Abundance Of Mica Research Articles

Extractive Waste as a Resource: Quartz, Feldspars, and Rare Earth Elements from Gneiss Quarries of the Verbano-Cusio-Ossola Province (Piedmont, Northern Italy)

The growing demand for raw materials requires the optimization of extractive processes and innovative approaches, such as the recovery of quarrying and processing waste. Waste materials from gneiss (ranging from blocks up to residual sludge) used as dimension stone (Beola and Serizzo from Piedmont, northern Italy) were characterized for chemistry, mineralogy, and petrography: quartz and feldspars (plagioclase and K-feldspar) are the most abundant minerals, followed by micas (biotite and minor muscovite) and traces of chlorite and epidote (allanite). Quartz and feldspars could be reused in the industrial minerals sector, especially in the ceramics industry; depending on the purity requirements of the raw materials, some mica separation treatments may be required. The most critical issues relate to the small grain size and the relative abundance of mica in some commercial varieties. The presence of allanite opens new possibilities for the recovery of rare earth elements (REE, critical raw materials).

Soil types and eolian dust in high-mountainous karst of the Northern Calcareous Alps (Zugspitzplatt, Wetterstein Mountains, Germany)

This study deals with the soil formation on pure limestone in the high-mountainous karst of Wetterstein Mountains (Northern Calcareous Alps). The study area in detail covers the alpine (2000 to 2350 m) and the subnivale zone (2350 to 2600 m) of Zugspitzplatt, a tertiary paleosurface situated next to the highest summit of Germany (Zugspitze 2963 m). The formation of autochthonous soils is determined by the following parameters: uniform geology and geochemistry of Triassic limestone (CaCO 3+MgCO 3≥98%), variable substrata (solid rock, debris, local moraine), hypsometric pattern of vegetation modified by microclimate and aspect, variety of micro-environments in karst relief. In the subnivale zone, only leptosols (lithic, skeletic) and regosols (calcaric, humic) occur, whereas in the alpine zone different stages of folic histosols and rendzic leptosols prevail due to the diversity of vegetation. The purity of limestone prevents a distinct contribution of residues to soil formation. Instead of expected A–B–C profiles, the residues are mixed with organic matter of folic horizons (O–OB–C). Only in karst depressions or on local moraines small Bt horizons (2 to 5 cm) occur. They mark a developed stage of folic histosol (O–OB–Bt–C) representing the climax of autochthonous mineral soil genesis in the study area. Special features are brown deposits (mean thickness 30 cm) covering large parts of the alpine zone. On the basis of mineralogical (X-ray diffraction, heavy minerals) and pedological data (grain size, soil chemistry), eolian origin is indicated. The resulting soils are classified as loess loam-like cambisols (Ah–Bw–2(Bt)–2C) and are related to late glacial loess deposition (Egesen-Stade of Younger Dryas). The abundance of mica and silt in the surface layers and the grain size distribution of snow dust samples prove that dust influx by southerly winds is still continuing. The major sources for both late glacial and present-day dust are magmatic and metamorphic rock formations of the Central Alps. Additionally, local dust transport from adjacent outcrops of Jurassic and Lower Cretaceous sediments is evident.

GEOLOGY AND MINERALOGY OF THE LITTLE NAHANNI RARE-ELEMENT GRANITIC PEGMATITES, NORTHWEST TERRITORIES

The Little Nahanni rare-element granitic pegmatite group (LNPG; ca. 82 Ma) in the western part of the Northwest Territories, occurs as subparallel dike swarms over an area of ~11 × 5 km in the walls of a series of cirques dominated by schists of the Upper Proterozoic Hyland Group. These pegmatite bodies, up to a few meter wide, are divisible into spodumene-bearing and spodumene-free varieties that occur close together; some dikes split into these two variants. The two types are mineralogically similar. Both contain K-feldspar, plagioclase, quartz, mica (muscovite to lepidolite), columbite-group minerals, cassiterite, tourmaline, beryl, lithiophilite and garnet; they differ in the abundance of mica and accessory phases. The spodumene-free pegmatites have more mica, particularly lepidolite, than the spodumene-bearing variety. Apatite and montebrasite occur primarily in the former, whereas most lithiophilite is present in the latter. Sparse galena, titanian rutile, fluorite and helvite are also found in both variants. Subsolidus phases are zeolite-group minerals, microlite, and secondary phosphate minerals such as triploidite. Internal zoning in both pegmatites varies from complex to symmetrical. Where well developed, the zoning is typical from border through wall and intermediate to core zone. Quartz and the feldspars occur throughout the dikes. Micas and columbite-group minerals initially increase from the border to the wall zone and subsequently decrease toward the core, whereas tourmaline becomes less abundant toward the core. Spodumene and cassiterite first appear in the wall zone and become more abundant toward the core zone, whereas the reverse is true for beryl. Phosphate minerals exist mainly in the intermediate zone of the lepidolite pegmatites, and lithiophilite in the spodumene pegmatites. Garnet remains a trace mineral in all zones, with the exception of the core zone. where it is absent. Sporadic small cavities containing quartz, K-feldspar, apatite, Mg-rich beryl, elbaite and calcite are present in some dikes. The composition of the rock-forming minerals in both types of pegmatite is similar. An example of the chemical evolution of the minerals is shown by tourmaline, which becomes richer in Al and Li, but poorer in Mg, and shows decreasing Na/(Na + vacancy) and increasing Al/(Al + Fe) values from the schist to the inner (wall + intermediate) zone of the pegmatite. These trends, together with the changes in the abundances and paragenetic sequence of the major minerals, are interpreted to reflect an increase in the Rb, Cs, Li, F, P, Be, and Ta contents, and a decrease in the contents of Mg, Fe, and B contents, in the felsic liquids during crystallization.

