The Madagascar Large Igneous Province
Ciro Cucciniello, Leone Melluso, Vincenzo Morra
Dipartimento di Scienze della Terra, dell’Ambiente e delle Risorse, Università degli Studi di Napoli Federico II, Via Mezzocannone 8, 80134 Napoli, Italy
Large Igneous Provinces Commission
The Madagascar large igneous province (LIP) is one of the largest magmatic events in the Late Cretaceous. It consists of lava flows, dikes, sills and intrusions (e.g., Storey et al., 1997; Melluso et al., 1997, 2001, 2002, 2003, 2005, 2006, 2009; Mahoney et al., 1991, 2008; Dostal et al., 1992). Remnants of this igneous province (the original pre-erosion extent of the province is difficult to estimate, although it probably exceeded 1 × 106 km2 including also the Madagascar Plateau and Conrad Rise; Storey et al. 1995) crop out along the rifted margin of the eastern coast, in the Mahajanga and Morondava basins of western Madagascar as well as the high plateau of the continental interior, and in western India (cf. Melluso et al. 2009). The igneous rocks are most voluminous in the Volcan de l’Androy complex (southern Madagascar; where more than 2000 m of lava flows are present) and the Mahajanga Basin (northwestern Madagascar). Significant outcrops, in the form of intrusive complexes, dikes and lava flows are in the Morondava Basin, the Maningoza area, and in two districts along the east coast: Sambava-Cap Masoala and Mahanoro-Manambondro. The main dike trends in each region form a radiating pattern which converges near the estimated 88 Ma location of the Marion hotspot (Ernst & Buchan, 1997). Rare, isolated outcrops are also known in the high plateau (tampoketsa) of the continental interior of Kamoro, Beveromay, and Analamaitso. The Antampombato-Ambatovy intrusion (Melluso et al. 2005) is rich in ultramafic rocks, and its lateritic soil is currently exploited for transition elements such as Ni and Co. The Ambohiby alkali granites cross-cut the central-western part of the Madagascan basement. Most of the volcanic successions are less than 200 m thick.The Madagascar LIP is dominated by mafic rocks; silicic rocks represent only a small volume of the province, overall (Melluso et al., 2001, 2005, 2009; Mahoney et al., 2008). The mafic rocks are mostly tholeitiic basalts and basaltic andesites. Detailed geochemical and petrological studies of the vulcanic successions of northwestern margin of Madagascar were reported by Melluso et al. (1997, 2001, 2003, 2006) and Cucciniello et al. (2010, 2013).
Current models of Madagascar flood basalt volcanism suggest that the Madagascar province occurred in response to rifting between Madagascar and Greater India and upwelling of Marion mantle plume (Storey et al., 1995; Torsvik et al., 1998). To date, there is no clear evidence of a chemical input of a plume component to the source of the basaltic rocks of Madagascar LIP.