Detrital chromites are commonly reported within Archean metasedimentary rocks, but have thus far garnered little attention for use in provenance studies. Systematic variations of Cr-Fe spinel mineral chemistry with changing tectonic setting have resulted in the extensive use of chromite as a petrogenetic indicator, and so detrital chromites represent good candidates to investigate the petrogenesis of eroded Archean mafic and ultramafic crust. Here, we report the compositions of detrital chromites within fuchsitic (Cr-muscovite rich) metasedimentary rocks from the Jack Hills, situated within the Narryer Terrane, Yilgarn Craton, Western Australia, which are geologically renowned for hosting Hadean (>4000 Ma) zircons. We highlight signatures of metamorphism, including highly elevated ZnO and MnO, coupled with lowered Mg# in comparison with magmatic chromites, development of pitted domains, and replacement of primary inclusions by phases that are part of the metamorphic assemblages within host metasedimentary rocks. Oxygen isotope compositions of detrital chromites record variable exchange with host metasedimentary rocks. The variability of metamorphic signatures between chromites sampled only meters apart further indicates that modification occurred in situ by interaction of detrital chromites with metamorphic fluids and secondary mineral assemblages. Alteration probably occurred during upper greenschist to lower amphibolite facies metamorphism and deformation of host metasedimentary rocks at similar to 2650 Ma. Regardless of metamorphic signatures, sampling location or grain shape, chromite cores yield a consistent range in Cr#. Although other key petrogenetic indices, such as Fe2O3 and TiO2 contents, are complicated in Jack Hills chromites by mineral non-stoichiometry and secondary mobility within metasedimentary rocks, we demonstrate that the Cr# of chromite yields significant insights into their provenance. Importantly, moderate Cr# (typically 55-70) precludes a komatiitic origin for the bulk of chromites, reflecting a dearth of komatiites and intrusive equivalents within the erosional catchment of the Jack Hills metasedimentary units. We suggest that the Cr# of Jack Hills chromite fits well with chromites derived from layered intrusions, and that a single layered intrusion may account for the observed chemical compositions of Jack Hills detrital chromites. Where detailed characterization of key metamorphic signatures is undertaken, detrital chromites preserved within Archean metasedimentary rocks may therefore yield valuable information on the petrogenesis and geodynamic setting of poorly preserved mafic and ultramafic crust.

How does one best subdivide nature into kinds? All classification systems require rules for lumping similar objects into the same category, while splitting differing objects into separate categories. Mineralogical classification systems are no exception. Our work in placing mineral species within their evolutionary contexts necessitates this lumping and splitting because we classify "mineral natural kinds" based on unique combinations of formational environments and continuous temperature-pressure-composition phase space. Consequently, we lump two minerals into a single natural kind only if they: (1) are part of a continuous solid solution; (2) are isostructural or members of a homologous series; and (3) form by the same process. A systematic survey based on these criteria suggests that 2310 (similar to 41%) of 5659 IMA-approved mineral species can be lumped with one or more other mineral species, corresponding to 667 "root mineral kinds," of which 353 lump pairs of mineral species, while 129 lump three species. Eight mineral groups, including cancrinite, eudialyte, hornblende, jahnsite, labuntsovite, satorite, tetradymite, and tourmaline, are represented by 20 or more lumped IMA-approved mineral species. A list of 5659 IMA-approved mineral species corresponds to 4016 root mineral kinds according to these lumping criteria.

Crustal growth and mantle differentiation through Earth's history are often traced using two radiogenic isotope systems - Lu-176-Hf-176 and Sm-147-Nd-143. Unlike most post-Archean igneous rocks that show correlated initial Hf and Nd isotopic compositions, many ancient rocks have broadly chondritic zircon initial epsilon Hf values but highly variable whole-rock initial epsilon Nd values. These features have classically been interpreted as differences in the behavior of the Lu-Hf and Sm-Nd isotope systems during either deep magma ocean crystallization, subduction zone processes, or post-crystallization metamorphism. To clarify the cause of early Archean Hf-Nd isotope relationships, which are essential for understanding early Earth's evolution, we investigated the in situ U-Th-Pb and Sm-Nd isotope systematics of co-existing titanite, apatite, and allanite the major Sm-Nd carriers in early Archean felsic rocks in a representative early Archean (3.5-3.4 Ga) tonalite- trondhjemite-granodiorite (TTG) suite from the Minnesota River Valley (MRV) terrane, northern USA. These rocks exhibit multiple generations of closed-system zircon growth with chondritic initial zircon Hf isotope signatures, and apparent decoupled zircon initial Hf and whole-rock Nd isotopic compositions, and thus serve as an useful test of the role of accessory minerals in controlling the whole rock isotopic signatures.

