Pejrology Geochemistry And Mineral Occurrences Of The Big Dubicha Metaultramafic Rocks Northeast Of Kibremengist Southern Ethiopia

The Big Dubicha metauitramafic mass is part of thy, east;,:l'n belt (Kenticha belt)Of, Adola area.rnLithologic units in the area include; biotite - muscovite - quartz schist, chlorite schist, taicrnschist and tremolite - actinolite - talc - serpentine schist.rnMineral assemblages of the Big Dubicha altered ultramafic rocks are characteristic of lowerrngreenschist facies, representing serpentinization, chloritization and carbonation reactionsrnamong others. These reactions are the result of low temperature water-rock interactions. Thernmetamorphic mineral assemblages of the enveloping metamorphosed sedimentary rock fallrnwithin lower to middle amphibolite facies, suggesting the presence of allofacial relationshiprnbetween the Big Dubicha altered ultramafic rocks versus the enveloping rock. In additionrnshallow angle westward dipping foliation is related to the thrusting event.rnWhole rock geochemical data examined in the system CaO - MgO - Si02 - H20 - CO2 for"rntremolite - actinolite - talc - serpentine schist and chlorite schist suggest harzburgitic andrndunitic anhydrous mineralogy, together with the limited metamorphic and structuralrnobservations, the Big Dubicha altered uitramafic rocks represent a slice or fragmcnt 01rnsubcontinental mantle lithosphere,rnFrom the geochemical maps of soil samples, anomalous zones of Ni, Cr, Co, Mn, and Zn arernobserved along the strongly deformed and serpentinized tremolite - actinolite - talc -serpentinernschist, indicating insitu weathering (lateritization) of the bedrock was responsible for the'rnobserved mineral occurrences.

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