INTRODUCTION

Ore – It is defined as a solid naturally occurring mineral aggregate of economic interest from which one or more valuable constituents may be recovered by treatment.

Ore deposit - Rocks containing minerals of economic value in such amount that they can be profitably exploited.

Ore deposit - Rocks containing minerals of economic value in such amount that they can be profitably exploited.

Tenor- It describes the metal content of an ore. In order to declare the ore economically workable, a deposit must contain a certain percentage of metal in it and the lowest admissible limit o metallic content of an ore is called its ‘tenor’.

Gangue- Rock or mineral matter of no value occurring with the metallic ore in a vein or deposit.

ORE BEARING FLUIDS:

The ore-bearing fluids concerns the following criteria's-

1. The source of the ore constituents and how they are obtained in
   solution.

2. The source and character of the ore-bearing fluids.

3. The migration of the ore bearing fluids.

4. The manner of deposition.

For the purpose of better understanding , the ore-bearing fluids are divided into four categories :-

(a) Magmas and magmatic fluids.

(b) Meteoric waters.

(c) Connate waters.

(d) Fluids associated with metamorphic processes.

MAGMA AND MAGMATIC FLUIDS:

Magma is a molten rock material generated within the Earth’s surface, and which often collects in a magma chamber. Magma may contain suspended crystals and gas bubbles. Solidification of magma produces igneous rocks.

Magmas are probably not homogeneous in composition; parts may be rich in ferromagnesian constituents, others in silica, sodium or potassium compounds, volatiles, reactive xenoliths etc. The composition of magma is thought to be constantly changing due to chemical reactions.

The magmatic deposits are formed during different stages of magma crystallization .

The magmatic ore deposits are classified into the following :-

1 Early magmatic deposits

2 Late magmatic

Early magmatic deposits:
early magmatic deposits are formed during the early stage of magmatic period .In this case the ore minerals crystallize earlier than rock silicates .the early magmatic deposits can be formed due to following two process :

Dissemination: When a mass of magma crystallize under deep seated condition , a granular igneous rock is formed . in such rocks early formed crystal of ore minerals may be occur in dissemination. Here grains ore found scattered more or less evenly throughout the whole rock.

Segregation: Early magmatic segreation deposits may be formed due to result of gravitational differentiation In this case ore minerals are concentrated in a particular part of the igneous mass .
The deposits thus formed is called segregation deposits .

Contd.............