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Olivine-bearing dolerite and gabbro-dolerite dykes intruded host Precambrian metamorphic rocks of oasis Schirmacher most likely represented Jurassic trap activities in this region of Antarctica. Olivine shows a wide composition range between Fo91.5 to Fo55, which proves strong influence of accumulation processes during melt differentiation. Most common olivine compositions correspond to Fo88 – Fo89...
The Uauá mafic dyke swarm is one of the Precambrian mafic dyke swarms in the São Francisco Craton, Brazil, but its tectonic significance is poorly understood. On the basis of geological mapping and field relations two dyke swarms are recognized in the Uauá block, a terrane bounded to the west and east by shear zones. The younger dyke swarm is composed of tholeiite and norite dykes, whereas the older...
The integration of paleomagnetic data with geochronological and geochemical analyses of mafic dyke swarms is a powerful tool for correlating the swarms on regional and global scales. The multidisciplinary approach may also provide important insights into various problems of Earth evolution. We present new results of our paleomagnetic and geochemical investigations of several Proterozoic dykes from...
Around and south of the southern margin of the ProterozoicCuddapah Basin of India, basic dykes are intruding into the Archaean basement. 18 dykes have been sampled for geochemical work from the five localities and the samples from these were analysed for major, trace and REE. Based on the geochemical characteristics these dyke rocks falls under four groups. The features of each group are discussed...
A palaeomagnetic and 40Ar/39Ar study is reported from a suiteof 41 mafic dykes comprising a dense E-W trending swarm intruding Archaean granitic basement near the southern margin of the Proterozoic Cuddapah basin in southern India. Rockmagnetic studies define a range of mixed domain with dominant multi domain (MD) ferromagnetic carriers. Twenty four dykes exhibit stable behaviors to progressive demagnetisation...
Analysis of palaeomagnetic database of the Palaeoproterozoic dykes of India indicates that during the geological time period from 2,500 to 1,800 the South Indian craton moved from high latitude to an equatorial position. Mafic dykes of ~2,400 Ma age from the Western Australia and the South India provide evidence for the juxtaposition of the Yilgarn craton against the east coast of India. The events...
In southwestern part of the Proterozoic Cuddapah basin, a major NW-SE trending picrite sill exposed over a stretch of 12 km from Peddakudala in northwest to Velpula in southeast has emplaced the sediments of Tadpatri Formation in the lower part of the Cuddapah Super Group. Petrographically the rock is composed of olivine, clinopyroxene, plagioclase, phlogophite, and orthopyroxene, while magnetite,...
The Wynad Gold Field, unlike Archaean greenstone-hosted gold mineralization that is commonly found in India, comprises a network (length >100 m, thickness ~ 1.5 m) of much younger (~450 Ma) auriferous hydrothermal quartz veins within migmatitic tonalitic gneisses of the Southern Granulite Terrain, north of the Moyar shear zone. The gold mineralization occurs closely associated with probable mantle-derived...
Mafic dykes of Rewa basin occur along the Son-Narmada lineament between the Deccan volcanics of western India and the mafic and ultramafic dykes of the Gondwana coalfields in eastern India. In the present area of study, Umaria is from the western part, Shahdol from the central and the Chirimiri dykes are from the eastern extremity. Palaeomagnetic determinations on the Shahdol and Chirimiri dykes of...
Dolerites traversing Raipur Group of Chhattisgarh Basin have been reported by various workers but their radiometric age is not determined for ascertaining the absolute age of Raipur Group. Recent works on magmatic zircon and monazite from tuffs of Raipur and Singhora Groups have added significant radiometric and authentic data to accept the age of Chhattisgarh Supergroup. Present study reports Rb/Sr...
The Tirodi basement gneisses of Betul region of the Central Indian Tectonic Zone (CITZ) has been dissected by numerous mafic dykes, Padhar mafic–ultramafic complex (PMUM: Pyroxenite and gabbro) and pillow lavas of Betul supra-crustal belt. Mafic dykes, PMUM and pillow lavas are predominantly sub-alkaline, of tholeiitic affinity, ranging in composition from basalt, basaltic-andesite to andesite. All...
Different generations of Precambrian mafic dyke swarms are well documented in different parts of the Archaean Bastar craton. Mafic dykes reported from southern part of the Bastar craton is well studied but those exposed in central part have limited petrological and geochemical information. This paper presents petrological and geochemical characteristics of mafic dykes exposed around Dondi, Bhanupratappur...
A number of mafic dykes have intruded the tremolite-zone siliceous dolomite of PalaeoProterozoic Mahakoshal Group of rocks of Central India exposed near Jabalpur, MP. While the central part of most of the dykes are massive, being constituted of randomly oriented coarse hornblende laths in a fine grained feldspathic matrix, the marginal parts near the contact of enclosing siliceous dolomite have been...
High-grade granulites of Chilka Lake area, northern part of Eastern Ghats Belt, India record multiple stages of metamorphism and deformation. The major mapable foliation is designated as transposed S2/S3 which shows folding due to later deformation. Dark-colored massive two pyroxene-bearing mafic granulites occur along the transposed S2/S3 fabric in metapelitic granulite, quartzofeldspathic granulite...
At Deoghar- Jashidihi, Jharkhand, India, a suite of mafic dykes amidst migmatitic felsic gneiss underwent superposed folding, polyphase boudinage, and was accompanied by syntectonic migmatization (in the host felsic gneiss) and emplacement of different generations of pegmatite. Structural features of the deformed and torned-out mafic dykes demonstrate that compared to the enclosing felsic gneiss,...
Rocks of Malani Igneous Suite (MIS) occur as isolated, circular/elliptical outcrop in the western flank of Aravalli ranges. They are comprising mainly of acid magmatism with minor basics which have various pulses viz. volcanic, plutonic and dyke. They are characterised as A-type, anorogenic and formed due to hot-spot tectonics. Petrological and geochemical studies of MIS dyke rocks indicate that they...
Geochemistry of five basaltic and three doleritic dykes traversing through Deccan Traps in Kawant with similar trace element characteristics revealed a genetic relation among them. Various discrimination diagrams clearly indicate that all these basalts and dolerites are tholeiitic in nature. Of these, one picrite dyke (12–13 wt% MgO, 47–48 wt% SiO2 and 2.06–2.19 wt% total alkali) has high Mg# value...
The occurrence of quartzo-feldspathic xenoliths is being reported here from the lamprophyre and picrobasalt dykes of Bakhatgarh-Phulmal area, Jhabua district, Madhya Pradesh. The xenoliths are of two types viz. Type-I xenoliths are nodular, having appreciable roundedness and sphericity, varying between 3 and 5 cm, either aphinitic or coarse grained, composed of quartz, crystoballite, high albite and...
Minor late-granitoids occur as leucocratic veins, apophyses and dykes cross-cutting gabbro, basalt and marine sediments of the Naga Hills Ophiolite (NHO) at the eastern edge of the Indian plate where it subducts under the Burmese microplate. These intrusives consist of diorite, granodiorite, granite, and quartz porphyry containing variable amounts of quartz, alkali feldspar, plagioclase, amphibole,...
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