Geochemical characterization and tectonic significance of the granite gneiss in the Tikiba Granitic Complex, Northwest Odisha, India Pratap Chandra Sethy, Prof. Ashutosh Naik, Ranjit Nayak Geologica Acta, 2025 The study explores the Precambrian tectonic evolution and the growth of continental crust in the southern region of the North Odisha Singhbhum Craton (NOSC), delving into the potential petrogenetic processes and source characteristics. The Tikiba Granitic Complex (TGC) is in the contact area of the Eastern Ghat Mobile Belt (EGMB) and the NOSC. The present study involves the geochemical characteristics of TGC granitoids and their geochemical variations. Petrographically, the TGC is comprised of alkali feldspar granite, monzogranite to granodiorite. The major element geochemistry reveals calc-alkalic, ferroan to magnesian affinities, and a metaluminous, peraluminous and peralkaline character. It is enriched in LILE and HFSE like Yb, Sm, Zr and Y. The (La/Yb)N values range from 4.0–26.1 and exhibit distinct negative Eu anomalies (Eu/Eu*) (0.4-0.6). This granitic complex shows high ΣREE contents of 176-860ppm with variable enrichment in LREE. Both REE and other incompatible element compositions define an A-type affinity. Based on geochemical data, we conclude that these granitoids have probably derived from a predominant crustal source with variable mantle characteristics in a post-orogenic setting.
Low-titanium clinopyroxene composition of Nidar ophiolite gabbros, southeastern Ladakh Himalaya, India: implications to geotectonic setting Ranjit Nayak, Debasis Pal Current Science, 2021 The Nidar ophiolite complex is one of the wellpreserved ophiolite sequences of the Indus Tsangpo Suture Zone (ITSZ) towards the southeastern part of Ladakh Himalaya, India. This study presents petrography and clinopyroxene mineral chemistry of gabbroic rocks from the Nidar ophiolite. These gabbros are massive, essentially composed of plagioclase and clinopyroxene with minor amounts of olivine, orthopyroxene, hornblende and magnetite. The clinopyroxenes are very low in TiO2 (0.05–0.77 wt%) and Na2O (0.12–0.85 wt%) but rich in SiO2 (52–55 wt%). It is observed that there is a wide variation of CaO (12.26– 23.88 wt%) and in the Wo–En–Fs ternary diagram, clinopyroxene shows augitic to diopside compositional variation. These low-titanium clinopyroxenes are inferred to be tholeiitic in nature with an island-arc boninitic affinities.
An island arc origin of Jurassic plagiogranite in the Shiquanhe ophiolite, western Bangong Suture, Tibet: Zircon U–Pb chronology, geochemistry, and tectonic implications of Bangong Meso-Tethys Wei Li, Nina Liu, Ranjit Nayak, Yaoliang Ma, Jinjun Wang, Xichong Hu, Jiehui Pang, Weile Huang, Yun Zhong, Weiliang Liu Geological Journal, 2021 The plagiogranites in ophiolites are minor in volume but can provide crucial information for the origin and tectonic evolution of ancient oceanic lithosphere. This paper presents the geochronology and geochemistry of a newly discovered plagiogranite in the Shiquanhe ophiolite, from the west end of the Shiquanhe‐Jiali ophiolite sub‐belt, Bangong Suture, central Tibet. Zircon U–Pb dating of two samples yields Middle Jurassic ages (167.4 ± 1.2 Ma and 167.5 ± 1.5 Ma). The plagiogranite has positive whole‐rock εNd(t) (4.2–4.9) and zircon εHf(t) (9.6–14.3) values, high Th/Nb ratios (0.6–2.8) but relatively low La/Nb ratios (0.9–9.9), indicating that it was possibly derived from a depleted mantle with the contribution of minor subducted sediments. The LREE‐enrichment but HREE‐flat patterns with negative Eu anomalies and negative Nb‐Ti anomalies resemble those of shear‐type plagiogranites, which mean that this rock was likely formed by partial melting of metabasite. Combined with the plagiogranite which does not exhibit chilled contacts against the Shiquanhe ophiolitic metabasite, suggests that the plagiogranite may have been derived from the associated ophiolitic metabasite. Geochemical calculating and modelling indicate that the plagiogranite was possibly produced by a low degree (<10%) partial melting of metabasite and replenished by minor sediments melts at low temperature (<800 °C) and low pressure (<0.1 GPa) conditions. The Shiquanhe plagiogranite, together with the contemporaneous Lagkorco plagiogranite in the same ophiolite sub‐belt, indicates that an intra‐oceanic island arc system was developed in the Bangong Meso‐Tethys during the Middle Jurassic.
