A single gem lithospheric diamond with five sulfide inclusions from the Udachnaya kimberlite (Siberia, Russia) has been analyzed non-destructively to track the growth conditions of the diamond. Sulfides are the most abundant mineral inclusions in many lithospheric diamond crystals and are the most favorable minerals to date diamond crystals by Re-Os isotope systematics. Our investigation used non-destructive, micro-techniques, combining X-ray tomography, X-ray fluorescence, X-ray powder diffraction, and Raman spectroscopy. This approach allowed us to determine the spatial distribution of the inclusions, their chemical and mineralogical composition on the microscale, and, finally, the paragenetic association, leaving the diamond host completely unaffected. The sample was also studied by X-ray diffraction topography to characterize the structural defects of the diamond and to obtain genetic information about its growth history. The X-ray topographic images show that the sample investigated exhibits plastic deformation. One set of {111} slip lamellae, corresponding to polysynthetic twinning, affects the entire sample. Chemical data on the inclusions still trapped within the diamond show they are monosulfide solid solutions of Fe, Ni and indicate a peridotitic paragenesis. Micro-X-ray diffraction reveals that the inclusions mainly consist of a polycrystalline aggregate of pentlandite and pyrrothite. A thorough analysis of the Raman data suggests the presence of a further Fe, Ni sulfide, never reported so far in diamonds: mackinawite. The total absence of any oxides in the sulfide assemblage clearly indicates that mackinawite is not simply a "late" alteration of pyrrhotite and pentlandite due to secondary oxidizing fluids entering diamond fractures after the diamond transport to the surface. Instead, it is likely formed as a low-temperature phase that grew in a closed system within the diamond host. It is possible that mackinawite is a more common phase in sulfide assemblages within diamond crystals than has previously been presumed, and that the percentage of mackinawite within a given sulfide assemblage could vary from diamond to diamond and from locality to locality.

Understanding magmatic processes is critical to understanding Mars as a system, butCuriosity'sinvestigation of dominantly sedimentary rocks has made it difficult to constrain igneous processes. Igneous classification of float rocks is challenging because of the following: (1) the possibility that they have been affected by sedimentary processes or weathering, and (2) grain size heterogeneity in the observed rock textures makes the small-scale compositions measured by rover instruments unreliable for bulk classification. We avoid these ambiguities by using detrital igneous mineral chemistry to constrain models of magmatic processes in the source region for the fluvio-deltaic Bradbury group. Mineral chemistry is obtained from X-ray diffraction of three collected samples and a new stoichiometric and visual filtering of similar to 5,000 laser induced breakdown spectroscopy (LIBS) spots to identify compositions of individual igneous minerals. Observed mineral chemistries are compared to those produced by MELTS thermodynamic modeling to constrain possible magmatic conditions. Fractionation of two starting primary melts derived from different extent of adiabatic decompression melting of a primitive mantle composition could result in the crystallization of all minerals observed. Crystal fractionation of a subalkaline and an alkaline magma is required to form the observed minerals. These results are consistent with the collection of alkaline and subalkaline rocks from Gale as well as clasts from the Martian meteorite Northwest Africa 7034 and paired stones. This new method for constraining magmatic processes will be of significant interest for the Mars 2020 mission, which will also investigate an ancient volcaniclastic-sedimentary environment and will include a LIBS instrument.

TheCuriosityrover's exploration of rocks and soils in Gale crater has provided diverse geochemical and mineralogical data sets, underscoring the complex geological history of the region. We report the crystalline, clay mineral, and amorphous phase distributions of four Gale crater rocks from an 80-m stratigraphic interval. The mineralogy of the four samples is strongly influenced by aqueous alteration processes, including variations in water chemistries, redox, pH, and temperature. Localized hydrothermal events are evidenced by gray hematite and maturation of amorphous SiO(2)to opal-CT. Low-temperature diagenetic events are associated with fluctuating lake levels, evaporative events, and groundwater infiltration. Among all mudstones analyzed in Gale crater, the diversity in diagenetic processes is primarily captured by the mineralogy and X-ray amorphous chemistry of the drilled rocks. Variations indicate a transition from magnetite to hematite and an increase in matrix-associated sulfates suggesting intensifying influence from oxic, diagenetic fluids upsection. Furthermore, diagenetic fluid pathways are shown to be strongly affected by unconformities and sedimentary transitions, as evidenced by the intensity of alteration inferred from the mineralogy of sediments sampled adjacent to stratigraphic contacts.

