key geology words and defintions

Question 1

Porphyry

Answer 1

Any of the various granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine grain silicate - rich grained silicate - rich, generally aphantic matrix or groundmass.

Question 2

Hydraulic breccia

Answer 2

they are usually formed by hydrofracturing of rocks by highly pressured hydrothermal fluids. Typical of epithermal ore environments and are intimately associated with intrusive - related ore deposits such as skarns, greisens and porphyry-related mineralisation.

Question 3

Skarns

Answer 3

Skarns or tactites are hard, coarse-grained metamorphic rocks that chemically and mineralogically altered by hot chemically active fluids and known as the metasomatism process. Tend to be rich in calcium, magnesium, iron, manganese, and aluminium silicate minerals and referred to as calc-silicate minerals.

Question 4

Dikes

Answer 4

Is a sheet of rock that is formed in a fracture of a pre-existing rock body. Dikes can be either magmatic or sedimentary in origin.

Question 5

Hydrothermal alteration

Answer 5

Is defined as any change in the mineralogic composition of a rock due to the action (by either physical or chemical means) of hydrothermal fluids in an open system.

Question 6

Pluton

Answer 6

Body if intrusive igneous rock the size, composition, shape, or exact type of which is in doubt; when such characteristics are known, more limiting terms can be used. Thus, plutons include dikes, laccoliths, batholiths, sills, and other forms of intrusions.