Introduction

The Eastern Ghats Belt (EGB) of India exposes a deep crustal section in the form of a 1000 km long edifice along the eastern coastline of India. Consisting of a lithologic ensemble of diverse chemistry, it has long been recognized as a mobile belt that sutured cratonic blocks of India with their transcontinental counterparts in the Precambrian time. Preliminary isotopic signatures from variedly disposed high-grade paragneissic and orthogneissic rocks led early researchers to believe that the entire mountain belt arose during a major orogeny in the Archean time. This idea was drastically changed when precise geochronological data identified no Archean metamorphic signatures in EGB. Petrological and structural data available from studies spanning the last three decades identified this belt as polymetamorphic and polydeformed (summarized in Dasgupta and Sengupta, 2003; Mukhopadhay and Basak, 2009). Geochronological data, on the other hand, clearly show that the entire crustal architecture of EGB was framed during mountain building activities in the Proterozoic eon (Dobmeier and Raith, 2003 and references therein).

Crustal evolution during the Proterozoic eon is heralded by assembly and break-up of several supercontinents. These supercontinents formed, stabilized and eventually dispersed in response to crust-mantle coupling and decoupling (Condie, 2005). Although there is disparity in opinion about the history of early-formed supercontinents like Columbia (~1900-1400 Ma), considerable agreement exists for the much younger supercontinent Gondwana (~550-300 Ma). The supercontinent Rodinia (~1000-750 Ma) existed in-between and there has been considerable effort to model its evolution through time and space (reviewed in Li et al., 2008). It is well established that global-scale orogenic activities played crucial roles in assembling each of these supercontinents under collisional and/or accretional tectonic settings. Traces of such activities are gathered from piecemeal evidenc from widely scattered areas in the present-day coordinates. Needless to say, compelling evidenceis pouring in day by day and strengthening the hypothesis of supercontinetal cycle.

EGB has long been identified as an important link in understanding the evolutionary history of the supercontinent Rodinia as petrological (Hoffman, 1991; Dalziel, 1991; Yoshida, 1995; Harley, 2003), and little reliable geochronological data has been found matching counterparts in east Antarctica (summarized in Dasgupta and Sengupta, 2003; Dobmeier and Raith, 2003). It is also exciting to find evidence of orogenic activities in EGB whose timeframe lies beyond Rodinia. With the arrival of new petrological, structural and most importantly, precise geochronological data, there is a need to re-look at this ancient mountain belt. We felt excited about the possibility of locating crustal segments belonging to extinct supercontinents within an apparently single geomorphological entity. With a continuous inflow of more precise data on deformation, magmatism and metamorphism in different continental blocks, it is possible to frame and correlate the events with higher resolution. However, at this point of time,there is also a need to review the existing database and understand the future demand of deep crustal studies.