https://www.adelaide.edu.au/directory/alan.collins?dsn=directory.file;field=data;id=2241;m=view

Amalgamating eastern Gondwana: The evolution of the Circum-Indian Orogens

The Archaean tonalite-trondhjemite-granodiorite (TTG) series is not an analogue of Cenozoic adakite

Progressive growth of the Earth's continental crust and depleted mantle: Geochemical constraints

Two terrestrial lead isotope paradoxes, forward transport modelling, core formation and the history of the continental crust

The thermal history of the Eastern Ghats Belt (India) as revealed by U–Pb and 40Ar/39Ar dating of metamorphic and magmatic minerals: implications for the SWEAT correlation

Early Archean crust in Bastar Craton, Central India—a geochemical and isotopic study

Discordant granite plutons at Kyrdem, Nongpoh and South Khasi intrude the basement gneisses and the overlying Shillong Group of metasediments in the Meghalaya Plateau. Porphyritic granitoids ranging in composition from quartz monzonite to granite represent the dominant component in all the three plutons. Common characteristics of these granitoids arc spatial association with hornblende dioritic rocks, dominantly potassic and metaluminous nature. A positive correlation of SiO 2 , Na 2 O + K 2 O, Rb, Rb/Sr and negative correlation of CaO, MgO, FcO(T), Sr, TiO 2 with Differentiation Index in the Kyrdcm pluton point to fractional crystallisation processes. Rb-Sr whole rock isochron data of the plutons yield ages in the range 480-690 Ma wiLh initia1 87 Sr/ 86 Sr ratios ranging from 0.70948 -0.71482. Absence of post emplacement tcctonolhennal event is suggested by near concordant K-Ar biotite ages. A protracted thennal event during late Proterozoic-early Palaeozoic (500-700 Ma), possibly related to mantle upwelling, possibly triggered the generation of these granitoids.

Geochronology and Geochemistry of Granite Plutons from East Khasi Hills, Meghalaya

The tonalitic suite of Kaptipada is high-Al 2 O 3 type with a highly fractionated REE pattern suggesting its derivation by partial melting of amphibolite with hornblende as a residual phase. The homblende/biotite-bearing granites of Nilgiri and Ramapahari areas also occurring along the southeastern fringe,are comparatively K-rich than the lonalite-granodiorite suite of Kaptipada. Based on whole rock Rb-Sr isotopic analyses, lhe Kaptipada tonalite-granodiorite suite yields an age of 3275 ± 81 Ma with initial Sr ratio of O.70130± 0.00045; ... the Nilgiri granite, an age of 2366 ± 126Ma with initial Sr ratio of 0.72526 ± 0.00832 and Ramapahari granite, an age of 1895 ± 46 Ma wilh initial Sr ratio of 0.76521 ± 0.00427. The temporal evolution of the tonalitic rocks of Kaptipada is indistinguishable from the earlier phases of Singhbhum and Bonai granitoids of the Singhbhum Craton. It is concluded that an extensive growth of tonalitic crust took place around 3.3 Ga in the region.

Rb-Sr Chronology and Petrochemistry of Granitoids from the South-Eastern Part of the Singhbhum Craton, Orissa

Late Proterozoic alkaline magmatism in the Eastern Ghats belt : Rb-Sr isotopic study on the Koraput complex, Orissa

Minor intrusive bodies of granite occur along the periphery of the Archaean trondhjemitic batholith of the eastern Indian craton. Small granite bodies intruding low-grade sediments and volcanics also occur north of the Dalma volcanic belt. Of these, Kuilapal granite body is the largest. Petrographic and geochemical characters of the minor granite bodies south of Dalma volcanics are similar to those of Kuilapal granite. On the basis of these characters, Kuilapal granite and Arkasani granophyre are inferred to have been produced by shallow-level fractional crystallisation of a crustally - derived granodiorite melt. Dominance of xenoliths in the Kuilapal granite suggests large-scale assimilation of crustal rocks. A Rb-Sr age of 1638 {+-} 38 Ma with Sr of 0.72173 {+-} 0.00156 (MSWD=11.3) has been obtained for the Kuilapal granite. This age is strikingly close to the Rb-Sr age of 1677 {+-} 11 Ma as obtained for the soda granite of Mosabani. The Rb-Sr age of 1638 {+-} 38Ma, it seems, is the minimum age of emplacement of Kuilapal granite. A Rb-Sr whole-rock age of 1052 {+-} 84Ma has been obtained for the Arkasani granophyre. Microstructural and textural evidence in some of the samples indicate deformation-induced and fluid-controlled recrystallization. The emplacement age of the Arkasani granophyre is likely to be older than 1052 Ma. (author). 31 refs., 8 figs., 4 tabs.

P. K. Bishui

Papers

Early Archean crust in Bastar Craton, Central India—a geochemical and isotopic study

Geochronology and Geochemistry of Granite Plutons from East Khasi Hills, Meghalaya

Rb-Sr Chronology and Petrochemistry of Granitoids from the South-Eastern Part of the Singhbhum Craton, Orissa

Late Proterozoic alkaline magmatism in the Eastern Ghats belt : Rb-Sr isotopic study on the Koraput complex, Orissa

Geochemical and Rb-Sr isotopic study of Kuilapal granite and Arkasani granophyre from the eastern Indian craton