Large and relatively pure diamonds like the historic 3,106 ct Cullinan, found in South Africa in 1905, have long been regarded as unusual based on their physical characteristics. For example, they often exhibit exceptional color and clarity, while routinely qualifying as type IIa, a rare designation of chemical purity. A new research discovery about these Cullinan-like diamonds is that they contain heretofore unknown, deeply derived inclusions that originate below the continental mantle keel and are thus known as "superdeep" diamonds (Smith et al., 2016). Originating from a depth between 360 and 750 km, they reveal information about the conditions within the convecting mantle, beneath the earth's rigid tectonic plates. Here we review the previously published findings, compare the Cullinan-like diamonds to the more abundant lithospheric diamond population, and offer evidence from some additional diamond samples that further verifies their superdeep origin. Cullinan-like diamonds contain minute and rare silicate and iron-rich metallic inclusions surrounded by a fluid jacket composed of methane and hydrogen. The inclusion compositions suggest that this deep mantle environment contains small pockets of oxygen-deficient metallic liquid out of which the diamonds crystallized. This new and unexpected observation made on the world's most expensive diamonds is important for understanding the chemical reactions between mineral assemblages in the deep earth. It shows that deep regions of the mantle contain metallic iron, as opposed to the shallower, more oxidized mantle rocks actively participating in plate tectonics and its associated volcanism.

Vera Rubin ridge (VRR) is an erosion-resistant feature on the northwestern slope of Mount Sharp in Gale crater, Mars, and orbital visible/shortwave infrared measurements indicate it contains red hematite. The Mars Science LaboratoryCuriosityrover performed an extensive campaign on VRR to study its mineralogy, geochemistry, and sedimentology to determine the depositional and diagenetic history of the ridge and constrain the processes by which the hematite could have formed. X-ray diffraction (XRD) data from the CheMin instrument of four samples drilled on and below VRR demonstrate differences in iron, phyllosilicate, and sulfate mineralogy and hematite grain size. Hematite is common across the ridge, and its detection in a gray outcrop suggest localized regions with coarse-grained hematite, which commonly forms from warm fluids. Broad XRD peaks for hematite in one sample below VRR and the abundance of FeO(T)in the amorphous component suggest the presence of nanocrystalline hematite and amorphous Fe oxides/oxyhydroxides. Well crystalline akaganeite and jarosite are present in two samples drilled from VRR, indicating at least limited alteration by acid-saline fluids. Collapsed nontronite is present below VRR, but samples from VRR contain phyllosilicate with d(001) = 9.6 angstrom, possibly from ferripyrophyllite or an acid-altered smectite. The most likely cementing agents creating the ridge are hematite and opaline silica. We hypothesize late diagenesis can explain much of the mineralogical variation on the ridge, where multiple fluid episodes with variable pH, salinity, and temperature altered the rocks, causing the precipitation and crystallization of phases that are not otherwise in equilibrium.

