In igneous petrology, which of the following is not considered an intrusive igneous body formed from magma below the Earth surface?

Introduction / Context:

This question tests knowledge of intrusive igneous structures in geology. Intrusive bodies form when magma cools and solidifies beneath the Earth surface, cutting through or lying between pre existing rock layers. Common intrusive bodies include dikes, sills, stocks, and batholiths. The term stope, however, belongs to mining engineering rather than igneous classification.

Given Data / Assumptions:

• We are choosing among stock, dike, stope, and batholith.
• Intrusive igneous bodies are formed from solidified magma beneath the surface.
• The question asks for the item that is not an intrusive igneous body.

Concept / Approach:

A dike is a tabular intrusive body that cuts across existing structures such as bedding planes. A sill is similar but lies parallel to bedding; however, sill is not listed here. A stock is a relatively small, irregular intrusive body, often part of a larger batholith. A batholith is a very large intrusive body, usually composed of coarse grained granite or similar rocks. In contrast, a stope is a term from mining that refers to an underground excavation where ore is removed. It is not a natural igneous rock body.

Step-by-Step Solution:

Verification / Alternative check:

Standard geology books list intrusive bodies in diagrams of igneous structures, showing dikes, sills, laccoliths, stocks, and batholiths. They do not include stopes in these diagrams. Mining engineering books, however, define a stope as a void left after ore extraction. The absence of stope from lists of igneous intrusions and its presence in mining terminology confirms that it is the only non intrusive body among the given options.

Why Other Options Are Wrong:

• Stock: A small intrusive igneous mass, often associated with larger batholiths.
• Dike: A narrow, tabular body of intrusive igneous rock that cuts across pre existing structures.
• Batholith: A very large intrusive igneous body that forms the core of many mountain ranges.

Common Pitfalls:

Learners sometimes assume that every unfamiliar geological word must be an igneous feature, especially in a list where most options are igneous terms. This can lead to choosing at random. Another mistake is to confuse stope with stoping, a geological process of rock failure, but in mining context stope clearly refers to man made excavations. Carefully recalling whether a term is natural or man made helps avoid this confusion.

Final Answer:

Stope is not an intrusive igneous body; it is a mining excavation.