Petrographic and borehole geology study of northwest nearshore area of Lantau Island

Abstract

A study of the geology of nearshore area of the northwest Lantau Island has been carried out because of the marine ground investigation work of the Hong Kong-Zhuhai-Macao Bridge. The objective of the study was to recreate a solid geological section of the northwest nearshore area and to resolve some of the discrepancy in the rock name. Data has been obtained from marine ground investigation by method of rotary drilling of rock cores and sampling of soil. Some of the rock specimens have been selected for thin section analysis. The borehole data is presented in the form a data base with projection of GIS software. Petrographic study has been carried out in the selected samples. The data has been interpreted in relation to the onshore geology of the Lantau Island. Which have been detailed in maps and geological memoir published by Geotechnical Engineering Office. (GEO) It is concluded that the area mainly composed of altered granite unit of the Lantau Granite and Chek Lap Kok Granite with minor mafic dyke intrusions. The area is structurally controlled by fault that can be traced onshore.