Chlorite alteration in pegmatite from the Madan Pb-Zn deposits: mineral association, chemical composition and temperature of formation

Chlorites are common constituent of the secondary mineral assemblage formed as alteration products after aluminosilicate host rocks in the Pb-Zn deposits in Madan district. In concordant pegmatite body from the Petrovitsa deposit, they are formed after mica flakes. Such transformation often results in abundant rutile grains. The dominant chlorite compositions fall in the clinochlore-chamosite series. Minor and trace elements incorporation of Li, B, V, Co, Ni, Zn, Ga, Rb, Sr, Cs, and Ba is detected. Calculated To of formation ranges within 298–306 °C.

Basalt - fluid interactions at subcritical and supercritical conditions: An experimental study

<p><b>To investigate the interaction between fluids and basalt at subcritical, near-supercritical, and supercritical hydrothermal conditions (350-400˚C/500 bar), eight experiments have been conducted. These used a continuous-flow, high temperature and pressure hydrothermal apparatus. The basalt was reacted with three fluids: distilled water; geothermal brine; and natural seawater. Two further experiments used only seawater as a control to determine its behaviour without the influence of basalt.</b></p> <p> With distilled water, the fluid chemistry results show elevated SiO2, K, Cl, SO4, and H2S in solution for the first 12 days of both experiments. This is due to volcanic glass dissolution. After glass was removed, fluid composition was controlled by the remaining rock minerals. At 400˚C, the secondary mineral assemblage at the bottom of the Reactor (fluid entry point) is composed of grossular, wollastonite, anorthite, and chlorite. These results show the effectiveness of distilled water, which lacks any alkali cations, at removing Na and K rapidly from the rock. At the top of the Reactor (fluid exit point) the secondary minerals are anorthite and celadonite. At 350˚C, the secondary mineral assemblage at the bottom is anorthite and chlorite, while celadonite is the dominant secondary mineral at the top. In both experiments, celadonite replaces solely olivine. The formation of celadonite through reaction with distilled water shows that it can be formed by the interaction of deuteric water and basalt without addition of other components.</p> <p> The geothermal brine contains high concentrations of SiO2, K, SO4, Na, Cl and has an acidic pH. At 400˚C, fluid chemistry displays elevated SiO2 concentrations for approximately two weeks due to glass dissolution. At 350˚C, SiO2 concentration is initially high after temperature increase, but decreases gradually over the remainder of the experiment. At 400˚C, the secondary mineral assemblage at the bottom of the Reactor is composed of anhydrite and biotite, while at the top of the Reactor, smectite is the only secondary mineral. At 350˚C, anhydrite and smectite are found at the bottom, while only smectite is found at the top. The lack of biotite at 350˚C suggests this mineral’s precipitation kinetics are too slow to outcompete chlorite precipitation.</p> <p> The seawater-only experiments were conducted as controls to determine its behaviour during heat-up and provide the input solution composition for the seawater-basalt experiments. Both seawater-only experiments (377˚C and 342˚C) show the precipitation of anhydrite, caminite and brucite due to their retrograde solubilities. The effluent solutions are greatly depleted in Ca, Mg and SO4.</p> <p> In the seawater-basalt experiments at near-supercritical (400˚C) and subcritical conditions (350˚C), elevated SiO2 concentrations due to glass dissolution are not observed. This is attributed to rapid secondary mineral precipitation. Fluid chemistry and mass balance calculations show almost complete removal of SO4, and in particular, Mg, from the seawater while Ca shows a considerable loss from the rock. Three mineralization fronts were identified: (1) glass dissolution; (2) chloritization; and (3) anhydrite precipitation. In both experiments, there is a switch from chloritization to smectitization. This is accompanied by a decrease in Mg/Fe ratio in smectite. This mineral was also found at the top of both experiments, but its composition was more reflective of the rock.</p> <p>In terms of reactivity, the order of phases from most to least reactive is glass – olivine – clinopyroxene – plagioclase – Fe-Ti oxide. For the aluminosilicate phases this is attributed their respective Al contents. The seawater-basalt experiments also emphasise the fast rate of reaction at which Mg is fixed by the rock, which is conjectured to take less than a few hours.</p> <p>Considering all experiments, the distilled water results show a rock control on fluid chemistry while in the remaining basalt experiments, the chemistry is largely controlled by the fluid.</p> <p>Temperatures calculated using standard Na/K geothermometer did not estimate, in most cases, values close to the experimental temperature. This is due to the inability of the rock to sufficiently adjust the Na/K ratio given the secondary mineral assemblages that form.</p> <p> </p>

