Temporal–Spatial Separation of Cu from Mo in the Jiama Porphyry Copper–Polymetallic Deposit, Southern Tibet, China

Jiama is a super-large porphyry copper–polymetallic deposit located in the Gangdese metallogenic belt of southern Tibet. The deposit consists of a combination of a polymetallic skarn, Cu–Mo mineralization at the contact between the Jiama Porphyry and hornfels, and distal Au mineralization in fault. The current metal reserves are 7.4 Mt Cu, 0.6 Mt Mo, 1.8 Mt Pb–Zn, 6.65 Moz Au, and 360.32 Moz Ag, with a skarn to porphyry–hornfels host-rock ratio of ~3:1. Based on detailed field and laboratory investigations, this paper indicates that: (i) the skarn and porphyry–hornfels orebodies are almost entirely preserved; (ii) the emplacement age of the Cu-bearing plutonic rocks is earlier than the plutons containing elevated Mo assays; (iii) the permeability of the wall rocks gradually decreases in an upward direction; (iv) the fluid temperature during the precipitation of Cu was higher than that of the Mo mineralization; (v) the lithospheric pressure during the precipitation of Cu and Mo was the same; (vi) the laser Raman spectroscopy shows that the fluid carrying the Cu was rich in magnetite, hematite, and anhydrite, and the fluid carrying Mo was rich in pyrite, CO2, and CH4; and (vii) the SR–XRF mapping shows that the concentration of Cu in the mineralizing fluid was high and that of Mo was low when Cu was deposited. Conversely, the concentration of Cu was relatively low and the concentration of Mo was relatively high during deposition of the Mo. This study also shows that the temporal and spatial separation of Cu and Mo in the porphyry copper–polymetallic deposit at Jiama was associated with the emplacement of the Jiama Porphyry. Transportation of mineralized fluid was controlled by the permeability of the wall rocks, and deposition of the metals related to changes along a redox front and pressure releases during hydrothermal brecciation at the roof of the Jiama Porphyry.

Correlative transmission electron microscopy and high-resolution hard X-ray fluorescence microscopy of cell sections to measure trace elements concentrations at the organelle level

Metals are essential to all forms of life and their concentration and distribution in the organisms are tightly regulated. Indeed, in their free form, metal ions are toxic. Therefore, an excess of physiologic metal ions or the uptake of non-physiologic metal ions can be highly detrimental for the organisms. It is thus fundamental to understand metals distribution and dynamics in physiologic or disrupted conditions, for instance in metal-related pathologies or upon environmental exposure to metals. Elemental imaging techniques can serve this purpose, by allowing the visualization and the quantification of metal species in a tissue or down to the interior of a cell. Among these techniques, synchrotron radiation-based X-ray fluorescence (SR-XRF) microscopy is the most sensitive to date, and great progresses were made to reach spatial resolutions as low as 20×20 nm2. Until recently, 2D XRF mapping was used on whole cells, thus summing up the signal from the whole thickness of the cell. In the last two years, we have developed a methodology to work on thin cell sections, in order to analyze the metal content at the level of the organelle. Herein, we propose a correlative method to couple SR-XRF to electron microscopy, with the aim to quantify the elemental content in an organelle of interest. As a proof-of-concept, the technique was applied to the analysis of mitochondria from hepatocytes exposed to silver nanoparticles. It was thus possible to identify mitochondria with higher concentration of Ag(I) ions compared to the surrounding cytosol. The versatility of the method makes it suitable to answer a large panel of biological questions, for instance related to metal homeostasis in biological organisms.

Hourly elemental concentrations in ambient aerosols in four cities in Asia and Europe – comparison and source apportionment

<p>Megacities worldwide are suffering from elevated air pollution due, e.g., to continuously increasing urbanization, and a sizeable amount of the population in such areas is exposed to particulate matter (PM) concentrations exceeding the WHO limits. Huge efforts are therefore undertaken to characterize the air pollution situation and to reduce or mitigate the impact on the population and the environment. Modern instrumentation allows for a quantitative determination of aerosol concentration and composition with high time resolution (minutes to hours), and subsequent source apportionment.</p><p>We collected PM<sub>10</sub> and PM<sub>2.5</sub> aerosols alternatingly with an online X-ray fluorescence (XRF) spectrometer in the cities of New Delhi (India) in 2019, Beijing (China) in 2017, and Krakow (Poland) in 2018, with time resolutions from 30 to 120 min, and in London (UK) in 2012 with 3-stage rotating drum impactors and subsequent offline SR-XRF analysis. Campaigns lasted for two to seven weeks in fall and winter. Elements from Al to Bi were analyzed in near-real time, except for London.</p><p>Our results show that some of the cities experience episodic extreme events, whereas extremely high elemental concentrations are chronic in others. Toxic metals are shown to be strongly location-dependent, and may occur in extreme plumes. Meteorological conditions also play an important role and will be discussed. The regional influence of fine PM, in comparison to the more local origin of coarse PM will be evaluated. The differences among the four cities, with substantially higher concentrations in the Asian cities than the European ones will be discussed. Highly time-resolved size-segregated sampling allowed for a rough classification of elements into five groups and will be described in detail. We demonstrate that the use of size information on toxic elements, diurnal patterns of targeted emissions, and local vs. regional effects are advantageous for formulating effective environmental policies to protect public health.</p>

Proof-of-concept for 2D/CT element analysis of entire cryofrozen islets of Langerhans using a cryoloop synchrotron X-ray fluorescence setup

This work reports on trace level chemical imaging of vitrified islets of Langerhans in 2D/CT mode using synchrotron X-ray fluorescence (SR-XRF). The newly developed method can be used for other biological samples that can be captured in a cryoloop.