BGYCT-135 · December 2025 · English
IGNOU BGYCT-135 December 2025 Previous Year Question Paper
PETROLOGY
Structured previous year question paper for BGYCT-135, December 2025 session.
Max marks: 50 · Questions: 4
Verified: 10 Aug 2026
BACHELOR OF SCIENCE (GENERAL)
(BSCG)
Term-End Examination
December, 2025
BGYCT-135 : PETROLOGY
Time : 2 Hours Maximum Marks : 50
Note: All questions are compulsory. Marks
allotted for each question are indicated
against it. Draw well-labelled diagrams
wherever necessary.
Q1.Briefly answer any five of the following questions : 5x2=10
(a) List the type of igneous rocks based on mode of occurrence.
(b) Differentiate between lithification and diagenesis.
(c) Define graphic texture.
(d) Define protolith.
(e) What are essential minerals ?
(f) Mention the volcanic equivalent of granite and gabbro.
(g) What is quartz arenite ?
(h) What is reaction rim texture ?
Q2.Write short notes on any four of the following : 4x5=20
(a) Types of sedimentary rocks
(b) Chemical weathering
(c) Components of classic texture
(d) Metamorphic minerals
(e) High-temperature limit of metamorphism
(f) IUGS classification
Q3.Answer any one of the following : 10
(a) Describe briefly the textures found in igneous rocks and_ give _ suitable examples.
(b) Explain the structures found in metamorphic rocks with the help of neat well-labelled diagrams.
Q4.(a)
(i) Discuss the factors affecting the textures in metamorphic rocks. 5
(ii) What are ultramafic rocks ? Discuss the megascopic characters of peridotite. 5
(b)
(i) Describe the five commonly found forms of igneous rock with the help of neat well-labelled diagrams. 5
(ii) Discuss any five types of commonly occurring primary structures in sedimentary rocks. 5 4x5=20