Geochemistry of the basalts from DSDP Leg 42A

Despite mineralogical and chemical alteration due to hydrothermal processes under the high heat flow regime in the Tyrrhenian marginal basin, petrological analogies to high-Al abyssal basalts can be traced. Two interlayered basalt groups have been recognized: (1) the lower-Ti group (core 5/1-2, core 7, 10), and (2) the higher-Ti group (core 5/3, core 6, core 11, core 12 and outer barrel), respectively.

We consider a distinction of two magma types: a more primitive magma leading to the plagioclase-bearing, lower-Ti basalts with affinities to high-Al abyssal tholeiites and a more differentiated magma leading to basalts with higher Ti.