GEOCHEMICAL HISTORY OF THE TELICA VOLCANIC COMPLEX, NICARAGUAN VOLCANIC FRONT: IMPLICATIONS OF NEW DATA

The Telica Volcanic Complex in northwestern Nicaragua is unusual in that its basalts exhibit nearly the full range of trace element variability seen amongst mafic lavas along the entire Central American volcanic front. The Telica Volcanic Complex is comprised of several NW-SE trending volcanic edifices, primarily older dissected cones and ridges with a few younger, more distinct cones. Volcanic activity within the complex is currently centered at Telica, a stratovolcano consisting of several individual vents. We present here additional geochemical data on 45 volcanic rocks that span the entire history of the Telica Volcanic Complex. The new major and trace element data are consistent with previous data for Telica from the Centam database and Lefebvre (1986). For the complex as a whole, the youngest lavas have the highest U/La ratios, whereas Ba/Th ratios decrease with time. Given that U/La and Ba/Th ratios have been interpreted to represent variable contributions to the mantle source from Cocos Plate sediments, hemipelagic versus carbonate, respectively (Patino et al., 2000), these data suggest that there have been increasing contributions of hemipelagic sediment to magma production beneath the complex over time. The youngest lavas from the Telica cone form two distinct groups—high-Ti and low-Ti—that differ in their trace element characteristics. The high-Ti lavas are distinctly low in Ba/La and more enriched in La/Yb, Sm/Yb and Ce/Pb ratios, suggesting they represent lower degrees of melting with an attenuated slab input. The new geochemical data indicate that slab input beneath this enigmatic arc volcano have been quite variable over both long and short time scales.