книги / Английский язык для горных инженеров

Earth’s surface. The terms “intrusive” and “extrusive” refer to the place where rocks solidified.

The grain size of igneous rocks depends on their occurrence. The intrusive rocks generally cool more slowly than the extrusive rocks and crystallize to a larger grain size. The coarser-grained intru­ sive rocks with grain size of more than 0.5 mm called plutonic or abyssal are referred to as intrusive igneous rocks because they are intruded into older pre-existing rocks. Extrusive or volcanic rocks have even finer grains, less than 0.05 mm and are glassy.

Exposed igneous rocks are most numerous in mountain zones for two reasons. First, the mountain belts have been zones of major deformation. Second, uplifts in mountain belts have permitted plutonic masses to be formed.

The largest bodies of igneous rocks are called batholiths (Fig. 2). Batholiths cooled very slowly. This slow cooling permitted large min­ eral grains to form. It is not surprising that batholiths are composed mainly of granitic rocks with large crystals called plutons. As is known, granites and diorites belong to the group of intrusive or plutonic rocks formed by solidification of igneous mass under the Earth’s crust. Granites sometimes form smaller masses called stocks, when the occurrence has an irregular shape but smaller dimensions than the batholiths.

Laccoliths and sills, which are very similar, are intruded be­ tween sedimentary rocks. Sills are thin and they may be horizontal, inclined or vertical. Laccoliths are thicker bodies and in some cases they form mountains.

Dykes are also intrusive bodies. They range in thickness from a few inches to several thousand feet. Dykes are generally much longer than they are wide. Most dykes occupy cracks and have straight parallel walls. These bodies cool much more rapidly and are commonly fine-grained. For example, granite may occur in dykes that cut older rocks.

Pegmatites (quartz, orthoclase and mica) also belong to the group of plutonic or intrusive rocks. They occur in numerous veins which usually cut through other plutonites, most often granite, or adjacent rocks.

Extrusive igneous rocks have been formed from lava flows which come from fissures to the surface and form fields of volcanic rocks such as rhyolite, andesite, basalt, as well as volcanic ashes and dust, tuff, etc. As a rule, these rocks of volcanic origin cool rapidly and are fine-grained. It is interesting to note that basalt is the most

2.Which types of igneous rocks do you know?

3.What does the grain size of igneous rocks depend on?

4.Can you give an example of intrusive or plutonic rocks?

5.Are diorites intrusive or extrusive formations?

6.What do you know about batholiths?

7.Do pegmatites belong to the group of plutonic or volcanic rodes?

8.How do pegmatites occur?

9.What minerals are igneous rocks rich in?

сочетаний слов:

б) Найдите в правой колонке английские эквиваленты следующих сочетаний слов:

10. Переведите сочетания слов, обращая внимание на место причастия прошедшего времени по отношению к определяемому существительному:

11. Найдите предложения, в которых имеются причастия прошедшего ■ремеии. Определите их функцию. Переведите предложения:

1.Igneous rocks form a large group of minerals which are eco­ nomically important.

2.The igneous rocks formed by cooling occur either as intrusive or extrusive rocks.

3.Orthoclase is particularly used in great quantities as raw mate­ rial in the production of porcelain (фарфор).

4.The clayey mass obtained by the decomposition oforthoclase is usually whiteand iscalled kaolin. The product obtained isused in industry.

5.Quartz occurs in the form of small grains. Quartz crystals found in the cracks and fractures of rocks are very hard and beautiful.

6.Pure quartz sands are used in the production of glass.

7.Actual observations of rocks exposed on the continent show that shale represents 46 per cent of the total, sandstone about 32 per cent, and limestone about 22 per cent.

12.Замените определительное придаточное предложение определитель­ ным причастным оборотом.

Образец: The igneous rocks which have crystallized from magma may rise through fissures to the surface of the Earth as lava. -> The igneous rocks crystallized from magma may rise to the surface of the Earth as lava.

1.The classification of igneous rocks which is given below is based on texture and composition of minerals.

2.Igneous rocks were a hot molten mass which was known as magma.

3.Observations have shown that the rock types which were pro­ duced by molten volcanoes, include, for example, rhyolite, andes­ ite, basalt and other rocks.

4.Andesite which was first found in the Andes Mountains in South America is the fine-grained rock, intermediate in composition between granite and basalt.

5.Copper is second only to iron among the important metals, which are widely used in modem engineering.

13. Найдите в тексте А и выпишите: 1) причастия прошедшего времени ■ функции левого определения вместе с существительными, которые они определяют; 2) причастия прошедшего времени, входящие в определитель­ ный причастный оборот; 3) причастия прошедшего времени, используемые для образования глагольных форм группы Perfect; 4) причастия прошедшего времени, используемые для образования страдательного залога.