutting a thin quartz vein in the granite. There is no apparent displacement of the vein,indicating that the dyke was not intruded along a fault zone.Tung Chung. In cut slopes 400 m eastnortheast of the ferry pier, there was a temporary exposure (1172 1656) of acompletely weathered basic dyke. The dyke, approximately 3 m wide, trends northnorthwest, and cuts themedium-grained granite on Lantau Island. Similar dykes, trending northnorthwest, occur on the eastern side ofChek Lap Kok, near Kwo Lo Wan.Northwest of Tung Chung (1374 1751), near Kei Tau Kok, a bifurcated, 0.1 to 0.3 m wide basalt dyke cutsfeldsparphyric rhyolite dykes. The dyke is grey and aphanitic, and dominantly consists of plagioclase and epidote,with some interstitial quartz (HK8576). It trends eastnortheast, parallel to the dominant trend of the older rhyolitedykes.Pak Mong. Along the coast (1462 1767) west of Pak Mong, there is an exposed basalt dyke, 0.3 rn wide, trendingeastnortheast, and parallel to the porphyritic microgranite country rock. The basalt is dark greenish- to bluish-grey,partially epidotized, and varies from aphanitic margins to a porphyritic centre. Feldspar phenocrysts are up to10 mm long, and quartz xenocrysts are up to 4 mm. There are also chloritized mafic phenocrysts, set in agroundmass dominated by small feldspar laths, but including chlorite and opaque minerals (HK8573).On a ridge about 1 km southwest of Pak Mong, there is a bluish-grey basalt, or microgabbro dyke, which intrudesfeldsparphyric rhyolite. The dyke, whose thickness cannot be determined, probably trends east, varying tosoutheast, across the ridge. Petrographically, the dyke is not porphyritic, and has a well-developed, sub-ophitictexture of plagioclase and augite. It also contains chlorite and opaque minerals, and small quantities of interstitialquartz. Minor amounts of pyrite can be seen in hand specimens (HK8318).Yam O Wan. Rarely, basalt dykes intrude the tuffs and rhyolite dykes around Yam O Wan. They do so especiallyat the contact between these two rocktypes or, between two rhyolite dykes. For example, a 0.3 m wide basalt dyke(2094 2132) occurs along the contact between two northeast-trending feldsparphyric rhyolite dykes on the east sideof Yam O Wan.At Yam Tsai Wan, there are a number of thin basalt dykes cutting both the Shek Lung Kung member tuff andfeldsparphyric rhyolite dykes. The basalt dykes are typically 0.3 to 0.5 m wide, and trend generally betweennorthwest and northnorthwest. In a 0.5 m wide, easterly-trending dyke, within tuff (1982 2117), there is a small,medium-grained granite xenolith.In the hills east of Yam 0 Wan, there is a 300 m long, 20 to 30 m wide basalt, or lamprophyre dyke (217212), Thehillside is strewn with debris from the dyke, which cuts both tuffs and a rhyolite dyke, The rock is light grey, witha thin, light brown-weathering rind around exhumed corestones. Petrographically, the basalt contains abundantmafic minerals and subordinate plagioclase laths, and includes a small proportion of quartz in the groundmass. Thedyke trends roughly east-west, parallel to the dominant dyke trend in the area.Tai Ho Wan. A swarm of narrow, northerly-trending basalt dykes crops out on the east side of Tai Ho Wan (159181). The dykes are 0.2 to 1 m wide, and intrude rhyolite dykes. They are typically olive green and aphanitic, withquartz-filled amygdales 3 to 4 mm across. The swarm is probably intruded along the northerly trending fault zonethat marks the eastern margin of the Lantau Caldera and which extends through Tai Ho Wan.Tai Che Tung. A large, easterly-trending andesite, or basalt dyke, crops out on the summit of Tai Che Tung (188195). The greenish-grey dyke is only seen as hard, well-rounded corestones with exfoliation shells. It containsprominent feldspar laths, up to 1 mm, set in a groundmass with a grain size of around 0,1 mm, The dyke cutsfeldsparphyric rhyolite and porphyritic microgranite dykes, which also trend dominantly east to eastnortheast.Discovery Bay. There are few basic dykes exposed in the Discovery Bay area, Slope formation in 1989, for thePhase IV development at Hai Tei Wan, exposed a deeply weathered, 2 m-wide lamprophyre, or basalt dyke,trending eastnortheast (2061 1741). The rock is bluish grey when fresh, brown when weathered, and cuts fine- tomedium-grained granite on Lantau Island.Hei Ling Chau. Basalt dykes have been recorded at only two localities on llei Ling Chau One trendseastoortheast, and is only 0.5 m wide. It is foliated, and contains small granite xenoliths (2242 1328). The other(2263 1264) trends eastsoutheast and is 2 m wide. Both dykes cut granite,, 88