Research Projects

The Himalaya, formed by the Indian–Eurasian plate collision since the early Eocene, provides a natural laboratory to study deep crustal processes including subduction, metamorphism, and exhumation.Eclogites and granulites record these events,with eclogites serving as key indicators of subduction and continental collision. Though rare in the Himalaya, they are found in two main varieties: coesite-bearing eclogites in the northwestern Himalaya (e.g., Kaghan Valley and Tso Morari) and granulitized eclogites in the eastern and east-central Himalaya (e.g., Ama Drime Range, Yadong region, and Sikkim). Granulitized eclogites were first identified in the Ama Drime Range and later reported from nearby locations including Yadong and Sikkim. These rocks, which belong to the Greater Himalayan Crystalline (GHC) unit, record high-pressure (HP) metamorphism linked to the India–Asia collision and provide valuable insight into the tectonic evolution of the orogen. Based on geochronological data, eclogite-facies metamorphism occurred at ~46 Ma in the Kaghan region and ~43–50 Ma in Tso Morari. In contrast HP/HT rocks (23–13 Ma) are found in the central and eastern Himalaya, including Sikkim. Whether these younger rocks formed due to prolonged HP metamorphism or a separate tectonic event remains unresolved. This uncertainty makes eastern Himalaya and particularly Sikkim a critical region for further study. Although HP and UHP rocks in the northwest and central Himalaya have been relatively well studied, similar research in the Sikkim Himalaya is limited, despite its tectonic importance. Addressing this gap can help clarify how HP rocks formed and evolved during and after continental collision. The rationale of the research lies in resolving outstanding questions regarding the timing, conditions, and mechanisms of HP metamorphism and subsequent granulite-facies overprint in the eastern Himalaya. Given the complex overprinting of eclogite by granulite-facies metamorphism and widespread high-temperature effects, it is critical to conduct microstructural and geochemical studies to recover original metamorphic signatures and reconstruct pressure-temperature-time (P-T-t) paths. A few research lacunae are the following: 1.Widespread high-temperature overprinting has led to poor preservation of HP assemblages, complicating to pinpoint the timing and magnitude of the HP metamorphism accurately. Prior work (Lombardo & Rolfo, 2000) suggests that eclogite formation predates granulite-facies overprinting and Miocene leucogranite intrusions. This necessitates detailed petrography and phase equilibrium modeling to identify relic HP phases and constrain their P-T conditions. 2.It remains unclear why eclogites are frequently overprinted by granulite-facies metamorphism in both ancient and modern orogens. 3.The role of reaction textures, retrogression, and symplectite formation in revealing the rate and style of exhumation of HP rocks in collisional settings is not well understood.