An enriched mantle source for potassic basanites: evidence from Karisimbi volcano, Virunga volcanic province, Rwanda

Article Abstract:

The lavas found in the Karisimbi volcano in Rwanda were found to contain primitive K-basanites (PKB) that came from mantle source regions. Lava samples with less than 4% MgO were formed from the combined interactions of assimilation and fractional crystallization while those with more than 4% MgO were formed from either PKB-melilite nephelinite reaction or lithospheric mantle extrusion. Moreover, Sr, Nd and Pb isotopic levels were determined from the Nyiragongo and Karisimbi mafic end-members. The results confirmed the isotopic fractionations that were involved in the volcanics of the two sites.

Research, Isotopes, Rwanda, Iron, Iron (Metal), Neodymium, Strontium, Petrogenesis, Isotope geology

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Geochemical constraints on crustal anatexis: a case study from the Pan-African Damara granitoids of Namibia

Article Abstract:

The low Rb/Sr and high Rb/Sr granitoids from the Pan-African Damara orogen, Namibia, originated from feldspar-limited, biotite dehydration melting, and biotite-limited, biotite dehydration melting respectively. Biotite dehydration melting of source rocks formed the leucogranites and Salem-type granitoids. Muscovite dehydration melting generated the alaskites of the Damara region. The leucogranites and Salem-type granites contain equilibrium concentration of Zr and light rare earth elements.

Geochemistry, Namibia, Granite, Biotite

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Isotope and trace element evidence for three component mixing in the genesis of the North Luzon arc lavas

Article Abstract:

An analysis of isotopic and trace elements from the Northern Luzon, Philippines area is presented. The volcanoes generated variations in the region's arc which extends over 500 km. It is shown that combined trace element and isotopic data implicate three end-members in the genesis of the lavas. These end-members include a mantle wedge end-member, a high LIL/HFS 'subduction component,' and an isotopically enriched end-member.

Soils, Trace analysis, Luzon Island

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