A systematic survey of 57 different paragenetic modes distributed among 5659 mineral species reveals patterns in the diversity and distribution of minerals related to their evolving formational environments. The earliest minerals in stellar, nebular, asteroid, and primitive Earth contexts were dominated by relatively abundant chemical elements, notably H, C, O, Mg, Al, Si, S, Ca, Ti, Cr, and Fe. Significant mineral diversification subsequently occurred via two main processes, first through gradual selection and concentration of rarer elements by fluid-rock interactions (for example, in hydrothermal metal deposits, complex granite pegmatites, and agpaitic rocks), and then through near-surface biologically mediated oxidation and weathering.

Data-driven discovery in geoscience requires an enormous amount of FAIR (findable, accessible, interoperable and reusable) data derived from a multitude of sources. Many geology resources include data based on the geologic time scale, a system of dating that relates layers of rock (strata) to times in Earth history. The terminology of this geologic time scale, including the names of the strata and time intervals, is heterogeneous across data resources, hindering effective and efficient data integration. To address that issue, we created a deep-time knowledge base that consists of knowledge graphs correlating international and regional geologic time scales, an online service of the knowledge graphs, and an R package to access the service. The knowledge base uses temporal topology to enable comparison and reasoning between various intervals and points in the geologic time scale. This work unifies and allows the querying of age-related geologic information across the entirety of Earth history, resulting in a platform from which researchers can address complex deep-time questions spanning numerous types of data and fields of study.

Some mafic-ultramafic intrusions in the North American Midcontinent Rift System host disseminated to massive sulfides of magmatic origin. Massive sulfides are also present in the immediate sedimentary country rocks to some of these intrusions, such as Partridge River, Tamarack, and Eagle. Our working hypothesis is that the country rock-hosted massive sulfides are also of magmatic origin. To test this hypothesis, we have carried out an integrated mineralogical, chalcophile elements, and isotopic (S-Os-Pb) study of the country rock-hosted massive sulfide samples from Partridge River, Tamarack, and Eagle. Data for the intrusion-hosted sulfides from previous studies are used for comparison. Like the intrusion-hosted massive sulfides, the country rock-hosted massive sulfides are mainly composed of pyrrhotite, pentlandite, chalcopyrite, and cubanite and have high Ni, Cu, and PGE tenors, consistent with the crystallization products of magmatic sulfide liquids. These two different types of sulfide occurrences at Partridge River are different in some chalcophile element ratios and S-Os-Pb isotopes, but such differences can be explained by different parental magmas with different degrees of crustal contamination and different R-factors during sulfide segregation. At Tamarack and Eagle, these two different types of sulfide occurrences have similar S-Os-Pb isotope compositions, but the similarity in chalcophile element compositions between them is restricted to only some of the samples. Negative Pt anomalies are more common for the country rock-hosted massive sulfide than the intrusion-hosted sulfide ores. Positive Pt anomalies are not observed in the country rock-hosted massive sulfide samples but are present in some of the intrusion-hosted sulfide ore samples. Our modeling results show that the observed similarities and differences between these two different types of sulfide occurrences in each of the deposits can be explained by a common parental magma, variable R-factors during sulfide-liquid segregation, and variable degrees of fractional crystallization of monosulfide solid solution from sulfide liquids. Given the fact that positive Pt anomalies are present in some of the intrusion-hosted sulfides ores, we suggest that the negative Pt anomalies in the country rock-hosted magmatic sulfides are due to a nugget effect or removal of early-crystallized platinum group minerals, such as sperrylite (PtAs2), from the sulfide liquids prior to their infiltration into the surrounding country rocks.

Tungsten tetraboride has been known so far as a non-stoichiometric compound with a variable composition (e.g. WB4-x, WB4+x). Its mechanical properties could exceed those of hard tungsten carbide, which is widely used nowadays in science and technology. The existence of stoichiometric WB4 has not been proven yet, and its structure and crystal chemistry remain debatable to date. Here we report the synthesis of single crystals of the stoichiometric WB4 phase under high-pressure high-temperature conditions. The crystal structure of WB4 was determined using synchrotron single-crystal X-ray diffraction. In situ high-pressure compressibility measurements show that the bulk modulus of WB4 is 238.6(2) GPa for B ' = 5.6(0). Measurements of mechanical properties of bulk polycrystalline sub-millimeter size samples under ambient conditions reveal a hardness of similar to 36 GPa, confirming that the material falls in the category of superhard materials.

The metal-silicate partition coefficients of Ni and Co in a model C1 chondrite were determined at pressures ranging from 1.2 to 12.0 GPa and temperatures between 2123 and 2750 K. At 5.0 GPa and 2500 K, the effect of variable oxygen contents on the partitioning of Ni and Co was also investigated. Graphite was chosen as the sample container. Carbon is an integral part of the system because about 5 wt% C dissolved in the metal liquid.