In mountain terrains of Himalaya, road and highway networks play a vital role in remote areas for transportation, public network and all kind of socio-economic activities. The stability of rock slopes along the roads and highways is a major concern in these hilly regions. Any kind of slope failure may lead to disruption in traffic, loss of properties and lives/injuries as well as environmental degradation. The unplanned excavations of rock slopes for construction or widening purposes may undermine the stability of the slopes. The present study incorporates the stability analysis of road cut slopes along NH-109 which goes to holy shrine of Kedarnath. Slope failure is not only a phenomenon of rainy season but it has also been encountered even in dry season. The study area experiences high vehicular traffic especially from March to August due to pilgrims since it is the only road to Kedarnath. The distance of about 20 km between Rudraprayag and Agastmuni has been investigated. The continuous slope mass rating (CSMR) technique has been used for slope stability analysis at five different locations. CSMR is modification of original slope mass rating (SMR) proposed by Romana which is based on well established rock mass rating (RMR) technique. Kinematic analysis was also carried out to evaluate these sites for types of failure and its potential failure directions. The potentially vulnerable sites were identified. The results indicate that the CSMR technique may be exploited to assess the stability of rock slopes in the Himalayan territory

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Rockfall is a major problem in high hill slopes and rocky mountainous regions and construction of highways at these rockfall prone areas often require stable slopes. The causes of rockfall are presence of discontinuities, high angle cut slopes, heavy rainfall, and unplanned slope geometry etc. Slope geometry is one of the most triggering parameters for rockfall, when there are variations in slope angle along the profile of slope. The Present study involves rockfall hazard assessment of road cut slopes for 15 km distance starting from Mahabaleshwar town along State Highway-72 (SH-72). The vertical to subvertical cut slopes are prone to instability due to unfavorable orientation of discontinuities in slope face of weathered and altered basaltic rockmass. The predominant type of instability has been found as wedge type failure involving medium to large size blocks. In order to investigate the existing stability conditions, analyses were carried out at two locations under different slope conditions. The kinematic analysis was performed using stereographic projection method. RockFall 4.0 numerical simulator software was used to calculate the maximum bounce heights, total kinetic energies and translational velocities of the falling rockmass blocks, and a comparative analysis is presented with increasing the mass of blocks and height of the slope. The result of numerical analysis shows that varying slope angle geometry creates more problems as compared to the mass of blocks in the scenario of rockfall.

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The Early Cretaceous Sung Valley Ultramafic-Alkaline-Carbonatite (SUAC) complex intruded the ProterozoicShillong Group of rocks and located in the East Khasi Hills and West Jaintia Hills districts of Meghalaya. The SUAC complex is a bowl-shaped depression covering an area of about 26 km 2 and is comprised serpentinised peridotite forming the core of the complex with pyroxenite rim. Alkaline rocks are dominantly ijolite and nepheline syenite, occur as ring-shaped bodies as well as dykes. Carbonatites are, the youngest intrusive phase in the complex, where they form oval-shaped bodies, small dykes and veins. During the course of large scale mapping in parts of the Sung Valley complex, eleven carbonatite bodies were delineated. These isolated carbonatite bodies have a general NW-SE and E-W trend and vary from 20-125 m long and 10-40 m wide. Calcite carbonatite is the dominant variety and comprises minor dolomite and apatite and accessory olivine, magnetite, pyrochlore and phlogopite. The REE-bearing minerals identified in the Sung Valley carbonatites are bastnäsite-(Ce), ancylite-(Ce), belovite-(Ce), britholite-(Ce) and pyrochlore that are associated with calcite and apatite. IntroductionCarbonatites are known to host high concentrations of rare earth elements (REE) [1]. Moreover, syenites, phonolites, alkali granite, pegmatite and secondary or supergene en- * E-mail: mohd.sadiq.gsi@gov.in richment in some bauxite, laterite, phosphorites, placers and beach sands are also potential hosts for REE's. Rare Earth Metals are becoming a critical strategic resource with an increase in demand mainly from scientific and military applications. About 95% of the REE export market is dominated by China who is a leading producer of REEs. In China, production is mainly from the Bayan Obo REE-iron ore deposits and clay deposits in southern China, and rest of the world has comparatively limited production [2]. Prior to the rise of Chinese REE production, monazite and xenotime-beach placer deposits in India, Brazil and Australia had been the main source for REEs. With the discovery of carbonatite-hosted REE deposits (mainly bastnäsite-(Ce)), carbonatite has become a primary resource of world REE production e.g. Mountain Pass, USA. In India, the first carbonatite-hosted REE deposit has been discovered at Kamthai, Barmer district, Rajasthan and contains a highest LREE grade of 17.31 wt% and a weighted average grade is 2.97 wt% LREO with a total volume of 1,38,428 tonnes [2]. The Shillong Plateau of northeastern India hosts four intrusive alkaline-carbonatite complexes, the Samchampi, Sung Valley, Jasra-Barpung and Swangkre complexes [3,4]. Sung Valley was the first carbonatite complex reported from north east India [5]. These complexes, especially the Sung Valley complex, has drawn attention of many researchers mainly for two reasons. Firstly, its petrogenesis, emplacement age and relationship with associated silicate rocks and secondly to assess mineral potential of the alkaline-carbonatite complex [3,4,[6][7][8][9][10][11]...

The Cambrian Nongpoh granitoids, intrusive into the Precambrian gneissic complex and metasediments of the Shillong Group, represent a major phase of granitic magmatism in the Shillong Plateau. The Nongpoh granitoids comprise diorite, granodiorite, porphyritic and grey granites. Porphyritic granite is the dominant lithology exposed in the Nongpoh granitoids, and contains three types of enclaves, viz. xenoliths of gneissic rocks, dark grey porphyry and biotite-rich microgranular enclaves. The mafic magmatic enclaves (MMEs) of various dimensions and shapes, including rounded, ellipsoidal, rectangular, angular to subangular, and stretched bodies, were produced by evolving nature and contrasting kinematics of interacting felsic and mafic magmas. The biotite-rich enclaves are due to the injection of syn-magmatic mafic dykes in felsic magma. The various textural assemblages and sub-linear variations between silica and major oxides, chemical mixing and element diffusion suggest that multistage magma hybridization was the key process during the evolution of the Nongpoh granitoids. The 501 Ma age obtained by chemical (U–Th–Pb) dating of monazite in MME ascertained the age of the magma hybridization event in the Nongpoh granitoids, which is equivalent to the igneous activity at 500 Ma during the amalgamation of Eastern Gondwana.