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Chapter 7StructureIntroductionThe solid geology of the Lantau district is dominated by late Jurassic igneous rocks. The majors^cturd features of the district also date from this period. The magmatism, of which thedevelopment of the JLantau Caldera is the most obvious expression in the district, is a localrepresentative of the yoluininous silicic^ volcanic and plutonic zone that extends along the broadcoastal belt of soutiieastern China, the belt is also characterized by a northeast-trending fold andfault zone and includes structurally complex basement terranes. The Jujassjcj^gbnal tectpmsmand magmatism are related to the Yenshanian Orogeny which exploited and reactivated basementstructures.The Lantau district, and Hong Kong in general, lie within the major, northeast-trending LianhuaShan Fault Systen^ift^,Jha»Yenshamdan, ojogenjc belt. The fault ^ejcomj^es^^mm^usindividual faults and shear zones, of which thruslsj^faults are the dominantcomponents, they typically' Tiave curvilinear traces, tens to'Post-Yenshanian faulting, which was largely brittle, is also evident on Lantau Island. The mainfaults in the Hong Kong area are shown in Figure 9.Most of the major events in the district's structural evolution occurred during a relatively shortperiod in the Late Jurassic, and include the following principal structural elements: reversefaulting involving basement rocks; structures related to Jurassic granitoid plutonism, dykeemplacement and the evolution of the Late Jurassic Lantau Caldera; and post-caldera faulting ofthree main orientations. The case for and against neotectonics is also briefly examined.NHuizhou0 10 20 30 kmLianhua Shan Fault SystemInShenzhen Fault Zone1 Nigang Fault2 Henggang Fault3 Tianluokeng Fault4 Yantian Fault5 Jingxinbei FaultHaifeng Fault ZoneFigure 9 - Main Faults in the Vicinity of Hong Kong (after Lai, 1993)95