Basalt - fluid interactions at subcritical and supercritical conditions: An experimental study

<p><b>To investigate the interaction between fluids and basalt at subcritical, near-supercritical, and supercritical hydrothermal conditions (350-400˚C/500 bar), eight experiments have been conducted. These used a continuous-flow, high temperature and pressure hydrothermal apparatus. The basalt was reacted with three fluids: distilled water; geothermal brine; and natural seawater. Two further experiments used only seawater as a control to determine its behaviour without the influence of basalt.</b></p> <p> With distilled water, the fluid chemistry results show elevated SiO2, K, Cl, SO4, and H2S in solution for the first 12 days of both experiments. This is due to volcanic glass dissolution. After glass was removed, fluid composition was controlled by the remaining rock minerals. At 400˚C, the secondary mineral assemblage at the bottom of the Reactor (fluid entry point) is composed of grossular, wollastonite, anorthite, and chlorite. These results show the effectiveness of distilled water, which lacks any alkali cations, at removing Na and K rapidly from the rock. At the top of the Reactor (fluid exit point) the secondary minerals are anorthite and celadonite. At 350˚C, the secondary mineral assemblage at the bottom is anorthite and chlorite, while celadonite is the dominant secondary mineral at the top. In both experiments, celadonite replaces solely olivine. The formation of celadonite through reaction with distilled water shows that it can be formed by the interaction of deuteric water and basalt without addition of other components.</p> <p> The geothermal brine contains high concentrations of SiO2, K, SO4, Na, Cl and has an acidic pH. At 400˚C, fluid chemistry displays elevated SiO2 concentrations for approximately two weeks due to glass dissolution. At 350˚C, SiO2 concentration is initially high after temperature increase, but decreases gradually over the remainder of the experiment. At 400˚C, the secondary mineral assemblage at the bottom of the Reactor is composed of anhydrite and biotite, while at the top of the Reactor, smectite is the only secondary mineral. At 350˚C, anhydrite and smectite are found at the bottom, while only smectite is found at the top. The lack of biotite at 350˚C suggests this mineral’s precipitation kinetics are too slow to outcompete chlorite precipitation.</p> <p> The seawater-only experiments were conducted as controls to determine its behaviour during heat-up and provide the input solution composition for the seawater-basalt experiments. Both seawater-only experiments (377˚C and 342˚C) show the precipitation of anhydrite, caminite and brucite due to their retrograde solubilities. The effluent solutions are greatly depleted in Ca, Mg and SO4.</p> <p> In the seawater-basalt experiments at near-supercritical (400˚C) and subcritical conditions (350˚C), elevated SiO2 concentrations due to glass dissolution are not observed. This is attributed to rapid secondary mineral precipitation. Fluid chemistry and mass balance calculations show almost complete removal of SO4, and in particular, Mg, from the seawater while Ca shows a considerable loss from the rock. Three mineralization fronts were identified: (1) glass dissolution; (2) chloritization; and (3) anhydrite precipitation. In both experiments, there is a switch from chloritization to smectitization. This is accompanied by a decrease in Mg/Fe ratio in smectite. This mineral was also found at the top of both experiments, but its composition was more reflective of the rock.</p> <p>In terms of reactivity, the order of phases from most to least reactive is glass – olivine – clinopyroxene – plagioclase – Fe-Ti oxide. For the aluminosilicate phases this is attributed their respective Al contents. The seawater-basalt experiments also emphasise the fast rate of reaction at which Mg is fixed by the rock, which is conjectured to take less than a few hours.</p> <p>Considering all experiments, the distilled water results show a rock control on fluid chemistry while in the remaining basalt experiments, the chemistry is largely controlled by the fluid.</p> <p>Temperatures calculated using standard Na/K geothermometer did not estimate, in most cases, values close to the experimental temperature. This is due to the inability of the rock to sufficiently adjust the Na/K ratio given the secondary mineral assemblages that form.</p> <p> </p>

Specific features of postmagmatic and hypergene kimberlite rock alteration research

Methods of studying postmagmatic and hypergene kimberlite rock alteration, as well as identifying secondary minerals and their associations are characterized. It is shown that secondary mineral formation processes took place in a wide temperature range and they are caused by their downward change of medium reaction from alkaline to acidic followed by neutralization, which resulted in dissolution, additional growth and emergence of new secondary mineral generations.

