Petrographic analysis of rocks and sediments around the seven lakes of San Pablo City, Laguna: Implications to sulfate distribution and provenance

Abstract

The seven lakes of San Pablo City are among the 20 small monogenetic volcanoes found at the Macolod Corridor of the Southwestern Luzon Volcanic Field. This study evaluated the relationship of sulfate distribution and provenance in sediments to the volcanic geology and origin of the lakes. Rock and sediment mineralogy indicated the absence of sulfursulfate bearing minerals. This is supported by the very low sulfate values in rocks from previous analyses. The elevated sulfate values (Fig. 1) previously noted in sediments, however, are not related to volcanism but are attributed to anthropogenic sources. Considered possible sources of sulfate are sewage, fertilizers, algicides, and fungicides.