TY - JOUR
T1 - Nd and Pb isotopic studies of an Archaean layered mafic-ultramafic complex, Western Australia, and implications for mantle heterogeneity
AU - Korsch, Michael J.
AU - Gulson, Brian L.
PY - 1986
Y1 - 1986
N2 - Nd and Pb isotopic ratios have been measured on the same samples from the Archaean layered Millindinna Complex in the western Pilbara Block of Western Australia. The Sm-Nd whole rock/mineral age is 2830 ± 20 Ma (2σ) and the initial 143Nd 144Nd ratio is 0.50892 ± 0.00002 (ε{lunate}Nd -0.7 ± 0.4). The dispersion in lead isotopic ratios is limited and the resulting Pb-Pb whole rock age is 2960 ± 20 Ma (2σ) with a calculated Mi of 8.3. Variations in calculated solTh U and initial 208Pb 206Pb ratios preclude a single source for this complex. Comparison with other Nd-Pb investigations of mafic/ultramafic complexes, particularly those in the time span from 2600-2900 Ma, reveals a trend from positive ε{lunate}Nd and low μ (7.7-7.9) values in Ontario (Munro Township, Alexo, Newton) to negative ε{lunate}Nd and higher μ values in the Suomussalmi, Millindinna and Stillwater Complexes. Although this trend could be the result of either mantle heterogeneity and/or crustal contamination, at the present time we favour crustal contamination.
AB - Nd and Pb isotopic ratios have been measured on the same samples from the Archaean layered Millindinna Complex in the western Pilbara Block of Western Australia. The Sm-Nd whole rock/mineral age is 2830 ± 20 Ma (2σ) and the initial 143Nd 144Nd ratio is 0.50892 ± 0.00002 (ε{lunate}Nd -0.7 ± 0.4). The dispersion in lead isotopic ratios is limited and the resulting Pb-Pb whole rock age is 2960 ± 20 Ma (2σ) with a calculated Mi of 8.3. Variations in calculated solTh U and initial 208Pb 206Pb ratios preclude a single source for this complex. Comparison with other Nd-Pb investigations of mafic/ultramafic complexes, particularly those in the time span from 2600-2900 Ma, reveals a trend from positive ε{lunate}Nd and low μ (7.7-7.9) values in Ontario (Munro Township, Alexo, Newton) to negative ε{lunate}Nd and higher μ values in the Suomussalmi, Millindinna and Stillwater Complexes. Although this trend could be the result of either mantle heterogeneity and/or crustal contamination, at the present time we favour crustal contamination.
UR - http://www.scopus.com/inward/record.url?scp=0022554513&partnerID=8YFLogxK
U2 - 10.1016/0016-7037(86)90042-6
DO - 10.1016/0016-7037(86)90042-6
M3 - Article
AN - SCOPUS:0022554513
SN - 0016-7037
VL - 50
SP - 1
EP - 10
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 1
ER -