No description available.

No description available.

<p> Recent debate has questioned the efficiency of magma differentiation in basaltic magma chambers (Marsh, 2013). As a result, petrologists are increasingly inclined to interpret olivine cumulate layers in small intrusive bodies as separately injected slurries, as opposed to the result of in-situ differentiation. Two sills with basal olivine layers, the 0601 sill, Victoria Island, NWT, Canada, and the Palisades Sill, Fort Lee, NJ have been examined in detail. First, it can be shown that the 0601 sill could have formed by the emplacement of a single phenocryst bearing magma, followed by settling of the initial phenocryst load, and in-situ differentiation. Second, a high-resolution analysis of the internal ordering of the Palisades Sill olivine horizon, widely recognized as the result of an olivine slurry, is described in order to create a generalizable model of basal olivine layers formed via slurry emplacement (Husch, 1990; Gorring, 1995). Both sills were analyzed for whole rock major and trace element compositions, mineral compositions, crystal size distributions and modal mineralogy. Parent-Daughter modeling, Pearce Element Ratio Analysis, trace element modeling, and MELTS (Ghiorso and Sack, 1995; Asimow and Ghiorso, 1998) were then used to model formation mechanisms. Finally, the 0601 sill olivine cumulate layer is com-pared with the Palisades Sill olivine horizon. While both olivine cumulate zones look superficially similar, detailed investigation reveals that a well developed trend of progressively increasing olivine upward from the base, as observed in the 0601 sill is best explained by crystal settling within an initial phenocryst-phyric magma, followed by in-situ differentiation, and cannot be explained by a slurry emplacement process.</p><p>

No description available.

No description available.

Isotopic data for the Bakircay granodiorite porphyry, give a Late Eocene age for the development of the porphyry copper system. They suggest a close temporal and genetic relationship between igneous and hydrothermal activity, and indicate that magmatic-hydrothermal fluids produced potassic alteration and that meteoric fluids enriched in radiogenic 87 Sr were responsible for propylitic alteration. The granodiorite porphyry is petrologically similar to porphyry copper-related intrusions from island arc and continental margin settings, which form a group with initial 87Sr/86Sr ratios of less than 0.7043, representing magmas produced in tectonic environments lacking any important component of old (i.e. Precambrian) continental material. The alteration assemblages present at the Bakircay prospect lend themselves to a geochemical study of the temporal variations in the hydrothermal fluids responsible for single- and multiple-stage alteration-mineralization. The chemical changes involved during single-stage potassic alteration are related to amphibole breakdown and the deposition of hydrothermal biotite (and chalcopyrite). These changes are manifested in LREE enrichment and HREE depletion reflecting the high k+ and Cl- activity of the hydrothermal fluids. During propylitic overprinting of potassic alteration changes in whole-rock geochemistry relate to the destruction of biotite (both igneous and hydrothermal) and the formation of chlorite, epidote, calcite and apatite. These changes result in the loss of all REE due to increasing fluid/rock ratios and further changes within the HREE relating to zircon stability and the deposition of new mineral phases, e.g. epidote. Conversion of pre-existing alteration types to the quartz-sericite-pyrite +- rutile +- calcite assemblage, typical of phyllic alteration, results in the loss of all elements not accommodated in these phases. The high fluid/rock ratios and low pH of the fluids cause progressive leaching of all REE, particularly the lightest (La and Ce).

The ancient continental massifs of the world are typically composed of granulite grade met metamorphic rocks of calc-alkaline affinity. A model, based on experimental work, is derived to explain the processes by which the igneous precursors of the deep crustal gneisses were generated. It is suggested that they are the results of melting of a mafic garnet - clinopyroxene rock, possibly with small amounts of amphibole and plagioclase. Their composition was subsequently modified by fractionation of amphibole and plagioclase under upper mantle/lower crustal conditions. Granulite grade gneisses are commonly found to be depleted in trace elements such as Th. U, and Rb when compared with rocks of equivalent major element composition that have not suffered granulite grade metamorphism. Possible models for the depletion of these elements are considered, and a model is derived that suggests that dehydration ration melting, involving the breakdown of biotite and amphibole. Best explains both the depleted and anhydrous nature of typical lower crustal granulites. Water activity (a(H20)) plays a key role in the determining the equilibrium mineral assemblage of rocks under lower crustal conditions. Gneisses from West Greenland and British Columbia are studied in detail, in order to constrain the variability of a(H20). Analysis of the mineral assemblages reveals that differences in a(H20) exist on a local scale under both amphibolite and granulite grade conditions. suggesting that a pervasive fluid phase of constant composition did not accompany metamorphism. It is suggested that the variability of a (H20) is due to the control exerted by the mineral phases.

