Question

The volcanic equivalent of nepheline syenite is

• A. rhyolite
• B. basanite
• C. phonolite
• D. andesite

Hint:

Phonolite is a volcanic rock that has a mineral composition similar to nepheline syenite, commonly found in alkaline volcanic regions.

Answer 1

The Correct Option is C

Step 1: Understanding the question.
Nepheline syenite is an intrusive igneous rock that contains a significant amount of nepheline, a feldspathoid mineral. The volcanic equivalent of nepheline syenite is phonolite. Phonolite is an alkaline volcanic rock that shares similar mineralogical features with nepheline syenite.
Step 2: Analyzing the options.
(A) rhyolite: Rhyolite is an acidic volcanic rock with high silica content, not the equivalent of nepheline syenite.
(B) basanite: Basanite is an alkaline volcanic rock, but it does not share the same mineral composition as nepheline syenite.
(C) phonolite: Correct — Phonolite is the volcanic equivalent of nepheline syenite, characterized by similar mineral compositions.
(D) andesite: Andesite is a volcanic rock with intermediate silica content, but not the equivalent of nepheline syenite.
Step 3: Conclusion.
The correct answer is (C) phonolite, as it is the volcanic equivalent of nepheline syenite.