Sr-Nd-Hf Isotopic Analysis of <10 mg Dust Samples: Implications for Ice Core Dust Source Fingerprinting
Combined Sr-Nd-Hf isotopic data of two reference materials (AGV-1/BCR2) and 50, 10, and 5 mg aliquots of carbonate-free fine grain (<10 lm) separates of three loess samples (Central Europe/NUS, China/BEI, USA/JUD) are presented. Good agreement between measured and reference Sr-Nd-Hf isotopic comp...
Published in: | Geochemistry, Geophysics, Geosystems |
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Main Authors: | , , , , |
Format: | Article in Journal/Newspaper |
Language: | Hungarian |
Published: |
Wiley
2018
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Subjects: | |
Online Access: | http://real.mtak.hu/83401/ http://real.mtak.hu/83401/7/ujvari_etal_2018_G-Cubed.pdf https://doi.org/10.1002/2017GC007136 |
Summary: | Combined Sr-Nd-Hf isotopic data of two reference materials (AGV-1/BCR2) and 50, 10, and 5 mg aliquots of carbonate-free fine grain (<10 lm) separates of three loess samples (Central Europe/NUS, China/BEI, USA/JUD) are presented. Good agreement between measured and reference Sr-Nd-Hf isotopic compositions (ICs) demonstrate that robust isotopic ratios can be obtained from 5 to 10 mg size rock samples using the ion exchange/mass spectrometry techniques applied. While 87Sr/86Sr ratios of dust aluminosilicate fractions are affected by even small changes in pretreatments, Nd isotopic ratios are found to be insensitive to acid leaching, grain-size or weathering effects. However, the Nd isotopic tracer is sometimes inconclusive in dust source fingerprinting (BEI and NUS both close to ENd(0) –10). Hafnium isotopic values (<10 lm fractions) are homogenous for NUS, while highly variable for BEI. This heterogeneity and vertical arrays of Hf isotopic data suggest zircon depletion effects toward the clay fractions (<2 lm). Monte Carlo simulations demonstrate that the Hf IC of the dust <10 lm fraction is influenced by both the abundance of zircons present and maturity of crustal rocks supplying this heavy mineral, while the <2 lm fraction is almost unaffected. Thus, EHf(0) variations in the clay fraction are largely controlled by the Hf IC of clays/ heavy minerals having high Lu/Hf and radiogenic 176Hf/177Hf IC. Future work should be focused on Hf IC of both the <10 and <2 lm fractions of dust from potential source areas to gain more insight into the origin of last glacial dust in Greenland ice cores. |
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