Minerals

Indium is a critical metal predominantly recovered as a by-product of Zn and Cu ores, reflecting its preferential incorporation into sphalerite in volcanogenic massive sulfide (VMS) systems. This study investigates the timing and mechanisms of indium remobilization during Variscan deformation at the Lagoa Salgada VMS deposit, Iberian Pyrite Belt (IPB), using integrated petrography, in situ geochemistry, and geochronology of sulfide-bearing stockwork veins. Optical petrography constrains mineral paragenesis, and micro-LIBS mapping revealed elemental distribution patterns. Mineral chemistry was quantified by SEM–EDS and EPMA, and LA-ICP-MS was employed for trace element analysis and Rb–Sr dating of white mica. Rb–Sr geochronology yields an age of 317.6 ± 7.5 Ma, dating deformation-related white mica contemporaneous with sulfide recrystallization and constraining syn-tectonic remobilization to late Bashkirian Variscan deformation. Textural and geochemical relationships indicate that indium redistribution occurred during orogenic shortening. These results provide direct evidence that the critical metal endowment in VMS deposits may be substantially modified by orogenic processes, highlighting the need to incorporate deformation-driven remobilization process into predictive exploration models. Understanding syn-tectonic mineralization is essential for refining exploration strategies in brownfield scenarios such as Lagoa Salgada and Neves-Corvo as well as in greenfield VMS exploration.

This study examines the relationship between diagenetic evolution and hydrocarbon inclusions in Ordovician Yingshan Formation carbonates from Well Tuoying 1, Tuoputai area, Tahe Oilfield, using petrography, cathodoluminescence, micro-fluorescence spectroscopy, Raman spectroscopy, and fluid-inclusion microthermometry. Three calcite generations, two dolomite generations, and several fracture-filling relationships are described. Four fluorescence-defined oil-inclusion populations (orange yellow, yellow, yellow green, and blue green) and three temperature-defined groups of gas-associated aqueous inclusions are recognized. These populations provide evidence of heterogeneous hydrocarbon-fluid histories but cannot, without independent age constraints and demonstrated fluid-inclusion assemblage relationships, be equated unequivocally with four separate oil-charging events and three gas-charging events. Regional tectonic evolution and previously published burial-history interpretations provide a possible geological context rather than direct ages of inclusion trapping. The anomalously high homogenization temperatures measured for some hydrocarbon inclusions warrant assessment of pressure effects and post-entrapment modification before attribution to hydrothermal pulses. Because the new observations come from one well, regional implications remain tentative.

Kimberlitic zircons represent a common type of mantle-derived zircon megacryst entrained in kimberlites, and they have been shown to reliably record ages of kimberlite emplacement. Here, we present results of U–Pb geochronology, as well as oxygen-isotope, trace-element, and mineral-inclusion analyses of zircon megacrysts from the Obnazhennaya and Olivinovaya kimberlite pipes of the Kuoika field, northern Siberian craton. These zircons exhibit mantle-like oxygen-isotope compositions (δ¹⁸O = 5.11–5.86‰), low U concentrations (5–90 ppm), low total rare-earth-element (REE) concentrations (8–186 ppm), relatively flat heavy-REE patterns, and weak or absent Eu anomalies. Together, these characteristics indicate that the analyzed megacrysts are mantle-derived kimberlitic zircons, an interpretation further strengthened by the identification of olivine inclusions in one of the zircons. As such, these are the first kimberlitic zircons reported from the Obnazhennaya and Olivinovaya kimberlites. U–Pb dating of these zircons yielded Late Jurassic concordia ages of 152.5 ± 2.7 Ma (2σ) for the Obnazhennaya pipe and 148.5 ± 3.4 Ma (2σ) for the Olivinovaya pipe, which are consistent with the Middle Jurassic-to-Early Cretaceous age range previously reported for kimberlite magmatism within the Kuoika field. Our U–Pb age for the Obnazhennaya pipe is consistent with previous age estimates obtained using other geochronological methods and therefore provides a new, independent constraint on its emplacement age. The U–Pb age obtained for kimberlitic zircons from the Olivinovaya pipe provides the first reliable age constraint for this kimberlite.