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The Mines and Geosciences Bureau Regional Office No. 08 has recently completed the 1:50,000 scale geological mapping of the Hilongos Quadrangle (Sheet 3951-III).

Based on the preliminary results from the fieldwork and the review of related literature, the Hilongos Quadrangle is underlain by four main lithologic units. Arranged from oldest to youngest, they are: the metamorphosed sedimentary and volcanic rocks intruded by diorite, the diorite-gabbro layered intrusive, the Middle Miocene limestone deposits, and the Upper Miocene sequences of marine clastics and sedimentary rocks.

Based on the Mining Tenements Control Map issued by the Mines and Geosciences Bureau in June 2021, there are seven (7) operating Industrial Sand and Gravel extraction sites within the Hilongos Quadrangle which has a total area of roughly 102.67 hectares. In addition, there are three (3) applications for Mineral Production Agreements (MPSAs) under review for the extraction of gold, copper, and silver within

the quadrangle that also covers parts of the adjacent Sogod and Plaridel Quadrangles.

The MPSA applications have a total area of 13,817.72 hectares, of which, roughly 55.41% or 7,656.75 hectares are within the Hilongos Quadrangle. One (1) Exploration Permit, which covers roughly 252.3 hectares, has also been granted for the quarrying of rock aggregates.

Quadrangle Geologic Mapping is one of the core projects of MGB. It has been implemented by MGB since mid-1950s. However, it was only in 2016 that a systematic implementation of the project was done.

Quadmapping aims to: a) identify and delineate the different rocks, mineralization, and geologic structures; b) determine relationship between different types of rocks and its ages, geologic structures and mineralization; c) propose a model on the geological and tectonic evolution of the target areas; and d) contribute and update the current database of the study areas. The final output of the activity is the production of the updated 1:50,000 scale geologic map with an accompanying technical report.

For the year 2021, MGB Regional Office No. 8 has five (5) target quadrangles in the region, namely: San Francisco, Catbalogan, Hilongos, Plaridel and Hingatungan. These quadrangles cover portions of the Provinces of Samar, Leyte, and Southern Leyte. MGB-08 has completed three (3) out of the five (5) targets, to date.

The quadrangle geologic mapping activities for the Hilongos Quadrangle (Sheet 3951-III) was conducted by technical personnel from the Geosciences Division of MGB RO8 from June 15 to July 2, 2021. The survey team was composed of Brent James E. Dayao (Senior Geologist), Celes Emilio D. Sia (Geologist II), Sofronio B. Cezar (Geologic Aide), and Luciano M. Redondo, Jr. (Driver).