ORE DEPOSITS FORMED BY WEATHERING AND FORMATION OF PLACER DEPOSITS

1. ORE DEPOSITSFORMED BY WEATHERING ANDFORMATION
OF PLACERDEPOSITS
Topic :
Submitted By:Nazir Hussain Submitted To Dr.Riyaz M.K Khan
Class : M.Sc Semester : 2nd

2. introduction
ORE DEPOSITS:-
An ore deposits, in its simplest terms, is a portion of the Earth’s
crust from which some industrial raw material can be extracted at a
profit.
As such, its characteristics are as much economic as geochemical.
ORE DEPOSITS FORMED BY WEATHERING
Many types of mineral deposit form by weathering .
Weathering is the breakdown and alteration of rocks by physical
and chemical processes,both of which may be added by organic
activity.

3. The fractionation of the rock occurs in response to change in
environmental condition since the rock was formed.
E.g : The mineral of ignous rocks formed, at high temperature in the
absence of abundant water are unstable in the cooler.
The mineral of these rocks are altered to low-temperature, water
bearing faces or dissolved and removed.
Physical weathering disintegrates the rock creating large surface
areas and greater access by fluids.
These mineral deposits are among the most important ores formed
by weathering and supergene enrichment is one of the best
underestood aspects of weathering.

4. Placer deposits are formed by the mechanical concentration of
resistate minerals, which are released by weathering from
source rocks in which their distribution is normally
subeconomic.
The main commodities derived from placer deposits are tin,
gold, platinum, niobium, tantalum, titanium, zircon and
diamonds.
Some metals, such as gold, occur within the entire spectrum
of placer deposits, but it is more common for a mineral to be
concentrated in a specific placer environment, which is
ultimately controlled by tectonic setting.
FORMATION OF PLACER DEPOSITS

5. The main environment of placer formation are reviewed with
particular emphasis appropiate exploration techniques.
CLASSIFICATION OF PLACER DEPOSITS
Various classification systems have been proposed for placer
deposits ( wells, 1969, Smirnov, 1976 ).
We prefer to use a simplified version of a classification proposed by
Macdonald ( 1983 ) which is based primarily on geological
environment.
Schematic cross-section which shows the distribution of the
sub-environment of placers.

8. PLACER DEPOSIT