Abstract
Mineral dust provenances are closely related to the orogenic processes which may have distinct Hf-Nd isotopic signatures. Here we report the clay-sized (<2 μm) Hf-Nd isotope data from Asian dust sources to better constrain the source and transport dynamics of dust deposition in the North Pacific. Our results show that there is a more positive radiogenic Hf isotopic composition with clay-sized fractions than the corresponding bulk sample and a decoupling of the Hf-Nd couplets in the clay formation during the weathering process. The clay-sized Hf-Nd isotopic compositions of the desert samples from the Sino-Korean-Tarim Craton (SKTC) are different from those of the Gobi and deserts from the Central Asian Orogeny Belt (CAOB) due to varying tectonic and weathering controls. The Hf-Nd isotopic compositions of dust in the North Pacific central province (NPC) match closely with those from the Taklimakan, Badain Jaran and adjacent Tengger deserts, implying that the NPC dust was mainly transported from these potential sources by the westerly jet. Our study indicates that dusts from the CAOB Gobi deserts either didn't arrive in NPC or were quantitatively insignificant, but they were likely transported to the North Pacific margin province (NPM) by East Asian winter monsoon.
Highlights
Hf-Nd isotopic variability in mineral dust from Chinese and Mongolian deserts: implications for sources and dispersal
The Hf-Nd isotopic signatures of the Chinese and Mongolia Gobi Deserts are consistent with previous Sr-Nd isotopic observations, suggesting that the isotopic composition of deserts is closely related to the tectonic setting of the surrounding mountains[8]
Hf isotopic systematics can distinguish between orogenic processes dominated by the generation and reworking of continental crust and those dominated by additions of juvenile crust[16]
Summary
Hf-Nd isotopic variability in mineral dust from Chinese and Mongolian deserts: implications for sources and dispersal. The recent conclusion that the oceanic ferromanganese crusts and terrigenous clays, deviate significantly from the Terrestrial Array towards higher eHf values relative to their eNd values, mainly result from the incongruent behavior of Hf during continental weathering[18,19,20,21,22,23] This Hf-Nd decouple is still under debate[18,21,24,25,26]. The clay-sized isotopic fingerprints from Asian deserts may be ideal targets for provenance tracing of long-distance transported mineral dust, and provide an unparalleled window for understanding the global dust cycle, especially, eolian dust preserved in deep-sea sediments
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