December 2, 2020

Hydrothermal Solution and Hydrothermal Deposits

What is Hydrothermal Solution?

The term can be simply defined as the fluids that remain after the crystallization process of the intrusive rocks and having a natural concentration of mineral is called the hydrothermal solutions. The fluid is hot in the physical characteristics and derived from the intrusive magma is usually called as the hydrothermal solution.

The solutions find their places in the cavities and fissures of the rock, to enter and from new minerals. The solvent in such cases is very often. Superheated steam, emanating from magmas towards the final stages of the crystallization process.

Metals originally present in magma, concentrate in this fluid. This fluid which is a hot watery solution containing mineralized liquids delivered from an intrusive magma is called “Hydrothermal Solutions” One thing you would like to know about the solution is that it never formed form pure water. Sometimes hydrothermal solutions may contain a significant amount of dissolved gases and solids in addition to water.

The main source of the generation of the hydrothermal solutions are

1) Water that takes part in the atmospheric circulation and that precipitates in Earth’s surface.

2) Sea water

3) Interstitial water that is in connection with the sediments and remain in contact with the atmosphere.

These solutions usually contain the Na, K, Ca Minerals in their formation. There are some extinct conditions like the high temperatures in which this solution is usually found.

What are Hydrothermal Deposits?

Deposits formed by hydrothermal solutions are called Hydrothermal ore Deposits. This type of deposits generally formed due to the hydrothermal process of gold, silver, copper, lead, and zinc type of the minerals. Hydrothermal deposits are usually formed due to hydrothermal fluids which take some chemical process after the formation of the intrusive igneous rocks.

How do minerals form from hydrothermal solutions?

.Hydrothermal deposits generally occur in various shapes and sizes. The most common it founds in veins and cavity fillings. The deposits which are the most commonly found due to the hydrothermal process are gold, silver, copper, lead, zinc, and mercury.

The hydrothermal solutions move through cracks and openings present in rocks and deposit their dissolved minerals there. Minerals that have the lowest temperature of crystallization, such as stibnite may migrate very far away while those having higher temperatures of crystallization, such as chalcopyrite, may precipitate close to the present igneous body.

During a magmatic event, there is usually a close relationship between intrusive activity and extrusive activity, but one cannot directly observe the intrusive activity. Only after the erosion of the extrusive rocks and other rock above the intrusions has exposed the intrusions do they become visible at the earth’s surface.

Hydrothermal solution and hydrothermal deposits

What is the formation process of Hydrothermal Deposits?

There are main three essential requirements for the formation of this types of deposits are

1) Highly active and reach mineral fluids.

2) Most suitable path for migration of fluid through rocks.

3) Suitable environment for the deposition to take place.

When magma starts cooling down then it has a high capacity of making deposits like gold, copper, tungsten, molybdenum, and some time it also capable of the production of the silver, lead and zinc, etc. When talking about the pathway for fluid to move then the features like joint, fissure, and fracture plays the most important part in the formation of this type of deposits. This formation provides space for fluid to flow on the surface of the earth.

One of the most important factors for the formation of the deposit is the physical- Chemical environment which is still the mystery for the geologists. Many hypotheses have been made to explain the role of the environment in the formation of hydrothermal deposit still no theory has given satisfactory results.

However some possible elements in changing environment which are responsible for making deposits are

1) Change in temperature or pressure

2) Chemical reaction between various components of liquid – gas solutions.

3) chemical reaction between the country/host rock with the magmatic liquids.

The minor factors that may responsible for the formation of the hydrothermal solutions are: Change in the PH of the solutions, deposition of mineral deposits.

Types of the Hydrothermal Deposits

This classification is based on the temperature and deposition of the solutions. On the basis of this, the deposits are classified into two types.

  • Mesothermal Deposit

The deposit that formed from the hydrothermal solution at some distance from the intrusive igneous rocks and temperature ranges between 200- 300 degrees is called the mesothermal deposit. These deposits are usually formed at depth of up to 1000m and more.

Mesothermal deposit first founded by the geologist name called W.Lindgren in 1906-07

  • Epithermal Deposit

The deposits that formed due to hydrothermal solutions and usually found very much away from the intrusive rock body are called the epithermal deposits. The temperature that commonly found in epithermal deposits is usually 50-200 degrees.

Hydrothermal deposit that formed at shallow depths below the spring system is generally called as the epithermal. Many of the famous deposits formed due to this solution are generally in epithermal in nature.

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