Question

En-echelon sigmoidal ‘gash’ veins indicate

• A. ductile shear zone
• B. brittle-ductile shear zone
• C. brittle shear zone
• D. saddle reef structure

Hint:

When studying fault zones and vein formation, remember that gash veins are indicative of zones where both brittle and ductile deformation occurs.

Answer 1

The Correct Option is B

Step 1: Understanding the question.
The question refers to the formation of 'gash' veins, which are typically found in geological shear zones. En-echelon sigmoidal veins are indicative of complex shear and deformation patterns.
Step 2: Analyzing the options.
(A) ductile shear zone: This is incorrect because gash veins are more characteristic of brittle-ductile shear zones.
(B) brittle-ductile shear zone: Correct — Gash veins are often found in brittle-ductile shear zones where both brittle fracturing and ductile deformation occur.
(C) brittle shear zone: Gash veins are not typically associated with purely brittle zones.
(D) saddle reef structure: This is unrelated to gash veins, as saddle reefs are a different geological structure.
Step 3: Conclusion.
The correct answer is (B) brittle-ductile shear zone, as gash veins are commonly associated with these zones.