II. Pre-reading task
1. Match the terms (or phrases) to the explanations.
1. precipitation from silicate melts A. change showing spatial and
temporary relationship to ore deposits
2. precipitation from aqueous
solutions
B.fluid in which crystals grow may
be trapped in tiny cavities.
3.replacement C.cyrstallization of sulphides because
of lower melting points after
associated silicates
4. fluid inclusion D.open spaces are permeated by
mineralizing solutions
5. wall rock alteration E.one mineral dissolves, another
mineral settles in its place, without
disturbing the development of open
spaces and no change in volume
2. Translate the following sentences, paying attention to the Gerund.
(SUPPLEMENTARY MATERIAL, pg.152)
1. If the prevailing physic- chemical conditions induce precipitation then
crystals will form.
2. Replacement is the dissolving of one mineral and the simultaneous
deposition of another mineral in its place without the intervening
development of appreciable open spaces
3. Nearly all ores, including those developed in open spaces show some
evidence of the occurrence of replacement processes.
4. Secondary replacement processes leading to sulphide enrichment by
downward percolating meteoric waters, are sometimes most dramatic and
fraught with economic importance.
5. They can be every bit as important as primary (hypogene) replacement
brought about by solutions emanating from crustal or deeper sources.
6. Halite-bearing inclusions, have salinities ranging up to more than 50%.
7. One common mode of formation is during the heating of fractures and this
leads to the development of planar arrays of numerous small inclusions.