Different enrichment patterns of magnetic particles modulated by primary
iron-phosphorous input
Abstract
Magnetic particles associated with iron (Fe) oxides are widespread on
the surface of Earth and Mars and serve as reasonable climatic
indicators. Ferrimagnetic maghemite (Mgh) and antiferromagnetic hematite
(Hm), which dominate magnetism and redness, often coexist or compete
with each other in soils and sediments. The formation efficiency of Mgh
relative to Hm could be modulated by geochemical background in addition
to climate, especially by phosphate (P), which has a high affinity on
the surface of precursor iron oxides in natural systems. We investigated
two Ferralsol sequences around a P mining field with comparable climate
but contrasting P/Fe ratios. High P/Fe retards iron oxide
crystallization as well as grain growth and transformation into Hm,
which thereby promotes more effective accumulation of ferrimagnetic Mgh
as intermediate products. The ligand-protected effect well interprets
asynchronous changes in magnetism and redness in soils and sediments
across large spatial and temporal scales.