Oxygen isotope geochemistry of the Mesozoic anorogenic complexes of Damaraland, northwest Namibia: evidence for crustal contamination and its effect on silica saturation

Article Abstract:

Oxygen isotope analyses of minerals from the Mesozoic anorogenic complexes of Damaraland in northwest Namibia provide an estimation of the delta-18O values of the original magmas, delta(sub magma). The values of delta(sub magma) are high in silica-oversaturated rocks and low in silica-undersaturated rocks. The high values may be due to crustal contamination. Granite rocks in the central zone of the Pan-African Damara Orogen complexes have the highest values of delta(sub magma).

Usage, Oxygen, Geology, Stratigraphic, Mesozoic Era, Stratigraphy, Oxygen isotopes, Namibia

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Reaction relationships in the Bayan Obo Fe-REE-Nb deposit Inner Mongolia, China: implications for the relative stability of rare-earth element phosphates and fluorocarbonates

Article Abstract:

Assemblages seen at Bayan Obo Fe-REE-Nb deposit located in Inner Mongolia, China, suggest a reaction between monazite, bastnasite and apatite. Relative proportions of each in the reaction zones imply the immobility of phosphate during the monazite and calcite reaction. Such immobility results in the creation of apatite and bastnasite. On the other hand, evidence suggest that formation of monazite plus fluorite or calcite occurs during the apatite-bastnasite reaction.

Research, Mineralogical research, Petrology, Phosphate minerals, Monazite

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Halogen geochemistry of the Great Dyke, Zimbabwe

Article Abstract:

The apatites from the Great Dyke of Zimbabwe show abundant amounts of hydroxy-fluorapatite end-members. Chlorapatite content decreases with fractionation throughout the dyke. However, the content of chlorine and other incompatible elements increase in concentration in a region at the top of the ultramafic sequence. The difference may be due to degassing of the dyke magma chamber at the top. Details of the geochemical analysis of the dyke are given.

Zimbabwe, Dikes (Geology)

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