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Mineralogical and petrological studies were conducted in mantle xenoliths included in a kaersutite lamprophyre dyke from Ubatuba (SP) (Serra do Mar Igneous Province), and in the Limeira 1 Kimberlite (Monte Carmelo, MG; Alto Paranaíba Alkalic Province), using petrography and major and trace element geochemistry in minerals by electron microprobe and LA-ICPMS. The Ubatuba spinel lherzolites, with equilibrium temperatures ranging from 750 to 950°C, represent a fertlie mantle affected by variable but moderate depletion. Evidence of two types of mantle metasomatis were detected in different samples. Clinopyroxene crystals of the samples with evidence of stronger previous depletion (olivine and pyroxenes with higher Mg#, pyroxenes with lower Al and Na, few proportion of spinel) show enrichment with high LILE/HFSE, attributed to fluids/melts derived from subduction zone. On the other hand, a spinelpoor wehrlite shows a clinopyroxene with both LILE and HFSE enrichment, suggestive of interaction with alkaline fluids/melts. The Limeira 1 mantle xenoliths correspond to lherzolites and dunites showing more textural and mineralogical variety and equilibrium temperatures ranging from 760 to 820°C. Modal metasomatism was identified by the presence of abundant pockets with concentration of LILE and HFSE-rich secondary minerals, including in some cases, exotic phases typical of upper mantle metasomatism. The chemical signature of the metasomatic minerals is similar to those found in MARID and in veined metasomatic peridotites from South Africa kimberlite xenoliths. Petrographic and chemical evidences of decompression (suggesting the former presence of garnet) were observed in a sample affected by enrichment with high LILE/HFSE. The different evidences of depletion and enrichment processes observed in the two groups of xenoliths (Ubatuba and Monte Carmelo) indicate a lateral variability of the spinelfacies upper mantle in southeast Brazil, which may reflect the distinct tectonic and magmatic processes that affected these two regions.

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Alkali-bearing Ti oxides were identified in mantle xenoliths enclosed in kimberlite-like rocks from Limeira 1 alkaline intrusion from the Alto Paranaíba Igneous Province, southeastern Brazil. The metasomatic mineral assemblages include mathiasite-loveringite and priderite associated with clinopyroxene, phlogopite, ilmenite and rutile. Mathiasite-loveringite (55-60 wt.% TiO 2 ; 5.2-6.7 wt.% ZrO 2 ) occurs in peridotite xenoliths rimming chromite (∼50 wt.% Cr 2 O 3 ) and subordinate ilmenite (12-13.4 wt.% MgO) in double reaction rim coronas. Priderite (Ba/(K+Ba)< 0 05) occurs in phlogopite-rich xenoliths as lamellae within Mg-ilmenite (8.4-9.8 wt.% MgO) or as intergrowths in rutile crystals that may be included in sagenitic phlogopite. Mathiasite-loveringite was formed by reaction of peridotite primary minerals with alkaline melts. The priderite was formed by reaction of peridotite minerals with ultrapotassic melts. Disequilibrium textures and chemical zoning of associated minerals suggest that the metasomatic reactions responsible for the formation of the alkali-bearing Ti oxides took place shortly prior the entrainment of the xenoliths in the host magma, and is not connected to old (Proterozoic) mantle enrichment events. Keywords

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