A mineral chemistry and whole-rock major element, platinum group element (PGE), and Re-Os isotope dataset is presented for a large suite of mantle xenoliths from 13 kimberlites that erupted through the Proterozoic mobile belts surrounding the Archean Kaapvaal craton of South Africa. The peridotites have compositions that are unusually infertile compared with post-Archean lithosphere outside southern Africa (e.g. mean olivine Mg-number = 91 center dot 4; mean whole-rock Al2O3 = 1 center dot 3 wt %) but are similar to xenoliths from the Gibeon kimberlites of southern Namibia, which also erupted through Proterozoic lithosphere. Rhenium depletion model ages (T-RD) determined from 58 Os isotope compositions of peridotites span a range from 2 center dot 6 to 0 center dot 6 Ga, with an average of 1 center dot 67 Ga. Latest Archean T-RD model ages were determined for three samples from different localities, but whether these indicate the off-craton presence of reworked Archean lithosphere or are simply artifacts of heterogeneity in the convecting mantle is unclear. Low and relatively restricted Al2O3 contents combined with variable Os-187/Os-188(i) in the peridotites are most consistent with a two-stage melt extraction history for southern African off-craton lithosphere, with initial formation in the earliest Proterozoic by widely varying (but, on average, moderate) degrees of melting, followed by a second melt extraction episode associated with the Namaquan orogeny at 1 center dot 3-1 center dot 0 Ga. Extensive metasomatism in the lithosphere beneath East Griqualand, SE of the craton, resulted in extreme clinopyroxene enrichment and addition of ilmenite along with disturbance of PGE abundances in many samples. This is probably due to percolation of melts similar to those parental to the Cr-poor megacryst suite, and related pyroxenites, which are abundant in East Griqualand kimberlites. In other regions, there is evidence for less extensive clinopyroxene addition and cryptic metasomatism. Southern African off-craton mantle xenoliths record evidence of a Mesozoic heating episode probably brought about by mantle upwelling linked to continental break-up and/or Karoo flood basalt magmatism. Prior to this, the thermal state, and hence the thickness, of southern African off-craton and cratonic lithosphere were probably roughly similar. The mantle upwelling responsible for lithospheric heating also appears to have caused moderate (approximate to 30 km) thermal erosion of the off-craton portions of the southern African lithosphere.

Peridotitic sulphide inclusions in diamonds from the central Slave craton constrain the age and origin of their subcontinental lithospheric mantle (SCLM) sources. These sulphides align with either a ca. 3.5 Ga (shallow SCLM) or a ca. 3.3 Ga isochron (deep SCLM) on a Re-Os ischron diagram, with variably enriched initial Os-187/Os-188. Since some Archaean to recent plume-derived melts carry a subducted crust (eclogite) signature and some cratonic SCLM may have been generated in plumes by extraction of komatiitic liquids, we explain these data by subduction of evolved lithospheric material (shallow SCLM) and melting in a hybrid mantle plume that contains domains of recycled eclogite (deep SCLM), respectively. In upwelling hybrid mantle, eclogite-derived melts react with olivine in surrounding peridotites to form aluminous orthopyroxene, convert peridotite to pyroxenite and confer their crustal isotope signatures. We suggest that it is subsequent to orthopyroxene enrichment of peridotite in an upwelling plume that partial melting of this Al- and Si- enriched source generated komatiites and complementary ultradepleted cratonic mantle residues. Although subduction is needed to explain some cratonic features, melting of a hybrid plume source satisfies several key observations: (1) suprachondritic initial Os-187/Os-188 in subsets of lithospheric mantle samples and in some coeval Archaean komatiites; (2) variable enrichment of cratonic mantle by high-temperature aluminous orthopyroxene; (3) high Mg# combined with high orthopyroxene content in cratonic mantle due to higher melt productivity of an Al- and Si-richer source; (4) variable orthopyroxene enrichment possibly linked to varying mantle potential temperatures (Tp), plume buoyancy and resultant eclogite load and/or variable availability of subducted material in the source; and (5) absence of younger analogues due to a secular decrease in Tp. Most importantly, this model also alleviates a mass balance problem, because it predicts a hybrid mantle source with variably higher SiO2 and Al2O3 than primitive mantle, and, contrary to a primitive mantle source, is able to reconcile compositions of komatiites and complementary cratonic mantle residues.

Mineral inclusions encapsulated in diamonds are the oldest, deepest, and most pristine samples of Earth's mantle. They provide age and chemical information over a period of 3.5 billion years-a span that includes continental crustal growth, atmospheric evolution, and the initiation of plate tectonics. We compiled isotopic and bulk chemical data of silicate and sulfide inclusions and found that a compositional change occurred 3.0 billion years ago (Ga). Before 3.2 Ga, only diamonds with peridotitic compositions formed, whereas after 3.0 Ga, eclogitic diamonds became prevalent. We suggest that this resulted from the capture of eclogite and diamond-forming fluids in subcontinental mantle via subduction and continental collision, marking the onset of the Wilson cycle of plate tectonics.

The Eagle Cu-Ni-(PGE) deposit is hosted by mafic to ultramafic intrusive rocks associated with the Marquette-Baraga dike swarm in northern Michigan. Sulfide mineralization formed in a conduit system during early stages in the development of the similar to 1.1 Ga Midcontinent Rift System. The conduit environment represents a prime location for melt-rock interaction. In order to better assess the extent of country rock contamination in the Eagle system, a combined trace element, Nd, Os, O and S isotope study of country rocks, sulfide-bearing igneous rocks and massive sulfide was undertaken.

