Question

Which one of the following processes is responsible for the formation of syngenetic Ni-Cu sulphide ore in gabbro-norite rocks?

• A. Hydrothermal replacement
• B. Volcanic exhalation
• C. Liquid immiscibility
• D. Contact metamorphism

Hint:

Liquid immiscibility occurs in magmatic systems, where different liquid phases separate, forming mineral deposits such as Ni-Cu sulphides.

Answer 1

The Correct Option is C

Step 1: Understanding the formation of Ni-Cu sulphide ores.
Ni-Cu sulphide ores in gabbro-norite rocks are formed through a process called liquid immiscibility. This occurs when magma separates into two immiscible liquids, one rich in sulphide minerals, which eventually solidifies as ore deposits.

Step 2: Analyzing the options.
(A) Hydrothermal replacement: This process involves the replacement of minerals by hydrothermal fluids but is not responsible for the formation of Ni-Cu sulphide ores.
(B) Volcanic exhalation: Volcanic exhalation is a process involving the release of gases, not related to the formation of these ores.
(C) Liquid immiscibility: This is the correct process, where the magma separates into sulphide-rich liquid, leading to the formation of Ni-Cu sulphide ores.
(D) Contact metamorphism: Contact metamorphism involves heat from an intrusion altering surrounding rocks, but it is not responsible for the formation of Ni-Cu sulphide ores.

Step 3: Conclusion.
The correct answer is (C) Liquid immiscibility because this process is responsible for the formation of syngenetic Ni-Cu sulphide ore.