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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Gurmeet Singh posted an Question
October 09, 2020 • 19:56 pm
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30 points
30 points
- IIT JAM
- Geology (GG)
Sir please explain last 2 lines
unstable. In view of the stability characters of the minerals, in most of the sedimentary rocks we find the minerals like quartz and muscovite whereas the presence of unstable minerals like augite, hypersthene etc. is rarely found. In general, the sandy rocks consist largely of stabler primary minerals, while the fine grained clayey materials are constituted mostly by the ferromagnesian silicates and feldspars.
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Sajan sarthak
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1.Sandyrocks means in general view point the snadstone have stable quartz in it. 2.where as in clay like shale there must be PLAGIOCLASE component PLAGIOCLASE breaks down to kaolinite. Ferromagnesian sillicate (olivine,pyroxene ) very much sussceptible to weathering as comes on the top of Bowen's series.
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Rahul kumar Best Answer
Answer: The last two lines convey that the sandstone mainly comprises stable minerals such as Quartz, muscovite, K-feldspar etc. It happens because sandstones commonly form by the intense weathering and leaching conditions. All unstable minerals (ferromagnesium minerals) are removed by weathering. Whereas fine grains are mainly clay and ferromagnesium minerals; it happens because larger unstable mineral clasts are rapidly degraded to finer grains as a result of weathering and erosion. This is why fine grain clasts contain relatively unstable minerals.