Processing of waste slag of non-ferrous metallurgy for the purpose of its complex utilization as a secondary mineral raw material

This article provides an overview of the methods of processing slag from welting is given, different approaches and attempts of scientists from a number of countries aimed at processing such slags are considered. In the course of the review it was found that a huge number of the following methods and methods of processing from waelz slag, there is not a single option that has sufficient complexity of processing, and that at the moment are in the dumps toxins from waelz never found its use as a secondary raw material. The elemental chemical composition of the slag from welting, which is represented by compounds of calcium, silicon, iron, aluminum, carbon and heavy nonferrous metals in the form of zinc and lead, is determined. Thus, it is established that for many years, the slags from waelz that have not found their application and are in the dump at the moment continue to have a polluting effect on the environment. Ill. 1. Ref. 63.

The Influence of Weathering, Water Sources, and Hydrological Cycles on Lithium Isotopic Compositions in River Water and Groundwater of the Ganges–Brahmaputra–Meghna River System in Bangladesh

The silicate weathering of continental rocks plays a vital role in determining ocean chemistry and global climate. Spatiotemporal variations in the Li isotope ratio (δ7Li) of terrestrial waters can be used to identify regimes of current and past weathering processes. Here we examine: 1) monthly dissolved δ7Li variation in the Ganges River’s lower reaches; and 2) the spatiotemporal variation of river water of the Brahmaputra, Meghna rivers, and groundwater in Bangladesh. From the beginning to maximum flood discharges of the rainy season (i.e., from June to September), Li concentrations and δ7Li in the Ganges River show remarkable changes, with a large influence from Himalayan sources. However, most Li discharge across the rainy season is at steady-state and strongly influenced by the secondary mineral formation in the low-altitude floodplain. Secondary mineral formation strongly influences the Meghna River’s Li isotopic composition along with fractionation lines similar to the Ganges River. A geothermal input is an additional Li source for the Brahmaputra River. For groundwater samples shallower than ∼60 m depth, both δ7Li and Li/Na are highly scattered regardless of the sampling region, suggesting the variable extent of fractionation. For deep groundwater (70–310 m) with a longer residence time (3,000 to 20,000 years), the lower δ7Li values indicate more congruent weathering. These results suggest that Li isotope fractionation in rivers and groundwater depends on the timescale of water-mineral interaction, which plays an essential role in determining the isotopic signature of terrestrial Li inputs to the ocean.

Mercury(II) chloride nonoccurrence in nature: A molecular-level investigation

Prepared by Chinese alchemists in the first millennium A.D., mercury(II) chloride (HgCl2) has been known since the Middle Ages. However, as it has never been found in mercury mines, its nonoccurrence in nature appears to be a basic assumption. Electrochemical principles were applied to show that the secondary mineral calomel in mercury mines is partly converted to HgCl2 in a multistep natural process. This showed how HgCl2 does occur naturally, providing a theoretical basis for the detection and quantification of solid HgCl2 as a mineral in mercury mines.

Characteristics of Chromite Deposits at North Kabaena District, Bombana Regency, Southeast Sulawesi Province, Indonesia

The study area is located in North Kabaena District, Bombana Regency, Southeast Sulawesi. This paper is aimed to describe characacristics of chromite deposits. This study is conducted in three stages, three stages including desk study, field work and laboratory analysis. Desk study mainly covers literature reviews. Field work includes mapping of surface geology and sampling of representative rocks types. Laboratory analysis includes the petrologic observation of handspecimen samples, petrographic analysis of the thin section and ore microscopy for polished section. The results of petrographic analysis show that olivine minerals are generally replaced by minerals orthopyroxene and has been alterated by lizardite type serpentine veins with a fractured structure. The mineral olivine is also replaced by the mineral chrysotile as a secondary mineral with a fibrous structure. Based on ore microscopy analysis show that chromite has generally experienced a lateritification process and has been replaced by magnetite, hematite and geotite minerals. Chromite has experience process of weathering and alteration from its source rock caused by tectonics that occurred in the study area. The results shows that the characteristics of chromite deposits in North Kabaena District Chromite deposits has generally encountered in peridotite rock which have a grain size of 0.3-20 cm. Furthermore, chromite deposits in the study area are also encountered in podiform deposits, distributed locally and shows podiform to tubular shape with the dimensions of 30-60cm.