The sedimentary rocks in the Central Cordillera, formed about 33–17 million years ago, came from volcanic rocks produced by an underwater volcanic region

Approximately 90% sedimentary rocks cover the Earth’s surface. These rocks are formed from the erosion and weathering of pre-existing rocks. In order to establish the geologic history an area has undergone, it is necessary to know the formation of the eroded rocks. However, due to their weathered and eroded nature, they are at times no longer accessible on the surface. As such, provenance analyses conducted in this study look into the remains of the eroded units recorded in the sediments. In this study, we examined the sedimentary rock units in Mountain Province dating back to the Late Oligocene to Early Miocene period (roughly 33 to 17 million years ago). Our objective was to determine the origin of the sediments within these units, which can reveal important details about the region’s geological history.

Using whole-rock geochemistry, we analyzed the chemical composition of the sediments. The results indicated that these sediments originated from volcanic rocks formed from an oceanic island arc–a volcanic region formed by underwater eruptions. Specifically, the analysis pointed to a “first-cycle mafic” source, meaning the sediments were directly derived from volcanic rocks.

The study identified the Cretaceous to Eocene Lepanto Metavolcanics as the likely source of the Oligocene to Miocene sediments. By identifying the source of the clastic units, the researchers have provided valuable insights into the region’s tectonic and volcanic history.

Overall, this research enhances our understanding of how the Central Cordillera region was formed and the geological processes that have shaped it over millions of years.

Authors:

Mark Joshua Novero (Rushurgent Working Group, National Institute of Geological Sciences,
College of Science, University of the Philippines Diliman), Kenneth Jan Sangalang (Rushurgent Working Group, National Institute of Geological Sciences, College of Science, University of the Philippines Diliman), Jillian Aira Gabo-Ratio (Rushurgent Working Group, National Institute of Geological Sciences, College of Science, University of the Philippines Diliman), Carla Dimalanta (Rushurgent Working Group, National Institute of Geological Sciences, College of Science, University of the Philippines Diliman), Betchaida Payot (Rushurgent Working Group, National Institute of Geological Sciences, College of Science, University of the Philippines Diliman), Ma. Yna Rose Garcia (Rushurgent Working Group, National Institute of Geological Sciences, College of Science, University of the Philippines Diliman),
Juan Alex Vianne Amoroso (Rushurgent Working Group, National Institute of Geological Sciences, College of Science, University of the Philippines Diliman), Pearlyn Manalo (Graduate School of International Resource Sciences, Akita University) and Ryohei Takahashi (Graduate School of International Resource Sciences, Akita University)

Read the full paper: https://iopscience.iop.org/article/10.1088/1755-1315/1373/1/012069/meta