About Us

The Geology of Hong Kong (Interactive On-line)
Tsing Shan Granite - Jms


The Tsing Shan Granite (Table 6.2) forms an elliptical pluton in the western New Territories with its outcrop extending from Lung Kwu Chau in the south to Tsim Bei Tsui in the north (Figure 6.3). The western boundary of the pluton is defined by the Deep Bay Fault and the eastern boundary by the Tuen Mun Fault. Contacts with adjacent rocks are faulted making determination of intrusive relationships impossible. However, offshore boreholes drilled between Pillar Point and Lung Kwu Chau suggest that the Tsing Shan Granite has intruded the Tai Po Granodiorite.


The Tsing Shan Granite is composed of variably deformed, equigranular to inequigranular two-mica monzogranite (Plate 6.11). It is typically strongly deformed and recrystallized although southernmost exposures on Lung Kwu Chau are only weakly deformed. The degree of deformation generally increases from southwest to northeast. In the porphyritic lithologies, large (7–9 mm) anhedral phenocrysts (megacrysts) of microcline, orthoclase, quartz and plagioclase are set in a fine-grained, partly recrystallized, granular matrix of quartz, alkali feldspar, plagioclase and biotite. Feldspar megacrysts are commonly veined by quartz. Plagioclase is weakly concentrically zoned and typically has cloudy cores. In the equigranular lithologies, alkali feldspar consists of weakly concentrically-zoned and weakly strained mesoperthite and microcline. Greenish brown biotite is the chief mafic mineral. Plagioclase is oligoclase to albite in composition. Muscovite typically occurs as a late stage primary mineral infilling interstices between quartz and feldspar. Accessory minerals include zircon, allanite, and monazite.


A whole-rock Rb–Sr isochron age of 152 ± 6 Ma has been obtained for the Tsing Shan Granite (Darbyshire, 1993). However, zircon U–Pb age-dating of the granite has indicated an age of <159.6 ± 0.5 Ma (Davis et al., 1997) suggesting a similar emplacement age to the Tai Lam Granite.




Details