Document Type : Research Article
Authors
1
Department of Geology, University of Karachi, Karachi, Pakistan
2
Department of Geology, University of Karachi
3
Geological Survey of Pakistan
4
Kohat Cement Company Limited, Kohat, Pakistan
Abstract
Physio-chemical characterization of Pab sandstone of Cretaceous age was carried out for its industrial applications. For this purpose, Sandstone samples (n = 25) were collected for petrographic and geochemical analysis from Pab Range in Khuzdar area. Petrographic data show that the sandstone is mainly composed of quartz followed by feldspar and heavy minerals in small amount. Textural analysis revealed that the grains are sub rounded to angular, moderately sorted and coarse to fine. Geochemical analysis revealed that the mean content of SiO2 is about 93.57% and Al2O3 is only about 1.65% suggesting the dominance of quartz. On the other hand, the mean concentration of Fe2O3, Na2O and K2O, CaO and MgO are found to be 1.54%, 0.11% and 0.05%, 2.26% and 0.45% respectively. On the other hand, SO3 content is found to be 0.02% as an average. It is concluded that, Pab sandstone is suitable for the production of glass products such as Egyptian glass, glass fiber, soda lime silica container glass, and Roman glass. Pab sandstone has more than 90% silica, and CaO and Fe2O3 are two major impurities that are to be removed so the silica content is increased up to 99%. Hence, making it suitable for foundries, ceramics, and silica gel. Beneficiation is required for the production of other types of glass, as well as for other industrial applications.
Silica sand is one of the most plentiful and second-most prevalent minerals in the earth crust (Edem et al., 2014). Silica solidifies at the final stage of Bowen's reaction sequence (Ketner, 1973; Bourne, 1994). Silica is commonly found in a variety of rocks, including sedimentary, igneous, and metamorphic rocks (Bourne, 1994). The utilization of silica sand relies upon its mineralogy, chemistry and textural properties (Sundararajan et al., 2009). The major source of silica sand include sandstone, quartzite, and deposits of loosely-cement or unconsolidated sand (Wilkinson, 2005). Silica occurs in the last stage of rock weathering and it is the important part of rock cycle (Shaffer, 2006). It exists in different crystalline forms such as the fibrous silica including chalcedony and semi-precious stones like agate, onyx, and carnelian. Jasper and flint are examples of granular variants (Malu et al., 2015). Whereas, diatomite and opal are examples of anhydrous kinds (Tsoar, 2004). Industrial sand and gravel, commonly known as "silica," "silica sand," and "quartz sand," contains sands and gravels with a high SiO2 content (Bolen, 1996). The term "silica sand" refers to quartz sand that contains more than 99% SiO2 and small amounts of the contaminating oxides like Al2O3, Fe2O3, CaO, MgO, TiO2, and less than 0.1% heavy minerals (Mansour, 2015).
Silica is widely used in the production of glass and glass fiber, ceramic and refractory materials, silicon carbide, sodium silicate, Portland cement, silicon alloys and metals, filter media for water treatment, sand paper, and a variety of other products (Sundararajan et al, 2009). Its specialized applications include products such as piezoelectric crystals, optical products, and vitreous silica. Due to its hardness, chemical inertness, heat resistance, resistance to weathering, and high melting point, which is caused by the strength of the atomic bonds, it is used in a variety of applications.
Silica sand has been used since ancient period and it was being used in the manufacturing of glass (Raghavan et al., 2006). Color, clarity, strength, and other physical characteristics of glass products are all influenced by the silica sand's purity. For glass manufacturing, sandstone should be very low in iron and high in silica content (Kuzwart, 1984). Quartz is the fundamental glass-forming compound in a glass batch (Kogel et al., 2009). If sandstone has a very high content of quartz, it might be crushed and used as a source of silica for glass manufacturing. During the creation of ceramics, silica serves as the skeleton structure to which clays and fluxes are affixed. This is because silica improves the integrity, drying, shrinkage, and thermal expansion that control heat transfer (Gupta et al., 1986). With the exception of bone china, silica sand is widely used in white ware ceramic formulations, making up about 40% of the ceramic body. In foundries, silica sand is essential for constructing the molds into which metal is poured to produce metal casting, as well as for metallurgical processing (Mansour, 2015).
In Pakistan, large deposits of silica sand are found near Thano Bula Khan, Abbottabad, Dera Ismail Khan, Nowshera, Dera Bugti and Dera Ghazi Khan .Silica sand is also reported in Toi and Kingri formations (Malkani et al, 2016). In Karachi, huge deposits of silica sand are reported in the Halkani sandstone member of Nari Formation (Khan et al., 2019). Beside all these deposits, Pab sandstone deposit of Late Cretaceous age is widely developed in the Kirthar-Sulaiman Province and the Axial Belt (Mughal, 2012) and exposed with significant thickness and large lateral extent in the sedimentary succession trending north south in the Pab Range of Baluchistan. In Kirthar Fold Belt, southern Pakistan, it is about 350 km long and 225 km wide and well exposed for thick marine siliciclastic successions. This sandstone is thinning toward the south and has a thickness range of 50 to 450 meters (Umer et al, 2010). At the type section, it is 490 meters thick, but to the south and west of Khuzdar, it is almost 600 meters thick (Shah, 2009). Despite the occurrence of such huge deposits of Pab sandstone in Pab Range, no work has been carried out so far on its suitability for the industrial applications. Therefore, present study is aimed at assessment of Pab sandstone exposed in Khuzdar area for its industrial applications with special focus on glass industry through textural, mineralogical and geochemical parameters.
Study area is located about 30 km west of Uthal and about 75 Km North East of Winder (Fig. 1). It is located in Khuzdar district, Balochistan which is part of Kirthar- Suleiman fold belt that lies in Pab Range. Geographic coordinates of study area lies between 240 52/ 35// to 24052/ 39//N and 660 57/ 26.59// to 660 56/ 32.67//E.
The study area is highly elevated (about 3000 feet high) with an average height of about 30 to 40 meters. The relief of study area is irregular, with alternate valleys and ridges. Ridges are dominated by Hogback or Cuesta types based on their relative slope relationship between the dip and scarp sides. The study area is in the semi-arid to arid zone. Due to low rainfall, vegetation in the study area is rare.
1.3. Geology of Study Area
In study area, Pab sandstone and Parh limestone of Cretaceous, Ranikot Formation of Paleocene, and Kirthar Formation of Eocene age are well exposed (Fig. 1). Some parts of this area are also covered by alluvium. Tectonically, study area lies in Kirthar fold Belt. Alongside the strike-slip western boundary of the Indian Plate, represented by the Ornach-Nal Fault System (ONF) and the Chaman Fault, the KFB makes up the southern portion of the Fold Belt west of Pakistan's Lower Indus Basin. The KFB passes into the LIB on the stable Indian foreland in the east. The southern KFB is bounded to the west by the Bela Ophiolite and to the west of the fold belt is the Porali Trough (Ahmed et al., 2015).
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