SITUATION ANALYSIS OF THE SMALL-SCALE GOLD ... - WWF

This distinction was useful at the time that the law was promulgated. It characterized the
two main categories of mining. The technology available to the small-scale in those days
was limited to a shovel and pick-axe, and later a small water pump that could process 5 to
10 m³ of ore per day. This limited miners to alluvial deposits or hand processing of quartz
veins. Large-scale enterprises, on the other hand, could explore for large scale deposits,
which could be hard rock but also alluvial or soft rock. If the grades were attractive and
the ore bodies large enough to capture the interest of investors, a mill could be built that
would process millions of tons of ore per year. Advances in geological expertise and
mine engineering during the past thirty to forty years, have changed the characteristics of
the gold mining sector. The classical distinction between primary deposits and secondary
deposits, though useful, no longer reflects new developments in the gold mining sector.
The lode or vein deposits are also referred to as primary deposits, and are formed by
hydrothermal processes, where gold precipitates during chemical reactions between hot
fluids, metal bearing solutions and rocks in the earth‟s crust. Volcanic activity or
intrusive rocks such as granite are a source of heat, and if there is a well developed
ground water table, hot fluids and gases are produced. As the hot, corrosive mineral laden
water moves up through crack and crevices in the rock it cools, and solidifying gold and
other minerals are deposited in fractures and pore spaces. Almost all gold deposits are
probably originally hydrothermal with the exception of placer deposits.
Alluvial or placer deposits are also referred to as secondary deposits. Gold bearing veins
located in moist climates with heavy rainfall such as in Suriname will erode away very
quickly once being exposed to the action of surface elements. Weathering and
disintegration of the rock matrix releases the gold particles. The place where the vein or
lode reaches the surface will also break down and decay, and as the softer and more
soluble parts of the rock are carried away by erosion, the native gold will become more
concentrated. As the gold gravitates down hill eluvial (hillside) places are created. As the
gold is transported greater distances from its original source alluvial placers are formed.
The gold will usually settle in the gravel layers of creeks or rivers above the dense tough
clays, or get trapped in cracks and crevices or behind rocks in the bedrock. If the land in a
given area is uplifted, the original creek will cuts its way down to a new “base level,”
leaving bench or terrace placers “high and dry” from the original stream that created it.
There are, however, also large quartz-pebble conglomerate deposits that are at times
difficult to distinguish from bench placer deposits. These conglomerate deposits supply
50% of the world‟s annual gold production, and have been classified by some geologists
as modified paleo-placers, while others consider these deposits to be of hydrothermal
origin. This is a subject of considerable controversy, which has been debated extensively
at mining conferences and in mining literature.
It is important to point out that there is no scientific consensus on where to draw the line
between lode or primary and placer or secondary deposits. It is particularly tricky to
classify saprolite. These soft-rock deposits consist of the top 50 to 100 meters of rock that
is altered by rainwater and chemical weathering. The weathered rock has retained much
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