(U–Th)/He thermochronology is an important tool for resolving the temporal evolution of thermally sensitive geological events, but significant intra-sample variation in single-grain (U–Th)/He ages is commonly observed. Zircon and apatite (U–Th)/He ages from the Jiao-Liao region, eastern China, reveal the factors that affect high- and low-U mineral He ages. Inclusions and surrounding U–Th-rich minerals have little effect on high-U mineral He ages, but do cause scatter in low-U mineral He ages. Improving sample quality is a key way to effectively improve this problem. Time and U content are the decisive factors that affect the function of ¹⁴⁷Sm. Radionuclide ¹⁴⁷Sm causes variations in low-U mineral He ages, particularly for grains with U <5 ppm and ages >100 Ma. The differences in closure temperature caused by grain size can be minimized by ensuring the difference between the maximum and minimum radius is <30 μm. Representative CL images indicated zircon (U-Th)/He ages are more susceptible to the interference of the internal heterogeneity than apatites. The error due to the alpha particle ejection correction can be neglected when using the laser ablation technique by analysing sites away from grain rims. The effects of radiation damage vary from high- to low-U minerals. Zircon ages show an inverted U-shaped pattern with increasing radiation damage. Radiation damage has a weak positive correlation with apatite He ages, probably due to its low U content. Besides, thermal histories experienced by our samples fail to significantly influence the effect of radiation damage on ages.

A new experimental method was developed to understand the partitioning of rare earth elements (REEs) on carbonate phases in oceanic columns. This method comprises of a mildly-oversaturated stage (Stage 1) and an undersaturated stage (Stage 2), mimicking natural oceanic columns consisting of the upper oversaturated and deeper undersaturated layers, in which carbonate particles of different sizes partition REEs with seawater. Saturation levels were adjusted by purging N₂ gas with different CO₂ concentrations. In this method, partitioning progress and equilibrium can be monitored via two viewpoints: differences in REE/Ca concentration among differently-sized carbonate particles and ionic activity products (IAPs) of the experimental solution.

The distribution coefficients obtained by the experiments, however, varied over three orders of magnitude. By analyzing the solution and carbonate particles, the presence of Fe in the carbonate particles (Fe/Ca) was observed to influence the partitioning of REEs. Microscopic mapping of Fe and proportionality of Fe amount to surface area strongly indicate that Fe is distributed evenly on the surface of carbonate, and Fe hydroxide is considered to be responsible for the REE enrichment. Neither the presence of Mn nor type of seed crystal (calcite or aragonite) was likely to significantly influence partitioning.

When Fe/Ca of carbonate was small, the ion activity products of the solution were found to modulate the distribution coefficient, implying that the presence of REE disturbs free relocation of carbonate ions. This may lead to overestimation and underestimation of distribution coefficients in Stages 1 and 2, respectively. We conclude that the distribution coefficient of REEs on calcium carbonate is not very high, but in natural settings carbonate is still important in controlling REE distribution by hosting Fe hydroxide, which effectively partitions REEs.

Carbonaceous matter (CM) in silica veins contained in the ~3.5 billion-year-old (Ga) Dresser Formation, Western Australia, can offer insights into biological activity in Earth’s oldest seafloor hydrothermal deposits, although a biological origin for this material remains debated. Herein, CM from Dresser hydrothermal vein deposits was analyzed using carbon X-ray absorption near edge structure (C-XANES) and Raman microspectroscopy. The CM is mainly composed of disordered aromatic structures, potentially containing minor aliphatic/ketonic/phenolic and carboxylic groups. These characteristics resemble those of biogenic Phanerozoic kerogen with high maturation, CM from the ~2.7 Ga Tumbiana Formation and the ~3.5 Ga Mount Ada Basalt in the Pilbara Craton, and abiotically synthesized graphite, but differ from those of CM produced via Fischer-Tropsch-type synthesis. Our observations indicate the presence of heteroatoms (hydrogen and possibly oxygen); however, the observed C-XANES spectra can be explained by either biotically or abiotically produced organic matter at this stage.