Geochemistry and petrogenesis of Tethyan ophiolites from northern Argolis (Peloponnesus, Greece)

Tethyan ophiolitic sequences from the northern part of the Argolis Peninsula in northeastern Peloponnesus (Greece) contain MORB-like basalts and rocks with boninitic characteristics. The former include basalts with enriched to depleted light REE patterns. The boninitic rocks show many similarities to those of Cenozoic age from the Western Pacific - as well as to the low-Ti ophiolites - including high contents of Mg, Ni and Cr and low abundances of Ti and incompatible trace elements. The boninites that are the most depleted in Al, Ca, Ti and heavy REE, display the highest relative enrichment in light REE and Zr. The boninitic rocks were probably formed in a back-arc/inter-arc setting where a rising MORB-source diapir facilitated melting of a progressively more depleted upper mantle peridotite that had been modified by Zr- and light REE-rich fluids. The compositional variations of MORB-like basalts are attributed to dynamic partial melting of the rising mantle diapir.