Hydrothermal events in Hong Kong: constraints on timing and depth of occurrence, by Prof Chan Lung Sang
Prof Chan Lung Sang
(PHKU and HKU SPACE)
Prof Chan Lung Sang is currently Principal of HKU SPACE Community College and HKU SPACE-Po Leung Kuk Stanley Ho Community College, as well as professor in Department of Earth Sciences at HKU. He received his bachelor degree from CUHK and his Masters and PhD in geology and geophysics from University of California-Berkeley. He taught geology at the University of Wisconsin for 10 years before he joined The University of Hong Kong in 1994. His research interests include the tectonics and geology of South China and applied geophysics. He has been actively promoting science education in Hong Kong. Currently he is a member of the Board of Directors of the HK Academy for Gifted Education and scientific advisor of HK Observatory. He chaired the Geological Society for the period 2001-2005 and was invited to be a guest host in several television documentaries on earth science subjects. In 2010, he was bestowed the first University Distinguished Teaching Award by The University of Hong Kong and the Best Original Research Award by HK Medical Journal in 2013.
About the talk
The Jurassic-Cretaceous magmatism in Hong Kong region was followed by multiple hydrothermal episodes during the Late Cretaceous through Cenozoic. The hydrothermal events resulted in deuteric mineralisation and silicification of sedimentary layers. A few hydrothermal episodes are found to postdate fold and thrust events as well as the Eocene Ping Chau formation. Authigenic aegirine and the cherty siltstone layer found in the lower member of Ping Chau formation are attributable to hydrothermal events with temperatures estimated at about 300oC. Stromatolitic structures are found to have been preserved in the silicified siltstone. In Double Island, folded sediments of the Pat Sin Leng formation were silicified within a, speculatively, breccia pipe. An examination of the hydraulic fractures in some quartz dikes on Lantau Island has enabled us to estimate the depth at which the fracturing occurred, based on thermodynamic consideration of the phase relation between water and gas as well as the geostatic gradient of the crust. The talk presents an overview of interesting hydrothermal features in Hong Kong and a discussion of their tectonic significance.