Exceptional Concentrations of Gold Nanoparticles in 1,7 Ga Fluid Inclusions From the Kola Superdeep Borehole, Northwest Russia

In the drill core of the Kola super-deep borehole (SG-3, 12,262 m depth) gold-bearing rocks of Archaean age have been located at depths of 9,500 to 11,000 m. In veins, between 9,052 and 10,744 m, within this gold zone, quartz contains fluid inclusions with gold nanoparticles. There are 4 types of fluid inclusions (1) gas inclusions of dense CO2, (2) liquid-vapor two-phase aqueous inclusions, (3) three-phase inclusions with NaCl daughter crystals, and (4) CO2-aqueous inclusions. In all inclusion types, there are extremely high concentrations of gold. The highest gold concentrations were found in the type 3 and 4 fluid inclusions with an average concentration of c. 750 ppm and may be as high as 6,000 ppm. The presence of gold as nanoparticles in the solutions of these fluid inclusions was determined by optical and spectroscopic methods. We suggest that these fluids could be a precursor of “orogenic gold fluids” which, at the gold concentrations determined, would reduce the requirements for large volumes of metamorphic fluids to form orogenic ore deposits. Further, as nanoparticles, gold could be transported in larger amounts than in true solution

Composition of Fluids Responsible for Gold Mineralization in the Pechenga Structure-Imandra-Varzuga Greenstone Belt, Kola Peninsula, Russia.

This study presents the first fluid inclusion data from quartz of albite–carbonate–quartz altered rocks and metasomatic quartzite hosting gold mineralization in the Pechenga structure of the Pechenga– Imandra–Varzuga greenstone belt. A temperature of 275–370°C, pressure of 1.2–4.5 kbar, and the fluid composition of gold-bearing fluid are estimated by microthermometry, Raman spectroscopy, and LA-ICP-MS of individual fluid inclusions, as well as by bulk chemical analyses of fluid inclusions. In particular, the Au and Ag concentrations have been determined in fluid inclusions. It is shown that albite–carbonate–quartz altered rocks and metasomatic quartzite interacted with fluids of similar chemical composition but under different physicochemical conditions. It is concluded that the gold-bearing fluid in the Pechenga structure is similar to that of orogenic gold deposits

Unraveling brain interactions in vision: The example of crowding.

Crowding, the impairment of target discrimination in clutter, is the standard situation in vision. Traditionally, crowding is explained with (feedforward) models, in which only neighboring elements interact, leading to a "bottleneck" at the earliest stages of vision. It is with this implicit prior that most functional magnetic resonance imaging (fMRI) studies approach the identification of the "neural locus" of crowding, searching for the earliest visual area in which the blood-oxygenation-level-dependent (BOLD) signal is suppressed under crowded conditions. Using this classic approach, we replicated previous findings of crowding-related BOLD suppression starting in V2 and increasing up the visual hierarchy. Surprisingly, under conditions of uncrowding, in which adding flankers improves performance, the BOLD signal was further suppressed. This suggests an important role for top-down connections, which is in line with global models of crowding. To discriminate between various possible models, we used dynamic causal modeling (DCM). We show that recurrent interactions between all visual areas, including higher-level areas like V4 and the lateral occipital complex (LOC), are crucial in crowding and uncrowding. Our results explain the discrepancies in previous findings: in a recurrent visual hierarchy, the crowding effect can theoretically be detected at any stage. Beyond crowding, we demonstrate the need for models like DCM to understand the complex recurrent processing which most likely underlies human perception in general

New data on the metallogeny and deep structure of the Kirovograd Polymetal ore district (Ukrainian Shield)

Structural and petrological localization conditions and age relationships of uranium and gold deposits are discussed. A specific type of adulariachlorite wallrock alteration is found to be associated with sulfidegold mineralization. The relation between uranium, gold, lithium deposits and the topography of K2 and M surfaces are described. A 3 D seismic model of the Kirovograd ore district is suggested

From surface structures to the integral depth model of the Kirovograd ore region (Ukrainian Shield). 1

The discovery of a middle-scale mantle trough in the Kirovograd ore district under uranium, gold and lithium deposits brought a new insight into metallogeny of the district and made it necessary to trace its surface structures to the M boundary.In this study, surface structures are described in more detales using numerous data from exploration drilling, relationships between the crustal Kirovograd-Novoukrainsk granitoid massif, mantle-related Korsun-Novomirgorod massif and M interface are discussed, surface and deep structures of uranium ore fields are correlated and vertical metasomatic and ore zonality of large uranium deposits is considered