Petrography and geochemistry of the Proterozoic sandstones of Somanpalli Group from Pomburna area, Eastern Belt of Pranhita–Godavari Valley, central India: Implications for provenance, weathering and tectonic setting

• Published in: Journal of Earth System Science 2018-08, Vol.127 (6), p.1-27, Article 90
• Main Authors: Rao, N K, Dora, M L, Baswani, S R, Malpe, D B, Deshmukh, M S
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Area; Basins; Belts; Chemical composition; Chemical weathering; Chondrites; Earth and Environmental Science; Earth Sciences; Fault lines; Ferric oxide; Geochemistry; Geology; Humid areas; Humid climates; Major elements; Metamorphism; Organic chemistry; Passive margins; Petrography; Petrology; Potassium oxides; Precambrian; Provenance; Ratios; Rocks; Sandstone; Scandium; Sedimentary rocks; Sediments; Silica; Silicon dioxide; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Stratigraphy; Tectonics; Titanium dioxide; Valleys; Weathering; Zirconium
• ISSN: 0253-4126; 0973-774X
• DOI: 10.1007/s12040-018-0991-7

In this paper, we, for the first time, report geochemistry of sandstone from Somanpalli Group from Pomburna area in the Eastern Belt of Pranhita–Godavari (PG) Valley, central India and studied to infer their provenance, intensity of paleo-weathering and depositional tectonic setting. Petrographic study of sandstones show QFL modal composition of arenite. Chemical results show high SiO 2 and CIA but lower Al 2 O 3 , TiO 2 , Rb, Sr, K 2 O indicating mixed sources. Major elements chemistry parameters such as, K 2 O/Al 2 O 3 ratio and positive correlation of Rb with K 2 O , reflects a warm and humid climate for study area. The tectonic discrimination plots ( SiO 2 / 20 – K 2 O + Na 2 O – TiO 2 + Fe 2 O 3 + MgO ; K 2 O / Na 2 O vs . SiO 2 ; Th–Sc–Zr/20) indicate dominantly passive margin and slight active tectonic setting. Concentrations of Zr, Nb, Y, and Th are higher compared to the UCC values and the trends in Th/Cr, Th/Co, La/Sc and Cr/Zr ratios support a felsic and mafic source for these sandstones and deposition in passive margin basin. Chondrite normalized REE pattern reflects LREE depletion, negative Eu anomaly and flat HREE similar to UCC, felsic components. ICV value (0.95) also supports tectonically quiescent passive margin settings. CIA values (74) indicate high degree of chemical weathering and warm and humid paleoclimatic condition.