Nd and Pb isotopic studies of an Archaean layered mafic-ultramafic complex, Western Australia, and implications for mantle heterogeneity
Nd and Pb isotopic studies of an Archaean layered mafic-ultramafic complex, Western Australia, and implications for mantle heterogeneity
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DOI：
10.1016/0016-7037(86)90042-6
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发表时间：
1986
影响因子：
5
通讯作者：
M. Korsch;B. Gulson
中科院分区：
文献类型：
--
作者：
M. Korsch;B. Gulson
对西澳大利亚皮尔巴拉地块西部的密林丁纳杂岩进行了Nd和Pb同位素测定。Sm-Nd全岩/矿物年龄为2830±20 Ma（2σ），初始143 Nd/144 Nd比值为0.50892±0.00002（Nd-0.7±0.4）。铅同位素比值的离散度有限，得到的Pb-Pb全岩年龄为2960±20 Ma（2σ），计算的Mi为8.3。在计算solTh U和初始208铅-206铅比的变化排除了单一的来源，这个复杂的。与其他镁铁质/超镁铁质杂岩的Nd-Pb研究，特别是那些在2600-2900 Ma的时间跨度的比较，揭示了一个趋势，从正的Nd-Nd和低μ（7.7-7.9）值在安大略（芒罗镇，Alexo，牛顿）的负Nd-Nd和较高的μ值在Suomussalmi，Millindinna和静水复杂。虽然这一趋势可能是地幔不均匀性和/或地壳污染的结果，但目前我们倾向于地壳污染。
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 143 Nd 144 Nd ratio is 0.50892±0.00002 (ϵNd− 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 208 Pb 206 Pb 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 ϵNd and low μ (7.7–7.9) values in Ontario (Munro Township, Alexo, Newton) to negative ϵNd 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.