The Lavas of Mauritius

Abstract

The geology and physical geography of Mauritius formed the subject of a communication to the Geological Society by Major H. de Haga Haig in 1895, 1 which has been the basis of subsequent descriptions of the island in the Encyclopædia Britannica and elsewhere. Major Haig showed that Mauritius is formed of basaltic lavas and tuffs, and that several of the hills in the interior of the island are volcanic cones, some of them having well-preserved craters. His description of the lavas is inadequate from a petrographic standpoint, being based on megascopic characters only. The basalts are described as dolerites and diorites; by the latter term, horn-blende-basalt seems to be intended. The most arresting feature in Major Haig's account is the record of ‘ crystalline chloritic schist ’ on Mt. La Selle, near the middle of the island. Students of Wegener's hypothesis will recall that Wegener believed the volcanic islands of the great oceans to be fragments of the lithosphere, left behind by the westward-drifting continents. The apparent absence of continental types of rock such as granite and schist from these islands was explained by Wegener as a consequence of the thick veneer of lava acquired by the islands since they broke away from the mainland. Major Haig's record of chloritic schist on Mauritius seemed to offer striking confirmation of Wegener's view, and called for confirmation and amplification. I visited Mauritius in January, 1931, with the intention of making such observations as time would permit among the lavas, and with the special