Immiscible sulfide melts in primitive oceanic magmas: Evidence and implications from picrite lavas (Eastern Kamchatka, Russia)
AMERICAN MINERALOGIST
Authors: Savelyev, Dmitry P.; Kamenetsksky, Vadim S.; Danyushevsksky, Leonid V.; Botcharnikov, Roman E.; Kamenetsksky, Maya B.; Park, Jung-Woo; Portnyagin, Maxim V.; Olin, Paul; Krasheninnikov, Stepan P.; Hauffff, Folkmar; Zelenskski, Michael E.
Abstract
Silicate-sulfide liquid immiscibility in mantle-derived magmas has important control on the budget of siderophile and chalcophile metals, and is considered to be instrumental in the origin orthomagmatic sulfide deposits. Data on primitive sulfide melts in natural samples, even those representing most voluminous magmatism in oceanic rifts, are very scarce due to the small size and poor preservation of incipient sulfide melt globules. Here we present the first detailed report of the crystallized sulfides melts in the oceanic picrites of the (presumably) Cretaceous age Kamchatsky Mys ophiolite complex in Eastern Kamchatka (Far East Russia). Sulfide melts are present in three forms; (1) as inclusions in olivine (87.1-89.6 mol% Fo), (2) interstitial to the groundmass minerals (clinopyroxene, plagioclase, and Ti-magnetite) of studied picrites, and (3) as daughter phases in silicate melt inclusions hosted by olivine and Cr-spinel phenocrysts. The sulfide melt inclusions in olivine and the groundmass of studied rocks are composed of several sulfide phases that correspond to the monosulfide (Fe-Ni; Mss) and intermediate (Fe-Cu-Ni; Iss) solid solutions. Several <0.5 mu m Pd-Sn, Pt-Ag, and Au-Ag phases are recorded within the matrix sulfides, commonly along phase boundaries and fractures. Major elements (S, Fe, Cu, Ni, Co), platinum group elements (PGE), and gold analyzed in the homogenized olivine-hosted sulfide melt inclusions, and phases identified in the matrix sulfides record the range of magmatic sulfide compositions. The most primitive sulfide liquids are notably enriched in Ni and Cu [(Ni+Cu)/Fe, at% > 0.5], continuously evolve with crystallization of (e.g., increasing Cu/Ni and Au/PGE) and demonstrate metal fractionation between Mss and Iss. Although the compositional systematics found in this study are consistent with those previously recorded, the compositions of individual sulfide phases are strongly affected by the noble metal (PGE, Au) "nuggets" that exsolve at subsolidus temperatures and form during serpentinization of the rocks. We conclude that the budget of noble metals in the studied picrites is controlled by sulfides, but the abundances of Pt and Au are influenced by mobility in post-magmatic alteration. Our data can be also used for modeling sulfide saturation at crustal pressures and understanding behavior of the noble metals in primitive oceanic magmas.
A motion-compensated error concealment scheme for H.264 video transmission
IIH-MSP: 2006 INTERNATIONAL CONFERENCE ON INTELLIGENT INFORMATION HIDING AND MULTIMEDIA SIGNAL PROCESSING, PROCEEDINGS
Authors: Hung, Chum-Ting; Leou, Jin-Jang
Abstract
For an entropy-coded video sequence, a transmission error in a codeword will not only affect the underlying codeword but may also affect subsequent codewords, resulting in a great degradation of received video frames. In this study, a motion-compensated error concealment scheme is proposed for H.264 video transmission. For H.264 inter-coded P frames, the predicted motion vector (PMV) for each corrupted block is first determined by the spatially neighboring motion vectors (MVs) around the corrupted block and the temporally motion projected overlapping MYs in the previous frame. With the PMV being the central search point, three rood search patterns are developed for motion-compensated error concealment of small-, medium-, and large-motion corrupted blocks. Then error concealment refinement using Lagrange interpolation is performed on all the initially concealed blocks. Finally, the improved ELA (edge based line average) algorithm [11] is employed to refine each concealed block in P frames.