Fig. 13 Rock cycle

sedimentary, weathering (x2), source rock, path/paths, breakdown, differentiation, magma, metamorphism, lithification, cycle, processes, transport, melting, igneous, crustal, crystallization, deposition.

The geochemical (1)_________ is a (2)___________ followed by an individual element or group of elements in the (3)____________ and subcrustal regions of the Earth. During the cycle there occur

(4) _____________ – both separation of elements and elemental recombination. For the lithosphere, the cycle begins with the (5)_____________ of (6)____________ at the surface or at depth. Decomposition of the (7)______________rock by surface alteration and (8)______________ is followed by (9)______________ and (10) _______________of the sediment, (11)____________ and possibly (12)______________and eventually (13)_____________ with the generation of a new magma. A number of different (14)_____________ could be followed within this idea cycle. Each element will be affected differently as the cycle progresses; for example, partial melting of (15)______________rock to form a (16)_____________ separates elements according to the melting characteristics of the constituent minerals. Magmatic (17)_____________ processes produce a wide range of chemical compositions among igneous rocks and in particular tend to increase the concentration of Si, Al, Ca, Na and K and other lithophile elements in the evolved magmas.

(18)___________ processes are also effective in separating chemical components, for example, during the (19)__________ of an igneous rock, magnesium released by the (20)___________ of ferromagnesian minerals can be removed solution.

(The Concise Oxford Dictionary of Earth Science, Oxford University Press, 1991)

2.5 Revision: Match the processes involved in the rock cycle with the definition and try to place them in the diagram. (R.P – 4.5, 4.6)

1. weathering	a. the process that converts a sediment into a sedimentary rock.
2. erosion	b. the process by which the volume / thickness of sediment is reduced due to pressure of overlying layers of sediment.
3. transportation	c. process that converts a solid into a liquid under temperature increase
4. deposition	d. set of processes that cause physical and chemical changes in sediment after it has been deposited and buried under another layer of sediment.
5. compaction	e. the process by which conditions within the Earth, below the zone of diagenesis, alter the mineralogical / chemical composition and structure of solid rock without melting it.
6. cementation	f. the process by which particles of rock and soil are loosened, then transported elsewhere.
7. diagenesis	g. temperature increase
8. metamorphism	h. the movement of a particle from one location on the Earth’s surface to another.
9. melting	i. the process by which exposure to atmosphere causes rocks and minerals to break down. This process takes place at / near the Earth’s surface.
10. heating	j. the process by which sediment grains are bound together by precipitated minerals originally dissolved during the chemical weathering of preexisting rocks.
11. lithification	k. accumulation of sediments by either physical / chemical sedimentation.

3. READING COMPREHENSION

3.1 SCANNING: Earth’s building blocks (R.P – 4.2)

3.1.1 Pay attention to the pronunciation of the following minerals:

Which minerals have the same translation in both languages and which do not?

hematite	magnetite
dolomite	halide
mica	fluorite
feldspar	halite
carbonate	hydroxide
quartz	limonite
asbestos	brucite
calcite	sulfate
aragonite	gypsum
galena	phosphates
silicate	apatite
oxide	monazite
sulfide	tungstate
pyrite	wolframite

3.1.2 Find the information you need to complete the following diagram from the text below.

ROCK-FORMING MINERALS

mineral

abundance

composition

examples

Rocks are mixtures of minerals. Most rocks consist of interlocking grains or crystals stuck together by natural cement. A few dozen minerals provide the main ingredients for the most common rocks. Here are brief details of some rock-forming minerals.

1. Silicates are the chief rock-forming minerals. Most features a metal combined with silicon and oxygen. Examples: asbestos, mica, and feldspar.

2. Carbonates, the second most abundant group of minerals, include carbon, oxygen and one or more metals. Examples: calcite, dolomite and aragonite.

3. Sulfides are compounds of sulfur and one or more metals. Examples: galena and pyrite.

4. Oxides are compounds of oxygen and one or more metals. Examples: quartz, hematite and magnetite.

5. Halides are compounds of a halogen and a metal. Examples: fluorite and halite (rock salt).

6. Hydroxides are compounds of hydrogen, oxygen and usually a metal. Examples: limonite and brucite.

7. Sulfates are compounds of sulfur, oxygen and a metal. The commonest sulfate is gypsum.

8. Phosphates are chemical compounds related to phosphoric acid. Examples: apatite, monazite.

9. Tungstates are salts of tungstic acid. Example: wolframite (a tungsten ore).

(Lambert “The Field Guide to Geology” 1988, Cambridge University Press)