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The formation of continents involves a combination of magmatic and metamorphic processes. These processes become indistinguishable at the crust-mantle interface, where the pressure-temperature (P-T) conditions of (ultra) high-temperature... more

The formation of continents involves a combination of magmatic and metamorphic processes. These processes become indistinguishable at the crust-mantle interface, where the pressure-temperature (P-T) conditions of (ultra) high-temperature granulites and magmatic rocks are similar. Continents grow laterally, by magmatic activity above oceanic subduction zones (high-pressure metamorphic setting), and vertically by accumulation of mantle-derived magmas at the base of the crust (high-temperature metamorphic setting). Both events are separated from each other in time; the vertical accretion postdating lateral growth by several tens of millions of years. Fluid inclusion data indicate that during the high-temperature metamorphic episode the granulite lower crust is invaded by large amounts of low H 2 O-activity fluids including high-density CO 2 and concentrated saline solutions (brines). These fluids are expelled from the lower crust to higher crustal levels at the end of the high-grade metamorphic event. The final amalgamation of supercontinents corresponds to episodes of ultra-high temperature metamorphism involving large-scale accumulation of these low-water activity fluids in the lower crust. This accumulation causes tectonic instability, which together with the heat input from the sub-continental lithospheric mantle, leads to the disruption of supercontinents. Thus, the fragmentation of a supercontinent is already programmed at the time of its amalgamation. Ó 2015, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

The high-K calc-alkaline rocks constitute a major portion of the post-Archaean granitoids around the globe. They are very common in orogenic belts (Continental arc) as well in post-collisional (Caledonian-type) tectonic setting (Bonin,... more

The high-K calc-alkaline rocks constitute a major portion of the post-Archaean granitoids around the globe. They are very common in orogenic belts (Continental arc) as well in post-collisional (Caledonian-type) tectonic setting (Bonin, 1990; Roberts and Clemens, 1993). These contrasting settings and petrogenetic diversity have invoked great interest among petrologists to better define the origin and decipher geodynamic significance of these granitoids. In this contribution, we present new petrological and geochemical data integrated with available geochronology of the high-K granitoids of the Kerala Khondalite Belt (KKB), and attempts to define the nature and origin of these granitoids for constraining their geodynamic setting. The KKB region of the southern granulite terrain (SGT) is particularly interesting for the study of high-K granitoids genesis because it provides an opportunity to examine the close association of these granitoids with their supposed tonalitic protolith. The petrological and geochemical evidences provide insights into possible arc-accretion processes that contributed to crustal reworking and formation of the granitic magmas. Further, the study presents key geochemical fingerprints for regional comparison of the widespread arc-related magma genesis in neighbouring continental fragments including Sri Lanka and Madagascar.

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