Which one of the following is an example of both an igneous as well as a metamorphic rock?
Rock Classification: Igneous and Metamorphic Context
This question asks us to identify a rock type that fits into both the igneous and metamorphic categories. Let's break down what these terms mean and analyze the options provided.
Understanding Rock Types
Igneous Rocks
Igneous rocks are formed from the cooling and solidification of molten rock material (magma or lava). They are often classified based on their composition (e.g., felsic, mafic) and texture (e.g., coarse-grained, fine-grained). Examples include Granite, Basalt, and Gabbro.
Metamorphic Rocks
Metamorphic rocks are formed when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are changed by heat, pressure, or chemical reactions. This transformation occurs deep within the Earth or where tectonic plates collide. The original rock does not melt, but its minerals and texture are changed. Examples include Gneiss, Slate, and Marble.
Analyzing the Rock Options
We need to evaluate each option based on its primary classification and its potential relationship with both igneous and metamorphic processes.
Granite Analysis
Granite is fundamentally classified as an igneous rock. It forms when magma slowly cools and solidifies beneath the Earth's surface. It is typically composed of quartz, feldspar, and mica.
However, rocks are not static. If granite is subjected to the high temperatures and pressures associated with metamorphism, it can transform. The process of metamorphism can change the texture and mineralogy of granite, often resulting in a rock called gneiss. Gneiss is a metamorphic rock characterized by distinct banding or layering (foliation). Sometimes, a metamorphic rock derived from granite might be referred to based on its original composition, like "granitic gneiss". While granite *itself* is igneous, it serves as a common protolith (the original rock that undergoes metamorphism) for metamorphic rocks like gneiss. The question might be interpreted as asking for a rock that originates as igneous and can be significantly altered by metamorphic processes, or is closely related to a metamorphic equivalent.
Other Options Analysis
- Gabbro: Gabbro is another example of an intrusive igneous rock, similar in composition to granite but typically coarser-grained and darker. It is not classified as metamorphic.
- Geyserite: Geyserite is a form of silica deposited by geyser water. It is classified as a sedimentary rock (specifically, a chemical sedimentary rock).
- Gneissoid: This term describes a *texture* characteristic of gneiss, specifically a parallel alignment of minerals giving it a banded appearance. It is not a rock type itself, but rather a descriptor of metamorphic rocks.
Conclusion on Rock Identity
Considering the options and the nature of rock transformation:
- Granite is primarily igneous.
- Metamorphism can act upon granite to form metamorphic rocks like gneiss.
- Gabbro is only igneous.
- Geyserite is sedimentary.
- Gneissoid describes a metamorphic texture.
Therefore, Granite is the most fitting answer, representing a rock that is fundamentally igneous but is also the direct precursor to common metamorphic rocks like gneiss, linking it contextually to both categories as potentially intended by the question.
Similar Questions
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Which one of the following is found in appreciable amount in Laterite soil in India?
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Important Questions from Rocks and Soils
Soil, in which nearly all our food grows, is a living resource that takes years to form. Yet it can vanish in minutes. Each year 75 billion tonnes of fertile soil is lost to erosion. That is alarming — and not just for food producers. Soil can trap huge quantities of carbon dioxide in the form of organic carbon and prevent it from escaping into the atmosphere.
On the basis of the above passage, the following assumptions have been made :
1. Large scale soil erosion is a major reason for widespread food insecurity in the world.
2. Soil erosion is mainly anthropogenic.
3. Sustainable management of soils helps in combating climate change.
Which of the above assumptions is/are valid ?
With reference to agricultural soils, consider the following statements :
1. A high content of organic matter in soil drastically reduces its water holding capacity.
2. Soil does not play any role in the sulphur cycle.
3. Irrigation over a period of time can contribute to the salinization of some agricultural lands.
Which of the statements given above is/are correct ?
Which of the following statements regarding laterite soils of India are correct?
1. They are generally red in colour.
2. They are rich in nitrogen and potash.
3. They are well-developed in Rajasthan and UP.
4. Tapioca and cashew nuts grow well on these soils.
Select the correct answer using the codes given below:
Which of the following adds/add nitrogen to the soil?
1. Excretion of urea by animals
2. Burning of coal by man
3. Death of vegetation
Select the correct answer using the codes given below:
When you travel in certain parts of India, you will notice red soil. What is the main reason for this colour ?