The source and nature of carbon on Mars have been a subject of intense speculation. We report the results of confocal Raman imaging spectroscopy on 11 martian meteorites, spanning about 4.2 billion years of martian history. Ten of the meteorites contain abiotic macromolecular carbon (MMC) phases detected in association with small oxide grains included within high-temperature minerals. Polycyclic aromatic hydrocarbons were detected along with MMC phases in Dar al Gani 476. The association of organic carbon within magmatic minerals indicates that martian magmas favored precipitation of reduced carbon species during crystallization. The ubiquitous distribution of abiotic organic carbon in martian igneous rocks is important for understanding the martian carbon cycle and has implications for future missions to detect possible past martian life.

Samoan shield-stage lavas (from the islands of Ta'u, Savai'i, and Ofu and the seamounts of Vailulu'u and Malumalu) with Os concentrations >30 ppt have Os-187/Os-188 ratios that exhibit a narrow range of values between 0.128 and 0.132. Lavas with <= 30 ppt Os show more radiogenic Os-187/Os-188 ratios, in some cases as high as 0.191, suggesting that the Os-187/Os-188 ratios of the extreme Samoan EM2 (enriched mantle 2) lavas likely have been compromised by assimilation of altered oceanic crust. The Os-187/Os-188 ratios for rejuvenated-stage lavas from Savai'i are lower than shield lavas, and they exhibit some of the lowest Os-187/Os-188 ratios in the global ocean island basalt database (Hauri and Hart, 1993). The difference may owe to contamination of the rejuvenated lavas with unradiogenic Os from disaggregated xenoliths from the mantle lithosphere, and their low Os isotopic composition does not reflect the EM2 mantle source of magmas. The limited range in (OS)-O-187/(OS)-O-188 ratios of the higher Os-abundance shield lavas (0.128-0.132), coupled with a tremendous range of Sr-87/Sr-86 (0.7045-0.7114), are characteristics of the EM2 source that can be explained by mixing a continental crustal sediment characterized by a high Sr/Os (similar to 10(7)) with a mantle peridotite that has low Sr/Os (similar to 10(4)).

Minerals containing chromium (Cr) as an essential element display systematic trends in their diversity and distribution. We employ data for 72 approved terrestrial Cr mineral species (http://rruff. info/ima, as of 15 April 2016), representing 4089 mineral species-locality pairs (http://mindat. org and other sources, as of 15 April 2016). We find that Cr-containing mineral species, for which 30% are known at only one locality and more than half are known from three or fewer localities, conform to a Large Number of Rare Events (LNRE) distribution. Our model predicts that at least 100 +/- 13 (1s) Cr minerals exist in Earth's crust today, indicating that 28 +/- 13 (1s) species have yet to be discovered-a minimum estimate because our model assumes that new minerals will be found only using the same methods as in the past. Numerous additional Cr minerals likely await discovery using micro-analytical methods.

A fundamental goal of mineralogy and petrology is the deep understanding of mineral phase relationships and the consequent spatial and temporal patterns of mineral coexistence in rocks, ore bodies, sediments, meteorites, and other natural polycrystalline materials. The multi-dimensional chemical complexity of such mineral assemblages has traditionally led to experimental and theoretical consideration of 2-, 3-, or n-component systems that represent simplified approximations of natural systems. Network analysis provides a dynamic, quantitative, and predictive visualization framework for employing "big data" to explore complex and otherwise hidden higher-dimensional patterns of diversity and distribution in such mineral systems. We introduce and explore applications of mineral network analysis, in which mineral species are represented by nodes, while coexistence of minerals is indicated by lines between nodes. This approach provides a dynamic visualization platform for higher-dimensional analysis of phase relationships, because topologies of equilibrium phase assemblages and pathways of mineral reaction series are embedded within the networks. Mineral networks also facilitate quantitative comparison of lithologies from different planets and moons, the analysis of coexistence patterns simultaneously among hundreds of mineral species and their localities, the exploration of varied paragenetic modes of mineral groups, and investigation of changing patterns of mineral occurrence through deep time. Mineral network analysis,

Single sulfides from abyssal peridotites have been analyzed for Pb and Re-Os to constrain the evolution of oceanic mantle composition. These represent the first analyses of Pb and Os isotopic compositions in the same sulfide grain. The sulfides are from Gakkel and Southwest Indian ridge peridotites, occur at < 0.1% modal abundances, and contain 0.001-0.4 ppm Re, 0.003-5 ppm Os, and 0.12-12 ppm Pb. Sulfide Pb isotopic compositions extend from depleted (e.g., Pb-206/Pb-204=17.0) to enriched (19.6), covering a larger range than associated basalts. The Os isotopic range of sulfides is more restricted, but extends from depleted (Os-187/Os-188 = 0.116) to enriched (0.150). Pb and Os concentrations and isotopic compositions co-vary, with correlation coefficients of 0.76-0.94. Both Pb and Re-Os isotopic data follow similar to 2 Ga isochrons, with isotopic compositions varying down to small ( << 1 km) length-scales and some sulfides containing supra-chondritic Re-187/Os-188 and Os-187/Os-188. These observations are best explained by long-term recycling of oceanic lithosphere combined with melt extraction and refertilization at ancient ocean ridges, rather than a specific event at 2 Ga.