Chipping of cratons and breakup along mobile belts of a supercontinent

Abstract

Probably one of the most significant heterogeneities of a continental lithosphere is the noticeable difference in the thickness and properties of its cratonic and mobile parts. The trans-continental mobile belts (Paleoorogens/paleo-sutures) represent a relatively thinner, warm, wet and weak lithosphere, which makes it more vulnerable to episodic mantle (or plume) upwellings and compressional forces. Here evidence is presented from the Indian continental lithosphere to show that these properties of mobile belts (MB) facilitate channeling of thermomagmatic fluxes (TMF) in both lateral as well as vertical directions. This, to a major extent, can account for the observed concentration (or focusing) of geophysical anomalies, tectonomagmatic features and strain along these MBs. In addition, a closer examination of the three continental breakups of Greater India since the Cretaceous reveals that the combination of a sufficiently weakened MB and mantle plume could become 'fatal' for the supercontinental stability. On the other hand, the thick (>200 km) or deep-rooted continental lithosphere beneath cratons is characterized by a relatively cold and dry lithosphere, which resists remobilization. From this relative impenetrability, TMFs are channeled mostly through the MBs following the long-term stability of the cratonic lithosphere. This difference in cratonic and MB regimes results in strongly heterogeneous thermal blanketing. However, in certain situations, the edge of a cratonic region may also get chipped-off following a number of thermotectonic rejuvenations of adjoining MBs-as exemplified by the breakup of the Antongil and Masora cratonic blocks (now lying on the Madagascar) from the Western Dharwar craton (India) during the IndiaMadagascar separation. From the study of supercontinental dispersals, it seems that the processes of breakup along pre-existing mobile belts may be globally applicable. This is, at times, also accompanied by chipping of cratons.

Geoelectric structure of northern Cambay rift basin from magnetotelluric data

“…In general, the release of fluids migrating upwards during underplating results in lower resistivities. The wide correlation between the mantle plume and flood basalts (Courtillot et al 1988;Raval and Veeraswamy 2000;Veeraswamy and Raval 2004;Isozaki 2009) suggests a huge basaltic eruption occurred from the rising mantle plume during the interaction. The buoyant basaltic melt rose to the surface due to its low density, and when it reached the neutral density point at the Moho, underplating occurred raising the Moho depth.…”

“…The structural architecture of the WCMI was also modulated by two major geodynamic events, the activity of the Reunion hotspot and the collision that formed the Indo-Eurasian continental plate. The interaction between the Reunion hotspot and the Indian continental lithosphere during the Cretaceous-Tertiary boundary (~ 65 Ma ago) resulted in a huge flood of basaltic eruptions, which formed the Deccan volcanic province (DVP) over the western and central Indian sub-continent (Raval and Veeraswamy 2000;Veeraswamy and Raval 2004). It covers an area of more than 500,000 km 2 , almost one-sixth of the total surface area of the Indian Peninsula.…”

“…The Narmada geofracture zone formed along the third arm, whereas the fourth arm resulted in the Cambay basin, due to extensional stresses associated with the separation and movement of the Indian plate away from the Seychelles. The second-stage rifting of the Cambay basin is considered to be coeval with the breakup of the Indian plate and the Seychelles as well as the eruption of Deccan basalts in the Late Cretaceous (Raval and Veeraswamy 2000;Veeraswamy and Raval 2004) by generating significant variations in volcanic intensity as observed in the Baikal rift zone, a Rio Grande rift system. Several geophysical studies were carried out to understand the tectonics, sediment thickness, and rifting processes of the Cambay basin (Kaila et al 1990;Tewari et al 1991Tewari et al , 1995Mishra et al 1998;Singh et al 2003;Dixit et al 2010;Kumar et al 2016).…”

Mapping of tectonic corridors through hidden parts of the Greater Dharwar Terrane, Southern India

“…The numbers in circle gives the approximate average values over different domains. (Veeraswamy and Raval, 2004) during the Marion plume activity and breakup (Mahoney et al, 1991;Storey et al, 1995). The chipping is supported by the incomplete oval shape of the WDC nucleus shown in the Fig.…”

Sub-surface structure of a craton–mobile belt interface: Evidence from geological and gravity studies across the Rengali Province–Eastern Ghats Belt boundary, eastern India

“…Geophysical studies across these suspected ancient sutures have revealed that they are commonly associated with a characteristic Bouguer gravity anomaly signature, with high positive values over the mobile belt dropping steeply to negative values across the contact into the adjoining craton (e.g. Black et al, 1979;Fountain and Salisbury, 1981;Gibb and Thomas, 1976;Gibb et al, 1983;Mathur, 1974;Mishra and Ravi Kumar, 2014;Nyblade and Pollack, 1992;Subrahmanyam and Verma, 1986;Tesha et al, 1997;Thomas and Tanner, 1975;Veeraswamy and Raval, 2004;Vijaya Rao et al, 2006). The negative part of this paired anomaly is commonly attributed to depression of the Moho in the craton adjacent to the suture, either because of crustal thickening at the collisional front (e.g.…”