Open AccessGeochemistry and Radioactivity of Mineralized Pegmatite from Abu Rusheid Area, South Eastern Desert, Egypt
Author(s) -
Ablah Ahmad Ragab Ablah Ahmad Ragab
Publication year - 2011
Publication title -
bulletin of the faculty of earth sciences, king abdulaziz university, jeddah
Language(s) - English
Resource type - Journals
ISSN - 1012-8832
DOI - 10.4197/ear.22-2.5
Subject(s) - pegmatite , geology , geochemistry , cassiterite , tourmaline , fluorite , columbite , zircon , pyrite , quartz , mineralogy , chemistry , paleontology , organic chemistry , phase (matter) , tin
The mineralized pegmatite of Abu-Rusheid area, S. EasternDesert, has quartz core and feldspars and mica margins. Thispegamtite was analyzed by the Inductively Coupled Plasma-MassSpectrometry (ICP-MS) to determine the content of the major andtrace elements including the rare earth elements (REE). Themineralized pegmatite vein trends NNW-SSE with dip of about 10-30° due WSW. It is emplaced parallel to foliation and banding of thecataclastic country rocks. The studied pegmatite is classified as raremetals-enriched and shows a zonal distribution from the barren core tothe mineralized wall-zone in the metals; Nb, Ta, Zr, Hf, Th, U, Y andGa. The main carriers of the trace metals are zircon, rutile, columbitetantalite, samarskite and other REE and Th-U minerals. Cassiterite,chlorite, deep violet fluorite, calcite, goethite, hematite, pyrite,magnetite, zinnwaldite, and phlogobite, are the main accessoryminerals. The studied pegmatite is highly differentiated, NYF-typeand characterized by high FeO/MgO ratio with high concentration ofNb, Y, Zr, Th, U, REE (except Eu), and Ga. It is derived from Fenriched proterozoic crustal source depleted in Cs, B and P. The rockis peraluminous and highly fractionated and had been affected byhydrothermal alteration. The pegmatite displays clear M-type tetradeffect of the REE. The calculated tetrad effect in the pegmatite ofAbu-Rusheid demonstrates clear tendency towards the ratios of thecommon isovalents such as Zr/Hf, Nb/Ta and Y/Ho. However, thetetrad effect seems not to be mutual with the content of Na2O andRb/Sr. The absence of coherence between tetrad effect and sodacontent may indicate insignificant role of the Na-metasomatism indeveloping the tetrad effect. The pegmatite has a prominent negativeEu anomaly and excessively low K/Rb ratio. The radioactivity of thestudied pegmatite is related to a) uranium mineral (autunite), b)thorium minerals (thorite, thorianite and uranothorite) and c)