Structural fabrics of schist belt, gneiss, migmatites and younger granitoids are different. Various morphology of migmatites is recognized for the first time in the southern part of EDC along with gneiss. The younger granite plutons are examined from northern through central to southern part of EDC. The paleosome-dominated portions of migmatite were possibly formed from low degree partial melting of older rocks and identified as metatexites. Whereas, the neosome dominated parts were developed by complete melting and marked as diatexites. There is a link between diatexite and granite in the southern part, which is chracterized as catazone segment. The four sub-types of metatexites are observed (viz, patch, dilatant, net and stromatic). The diatexites are dominated by two major structures (viz, schollen or raft and schlieren). Gneisses show lit-per-lit as well as fold and leucocratic material flow features. The litho-structural variation from north to south connotes systematic changes from epizone through mesozone to catazone. The qualitative study of mineral content and textural aspects from rocks at different localities suggest preserved portions of different parts of a pressure–temperature path. However, exact quantification should be possible after thermo-barometry and pseudo section study. The present contribution focuses on documentation of classic representative outcrops and petrographic features of gneissic and migmatitic rocks of EDC. It is observed that the six (6) major ductile deformation stages of Kenoran orogeny implies ductile signature before granite plutonism. Subsequently post granite emplacement deformation phenomenon indicates a transition from ductile to brittle regime and entrance into Hudsonian orogeny.
The southern basement of the Cuddapah Basin comprises the Dharwar Batholith and greenstone belt complex. Granitoids of the batholith exhibit extensive variation in terms of geomorphology, age, mineralogy, and micro/meso scale structures. The eastern part of Dharwar Craton along 13°50′ to 14°8′N latitude and 78°45′ to 79°05′E longitude was studied to enlighten the rheological influence on crustal evolution. Frequent occurrences of migmatites of restricted dimension are observed in the south of 14°10′N latitude. The granite‐migmatite contacts are not sharp in general. Different types of migmatite complex and their relationships with granitoids as well as older country rocks represent an exhumed segment of the crustal catazone. The widespread group of migmatitic rocks are classified in a composite manner on the basis of morphology and structure. Furthermore, genetic implication vis‐a‐vis anatexis history is also evaluated. Static and dynamic modes of migmatites are recognized with reference to geothermal gradient and tectonics. Based on the degree of anatexis, two categories of migmatites are identified in the field, that is, metatexites and diatexites. In addition, metatexites are classified into four sub‐types (viz, patch, dilatant, net, and stromatic) and diatexites are also sub‐divided into two categories (viz, schollen or raft and schlieren). The hybrid nature of migmatitic rocks with both metamorphic and igneous characteristics are used to analyse pre‐ and post‐anatectic events. The preserved evidences of partial melting are marked as leucocratic patches. In situ stagnation of the melt or subsequent separation from the remaining solid provides different morphology of static mode. Importance of dihedral angle at solid–liquid contacts is also considered in the present context to describe the grain boundary penetration by partial melt. Folds, veins, and boudins of different styles and generations played significant role in dynamic mode migmatitization. The syn‐ and post‐metamorphic deformation events and granite melt generation from migmatites are schematically defined. Spatial and temporal relationships of schist‐gneiss‐migmatites of both static as well as dynamic mode reveal initiation of the crustal development by vertical accretion of ultramafic‐mafic lava and TTG. Cyclic partial remelting of the metabasic lava and TTG and underplating led to development of the lithospheric plate. Later upwelling material at convergent plate and associated heat transfer led to generation of granitic magma. The established prograde and retrograde cycle of metamorphism were possibly interrupted by crustal reworking events. This study confirms about the crustal catazone segment (with >15 km depth and >500°C) in which physical processes control generation, segregation, ascent, and emplacement of juvenile granite from migmatites.
A next-to-leading order QCD calculation of nonsinglet spin structure functiong1NS(x,t)at smallxis presented using the analytical methods: Lagrange’s method and method of characteristics. The compatibility of these analytical approaches is tested by comparing the analytical solutions with the available polarized global fits.
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The DGLAP equation for the nonsinglet structure functionF2NS(x,t)at LO is solved analytically at lowxby converting it into a partial differential equation in two variables: Bjorkenxandt(t=ln(Q2/Λ2)and then solved by two methods: Lagrange’s auxiliary method and the method of characteristics. The two solutions are then compared with the available data on the structure function. The relative merits of the two solutions are discussed calculating the chi-square with the used data set.