Parent Paper: A pre-Rodinian ophiolite involved in the Variscan suture of Galicia (Cabo Ortegal Complex, NW Spain)
S. Sánchez Martínez, T. Jeffries, R. Arenas, J. Fernández-Suárez & R. García-Sánchez
Appearing in Journal of the Geological Society, Vol. 163, Part 5, August 2006, pp. 737-740.
Figure 1: Chemical diagrams for the Purrido amphibolites. (a) Nb/Y-Zr/Ti diagram of Winchester and Floyd (1977; Chemical Geology, 20, 325-343) modified according to Pearce (1996; Short Course Notes, Geological Association of Canada, 12, 79-113). (b) Incompatible element ratio plot of Ta/Yb-Th/Yb (after Pearce, 1983; Continental basalts and mantle xenoliths, Shiva, Nantwich, 230-249). (c)Ti-Zr-Y tectonic discrimination diagram (Pearce and Cann, 1973; Earth and Planetary Science Letters, 19, 290-300). (d) N-MORB-normalized trace element patterns of the composition of each amphibolite sample; normalizing values are from Pearce (1996). In the last plot the negative Nb anomaly and the relative depletion in some elements are compatible with a subduction related origin.
Table 1: U-Pb and Pb-Pb ratios and ages for the 20 selected analyses are given. Within the dataset, there is a statistically coherent group of 10 analyses (based on robust median algorithm of Ludwig (2003)) whose 207Pb/206Pb ages range between 1109±18 and 1208±66 Ma (shown in bold type). These analyses have consistent Th/U ratios with typical magmatic values mostly between 0.3 and 0.4.