Characterizing magnetic mineral assemblages of surface sediments from major Asian dust sources and implications for the Chinese loess magnetism

Abstract

Eolian dust plays an important role in the Earth's climate system. Environmental magnetism has been widely used to trace dust variations at different spatial and temporal scales. However, the magnetic properties of sediments from key dust sources have not been well determined. In this study, surface samples from potential dust sources in inner Eastern Asia were systematically investigated. Our results indicate that ferrimagnetic and antiferromagnetic minerals are both present in surface sediments and that they have broad grain size distributions. Ferrimagnetic components are dominated by partially oxidized coarse-grained (pseudo-single domain and multi-domain) lithogenic magnetite particles with minor contributions from pedogenic fine-grained (single domain and superparamagnetic) particles. Antiferromagnetic hematite can be classified into three groups in terms of diffuse reflectance spectroscopy (DRS) band positions (P 560 nm , P 545 nm , and P 535 nm , where numbers indicate the DRS band wavelength for hematite). The first group (P 560 nm ) is the coarse-grained hematite of lithogenic origin and is mostly confined to western China. The P 535 nm group is of pedogenic origin. The P 545 nm group is an intermediate phase that is present both in surface samples from the source regions and in loess. Therefore, the P 545 nm and P 535 nm groups are related to eolian inputs to the Chinese Loess Plateau and pedogenic processes, respectively. In addition, significant differences exist between the magnetic properties of eolian material from sources and depositional regions due to gravitational sorting. These insights provide strong constraints on interpretation of dust signals recorded by the Chinese loess and marine sediments from the North Pacific Ocean.

Changes in diffuse reflectance spectroscopy properties of hematite in sediments from the North Pacific Ocean and implications for eolian dust evolution history

“…In this study, two groups of hematite band position (P 560 and P 540 ) have been identified in the pelagic sediments of ODP Hole 885A from late Pliocene to early Pleistocene. Previous study has found that the signal of P 560 is the coarse‐grained hematite of lithogenic origin and is mostly confined to non‐CLP‐sources, such as the Taklimakan Desert, and P 540 is an intermediate phase that is present both in surface samples from CLP‐sources and non‐CLP‐sources (Liu QS et al, ). The band position of hematite obtained from DRS can also been used to distinguish the eolian provenance of the pelagic sediments in this hole.…”

“…For stoichiometric hematite, the band position is located at about 560 nm and will shift from 560 nm to shorter wavelengths with increasing Al substitution. Liu QS et al () systematically investigated surface samples from potential dust sources in the Asian inland based on DRS, and revealed that hematite band position can be employed to distinguish the sources of hematite derived from Asian inner source regions. It has been demonstrated that the eolian components in the ODP Hole 885A, including silicates and antiferromagnetic minerals, are derived mainly from the Asian inland (Pettke et al, ; Nie JS et al, ; Zhang Q et al, ); hence the hematite band position of hematite can also been used to distinguish the eolian provenance of the pelagic sediments in this hole, which can be characteristic by higher resolution.…”

Dust Sources of Last Glacial Chinese Loess Based on the Iron Mineralogy of Fractionated Source Samples

“…Previous studies have shown that the χ of surface sediments in NW China is dominated by magnetite (Mt; Liu et al, 2015;Wei et al, 2009;Xia et al, 2011), which is typically composed of multidomain (MD) and pseudosingle domain (PSD) grains (Liu et al, 2015). Mass-specific magnetic susceptibility (χ) was measured with a Bartington MS2 meter and MS2B sensor (470 Hz).…”

Special issue on “Recent advances in environmental magnetism and paleomagnetism”

“…Liu et al (2015) presented a characterization of iron oxides in surface sediments from potential dust source regions distributed throughout western and northern China. Magnetic mineral assemblages in the studied samples contain both antiferromagnetic (hematite and goethite) and ferrimagnetic (magnetite and maghemite) minerals with broad grain size distributions indicating multiple origins.…”