Patterns and origin of igneous activity around the Tanzanian craton

摘要: Abstract Tertiary and later igneous activity is common on around the Tanzanian craton, with primitive magma compositions ranging from kimberlites varieties of picrites through nephelinites, basanites alkali basalts. This review focuses elucidating conditions origin melts, addressing question state involvement cratonic lithosphere in genesis. The craton anomalous a surface elevation >1100 m reflecting buoyancy supported by subcratonic plume whose effects are seen volcanics both western eastern rift branches. Magmatism at its edge has high K/Na melts show fractionation dominated olivine. Slightly further pyroxene dominates ratios magmas lower. Off-craton basalts low K/Na. Potassium enrichment correlates occurrence phlogopite mantle-derived xenoliths, also carbonate magmas. attributed to melting >140 km depths mixed source regions containing pyroxenite peridotite, whereby derived oxidation diamonds concentrated near base lithosphere. Mixed required arrays radiogenic isotopes such as Os Sr volcanic rocks. temporal progression lamproites phlogopite + carbonate-rich rocks melilitites, nephelinites during erosion North Atlantic coeval kimberlites, kamafugites related rocks, showing spatial instead variation. due different stages development rifting craton: northwestern Uganda northern Tanzania, K-rich volcanism occurs edge, whereas occur where shallower level well-developed rifts. presence melt sources rifts Ni intermediate Mg#, underplated basaltic material may explain production voluminous flood phonolites branch.