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Analysis of the thermal metamorphism of the ordinary chondrites is a key premise for gaining insights into the accretion and heating of rocky bodies in the early solar system. Such an analysis also represents an essential condition for constraining the early thermal and evolutionary histories of asteroids and terrestrial planets. Classifying ordinary chondrites into petrologic type (type 3–6) is the criterion for studying the thermal metamorphism of their parent bodies. However, the boundary between the unequilibrated (type 3) and equilibrated (type 4–6) chondrites is ambiguous at present, thus, limiting the understanding of their thermal metamorphism. In this study, the petrology, mineralogy and chemical composition of a set of seven ordinary chondrites with different degrees of thermal metamorphism collected from Grove Mountains (Antarctica) have been studied. The results demonstrated that these chondrite samples were L3.7, L3.8, L3.9, L3.9/4, L4, L5 and L6 type meteorites, with optimal correlations of Si, Mg, Fe, Mn and Ca with equilibrium degree of the olivine and low-calcium pyroxene and petrologic type. In this respect, the multi-parameter classification standard PMD (SiO2)-PMD (MgO)-PMD (MnO)-PMD (CaO) based on the percent mean deviation (PMD) of the chemical compositions of the olivine and low-calcium pyroxene was proposed to distinguish between the unequilibrated and equilibrated meteorites. The proposed standard exhibited high "resolution" in terms of classification, thus, also deepening the understanding of the effect of the silicate mineral composition in the thermal metamorphism of chondrites.

Stable isotopic data of meteorites are critical for understanding the evolution of terrestrial planets. In this study, we report high-precision vanadium (V) isotopic compositions of 11 unequilibrated and equilibrated L chondrites. Our samples show an average δ51V of − 1.25‰ ± 0.38‰ (2SD, n = 11), which is ~ 0.5‰ lighter than that of the bulk silicate Earth constrained by mantle peridotites. Isotopic fractionation in type 3 ordinary chondrites vary from − 1.76‰ to − 1.29‰, whereas the δ51V of equilibrated chondrites vary from − 1.37‰ to − 1.08‰. δ51V of L chondrites do not correlate with thermal metamorphism, shock stage, or weathering degree. Future studies are required to explore the reason for V isotope variation in the solar system.

We report the petrography, mineral chemistry and oxygen isotopic composition of GRV 99027, a new Martian meteorite recently collected during the 16th Chinese Antarctic Research Expedition. This meteorite consists of two textural regions. The interstitial region is characterized by the presence of plagioclase and phosphate, and higher FeO contents of olivine and orthopyroxene, in comparison with the poikilitic region. All of the observations are similar to the three known Martian lherzolites. We classify GRV 99027 as the fourth sample of Martian lherzolite.