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PETROLOGY. TOPICS COVERED – Igneous rocks – Sedimentary rocks – Metamorphic rocks TOPIC TO BE COVERED – Engineering properties of different types of rocks.

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Presentation on theme: "PETROLOGY. TOPICS COVERED – Igneous rocks – Sedimentary rocks – Metamorphic rocks TOPIC TO BE COVERED – Engineering properties of different types of rocks."— Presentation transcript:

1 PETROLOGY

2 TOPICS COVERED – Igneous rocks – Sedimentary rocks – Metamorphic rocks TOPIC TO BE COVERED – Engineering properties of different types of rocks and its uses – Types of engineering tests performed on rocks

3 GRANITE

4 Plutonic igneous rock with holocrystalline and leucocratic type. Acidic and oversaturated because of its silica content (72%) Mainly consists of feldspar, quartz, mica and amphibole minerals. Consists of 20% quartz, 65% alkali feldspar Density g/cm 3

5 OCCURRENCE-STRUCTURE Compact, dense, massive and hard rock. Mural joints- (two sets vertical, one horizontal- all mutually perpendicular) occurs in some. Consists of rock into a number of rectangular blocks –quarrying. Granites are unstratified

6 PHYSICAL PROPERTIES-GRANITE 1.Massive un-stratified and dense 2.Interlocking texture-more strength 3.Equiangular or porphyritic texture (mosaic appearance) 4.Non permeable-will not become weak when dissolved in water 5.Rich in silica-resistant against weathering 6.Rich in minerals-resistant against abrasion 7.Presence of mural joints-easy for quarrying 8.Easily available 9.Having pleasing colour occurrence-decorative 10.Ability towards polishing 11.Resistance to fire and frost-minerals

7 GRANITE-USES Old times-antiquity

8 Granite uses-Modern Sculpture and memorial Buildings Engineering Rock climbing

9 DOLERITE o Dolerite is a hypabyssal rock. o It is found in sills and dykes. o It has dark gray or sometimes black texture. o Texture is medium to fine grained. o It is composed of Plagioclase, Augite and Iron Oxide with some Olivine. o Dolerite is an intermediate rock between Gabbro and Basalt. o As the texture increases in its coarseness, it approached Gabbro and as the texture becomes finer, it approaches Basalt.

10 DOLERITE-PHYSICAL PROPERTIES 1.Having similar properties like granite but the only difference is colour (Pure black-highly demanded) 2.More fine grained-more stronger 3.Difficulty in quarrying-more tough 4.Springs and seepages are also occurs due to dolerite

11 USES OF DOLERITE o Due to interlocking of crystals, the rock is very tough and is widely used as a road metal. o It has a quality of making firm grip with coal tar. o Extensively used as aggregate for concrete work. o In its unearthed state, Dolerite is one of the strongest building stone.

12 BASALT

13 o Formed by rapid cooling of basaltic lava exposed very near to the surface o On Earth, most basalt magmas have formed by decompression melting of the mantle. o The crustal portions of oceanic tectonic plates are composed predominantly of basalt, produced from upwelling mantle below, the ocean ridges.

14 MORPHOLOGY AND TEXTURES Sub aerial eruptions Columnar basalt Submarine eruptions-pillow basalt

15 1.SUB AERIAL ERUPTIONS Basalt which erupts under open air (that is, sub aerially) forms three distinct types of lava or volcanic deposits: scoria; ash or cinder (breccia); and lava flows. Basalt in the tops of sub aerial lava flows and cinder cones will often be highly vesiculated, imparting a lightweight "frothy" texture to the rock. Basaltic cinders are often red, coloured by oxidized iron from weathered iron-rich minerals such as pyroxene.

16 2. COLUMNAR BASALT o During the cooling of a thick lava flow, contractional joints or fractures form. o If a flow cools relatively rapidly, significant contraction forces build up. While a flow can shrink in the vertical dimension without fracturing, it can't easily accommodate shrinking in the horizontal direction unless cracks form; the extensive fracture network that develops results in the formation of columns.

17 3. SUBMARINE ERUPTIONS-PILLOW BASALT o When basalt erupts underwater or flows into the sea, contact with the water quenches the surface and the lava forms a distinctive pillow shape, through which the hot lava breaks to form another pillow. o This "pillow" texture is very common in underwater basaltic flows and is diagnostic of an underwater eruption environment when found in ancient rocks. o Pillows typically consist of a fine-grained core with a glassy crust and have radial jointing. The size of individual pillows varies from 10 cm up to several meters.

18 BASALT-PHYSICAL PROPERTIES AND USES Refers to massive, fine grained melanocratic rock Massive basalts are highly durable and strongest (high load carrying capacity) More fine grained then dolerite Used as a building stone Used as a road metal

19 SAND STONES 15% of sedimentary rocks represented by sand stones. Sand grains in sand stones are mostly quartz Colourless, fresh and with vitreous lustre Based on the size of sand grains, the sand stones may be coarse grained, medium grained or fine grained. Present in rounded or sub rounded or angular in shape. Occurs in different color's i.e. white, red, brown, yello and green. Colour is mainly due to its cementing material (mostly quartz) – Red/yellow/brown – ferruginous – White- reacts with acid –cementing material calcium carbonate – Dirty pale – mostly clay as cementing material – White or dirty white with hard material property – silica as cementing material

20 SAND STONES-TYPES I BASED ON GRAIN SIZE 1. Coarse grained – 1 to 2 mm 2. Medium grained – 0.5 mm 3. fine grained – less than 0.5 mm

21 II. BASED ON THE COMPOSITION 1.Ferruginous – Cementing mixture oxides and hydroxides 2.Calcareous – cementing mixture calcium carbonate 3.Argillaceous – cementing material clay 4.Siliceous – cementing material silica 5.Glauconitic – cementing material glauconitic SAND STONES-TYPES

22 III BASED ON MINERAL CONTENT – Arkose – rich in feldspar – Graywacky - dark in colour and rich in clay – Micaceous sandstone – mica flakes content SAND STONES-TYPES

23 IV BASED ON SHAPE OF GRAINS Grit – coarse grained, angular V BASED ON STRUCTURE – Flaggy – thin slab like structure – Free stone – massive, uniform and thick bedded – Ganister – fine grained – Ortho quartzite – siliceous stone with negligible porosity SAND STONES-TYPES


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