Feldspar thermometry in pegmatites: truth and consequences
Otherwise, the observed patterns of K/Rb or K/Cs in K-feldspar and micas in pegmatites conform to crystal-melt fractionation in which an aqueous solution plays no part. From the viewpoint of the ...
GEOCHEMISTRY OF FELDSPARS AND MUSCOVITE IN …
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-
The Tanco Pegmatite At Bernic Lake, Manitoba. XVII.
The alkali-feldspar paragenetic sequence in the Tanco pegmatite spans the entire crystallization and cooling history of the pegmatite and includes several different K-feldspar and albite varieties.
(PDF) The evolution of twin patterns in perthitic K-feldspar …
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 ...
Petrology and Mineralogy of Pegmatite Deposits
Lead isotope analyses of K-feldspar from late Sveconorwegian (900–1000 Ma) granitic pegmatites and A-type, ferroan granitic intrusions in four different areas of southern Norway analyzed by laser-ablation inductively coupled plasma source mass spectrometry (LA-ICPMS) give compositions in the range 206 Pb/ 204 Pb = 16.637 to 17.555, 207 Pb ...
The potential of lithium in alkali feldspars, quartz, and …
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, …
Distribution of trace elements in feldspars of granitic aplites …
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 ...
K-feldspar composition as an exploration tool for pegmatite …
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 …
Pegmatite: Formation, Composition, Properties, Uses
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 …
Why is amazonitic K-feldspar an earmark of NYF-type granitic pegmatites
Abstract The presence of amazonitic K-rich feldspar is considered an earmark of evolved granitic pegmatites of NYF type. Elements of an explanation of the "NYF pegmatite-amazonite" connection emerged in a study of the classic Anjanabonoina "hybrid" granitic pegmatite in Madagascar. The NYF assemblages there and at the Sakavalana and …
The pegmatites of the Lower Orange River
Common for homogeneous pegmatites. Quartz and feldspar with minor muscovite are commonly the only minerals present; However in some cases minor accessories are present, such as tourmaline. Heterogeneous; …
(PDF) Geochemistry of feldspar and muscovite …
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 …
THE EVOLUTION OF TWIN PATTERNS IN PERTHITIC K-FELDSPAR …
Abstract. 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-equilibrations owing to slow kinetic and localized effects of aqueous fluids (catalyst), with geological environment and chemical impurities playing only a …
THE DISTRIBUTION OF RARE-EARTH ELEMENTS IN K …
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 ...
(PDF) Stranded and Equilibrated Assemblages of Late
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 ...
(PDF) Geochemistry of feldspar and muscovite from …
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 Karagwe Ankole Belt for the study of rare-element ... Mineral abbreviations: Fsp: Feldspar, Bt: Biotite, Qtz: Quartz, Ms: Muscovite Vol.:(0123456789) Short ...
Ternary Diagrams of the Quartz-Feldspar Content of …
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 ...
Rubidium feldspars in granitic pegmatites
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 …
The Industrial Might of Connecticut Pegmatite
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 ...
Rb enrichment processes in highly evolved granites: Insights …
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.
EVOLUTION OF FELDSPARS IN GRANITIC PEGMATITES
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 …
A DYNAMICMODEL FOR GRAPHIC OUARTZ_FELDSPAR …
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 ...
RUBIDIUM FELDSPARS IN GRANITIC PEGMATITES
(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.
GRAPHIC QUARTZ-FELDSPAR INTERGROWTHS IN PEGMATITES …
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), …
Geochemistry of K‐feldspar and Muscovite in Rare‐element Pegmatites …
1. Introduction. Internal zoning in granitic pegmatites reflects the different distribution and disposition of rock-forming and accessory minerals (Cameron et al., 1949; Jahns, 1955; Černý, 1991), and these paragenetic features are generally complemented by trends in the geochemical evolution of individual mineral species.K-feldspar, albite, quartz and muscovite …
The potential of lithium in alkali feldspars, quartz, and …
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 …
Feldspar Potential in Namibia
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
Distribution of trace elements in feldspars of granitic aplites …
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 …
Geochemistry of K-feldspar and Muscovite in Rare …
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-
Pegmatite
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 ...