Question

Match the magma series in Column 1 to the geological settings in Column 2.

• A. P-i; Q-iv; R-iii; S-ii
• B. P-ii; Q-iv; R-iii; S-i
• C. P-i; Q-i; R-iii; S-iv
• D. P-iv; R-ii; Q-i; S-iii

Hint:

Alkaline and shoshonite magmas are generally associated with oceanic intraplate settings, while calc-alkaline and tholeiitic magmas are found at convergent plate boundaries or back arcs.

Answer 1

The Correct Option is C

Step 1: Understanding the magma series and geological settings.
- Alkaline Series: Typically associated with oceanic intraplate settings, where mantle plumes or hotspots are involved. These magmas are rich in alkalis such as sodium and potassium. - Shoshonite Series: This series forms in oceanic intraplate settings as well, typically in tectonic environments where partial melting occurs beneath a stable crust. - Calc-alkaline Series: This series is common at convergent plate margins, particularly in subduction zones where oceanic crust subducts under continental or other oceanic plates. - Tholeiitic Series: Found in convergent plate margins close to the back arc, where the volcanic activity is associated with subduction but further from the actual trench.

Step 2: Analyzing each option.
- (A) P-i; Q-iv; R-iii; S-ii: This option places the alkaline series in a divergent oceanic margin (incorrect), the shoshonite series in a back arc (incorrect), and the tholeiitic series in an intraplate setting (incorrect). - (B) P-ii; Q-iv; R-iii; S-i: Incorrect assignment of the alkaline series to oceanic intraplate (correct), shoshonite series to back arc (incorrect), and tholeiitic series to divergent oceanic margin (incorrect). - (C) P-i; Q-i; R-iii; S-iv: Correct assignment: Alkaline series to oceanic intraplate, shoshonite series to oceanic intraplate, calc-alkaline series to convergent plate margin, and tholeiitic series to back arc. - (D) P-iv; R-ii; Q-i; S-iii: Incorrect as it places the alkaline series at a back arc (incorrect), calc-alkaline series in an oceanic intraplate setting (incorrect), and tholeiitic series in a convergent margin (incorrect).

Step 3: Conclusion.
The correct answer is (C), as the geological environments correspond correctly with the magma series based on tectonic settings and magma compositions.
\[ \boxed{\text{P-i; Q-i; R-iii; S-iv}} \]