On the possibility of high-velocity tidal streams as dynamic barriers to longshore sediment transport: Evidence from the continental shelf off the Gulf of Kutch, India

Differences in the bathymetry, bottom topography and the abundance of mica and clay minerals on the continental shelf north and south of the Gulf of Kutch, a macrotidal bay, indicate the presence of two distinct sedimentary environments. The northern part is characterised by accumulation of sediments (prograding sediments of the Indus delta) and higher concentrations of mica and clay minerals, whereas the southern part is deprived of sediments and has relatively lower concentrations of mica and clay minerals. The distinct differences have resulted because the high-velocity (2 to 2.5 knots) tidal stream at the gulf mouth acts as a dynamic barrier inhibiting sediment transport across the mouth. Differences in the distribution of sand-size and clay-size sediments further indicates that it acts as a selective filter that is more effective against the coarser end of the size spectrum.

Experimental sliding friction and cataclasis of foliated rocks

Forty-five degree sawcuts were made in 80 cores of gneiss and mylonite such that foliation-to-sawcut angles of 0, 15, 75, 90, and 135° were produced. Triaxial compression sliding friction tests at confining pressures of 140 and 500 bars indicate that the coefficient of sliding friction is influenced by variation of foliation to sliding surface angles. In clean surface tests there is reactivation of micaceous foliation planes causing interlocking steps to form on the sliding surface. A 1-mm thick layer of gouge inserted between sliding surfaces prevents the interlocking of steps and lowers the coefficient of sliding friction. Variation in grain size exerts no systematic influence on the coefficient, nor does quartz or mica abundance; however, the incidence of stick-slip increases with quartz content at 140 bars confining pressure. Stick-slip was the dominant behavior for all compositions and orientations at 500 bars and a strain rate of 10−4/sec. Stick-slip as an earthquake mechanism probably depends on composition only at very shallow depths. Grooves developed on the sliding surfaces probably are modified Riedel shear fractures. Glass-like material produced in both the clean-surface and gouge-included tests suggests the local development of very high temperatures during sliding. Sliding-induced cataclasis occurs with very small displacements and the width of the cataclastic zone depends on grain size.

II.—On the Lias of the Coast, in the Vicinity of Lyme Regis, Dorset.

In a former communication to the Geological Society I presented an outline of the features of the coast in the vicinity of Lyme Regis; but having there described the lias only in a general manner, it is my present purpose to offer a more detailed account of that formation, as I am not acquainted with any situation where its geological structure and composition, and the organic remains which it contains, can be better studied. The relative position of the cliffs referred to in the following description is represented in the section connected with my former paper upon this subject*:—And the annexed sketch (Pl. III. fig. 1.) represents the order of superposition of the inferior oolite sands, the lias formation, and the upper beds of the red marl, as they appear in the section between Down Cliff and Culverhole Point; the beds being supposed to be placed horizontally above each other, and the superincumbent chalk and green-sand removed. The uppermost beds of the lias rise from beneath the sands of the inferior oolite at Down Cliff, on the west of Bridport Harbour; where a section is afforded of about one hundred and eighty feet of sand, in which large flattened masses of limestone occur, containing Pectens, Belemnites, Terebratulæ, &c. These sands are calcareo-siliceous, their colour is a ferruginous yellow, and they contain an abundance of mica in their lower parts. A bed of grey marl occurs in them about one hundred feet above the commencement of the lias. The calcareous