Indirect crustal contamination: evidence from isotopic and chemical disequilibria in minerals from alkali basalts and nephelinites from northern Tanzania
Article Abstract:
Contamination of alkali basaltic magma by crustal material has produced the pyroxene and nepheline present in the alkali basalts and nephelinites of northern Tanzania. Sr, Nd and Pb isotopic content of these rocks shows the abnormal presence of minerals that have crystallized from a liquid different from that which formed the host rocks. The contaminated basaltic magma mixed with different batches of magma that erupted at the same place. The rocks have probably developed in an open system. The crustal contamination of the magma altered the 206Pb/204Pb content of the lavas by < 0.25%.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1996
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Geochemical characteristics of lava-field basalts from eastern Australia and inferred sources: connections with the subcontinental lithospheric mantle?
Article Abstract:
A study shows that in 11 lava-field provinces in New South Wales and Queensland, eastern Australia, oceanic island basalt (OIB)-type source is the dominant component. Subcontinental lithospheric mantle (SCLM) contributes other significant components. These facts are obtained from the analysis of isotopic signatures and trace element patterns. The geochemical characteristics of SCLM elements are similar to those of spinel lherzolite xenoliths.
Publication Name: Contributions to Mineralogy and Petrology
Subject: Earth sciences
ISSN: 0010-7999
Year: 1995
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