Geochemical investigations across Malta and Gozo

Abstract

The Maltese Archipelago consists of three major islands; Gozo, Malta and Kemmuna. The islands’ geology is considered young in geological terms since the oldest dated rock reaches only the Tertiary Period. A fault, the Great Fault cuts Malta in half trending from southwest to northeast. A fault is a break in a plane caused by tectonic activity beneath the Earth’s crust, and an active fault releases gases once the rock is in motion. An inactive fault still releases gases due to the high storage of gas in the rocks while it was still active. This dissertation used the dynamic concentration method to observe if any carbon dioxide gas is still being released by the Great Fault. To compare and to confirm the degassing, two faults with two separate points were also investigated in Gozo. An on-going hydrological study in Malta was utilised to follow certain points and take degassing measurements near them to further confirm the movement of degassed carbon dioxide with water. Some points were also taken from the surroundings of the Magħtab Environmental Complex where waste from the islands is managed and treated. A doline in Xemxija was investigated as part of the study also, to see if any gases percolate from a structure which formed due to tectonic motion or a large weight above the cave roof. The results show that a slight but detectable amount of carbon dioxide is degassed from the islands of Malta and Gozo. The gas study does not indicate the origin of the gas that could be either organic carbon dioxide produced by decomposition of organic matter and stored in the sedimentary layers of the islands, or gas of endogenic origin continuously released through the tectonic lines although seismically inactive.