Hydrothermal high sanidine and specular hematite are found within ferric-rich and gray-colored cemented basaltic breccia occurring within horizontal, weathering-resistant strata exposed in an erosional gully of the Pu'u Poliahu cinder cone in the summit region of Maunakea volcano (Hawai'i). The cone was extensively altered by hydrothermal, acid-sulfate fluids at temperatures up to similar to 400 degrees C, and, within strata, plagioclase was removed by dissolution from progenitor Hawaiitic basalt, and sanidine and hematite were precipitated. Fe2O3T concentration and Fe3+/ n-ary sumation Fe redox state are similar to 12 wt.% and similar to 0.4 for progenitor basalt and 46-60 wt.% and similar to 1.0 for cemented breccias, respectively, implying open-system alteration and oxic precipitation. Hydrothermal high sanidine (adularia) is characterized by full Al,Si structural disorder and monoclinic unit-cell (Rietveld refinement):a = 8.563(19) angstrom, b = 13.040(6) angstrom, c = 7.169(4) angstrom, beta = 116.02(10)degrees, andV = 719.4(19) angstrom(3). Hematite (structure confirmed by Rietveld refinement) is the predominant Fe-bearing phase detected. Coarse size fractions of powdered hematite-rich breccia (500-1000 mu m) are dark and spectrally neutral at visible wavelengths, confirming specular hematite, and SEM images show platy to polyhedral hematite morphologies with longest dimensions >10 mu m. Smectite and 10-angstrom phyllosilicate, both chemically dominated by Mg as octahedral cation, are additional diagenetic hydrothermal alteration products. By analogy and as a working hypothesis, high sanidine (Kimberly formation) and specular hematite (Mt. Sharp group at Hartmann's Valley and Vera Rubin ridge) at Gale crater are interpreted as diagenetic alteration products of Martian basaltic material by hydrothermal processes.

The timing and mechanisms of continental crust formation represent major outstanding questions in the Earth sciences. Extinct-nuclide radioactive systems offer the potential to evaluate the temporal relations of a variety of differentiation processes on the early Earth, including crust formation. Here, we, investigate the whole-rock W-182/W-184 and Na-142/(144) Nd ratios and zircon Delta O-17 values of a suite of well-studied and lithologically-homogeneous meta-igneous rocks from the Acasta Gneiss Complex, Northwest Territories, Canada, including the oldest-known zircon-bearing rocks on Earth. In the context of previously published geochemical data and petrogenetic models, the new Nd-142/Nd-144 data indicate that formation of the Hadean-Eoarchean Acasta crust was ultimately derived from variable sources, both in age and composition. Although 4.02 Ga crust was extracted from a nearly bulk-Earth source, heterogeneous it Nd-142 signatures indicate that Eoarchean rocks of the Acasta Gneiss Complex were formed by partial melting of hydrated, Hadean-age mafic crust at depths shallower than the garnet stability field. By similar to 3.6 Ga, granodioritic-granitic rocks were formed by partial melting of Archean hydrated mafic crust that was melted at greater depth, well into the garnet stability field. Our W-182 results indicate that the sources to the Acasta Gneiss Complex had homogeneous, high-mu W-182 on the order of +10 ppm- a signature ubiquitous in other Eoarchean terranes. No significant deviation from the terrestrial mass fractionation line was found in the triple oxygen isotope (O-16-O-17-O-18) compositions of Acasta zircons, confirming homogeneous oxygen isotope compositions in Earth's mantle by 4.02 Ga. Crown Copyright (C) 2018 Published by Elsevier B.V. All rights reserved.

The advancement of science depends upon developing classification protocols that systematize natural objects and phenomena into "natural kinds"-categorizations that are conjectured to represent genuine divisions in nature by virtue of playing central roles in the articulation of successful scientific theories. In the physical sciences, theoretically powerful classification systems, such as the periodic table, are typically time independent. Similarly, the standard classification of mineral species by the International Mineralogical Association's Commission on New Minerals, Nomenclature, and Classification relies on idealized chemical composition and crystal structure, which are time-independent attributes selected on the basis of theoretical considerations from chemical theory and solid-state physics. However, when considering mineral kinds in the historical context of planetary evolution, a different, time-dependent classification scheme is warranted. We propose an "evolutionary" system of mineral classification based on recognition of the role played by minerals in the origin and development of planetary systems. Lacking a comprehensive theory of chemical evolution capable of explaining the time-dependent pattern of chemical complexification exhibited by our universe, we recommend a bootstrapping approach to mineral classification based on observations of geological field studies, astronomical observations, laboratory experiments, and analyses of natural samples and their environments. This approach holds the potential to elucidate underlying universal principles of cosmic chemical complexification.