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The correct choice of a stone aggregate for railway ballast is directly related to the stability, safety, efficiency, and maintenance costs of the track. The aggregate must meet several criteria to ensure it is the most appropriate material. Thus, the present study aimed to evaluate four distinct stones: two granites, a diabase, and a basalt, all mined in the eastern region of the state of São Paulo, Brazil, regarding their applicability as ballast. Using Brazilian and ASTM procedures for stone samples, the tests were conducted on 55 and 75-mm specimens, in dry and wet conditions. As a result, all stones met the physical properties established by the standards. Among the mechanical properties, uniaxial compressive strength stood out, with all stones where the tested materials advantageously exceeding the 100 MPa required by the Brazilian standard. Regarding the accelerated weathering test with ethylene glycol, only basalt showed more significant changes, although its resistance to weathering was still lower than 10%. Our findings indicate that these stones perform adequately as ballast for railway applications. The study is expected to contribute to revisions of technical standards and the improvement of a database on Brazilian stone materials for use as railway ballast. [ABSTRACT FROM AUTHOR]

The typochemical features of spinels forming continuous series from Al–Cr spinels to ferrispinel and ulvöspinel from basic–ultrabasic rocks of the North Siberian Platform are considered. Their composition features are compared with those of alkali basalts of oceanic islands and lunar marine basalts in the modified Al–Cr–(Fe3+ + 2Ti)–Fe2+ 3D diagram proposed by the author. The identified continuous isomorphous series from Cr-spinel to ulvöspinel is one of the mineralogical indicators of a possible paragenetic relationship between picrite–basalt, alkali olivine–basalt, alkali–ultrabasic, and kimberlite rocks in the North Siberian Platform. The Ballhaus–Berry–Green olivine–Cr-spinel oxythermobarometer used in the rock study in the North Siberian Platform has made it possible to demonstrate that oxygen volatility log fO2 is from two to four orders of magnitude higher than that specified by the fayalite–magnetite–quartz buffer and corresponds to the oxidation state of Pt-bearing dunite–clinopyroxenite rock assemblages of the Ural–Alaskan and Aldan types. [ABSTRACT FROM AUTHOR]

The scarcity of the early Precambrian geological record limits our comprehension of crucial information concerning interactions between the crust and mantle, mechanisms involved in subduction zone arc-continental collisions, as well as patterns of mantle enrichment and crustal growth during this epoch. The Dengfeng terrane in the North China Craton provides significant data on Precambrian crustal evolution, particularly within the Neoarchean magmatic suites. Our study focuses on a variety of basic rocks across several locations in this region. Basic rocks from Huishansi and Sanhuangzhai (2558–2525 Ma) exhibit characteristics such as low SiO2 (45.44–56.54 wt%), K2O (0.77–2.7 wt%), Na2O (1.66–4.51 wt%), and high MgO (4.66–11.22 wt%) and FeOT (8.17–13.77 wt%). Similarly, basic rocks from Shipaihe and Guojiayao (2480 Ma) also display low SiO2 (46.16–52.48 wt%), K2O (0.24–1.28 wt%), and Na2O (1.87–3.75 wt%), with FeOT (1.07–2.31 wt%), but feature higher content of MgO (5.33–8.83 wt%) and Mg# (44–62, averaging 53). Both sets exhibit relatively flat REE patterns and weak negative anomalies in Nb, Ta, and Ti, corresponding to a tholeiitic basalt composition for the protoliths. Analyzing low (Hf/Sm)N, (Nb/La)N, and Th/Yb ratios, coupled with depleted HFSE, suggests potential crustal contamination in the rocks from Huishansi and Sanhuangzhai. Further, based on low V/Sc ratios (5.38–10.27, average 7.02) and depleted zircon ƐHf(t) values, our proposition is that the magma was sourced through partial melting of a depleted and relatively reduced mantle source. These findings offer valuable insights into the tectonic evolution of the Dengfeng terrane, spanning from subduction to post-collisional extension.