Conditions for secondary enrichment (prerequisite conditions for the secondary sulphide enrichment)
A warm climate, in so far as it favors chemical action, is favorable to sulphide enrichment. Deposits in high latitudes are not so likely to show extensive migration .of the metals, because low temperature decreases chemical activity, and freezing prevents solution.
Since water is the agent of ore enrichment, abundant rainfall is favorable to the formation of secondary ores.
As a rule, the relief is great in areas of high altitudes, and erosion is consequently more rapid. Moreover, in such areas temperatures are lower and conditions are less favorable to solution.
Deposits located at very high altitudes, where rocks are disintegrated by frost and carried away
un-weathered as talus and boulders, are not so likely to be extensively enriched as are deposits
that lie at lower altitudes.
In so far as strong relief supplies head, it is favorable to deep and rapid circulation of
underground water, and it is likewise favorable to relatively deep enrichment. In base-leveled
(flat land) regions underground circulation is sluggish and the nearly stagnant waters cannot
descend far into the zone of primary sulphides without losing the valuable metals which they
dissolve higher up.
to the lower horizons the metals dissolved near the surface may be scattered.
Permeability is essential for sulphide enrichment. If the primary deposits are not permeable the
solutions that pass downward through the oxidized zones will move laterally along the contact
between oxidized and sulphide ores and ultimately will escape into fractures in the wall rock or
reissue as springs at some level below the points of entry. If they do not encounter a reducing
environment the metals may be scattered.
- The climate, (temperature, rainfalls)
A warm climate, in so far as it favors chemical action, is favorable to sulphide enrichment. Deposits in high latitudes are not so likely to show extensive migration .of the metals, because low temperature decreases chemical activity, and freezing prevents solution.
Since water is the agent of ore enrichment, abundant rainfall is favorable to the formation of secondary ores.
- Altitude
As a rule, the relief is great in areas of high altitudes, and erosion is consequently more rapid. Moreover, in such areas temperatures are lower and conditions are less favorable to solution.
Deposits located at very high altitudes, where rocks are disintegrated by frost and carried away
un-weathered as talus and boulders, are not so likely to be extensively enriched as are deposits
that lie at lower altitudes.
- Relief;
In so far as strong relief supplies head, it is favorable to deep and rapid circulation of
underground water, and it is likewise favorable to relatively deep enrichment. In base-leveled
(flat land) regions underground circulation is sluggish and the nearly stagnant waters cannot
descend far into the zone of primary sulphides without losing the valuable metals which they
dissolve higher up.
- Permeability of the deposits is an essential condition, for if solutions cannot find access
to the lower horizons the metals dissolved near the surface may be scattered.
Permeability is essential for sulphide enrichment. If the primary deposits are not permeable the
solutions that pass downward through the oxidized zones will move laterally along the contact
between oxidized and sulphide ores and ultimately will escape into fractures in the wall rock or
reissue as springs at some level below the points of entry. If they do not encounter a reducing
environment the metals may be scattered.
- The duration of the period of weathering as well as time taken to concentrate the deposit
No comments:
Post a Comment