The composition of heavy minerals of the sandy lands, Northeast China and their implications for tracing detrital sources

Our plain-English summary of The composition of heavy minerals of the sandy lands, Northeast China and their implications for tracing detrital sources, by L. Sun, Y. Xie, C. Kang, et al (PloS One, 2022).

The study

• Authors: L. Sun, Y. Xie, C. Kang, Y. Chi, P. Wu, Z. Wei, S. Li, Q. Zhao, S. Liu
• Journal: PloS One
• Published: 2022;17(10):e0276494
• Read it: PubMed · Publisher · Free full text

Abstract

Comprehending heavy mineral composition of the sandy land in Northeast China (NESL) is of great significance for interpreting generation, pathways, source and geochemistry of sediments in this area. To this end, the fine-grained (<63 μm) aeolian-fluvial sediments and loess deposits, which were taken from the Onqin Daga Sandy Land, the Horqin Sandy Land, the Hulun Buir Sandy Land and the Songnen Sandy Land, and from the downwind loess section (L1), respectively, were analyzed to construct the heavy mineral data set of NESL source and sink and to evaluate feasibility of the heavy mineral method in tracing the source of aeolian dust in Northeast China. Additionally, the <63 μm, 63-125 μm and 125-250 μm fractions of the fluvial sands from the different Balan River reaches having a same source, were analyzed to valuate the impact of the river transport-sedimentation process on the heavy mineral composition. The results show that the NESL shows moderate similarities in the heavy mineral composition, with ilmenite, epidote, zircon and amphibole as the primary minerals. In the source-to-sink system in the NESL, limited by sedimentary differentiation, post-deposition alteration and similar source material composition, the heavy mineral composition of the loess and that of sandy-land sources does not well correlate, indicating single heavy mineral method is incapable of unequivocally detecting loess sources when not considering the physical geographical conditions. The sediments in the different Balan River reaches show clear diversities and grain-size dependency in heavy minerals composition, indicating the river transport-deposition processes exert a clear control on the heavy-mineral composition in the sediment downstream. Both a wide grain-size window and more numbers of samples are needed to obtain a complete heavy-mineral picture in the source area.

In plain English

This geology study did not examine asbestos, asbestos exposure or any human health outcome. The authors analysed heavy minerals in sediments from four sandy lands in Northeast China (Onqin Daga, Horqin, Hulun Buir and Songnen). They used 33 wind- and river-deposited sand samples, 13 loess (wind-blown silt) samples from four sites, and 8 river sand samples from the Balan River. Ilmenite, epidote, zircon and amphibole were among the main minerals in the sandy lands. The article treats amphibole only as a mineral group and does not discuss asbestos or fiber shape. The minerals in the loess could not be clearly matched to particular sandy-land sources. In one plot, the Chifeng loess fell in or near the Onqin Daga field. In the Balan River, samples from the same source differed considerably downstream, and mineral content depended on grain size. The authors concluded that heavy minerals alone are a weak way to identify loess sources unless physical and geographical conditions are considered. They also concluded that a wider grain-size range and more samples are needed.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Field sampling of sediments with laboratory heavy-mineral separation and identification, plus statistical comparison (non-metric multi-dimensional scaling); a geological provenance study, not a health study
• Who was studied: Sediment samples, not people. There were 33 aeolian-fluvial sand samples from the Northeast China sandy lands: 13 from Onqin Daga, 9 from Horqin, 6 from Hulun Buir and 5 from Songnen. There were also 13 last-glaciation loess samples, 4 each from Chifeng, Kulungou and Harbin and 1 from Xingshan. Finally, there were 8 point-bar sand samples from a 42 km stretch of the Balan River.
• Exposure: No human or asbestos exposure was studied. The study measured natural heavy-mineral composition, including amphibole as a mineral group, in grain-size fractions finer than 63 micrometres, 63 to 125 micrometres, and 125 to 250 micrometres.
• Main results:
  • Across the four sandy lands, ilmenite, epidote, zircon and amphibole were primary minerals. Some characteristic minerals differed between sandy lands.
  • In a ternary plot of characteristic stable heavy minerals, the Northeast China loess samples could not be well linked to their respective dust sources. The exception was the Chifeng loess, which fell into or next to the Onqin Daga field.
  • The Harbin loess had high hematite+limonite and low garnet contents. In the authors' view, this excluded the Onqin Daga and Horqin sandy lands as its main dust source.
  • The eight Balan River samples varied in heavy-mineral composition downstream. Variation coefficients ranged from 0.2 to 1.4 (0.7) for the finer-than-63-micrometre fraction, from 0.2 to 2.8 (0.9) for 63 to 125 micrometres, and from 0.1 to 2.8 (1.1) for 125 to 250 micrometres. Abundances did not change regularly downstream.
  • In the Balan River, heavy minerals made up the largest share of the 63 to 125 micrometre fraction (1.9%-15.8%, 5.8%). The 125 to 250 micrometre fraction followed (0.7%-4.7%, 2.1%), then the finer-than-63-micrometre fraction (0.6%-4.1%, 1.9%).
  • Zircon, apatite, rutile, anatase, monazite, pyroxene, amphibole and tourmaline were more frequent in the fine fraction (finer than 63 micrometres). Sphene, hematite+limonite, magnetite and garnet were enriched in the coarser fractions.
• The authors' conclusion: The authors concluded that determining loess provenance by the heavy-mineral method is weak unless physical and geographical conditions are taken into account. They also concluded that a wide grain-size window and more samples are needed to get a complete picture of the source area.
• Limitations the authors state:
  • The authors stated that the heavy-mineral data could not determine whether the Songnen or the Hulun Buir sandy land was the dust source of the Harbin loess.
  • The authors stated that some minerals were diluted or enriched in the loess samples, which can add noise to the data analysis.

Topics

Medical terms in this study, explained in our Lexicon: Amphibole Group, Deposition.

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