This study presents the field, petrography and geochemical data of the late Neoproterozoic pegmatites and host rocks in northcentral basement complex of Nigeria. Wamba pegmatites are emplaced within the reworked belt of the Nigerian basement complex. The pegmatites are composed of complex partly zoned (rare-metal …

Corpus ID: 130332957; A dynamic model for quartz-feldspar graphic intergrowths from granitic pegmatites in the southwestern Grenville Province @article{Lentz1992ADM, title={A dynamic model for quartz-feldspar graphic intergrowths from granitic pegmatites in the southwestern Grenville Province}, author={David Richard Lentz and Anthony D. …

We combined field study, pegmatites petrology and feldspar chemistry. Pegmatites occur as N110E, N150E, N160E veins (5–8 m long, 0.4–1.5 m wide) truncating the Precambrian basement and ...

The dominant feldspar in pegmatites evolve from microcline to albite, and the content of biotite decreases. Muscovite and tourmaline are present in the pegmatite at various depths. Spodumene is the only primary lithium mineral observed in the drill core samples, and is present at 1123 m to 56 m, especially near the surface in albite …

intergrowths. The transition from planar, to edge, to cellular growth, and changes in the lobate inner feldspar-quartz boundary occurred in response to changes caused by crystallization that affect rates of Si-Al diffusion. Evidence of saturation in a volatile phase in these pegmatites indicates that water was a catalyst for feldspar growth and ...

Feldspar is the name given to a group of naturally occurring alumino-silicate minerals containing varying amounts of potassium, sodium, calcium, and/or lithium. The feldspar group of minerals is by far the most abundant group of minerals in the Earth's crust, making up about 50% of all rocks. Feldspar minerals are essential components in ...

The 579.8 ± 2.2 Ma (40Ar-39Ar, muscovite) Georgeville Pluton in mainland Nova Scotia is an epizonal body consisting of alkali feldspar granite and related pegmatite.

The pegmatites consist of four lithological units: alkali feldspar unit, graphic granite unit, quartz-albite-muscovite-tourmaline unit and saccharroidal albite-muscovite-tourmaline-garnet unit. A K/Rb ratio …

The geochemistry of K-feldspar for K, P, Sr, Ba, Rb, Cs, Ga, and of muscovite for the same elements plus Nb and Ta, was used for proving the parental relationships of S-type granites and LCT (Li, Cs, Ta) rare-element pegmatites in the southernmost pegmatitic field of the Pampean pegmatite province in Argentina.

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Albite is a rock forming mineral in pegmatites and the characteristic, interlocking blady variety known as cleavelandite is a sign of the presence of possible pockets. Albite also forms very fine crystals in vuggy alkali foidic syenites. In pegmatites, albite forms crystals up to about 8cm in pegmatite which can sometimes be gemmy.

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. ... The granitic pegmatites of the Fregeneda area (Salamanca, Spain): characteristics and petrogenesis. Mineralogical …

Pegmatite is an intrusive igneous rock defined by its very large, interlocking crystals that can range in size from 1 cm to over 1 meter. It is usually primarily composed of quartz, feldspar, and mica, but often includes rarer minerals and gemstones. Pegmatite forms in the last stages of magma crystallization.

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.

Abstract. Deformation microstructures of albitic plagioclase and K-feldspar were investigated in mylonitic pegmatites from the Austroalpine basement south of the western Tauern Window by polarized light …

Reading Pegmatites: Part 4—What Quartz and Feldspars Say. July 2018. Rocks & Minerals 93 (4):320-336. DOI: 10.1080/00357529.2018.1454105. Authors: David London. To read the full-text of this ...

In most geological categories of granitic pegmatites, the feldspar minerals crystallize under conditions of disequilibrium fractionation facilitated by increasing concentration of some or all of H 2 O,F,B,P, and Li. This departure from cotectic-to-eutectic or peritectic termination of ordinary granitic crystallization generates zoning in textures and feldspar …

The presence of amazonitic K-feldspar is a hallmark of NYF pegmatites [31]. The bodies also sit astride bands of marble and quartzite; the magma may be migrating upward along that interface ...

in blocky K-feldspar crystals decreases; the Li, Rb, and Cs contents of K-feldspar and muscovite increase; the Na/Li ratio decreases and the Cs content increases in beryl; and the Nb/Ta ratio in columbite-group minerals decreases (Cern ˇ ý 1989). These parameters vary continuously from barren through Be–Nb-rich to complex LCT pegmatites ...

It is rarely found at the Earth's surface, It is denser than basaltic rocks, It is composed almost entirely of olivine and pyroxene. Rocks that contain high amounts of silica typically also contain. aluminum, sodium, and potassium. Intrusive igneous rock are often characterized as coarse-grained because.

The investigation of feldspar in granites and pegmatites from the Qongjiagang area reveals insights into the genesis of large-scale lithium deposits in the region. Our findings suggest that fractional crystallization and structural control during magma migration were essential processes that led to the early lithium enrichment, also …

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 ...

Volyn Pegmatite Deposit. The Volyn pegmatite deposit of gem stones (Zhytomyr region, Ukraine) is geologically related to southwestern part of the Korosten pluton (1.80–1.74-Ga gabbro–anorthosite–rapakivi granite complex of the Ukrainian Shield). More than 150 isolated pegmatitic bodies with miarols are identified and mined up to …

The pegmatites of group II can be distinguished only partially from the pegmatites of group III and IV (the two groups of LCT pegmatites) by means of the ratio Ga/Ge. Note that in contrast with the behaviour of the M cations (including REE), there are no sharp differences in most cases between the values of the K-feldspar matrix and the …

Pegmatite is an igneous rock that form end of the stage a magma's crystallization. Pegmatites contain exceptionally large crystals and they contain rarely minerals than other types of rocks. They have interlocking crystals usually larger than 2.5 cm in size. Generally most Pegmatites are found in sheets of rock that are dikes and …

Reading Pegmatites: Part 4—What Quartz and Feldspars Say. D. London. Published in Rocks & Minerals 25 June 2018. Geology. THIS IS THE FOURTH OF SEVERAL ARTICLES THAT ARE MEANT TO INFORM MINERAL MINERS, COLLECTORS, AND AMATEUR SCIENTISTS ABOUT THE GEOLOGIC …

The Winneba and Mankoadze pegmatites present all characteristics of pegmatites from the rare-element class and Lithium–Cesium–Tantalum (LCT) family as described by Černý and Ercit (2005). They are granitic and peraluminous in composition, with K-feldspar, albite, quartz, and muscovite (no biotite) as major minerals, and garnet, …

Li-rich magma probably forms by partial melting of Li-bearing metasediments at temperatures 75°C or more below the minimum melting temperature at the same. P H 2 O of the simplified "granite" system KAlSi 3 O 8 –NaAlSi 3 O 8 –SiO 2 –H 2 O. An origin by anatexis is most consistent with the irregular distribution of Li-rich pegmatites ...

Pegmatites are intrusive igneous rocks of exceptionally coarse grain size, in which individual crystals can reach as much as tens of metres in size. Examples of giant crystals reported from pegmatite are a microcline measuring 49.4 × 36 × 13.7 m and weighing nearly 15,000 tons or a phlogopite plate with a size of 10 × 4.3 m (Rickwood …

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 ...