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The K/Rb in K-feldspar constitutes a good indicator of a pegmatite body's evolution ( Cernˇ ´y et al. 1985). The K/Rb ratio ranges between 140 and 467 for type-I pegmatites (the higher values were obtained in feldspars from the late-necking zones), 88 to 264 for type-II pegmatites, and 23 to 59 for type-III pegmatites (exclu-
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Ca, Sr and Ba in K-feldspars from rocks and pegmatites. comparatively finer grained rock feldspars than the coarse pegmatite crystals. This may explain the relatively higher Na …
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On the basis of both experimental evidence and natural pegmatites, it is more plausible that the elevated Li content of alkali feldspar, quartz and muscovite reflects the …
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Feldspar mining peaked in Connecticut in the early 1900s; in 1908 Connecticut, with its four "spar" mills, was the leading producer of this mineral in the United States. ... While feldspar was the most sought-after mineral mined from pegmatites, quartz and mica also had important industrial uses. Mica is the common name for a group of ...
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A distinction has been made between the fractionated (filled triangles) and flat (open triangles) REE patterns of the two-mica pegmatite zone (zone 1 = biotite pegmatites, zone 2 = two-mica ...
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4. GRAPHIC QUARTZ-FELDSPAR INTERGROWTHS IN PEGMATITES 85 The pegmatites under consideration are late tectonic (565 to 600 Ma, Sr-Rb Zircon; Stern and Hedge, 1985) with respect to the Hafafit orogeny (~ 682 Ma) and were emplaced into the Hafafit gneiss rocks at pressures and temperatures less than peak metamorphic conditions (Rashwan, 1991), …
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Granitic rare-element pegmatites host several economic commodities, such as the lithium hosted in spodumene and petalite, the rubidium contained in lepidolite and K-feldspars, cesium in pollucite, the beryllium in beryl, and the niobium and tantalum hosted in Nb-Ta-oxide minerals, ceramic grade feldspar, and industrial mica (e.g., Linnen et al., 2012, London, 2008 …
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The relatively high content of P 2 O 5 (> 0.99) in K-feldspar (microcline) and its increasing narrow range in plagioclase (from Penja to Manjo) indicate that the pegmatites are evolved, but the ...
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Mining, import and export of feldspar raw materials in the SADC region 24. Mining, import and export of feldspar raw materials in the SADC region 24.1 Current feldspar production 24.2 Past feldspar production in Namibia 25.3 Trade data 26.4 Import 26.5 Export 29. Feldspar demand in Namibia 30. 7.1 Direct demand 30. 7.2 Indirect demand 30
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Granitic rare-element pegmatites host several economic commodities, such as the lithium hosted in spodumene and petalite, the rubidium contained in lepidolite and K-feldspars, cesium in pollucite, the beryllium in beryl, and the niobium and tantalum hosted in Nb-Ta-oxide minerals, ceramic grade feldspar, and industrial mica (e.g., Linnen et al., 2012, London, 2008 …
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THE DISTRIBUTION OF REE IN K-FELDSPAR IN NORWEGIAN PEGMATITES 139 uncommon in both Evje–Iveland and Froland (Bjørlykke 1935, Fought 1993, Stockmarr 1994). Re-cent studies document that the late ...
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Thirty-four samples of K-feldspar and 34 of albite from these veins and host granites were analysed to establish the distribution of elements and their fractionation trends in the …
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Three types of pegmatite have been identified at Dibilo. Type I: barren; Type II-a: Nb-Ta; Type II-b: Nb-Ta, Mo; Type III: Li, Nb-Ta. Barren pegmatites result from the partial …
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Thirty-four samples of K-feldspar and 34 of albite from these veins and host granites were analysed to establish the distribution of elements and their fractionation trends in the sequence of feldspar crystallization. Rubidium and Cs increase, and Ba, Sr, Ba/K, Sr/K and K/Rb decrease in K-feldspar, whereas Na increases and Sr and Ca decrease in ...
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The studied pegmatites suggest a sodium-dominant pegmatitic melt where micas and albites are dominant over potassium minerals. The mapped pegmatites from the Gatumba area are of interest in...
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The Cap de Creus pegmatite field exhibits a well-defined regional zonation of four types of granitic pegmatite: barren K-feldspar-rich pegmatites (type I), beryl–columbite-subtype …
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These deviations from the classic formula of a feldspar are to be expected: both substitutions are widespread in K-feldspar of broadly variable structural state from peraluminous granitic pegmatites, in contrast to their counterparts from plutonic rocks and at least some pegmatites with peralkaline tendencies (e.g., Teerststra 1997, Teertstra ...
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K-feldspar from the Cap de Creus pegmatites exhibits higher contents in Ba, Rb, Cs, Nb, Y, Sn, V and Cr than albite. Albite is richer in Sr, Zr, Cu, As, Ce and Ga. Pb, Zn, W, Co and Ni have similar affinity for K-feldspar and albite. Muscovite exhibits similar geochemical evolution to K-feldspar. These progressive trends suggest a common origin ...
