Igneous petrology — select the hypabyssal (subvolcanic) rock from the list, i.e., an intrusive rock that solidified at shallow depth with typically medium grain size.

Introduction / Context:
Igneous rocks are classified by composition and texture as plutonic (deep intrusive), hypabyssal (shallow intrusive), or volcanic (extrusive). Recognizing the emplacement environment helps predict grain size, jointing, and engineering behaviour. This question asks you to pick the hypabyssal rock from common examples.

Given Data / Assumptions:

• Granite: coarse-grained felsic plutonic rock.
• Basalt: fine-grained mafic volcanic rock.
• Dolerite (also called diabase): mafic shallow intrusive rock with medium grain size.

Concept / Approach:

Hypabyssal (subvolcanic) rocks crystallize at shallow depths (dykes, sills, laccoliths), leading to textures intermediate between coarse plutonic and fine volcanic rocks. Dolerite/diabase typically shows an ophitic or intergranular texture with plagioclase and pyroxene, indicative of moderate cooling rates. Granite is plutonic (deep, coarse-grained), while basalt is volcanic (surface, fine-grained). Hence, dolerite is the correct hypabyssal rock among the options.

Step-by-Step Solution:

Verification / Alternative check:

Geology references consistently label dolerite/diabase as a hypabyssal equivalent of gabbro (plutonic) and basalt (volcanic), closing the compositional–textural triangle.

Why Other Options Are Wrong:

Granite — Deep intrusive (plutonic), not hypabyssal.
Basalt — Extrusive volcanic, not hypabyssal.
All the above — Incorrect because only dolerite fits the hypabyssal category.

Common Pitfalls:

Confusing dolerite with basalt due to similar dark colour; the key difference is texture and emplacement depth.

Final Answer:

Dolerite