A single piece of meteorite fell on Kamargaon village in the state of Assam in India on November 13, 2015. Based on mineralogical, chemical, and oxygen isotope data, Kamargaon is classified as an L‐chondrite. Homogeneous olivine (Fa: 25 ± 0.7) and low‐Ca pyroxene (Fs: 21 ± 0.4) compositions with percent mean deviation of <2, further suggest that Kamargaon is a coarsely equilibrated, petrologic type 6 chondrite. Kamargaon is thermally metamorphosed with an estimated peak metamorphic temperature of ~800 °C as determined by two‐pyroxene thermometry. Shock metamorphism studies suggest that this meteorite include portions of different shock stages, e.g., S3 and S4 (Stöffler et al. ); however, local presence of quenched metal‐sulfide melt within shock veins/pockets suggest disequilibrium melting and relatively higher shock stage of up to S5 (Bennett and McSween ). Based on noble gas isotopes, the cosmic‐ray exposure age is estimated as 7.03 ± 1.60 Ma and nitrogen isotope composition (δ15N = 18‰) also correspond well with the L‐chondrite group. The He‐U, Th, and K‐Ar yield younger ages (170 ± 25 Ma 684 ± 93, respectively) and are discordant. A loss of He during the resetting event is implied by the lower He‐U and Th age. Elemental ratios of trapped Ar, Kr, and Xe can be explained through the presence of a normal Q noble gas component. Relatively low activity of 26Al (39 dpm/kg) and the absence of 60Co activity suggest a likely low shielding depth and envisage a small preatmospheric size of the meteoroid (<10 cm in radius). The Kr isotopic ratios (82Kr/84Kr) further argue that the meteorite was derived from a shallow depth.
Geochronology is useful for understanding provenance, and while it has been applied to the central and western Himalaya, very little data are available in the eastern Himalaya. This study presents detrital zircon U-Pb ages from the late Palaeocene-Eocene Yinkiong Group in NE India. The samples are from the late Palaeocene to early Eocene Lower Yinkiong Formation, and the Upper Yinkiong Formation deposited during the early to mid-Eocene within the Himalayan foreland basin. The U-Pb ages of the detrital zircon within the Lower Yinkiong Formation are older than late Palaeozoic, with a cratonic and early Himalayan Thrust Belt affinity, whereas the Cenozoic grains in the Upper Yinkiong Formation indicate a Himalayan Thrust Belt source and possibly a granitic body within the Asian plate. The shift of the sources and the changes in the foreland basin system strongly suggest that the India-Asia collision in the Eastern Himalaya began before or immediately after the deposition of the Upper Yinkiong Formation, i.e., within the early Eocene (c. 56 to 50 Ma).
The geomorphic analysis of mountain fronts and related drainage networks can provide valuable insights about the recorded tectonic history of any given region especially when the area shows higher seismic activity in recent times. Therefore, such studies at a regional scale have been frequently undertaken using morphotectonic analysis to delineate areas having higher tectonic activity. Also, study of active tectonics in an area is very important for any development activity especially hydropower projects as it has a direct implication on the stability and life of that project. The area along the SouthEast part of the Mikir massif is considered as one of the deformed zones of the northeastern region of India which is demonstrated by its seismicity. In the present study, an attempt has been made to study the active tectonic in the study area with the help of eight geomorphic indices and to correlate the results with the recent seismic activity and other ground evidence and finally an assessment of the potential for irrigation and hydropower development project in that area. The results of the study show that the area is tectonically more active along the Kaliyani shear zone and close to the Naga orogenic front. This has also been confirmed by the soft sediments deformation in Quaternary deposits. Despite this higher tectonic activeness, the area is having good potential for the development of small-scale hydropower and irrigation projects.
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