GEOCHEMISTRY OF PREVIOUSLY UNDIFFERENTIATED LAVAS AND WELDED TUFFS AROUND SANARATE AND JALAPA, GUATEMALA

Guatemala has abundant volcanic activity due to its location at the intersection of three major plate boundaries: North American, Cocos, and Caribbean plates. This study researched volcanic outcrops around Sanarate and Jalapa Guatemala to characterize the diversity of previously undifferentiated volcanic deposits in the area. Five lavas and two welded ignimbrites were sampled to identify any relationships between the deposits and evaluate their origins. This study used field observation, X-Ray fluorescence (XRF), Inductively Coupled Plasma Mass Spectrometry (ICP-MS), thin section, and hand sample examinations to characterize each deposit. All seven deposits show typical subduction calcalkaline compositions. The are three basaltic andesite lavas with SiO₂ contents between 53.95-56.07%, with a distinctive depletion in Nb (17.95-25.95 ppm) and heavy rare earth elements (REE) such as Yb. Two rhyolite obsidian lavas were collected from different outcrops have nearly identical SiO₂ content (75.08-75.51%) and have a similar Sr depletion (145-166 ppm). The welded tuff samples have Sr compositions of 15 ppm and a range of 67-76 ppm respectively. Of the basaltic andesites, two samples found in Sanarate were chemically similar and close indicating they came from the same flow. Two additional samples were collected near the Jumay stratovolcano with a silica content of 53.95% and 55.31%, one is relatively enriched in light REE. Although these lavas can both be correlated to the Pleistocene Jumay stratovolcano their compositions suggest they are from different eruptions. The obsidians were collected nearly 38 km apart, so it is unlikely they are the same lava flow. The welded tuffs and obsidians have not been dated and are likely older than the basaltic andesites, the welded tuff samples are good candidates for geochronology. This research is a first step to constrain the eruptive history and diversity of volcanic events in this region to better understand past and future volcanic hazards.