Guna volcanic massif is found in Northwestern Ethiopia plateau. It has an average basal diameterrnof about 40 km and a height of 1553 m with elevation of 4135m at the peak. It covers an estimatedrnarea of about 760 m2. A recent work of kieffer et al., 2004, provided an Ar/Ar age of 10.7 ma.rnThe general objective of this thesis research work is to study the geology and the petrogeneticrnprocesses responsible to produce the rock suites of the volcanic massif. The methodologiesrnemployed to achieve the objectives includes fieldwork for mapping and sampling, petrographicrninvestigations, electro microprobe analysis on major phenocryst phases of phonolte lavas, majorrnand trace element geochemical analysis by ICPMS method, analysis and interpretation of datarnusing different computer soft wares.rnGeologically the massif overlying the flood basalt mainly consists of rhyolite lava flow,rnpyroclastic flow deposit and phonolite lava flow from bottom to top.rnThe rhyolites occur as layered lava flows, glassy with columnar jointing and huge domes. In thinrnsection they have vitrophyric, perlithic and porphyrithic textures with essential mineralrncomposition of alkali fieldspars, plagioclase and quartz. The pyroclastic flow deposit includes ash,rntuffs, ignimbrite and trachyte flows. The phonolite occurs as thick viscous lava flow. They showrnporphrithic and trachythic textures with phenocrysts of alkali feldspar, feldesphathoids (nepheline,rnleucite and nosean) and alkali pyroxenes.rnThe lavas are rich in silica and alkalis. Major element variation plots displays features agreeablernwith fractionation of major phenocryst phases, Fe-Ti oxides and apatites.rnThe chondrite normalized Rare earth element (REE) patterns shows enriched light rare earthrnelement LREE, strong negative Eu anomaly and fairly flat heavy rare earth (HREE) pattern thatrnindicates fractionation processes.rnIn the Primitive mantle normalized profiles (spider diagrams) Ba , Sr, Ti and P shows strongrnnegative anomaly which verifies fractionation. In most samples, Nb shows a remarkable positivernanomaly. The lavas have low Rb/Nb (0.31-1.31) and La/Nb (0.34-1.03) ratios high La/Lu ratiosrnthat increase from rhyolite through trachyte to phonolite.rnThe field observations, petrography, mineral chemistry and whole rock geo chemical data of thisrnwork indicates that Guna is not a basaltic shield volcano; instead it is a huge felsic centre mainlyrnconsisting of pyroclastic flow deposits, rhyolite, phonolite and trachyte lava flows. The lavas arernco genetic and derived from mantle origin basaltic magma through low-pressure extensivernfractional crystallization and limited crustal contamination