Exploration for Weathered Granite in the Al-Madinah-Yanbu Area as a Source of Silspar

SGS-TR-2012-5 Khaled H. Abdul Hafez, Rafat Ghandourah, Saeed A. Ghamdi, Hani Kurdi, Abdulaziz H. Zahrani, Mazin A. Al Tamimi, and Nader Eskander
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ABSTRACT


In view of the increasing demand for feldspar in the ceramics and glass industries, the Saudi Geological Survey made a feasibility study on sourcing silspar, an alternative product for commercial feldspar, from weathered leucocratic granite and pegmatitic rocks at some selected sites north of the Al Madinah area. These materials were chosen not only for their feldspar and quartz contents but also for their relative ease of particle-size reduction compared to fresh rocks.The investigated area is crossed by the asphalted old Madinah–Tabuk road and is located 40 km north of the Al Madinah Al Munawwarah (between latitude 24°37´00˝N to 24°52´3˝N and longitude 39°22´30˝E to 39°37´30˝E. Fifteen trenches were dug (15 to 50 m long, 2 m deep, 1.5 m wide). A total of 445 samples were collected and subjected to chemical analysis, grain size analysis, and mineralogy studies. On the basis of the chemical analysis results for SiO2, Al2O3, Fe2O3, K2O, and Na2O, the investigated area was divided into eight zones containing 16 locations. Petrographic examination of surface and trench samples indicate granitic compositions essentially comprising alkali feldspar, quartz, plagioclase, and secondary minerals biotite, amphiboles, zircon, and sphene. Mineralogical analysis shows that the Al Madinah silspar contains high amount of  potassium feldspar. Chemical compositions of representative samples indicate low amount of Fe2O3 and their non-suitability for use as is due to their high SiO2 content. The weathered granite and feldspathic sand are suitable for producing high-quality feldspar.

 

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Abdulhafez, K.H., Ghandourah, R.A., Al Ghamdi, S.A.,  Kurdi, H.H., Zahrani, A.H., Tamimi, M.A., and Eskander, N.S. 2014, Exploration for weathered granite in the Al-Madinah-Yanbu area as a source of Silspar: Saudi Geological Survey Technical Report SGS-TR-2012-5, 22 p., 11 figs., 22 tables.