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Evidence of saturation in a volatile phase in these pegmatites indicates that water was a catalyst for feldspar growth and that lower activities of H2O in the melt decrease Si diffusivity at the ...
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Pegmatites resemble granitic intrusive rocks as far as the major minerals, K-Na feldspar, quartz and mica and their granular textures are concerned. On the other hand, pegmatites strongly contrast with these common felsic magmatic rocks with regard to the grain size of their minerals, which can achieve the level of mega crystals.
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K-feldspar in rocks is commonly seen as a heterogeneous mixture of mineral species and varieties with random microstructures. Most consider that observable features arise from incomplete re ...
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of K/Rb-Cs, K/Cs-Rb, K/Rb-Rb/Sr, K/Rb-Ba in K-feldspar from the granites and pegmatites show that they form an association with the evolutional sequence: granites → barren- to transitional pegmatites → beryl type, beryl-columbite-phosphate pegmatites → complex type of spodumene subtype pegmatites → albite-
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In this work, two granite-pegmatite fields were studied: the Bugarula field in the northern part of Idjwi island and the Kalehe field, along the west coast of Lake Kivu, with a view to determine the co-genetic link between different pegmatites …
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Thurston's statement (1955, p. 36) that the quartz-rich pegmatites (or feldspar-bearing quartz veins, as they could be called) are grada- tional with the more normal pegmatites falls short of being strictly correct. Nevertheless the upward-reaching tongue formed by the zero contour, which extends toward the quartz apex but does not ...
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generalization of the evolution of feldspars in granitic pegmatites is based not only on published information, but also on a backlog of unpublished data. If this review stimulates new studies of …
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pegmatites feldspar di gambia. Kebanyakan pegmatit terdiri dari kuarsa, feldspar, dan mika; pada dasarnya "granit." Pegmatite "intermediate" dan "mafic" yang lebih jarang mengandung amphibole, feldspar kalsium-plagioklas, piroksen dan mineral lainnya diketahui, ditemukan di zona rekristalisasi dan apofisis yang terkait …Albite and K-feldspar ...
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Rubidium typically replaces K in K-feldspar and mica, and can crystallize under a wide range of physicochemical conditions in granitic and pegmatitic systems (Murray and Rogers, 1973, Tischendorf et al., 1997, Černý et al., 2003).Mica and K-feldspar are two of the most important constituent minerals of granites and pegmatites.
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Rubidium feldspars form under low-temperature conditions in the interior zones of many pollucite-bearing rare-element granitic pegmatites. The (K-Rb)-feldspars lie close to the KAlSi 3 O 8-RbAlSi 3 O 8 join and have up to 26.2 wt.% Rb 2 O (91 mol.% Rbf) and 1.5 wt.% Cs 2 O (3 mol.% Csf). Three subsolidus processes generate rubidium feldspars at a microscopic …
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saturation in a volatile phase in these pegmatites indicates that water was a catalyst for feldspar growth and that lower activities of H2O in the melt decrease Si diffusivity at the crystal ...
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On average, muscovite Li contents are greater in spodumene-bearing pegmatites at 0.21 ± 0.12 wt. % than for common quartz-feldspar pegmatites at 0.14 ± 0.08 wt. %.
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Gambia USD $ Georgia USD ... Most pegmatites are found in sheets of rock (dikes and veins) near large masses of igneous rocks called batholiths. The word pegmatite derives from Homeric Greek, πήγνυμι (pegnymi), which means "to bind together", in reference to the intertwined crystals of quartz and feldspar in the texture known as ...
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A high Rb content occurs in K-feldspar from granitic pegmatites of the rare-element class, and particularly in the highly fractionated, complex, pollucite-bearing pegmatites of the LCT family [peraluminous, Li,Cs,Ta-enriched; cf. dernf (1991) for classificationl. These pegmatites aftain a …
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Feldspar: Potassium feldspar (microcline) and plagioclase feldspar are both common, adding to the rock's overall strength and stability. Mica: Muscovite and biotite are the most common …
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Li-bearing pegmatites are common in the northernmost part of the area, where they can be classified in four groups: (a) petalite-bearing pegmatites; (b) spodumene-bearing pegmatites; (c ...
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The Li concentration of alkali feldspars, quartz, and muscovite from the spodumene-rich Main Sill of the Moblan pegmatite in Quebec, Canada, was used to evaluate the potential of the most common minerals in granitic pegmatites as indicators for the presence of Li-aluminosilicate mineralization. In Moblan, alkali feldspar crystals incorporate 9–350 ppm Li, …
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(Rb,K)-feldspar also coprecipitates with end-member K-feldspar (+ cookeite), in metasomatic reactions of hydrothermal fluid with early Rb-bearing feldspar and pollucite at -300 to 150'C.
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