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About 1 km east of Nam Shan, exposures (1730 1280) of feldsparphyric rhyolite are partly hydrothermally alteredwithin, and adjacent to, the syenite outcrop, indicating that the syenite is younger than the rhyolite dykes.long Fuk Quartz syenite at Tong Fuk crops out as four discrete bodies. The largest, underlying Ma Po PingPrison, gives rise to the boulder-strewn hillside, and is well exposed in cuttings on the South Lantau Road. Anoffshoot of this body occurs on the coast to the south. A third body, north of Tong Fuk, is poorly exposed along thecatchwater, and a fourth, very small body is well exposed on the coast west of the prison.The contact between quartz syenite, with a trachytoid texture, and banded lava cannot be seen on the road to theprison, although both rock types have been observed within a few metres of each other (1068 0987). The syenitealso has a fine-grained groundmass, probably resulting from chilling at the margin.Exposures (1065 0964) of typical, fresh syenite occur on the South Lantau Road, south of the prison. The rock islight grey, with feldspar megacrysts up to 7 mm long, set in a fine-grained groundmass. No xenoliths can be seen,and they have not been observed in corestones in the area either. These corestones are typically set in areddish-brown, clay-rich saprolitic soil.Coastal exposures west of the prison (1016 0973) are dominantly composed of sparsely porphyritic, quartz syenite,contrasting with the markedly porphyritic boulders on the shoreline 100 m to the east. The rock is pale grey, with amarked flow-banding in the western part of the exposure. This flow-banded margin, composed of porphyritictrachyte, has sparse quartz phenocrysts, up to 2 mm, and feldspar phenocrysts up to 4 mm long. The contact withthe overlying lavas dips 39° southwest. The syenite is intruded by two basalt dykes, respectively 0.1 and 0,3 mwide. These dykes do not cross the adjacent lavas. The trachytic contact clear indicates that the syenite formed adome-like intrusion in the older lavas.Fan Lau. Quartz syenite extends from the north shores of Fan Lau Tung Wan and Fan Lau Sai Wan, throughHeung Chung Au to Peaked Hill (Kai Yet Kok). A small body also occurs east of Fan Lau Fort. At the northern endof the pier at Fan Lau Sai Wan (0242 0740), the rock is typically pinkish-grey, mottled black, porphyritic,fine-grained quartz syenite. Feldspar megacrysts are up to 15 mm long, although most are less than 8 mm, and thegroundmass has a grain size of less than 0.5 mm. Boulder-strewn hill slopes occur to the north, and the edge of theintrusion is marked by the change from cuboidal corestones to rubbly debris on the lower flanks of the hill.Contact relationships with the adjacent, fine-grained granite can be seen 230 m west of the Fan Lau Sai Wan pier.The contact is sharp, trends southeast, and is marked by a biotite enrichment in the syenite. Quartz veins in thegranite do not cross into the quartz syenite, confirming that the syenite is the younger of the two. 300 m furtheralong the coast, there are exposures of partially mylonitized granite close to syenite. The quartz syenite containslarge xenoliths, including fine-grained granite, up to 2 m across. About 300 m to the northwest, there is a 0.6m-wide dyke of quartz syenite, trending eastnortheast, which intrudes the fine-grained granite country rock.Porphyritic, fine-grained quartz syenite is exposed around high water mark on the northeastern tip (0138 0878) ofPeaked Hill (Kai Yet Kok). Flow-aligned alkali feldspar laths, up to 15 mm long, define a trachytoid texture. Thequartz syenite is in close proximity to boulders of fractured granite and exposures of fine- to medium-grainedgranite, and appears to have been intruded along a fault zone within the older granite that trends northwest fromFan Lau to Peaked Hill.To the east of Fan Lau Tsuen, a contact (0321 0717) between quartz syenite and granite occurs at the northern endof the beach. About 200 m to the east (0344 0725), a trachytoid texture and contact with adjacent raetavolcanicshas been observed.No contact relationships were seen in the outcrop near Fan Lau Fort, although at one locality (0286 0658) thesyenite has a marked north-south trending trachytoid texture.Sha Lo Wan. The only outcrops of quartz syenite on the north side of Lantau Island are between Tung Chung Wanto the east and Sha Lo Wan in the west. The outcrop consists of two elongate bodies, each over 1 km long but lessthan 500 m wide, trending westnorthwest along the contact between volcanics to the south, and granite intrusionsto the north, /fft addition, a small syenite dyke lies close to the contact between granite and Carboniferoussedimentary rocks at San Shek WanThe largest outcrop of syenite is south and east of Sha Lo Wan Village, but exposures are poor on the steep, thicklyvegetated slopes. In a stream bed (0787 1607) south of the village, there are exposures of porphyritic, fine-grainedquartz syenite with tabular, euhedral alkali feldspar megacrysts up to 10 mm across. The syenite is also exposedclose to fine-to medium-grained granite in a stream 300 m to the east (0618 1616), and on the hillside to thesoutheast (0640 1597).75