Thermal evolution of Andean iron oxide–apatite (IOA) deposits as revealed by magnetite thermometry

Magnetite is the main constituent of iron oxide–apatite (IOA) deposits, which are a globally important source of Fe and other elements such as P and REE, critical for modern technologies. Geochemical studies of magnetite from IOA deposits have provided key insights into the ore-forming processes and source of mineralizing fluids. However, to date, only qualitative estimations have been obtained for one of the key controlling physico-chemical parameters, i.e., the temperature of magnetite formation. Here we reconstruct the thermal evolution of Andean IOA deposits by using magnetite thermometry. Our study comprised a > 3000 point geochemical dataset of magnetite from several IOA deposits within the Early Cretaceous Chilean Iron Belt, as well as from the Pliocene El Laco IOA deposit in the Chilean Altiplano. Thermometry data reveal that the deposits formed under a wide range of temperatures, from purely magmatic (~ 1000 to 800 °C), to late magmatic or magmatic-hydrothermal (~ 800 to 600 °C), to purely hydrothermal (< 600 °C) conditions. Magnetite cooling trends are consistent with genetic models invoking a combined igneous and magmatic-hydrothermal origin that involve Fe-rich fluids sourced from intermediate silicate magmas. The data demonstrate the potential of magnetite thermometry to better constrain the thermal evolution of IOA systems worldwide, and help refine the geological models used to find new resources.

Long-term inhibition of ferritin2 synthesis in trophocytes and oenocytes by ferritin2 double-stranded RNA ingestion to investigate the mechanisms of magnetoreception in honey bees (Apis mellifera)

Behavioral studies indicate that honey bees (Apis mellifera) have a capacity for magnetoreception and superparamagnetic magnetite is suggested to be a magnetoreceptor. The long-term inhibition of magnetite formation can be employed to explore the bee’s magnetoreception. A recent study shows that magnetite formation, ferritin2 messenger RNA (mRNA) expression, and the protein synthesis of ferritin2 in trophocytes and oenocytes were all inhibited by a single injection of ferritin2 double-stranded RNA (dsRNA) into the hemolymph of honey bees but how to maintain this knockdown of ferritin2 for the long-term is unknown. In this study, we injected ferritin2 dsRNA into the hemolymph of worker bees three times every six days to maintain long-term inhibition; however, multi-microinjections accelerated the death of the bees. To overcome this problem, we further reared newly emerged worker bees daily with ferritin2 dsRNA throughout their lives, demonstrating no impact on their lifespans. Follow-up assays showed that the mRNA expression and protein synthesis of ferritin2 were persistently inhibited. These findings verified that daily ferritin2 dsRNA ingestion not only displays the long-term inhibition of mRNA expression and protein synthesis of ferritin2, but also did not damage the bees. This method of long-term inhibition can be used in behavioral studies of magnetoreception in honey bees.

Thermal Evolution of Andean Iron Oxide-Apatite (IOA) Deposits as Revealed by Magnetite Thermometry

Magnetite is the main constituent of iron oxide–apatite (IOA) deposits, which are a globally important source of Fe and other elements such as P and REE, critical for modern technologies. Geochemical studies of magnetite from IOA deposits have provided key insights into the ore-forming processes and source of mineralizing fluids. However, to date, only qualitative estimations have been obtained for one of the key controlling physico-chemical parameters, i.e., the temperature of magnetite formation. Here we reconstruct the thermal evolution of Andean IOA deposits by using magnetite thermometry. Our study comprised a >3000 point geochemical dataset of magnetite from several IOA deposits within the Early Cretaceous Chilean Iron Belt, as well as from the Pliocene El Laco IOA deposit in the Chilean Altiplano. Thermometry data reveal that the deposits formed under a wide range of temperatures, from purely magmatic (~1000–800 °C), to late magmatic or magmatic-hydrothermal (~800–600 °C), to purely hydrothermal (<600 °C) conditions. Magnetite cooling trends are consistent with genetic models invoking a combined igneous and magmatic-hydrothermal origin that involve Fe-rich fluids sourced from intermediate silicate magmas. The data demonstrate the potential of magnetite thermometry to better constrain the thermal evolution of IOA systems worldwide, and help refine the geological models used to find new resources.

Variations in magnetic properties of Mexican serpentinites and related micro-textures

&lt;p&gt;Magnetite formation of serpentinized ultramafic rocks leads to variations in the magnetic properties of serpentinites; however, magnetite precipitation is still on debate.&lt;/p&gt;&lt;p&gt;In this work, we analyzed 60 cores of ultramafic rocks with a variety of serpentinization degrees. These rocks belong to the ultramafic-mafic San Juan de Otates complex in Guanajuato, Mexico. Geochemical studies have been previously conducted, enabling us to compare changes in the magnetic properties against the chemical variations generated by the serpentinization process. By studying the density and magnetic properties such as anisotropy of magnetic susceptibility, hysteresis curves as well as magnetic and temperature-dependent susceptibility and, we were able to identify the relationship between magnetic content and serpentinization degree, the predominant magnetic carrier, and to what extent the magnetite grain size depends on the serpentinization. &amp;#160;Variations in these parameters allowed us to better constrain the temperature at which serpentinization occurred, the generation of other Fe-rich phases such as Fe-brucite and/or Fe-rich serpentine as well as distinctive rock textures formed at different serpentinization degrees.&lt;/p&gt;

Investigation on the transformation behaviours of Fe-bearing minerals of coal in O2/CO2 combustion atmosphere containing H2O

The ratio of Fe2+-glass to Fe3+-glass in ashes from O2/CO2 atmosphere is significantly increased. The iron oxides (hematite or magnetite) formation of included iron minerals may be delayed in O2/CO2. H2O promotes iron oxides formation.