We present field and petrographical characteristics, zircon U–Pb ages, Nd isotopes, and major and trace element data for the magmatic epidote-bearing granitic plutons in the Bellur–Nagamangala–Pandavpura corridor, and address successive reworking and cratonization events in the western Dharwar Craton (WDC). U–Pb zircon ages reveal three stages of plutonism including: (i) sparse 3.2 Ga granodiorite plutons intruding the TTG (tonalite–trondhjemite–granodiorite) basement away from the western boundary of the Nagamangala greenstone belt; (ii) 3.0 Ga monzogranite to quartz monzonite plutons adjoining the Nagamangala greenstone belt; and (iii) 2.6 Ga monzogranite plutons in the Pandavpura region. Elemental data of the 3.2 Ga granodiorite indicate their origin through the melting of mafic protoliths without any significant residual garnet. Moderate to poorly fractionated REE patterns of 3.0 Ga plutons with negative Eu anomalies and Nd isotope data with εNd(T) = 3.0 Ga ranging from −1.7 to +0.5 indicate the involvement of a major crustal source with minor mantle input. Melts derived from those two components interacted through mixing and mingling processes. Poorly fractionated REE patterns with negative Eu anomalies of 2.6 Ga plutons suggest plagioclase in residue. The presence of magmatic epidote in all of the plutons points to their rapid emplacement and crystallization at about 5 kbars. The 3.2 Ga intrusions could correspond to reworking associated with a major juvenile crust-forming episode, whilst 3.0 Ga potassic granites correspond to cratonization linked to melting of the deep crust. The 2.6 Ga Pandavpura granite could represent lower-crustal melting and final cratonization, as 2.5 Ga plutons are absent in the WDC.

No abstract

A widely spaced Neoarchean shear zone network traverses the granite-greenstone terrains of the Western Dharwar craton (WDC). The NNW-SSE trending Balehonnur shear zone traverses the largest part of the preserved tilted Archean crustal ensemble in the Western Dharwar craton (WDC) from the amphibolite-granulite transition in the south to greenschist facies in the north and eventually concealed under Deccan lava flows. Published tectonic fabrics data and kinematic analysis, with our data reveal a sinistral sense of shearing that effectuate greenstone sequences, Tonalite-Trondhjemite-Granodiorite Gneisses (TTG), and Koppa granite as reflected in variable deformation and strain localization. A profound increase of strain towards the core of the shear zone in the ca. 2610 Ma Koppa granite is marked by a transition from weak foliation outside the shear zone through the development of C-S structures and C-prime fabrics, mylonite to ultramylonite. The mineral assemblages in the Koppa granite and adjoining greenstone indicate near peak P-T conditions of 1.2 Gpa, 775-800°C following a slow cooling path of 1.0 GPa and 650°C. Field-based tectonic fabrics data together with U-Pb zircon ages reveal that the Koppa granite emplaced along the contact zone of Shimoga-Bababudan basin ca. 2610 Ma, coinciding with the emplacement of ca. 2600 Ma Arsikere-Banavara, Pandavpura, and Chitradurga granites further east which mark the stabilization of WDC. Significant variation in major element oxide (SiO2 = 56-69 wt.%) together with high content of incompatible elements (REE, Nb, Zr, and Y) and high zircon crystallization temperatures (~1000°C) of Koppa granite suggests derivation by partial melting of composite sources involving enriched uppermost mantle and lower crust. The development of widely spaced shear zones is probably linked to the assembly of eastern and western blocks through westward convergence of hot oceanic lithosphere against already cratonized thick colder western block leading to the development of strain heterogeneities between greenstone and TTGs due to their different mineral assemblages leading to rheological contrast in the cratonic lithologies.

No abstract

Radioactive granitoids and cherty cataclasites are delineated in Thadisaoli-Khatgaon and Shahpur-Sujayatpur sectors in southeastern part of Nanded district, Maharashtra, which have recorded anomalous radioelemental contents (Granites: upto 1% U 3 O 8 and 0.20% ThO 2 ; Cherty cataclasites upto 0.11% U 3 O 8 and <0.005% ThO 2 ) and enrichment in trace element and rare metal and rare earth element concentration (Nb: upto 146ppm, Y: upto 226ppm, Zr: upto 559ppm and total REE: upto 2010ppm). The mineralised granitoids are affected by profuse pegmatitic/quartzo-feldspathic, quartz and epidote venations and mainly confined along the NE-SW and NNE-SSW faults/shear zones. Radioactive phases are represented by discrete uranium/thorium ore minerals (uraninite, βuranophane and thorite) and high content of resistates viz., apatite, zircon, allanite, sphene, cerianite, monazite and ilmenite.Fluid inclusion studies of the mineralised and sheared granites, quartzo-feldspathic veins (QFV's) and quartz veins indicate the presence of 6 to 32µm size aqueous and carbonic inclusions of three principle types and represented by six phases viz., aqueous mono-, bi-and poly-phases, aqueous-carbonic, carbonic mono-, bi-and poly-phases. Aqueous biphase inclusions show wide range of salinity (0.71 to 19.99 wt.% eNaCl) and homogenisation temperatures (T h : 127.5-280.8ºC ), while aqueous-carbonic inclusions exhibit restricted salinity (5-8.4 wt.% eNaCl ) and T h (28.3-30.9ºC). The composition of these aqueous fluids varies from NaCl-KCl dominant in quartz veins and radioactive granite to MgCl 2 dominant in sheared radioactive granite. Similarly, co-eval aqueous biphase and aqueous-carbonic inclusions have yielded 678-958 bar pressure and 201-233ºC temperature in quartz vein samples while higher values of 1120-1550 bar and 304-360ºC are indicated by sheared granite. The presence of more than one population without much change in fluid composition signifies their origin at different stages of deformation. Besides, mixing of a moderate temperature and low salinity fluid (meteoric/basinal brine) with a comparatively high temperature and hypersaline fluid (magmatic/ evolved brine) might have also played an important role in inclusion characteristics. Based on these fluid inclusion characteristics, it appears that multi-episodic hydrothermal activity under an extensional tectonic regime in this fertile granitic province has led to precipitation of uranium along suitable structural aureoles from uraniferous hydrotherms.

No abstract

The roots of Hemidesmus indicus, belonging to the family Ascelpidaceae, are used as blood purifier, antileucorrhoeic, galactogenic, antidiarrhoeal, antirheumatic, antisyphilitic, febrifuge and possesses chemical constituents like triterpenoids (lupeol), flavonoids, glycosides and tannins. Roots were dried and extracted with petroleum ether, chloroform and methanol by using Soxhlet apparatus. Two simple and sensitive chromatographic methods, namely, HPTLC and HPLC, were developed for determination of lupeol from the extract of H. indicus and its polyherbal formulation and validated according to ICH guidelines. The HPTLC method linear regression data for the standard lupeol a concentration range of 400-900ng/spot and correlation coefficient (r) was 0.9904. The HPLC calibration curves of standard lupeol showed good linearity range from 20 to 100μg/ml and correlation coefficient (r) was 0.9929. The HPTLC and HPLC methods are simple, precise, accurate and specific. Hence, these methods can be used for the standardization of lupeol in herbal plants and polyherbal formulations.