Geochemistry and petrogenesis of late Pleistocene to Recent volcanism in Southern Dominica, Lesser Antilles

Application to the PPVC and Morne Anglais samples of magnetite-ilmenite, hornblende-plagioclase and two-pyroxene geothermometry yielded temperature estimates in the range of 800 to 890 °C for silicic andesite and dacite, and 970-1100 °C for basaltic andesites from Morne Anglais. Pressure estimates from magnetite-ilmenite-orthopyroxene equilibria are 200-300 MPa, similar to an estimate of 200 MPa derived from dissolved Cl and H2O contents in melt inclusions, and consistent with the 5-6 km depth of volcanic seismicity observed in the PPVC area between 1998 and 2000. The similarity of chemical and isotopic compositions, regular differentiation trends and P-T conditions for the different units of the PPVC suggest that recurrent eruptions in the last 40 ka have tapped a common, rather homogeneous magma source. Variations are due to local differences in the degree of differentiation before eruption. The long eruptive history at the PPVC, including episodic dome growth over the last 40 ka, may indicate rejuvination of the system by mafic magma recharge and this is supported by the proximity to the contemporaneous mafic Anglais center which itself shows some evidence of basaltic magma recharge. Despite this, we find no convincing petrographic or geochemical evidence in its eruptive products for mafic recharge into the PPVC magma system.