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Correct the following statements where necessary (Igneous rocks)
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1. Igneous rocks comprise the smallest proportion of the continental crust and the largest of the oceanic crust.
2. Most igneous rocks are formed from the crust.
3. Most igneous rocks are remelted oceanic and continental materials.
4. Igneous rocks have rather limited compositional variations.
5. The main constituent is oxide.
6. Silica has an average weight in the common rock types.
7. Magnesium and iron oxides are also major components.
8. There are two categories of igneous rocks-extrusive and intrusive.
9. Intrusive is those that have come to the surface of the Earth in a molten condition.
10. The second category is composed of those that are crystallized from magma that solidified before reaching the surface of the Earth.
11. The processes of the formation of igneous rocks can be studied in uplifted and deeply eroded parts of the crust.
3.1.2. You have one minute to read this part of the text - Classification and chemical differentiation of igneous rocks
Complete the following text with the missing information. DON’T PEEP INTO THE TEXT!
Igneous rocks are distinguished on contrasting_____________ (1). Because the bulk-rock chemistry is reflected in the nature and proportions of the mineral present, we will utilize a simple ________ (2) based on the proportions of ___________ (3), feldspars and dark ferromagnesian, minerals and on the composition of the plagioclase.
The most refractory minerals (i.e. those stable at the highest_________ _________ (4) form first and as the melt cools, crystallize, in some cases replacing earlier ones. This ________ (5) takes place discontinuously, formation of another group of minerals proceeds continuously, as in the feldspars.
Bulk compositions reflect differences in ___________ ________ (6) among the various rock types. The ____________ (7) and the ________________ (8) can be separated at this stage as well. The process is known as _____________ ________________ (9) and explains the contrasts in compositions of melts and solids produce during either partial ___________ (10) and / or partial __________(11).
3.2 INFORMATIVE READING – Igneous Rocks (R.P.-5.4)
Дата публикования: 2014-11-03; Прочитано: 674 | Нарушение авторского права страницы | Мы поможем в написании вашей работы!
