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The identification of syngenetic inclusions in diamond (i.e. inclusions of minerals that crystallized at the same time and by the same genesis as their host) has long been of paramount importance in diamond studies. However, the widespread assumption that many or most inclusions in diamonds are syngenetic is based on qualitative morphological criteria and few direct measurements. In order to provide statistically significant information on inclusion–host genetic relations for at least one kimberlite, we have determined the crystallographic orientations of 43 olivine inclusions with diamond-imposed morphology, a feature generally interpreted to indicate syngenesis, in 20 diamonds from the Udachnaya kimberlite (Siberia). Our unprecedented large data set indicates no overall preferred orientation of these olivines in diamond. However, multiple inclusions within a single diamond frequently exhibit similar orientations, implying that they were derived from original single monocrystals. Therefore, regardless of the possible chemical re-equilibration during diamond-forming processes, at least some of the olivines may have existed prior to the diamond (i.e. they are protogenetic). Our results imply that a diamond-imposed morphology alone cannot be considered as unequivocal proof of syngenicity of mineral inclusions in diamonds

Organic matter, showing variable degrees of crystallinity and thus of graphitization, is an important source of carbon in subducted sediments, as demonstrated by the isotopic signatures of deep and ultra-deep diamonds and volcanic emissions in arc settings. In this experimental study, we investigated the dissolution of sp 2 hybridized carbon in aqueous fluids at 1 and 3 GPa, and 800°C, taking as end-members i) crystalline synthetic graphite and ii) X-ray amorphous glass-like carbon. We chose glass-like carbon as an analogue of natural "disordered" graphitic carbon derived from organic matter, because unlike other forms of poorly ordered carbon it does not undergo any structural modification at the investigated experimental conditions, allowing approach to thermodynamic equilibrium. Textural observations, Raman spectroscopy, synchrotron X-ray diffraction and dissolution susceptibility of char produced by thermal decomposition of glucose (representative of non-transformed organic matter) at the same experimental conditions support this assumption. The redox state of the experiments was buffered at ∆FMQ ≈-0.5 using double capsules and either fayalite-magnetite-quartz (FMQ) or nickel-nickel oxide (NNO) buffers. At the investigated P-T-fO 2 conditions, the dominant aqueous dissolution product is carbon dioxide, formed by oxidation of solid carbon. At 1 GPa and 800°C, oxidative dissolution of glass-like carbon produces 16-19 mol% more carbon dioxide than crystalline graphite. In contrast, fluids interacting with glass-like carbon at the higher pressure of 3 GPa show only a limited increase in CO 2 (fH 2 NNO) or even a lower CO 2 content (fH 2 FMQ) with respect to fluids interacting with crystalline graphite. The measured fluid compositions allowed retrieving the difference in Gibbs free energy (ΔG) between glass-like carbon and graphite, which is +1.7(1) kJ/mol at 1 GPa-800°C and +0.51(1) kJ/mol (fH 2 NNO) at 3 GPa-800°C. Thermodynamic modeling suggests that the decline in dissolution susceptibility at high pressure is related to the higher compressibility of glass-like carbon with respect to crystalline graphite, resulting in G-P curves crossing at about 3.4 GPa at 800°C, close to the graphite-diamond transition. The new experimental data suggest that, in the presence of aqueous fluids that flush subducted sediments, the removal of poorly crystalline "disordered" graphitic carbon is more efficient than that of crystalline graphite especially at shallow levels of subduction zones, where the difference in free energy is higher and the availability of poorly organized metastable carbonaceous matter and of aqueous fluids produced by devolatilization of the downgoing slab is maximized. At depths greater than 110 km, the small differences in ΔG imply that there is minimal energetic drive for transforming "disordered" graphitic carbon to ordered graphite; "disordered" graphitic carbon could even be energetically slightly favored in a narrow P interval.

The thermo-elastic behaviour of synthetic single crystals of grossular garnet (Ca 3 Al 2 Si 3 O 12 ) has been studied in situ as a function of pressure and temperature separately. The same data collection protocol has been adopted to collect both the pressure-volume (P-V) and temperature-volume (T-V) datasets in order to make the measurements consistent with one another. The consistency between the two datasets allows simultaneous fitting to a single pressure-volume-temperature equation of state (EoS), which was performed with a new fitting utility implemented in the latest version of the program EoSFit7c. The new utility performs fully weighted simultaneous fits of the P-V-T and P-K-T data using a thermal pressure Equation of State combined with any PV EoS. Simultaneous refinement of our P-V-T data combined with that of K T as a function of T allowed us to produce a single P-V-T-K T equation of state with the following coefficients:V 0 = 1664.46(5) Å 3 , K T0 = 166.57(17) GPa and K` = 4.96(7) α (300K, 1bar) = 2.09(2)*10 -5 K -1 with a refined Einstein temperature (θ E ) of 512K for a Holland-Powell-type thermal pressure model and a Tait 3 rdorder EoS. Additionally, thermodynamic properties of grossular have been calculated for the first time from crystal Helmholtz and Gibbs energies, including the contribution from phonons, using density functional theory within the framework of the quasi-harmonic approximation.

I . I N T R O D U C T I O NThe recent development of multimedia devices and editing tools, together with the proliferation of communication infrastructures and content sharing applications, has made the acquisition, the editing, and the diffusion of images and videos relatively-easy tasks. A single multimedia content downloaded from the internet can be the outcome of a long chain of processing steps. This fact introduces several concerns about the origin, the authenticity, and the trustability of images and videos downloaded from the network [1,2]. Moreover, identifying the origin and the authenticity (i.e., the absence of alterations after acquisition) of images proves to be a crucial element in court cases for the validation of evidences [3]. Moreover, detecting alterations permits inferring an objective quality evaluation of the analyzed multimedia content.From these premises, multimedia forensic analysts have been recently focusing on detecting alterations on images since they can be easily acquired and modified even by a non-expert user. In order to fulfill this task, many of the proposed works aim at identifying images, which have been compressed more than once estimating the coding parameters that characterize the coding stages that precede the last one [4]. This fact is justified by the observation that most Dipartimento di Elettronica, Informazione, e Bioingegneria (DEIB), Politecnico di Milano, P.za Leonardo da Vinci 32, 20133 Milano, ItalyCorresponding author: S. Milani Email: simone.milani@polimi.it of the digital multimedia contents are available in compressed format. Indeed, most of the images distributed over the internet are coded according to the JPEG standard [5].All the solutions proposed in the literature aim at detecting double compression on images assuming that some alterations can be performed between the first and the second compression stages. However, we believe that this assumption does not hold in many practical scenarios since analyzing the feasible processing chains for a given downloaded image it is deducible that more than two compression stages may have been applied. As an illustrative example, let us consider an image, which is originally compressed by the acquisition device (i.e., a video or photo camera) to be stored in the onboard memory. A second compression is performed by the owner, after editing the image to enhance the perceptual quality and adjust the format (e.g., brightness/contrast adjustment, rescaling, cropping, color correction, etc.). A third compression is performed whenever the content is uploaded to a blog or to an on-line photo album. As a matter of fact, it is reasonable to assume that a large number of digital images available online have gone through more than two compression stages performed by its owner, and could be further compressed by other users. In these cases, a method that identifies the number of compression stages proves to be extremely important in reconstructing the processing history of a content [6].This paper aims at identifying traces of...