1. What minerals are most common in detrital (clastic) sedimentary rocks? Why ar

Question

1. What minerals are most common in detrital (clastic) sedimentary rocks? Why are these minerals so abundant?

2. How are the degree of sorting and the amount of rounding related to the transportation of sand grains?

3. What are evaporite deposits? Name a rock that is an evaporite.

4. When a body of seawater evaporates, minerals precipitate in a certain order. What determines this order?

5) How does grain size relate the energy needed to transport the sediment grains? How does grain size relate to the energy of deposition?

Explanation / Answer

The most common mineral in detrital (claustic) sedimentary rocks are Quartz - SiO2, clays and calcite.

Out of these three quartz is by far, most abundant. The main reason for this is, because it does not dissolve or react with ground water in order to form some other mineral. Quartz can survive very long term erosions.
Other common minerals are clay minerals, which result from the weathering of feldspars, and other minerals to form clay and ions in solution. Mudrocks consist of very fine quartz (silt) and clay minerals.
In some rocks, the grains consist of rock fragments, minerals like felspars, amphiboles and micas - these are called mineralogically immature as these minerals would eventually break down to form clays. Accessory minerals also occur, like zircon, ilmentite and garnet, but they are rare.

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