No description available.

No description available.

This thesis presents laboratory studies of sulphidic mine tailings remediated by flooding, and a pilot-scale study of dry cover for remediation of unoxidised sulphide-rich tailings. At the Kristineberg Zn-Cu mine in northern Sweden, sulphide-rich, poorly buffered tailings have been deposited in five impoundments located along a valley. By increasing pH by liming, thereby reducing metal mobility, a water-covered downstream impoundment is made to function as a trap for metals released from the till-covered impoundments upstream. As a result of the liming, a calcite-gypsum sludge has been formed on the tailings. The potential metal release from the sludge during resuspension events and in a long-term perspective was investigated by performing a shake flask test and sequential extraction of the sludge. A laboratory mixing experiment was performed to simulate the flocculation processes that occur in limed tailings ponds if stream water is diverted through a pond as a part of a remediation programme. The laboratory studies showed that the sequentially extracted carbonate and oxide fractions together contained ≥ 97% of the total amount of Cd, Co, Cu, Ni, Pb and Zn in the sludge. The association of these metals with carbonates and oxides appears to result from sorption and/or co-precipitation reactions at the surfaces of calcite and Fe, Al and Mn oxyhydroxides forming in the impoundment. In the shake flask test, remobilisation of Zn, Cu, Cd and Co (at a pH of 7-9) from the sludge resulted in dissolved concentrations of these metals that were significantly lower than those predicted to result from dissolution of the carbonate fraction of the sludge. This may suggest that cationic Zn, Cu, Cd and Co remobilised from dissolving calcite, gypsum and Al oxyhydroxides were readsorbed onto Fe oxyhydroxides remaining stable under oxic conditions. The laboratory mixing experiment showed that the flocculants that settled were rich in C (18 wt%) and acid leachable Fe (14-19wt%). Thus, organic matter and Fe oxyhydroxides appear to form substantial fractions of the flocculants. Trace metal uptake in the flocculants that settled in the mixing bottles resulted in removal of Cd, Co, Cu and Zn from the dissolved phase. Another part this thesis work focuses on the hydrological aspects of dry covers. The water balance in well-defined, pilot-scale systems with various types of dry cover applied on mine tailings at the Kristineberg site has been studied. Experimental studies of water infiltration through dry covers on sulphidic tailings can be used for predicting cover performance and cover design parameters relating to the same climate conditions and the same type of tailings. For this purpose, different multilayer covers have been applied in pilot-scale test cells. Clayey till, sewage sludge, Trisoplast (a mixture of a polymer, bentonite and tailings sand) and fine-grained apatite are used as sealing layers, on top of which a protective cover of unspecified till has been applied. To be able to evaluate the behaviour of the multilayer covers in tailings-impoundment scale, and to predict how the different barrier constructions influence infiltration rate and water balance, the experimental soil covers have been monitored for water percolation, climate conditions and frost penetration. The different infiltration rates in different cells were discussed. The initial results for the first two years of monitoring suggest that the apatite concentrate as a sealing layer is more promising in reducing net infiltration than a 0.3 m thick clayey till. The high fractions of water percolated through the sealing layers (~30% of precipitation) may be explained by the absence of natural run-off from the experimental cells. The results show that snowmelt, freezing of the soil and differences in soil hydraulic properties appear to have effects on the differences in water balance in the cells. / <p>Godkänd; 2006; 20070109 (haneit)</p>