Comparable rodingitization processes identified in ophiolites from Pindos (Greece) and Krrabi (Albania)

The Jurassic western-type ophiolites of the Tethyan Pindos oceanic basin are part of an ophiolite belt that extends within the Apulian and Pelagonian subcontinents in the Balkan Peninsula. These ophiolites tend to display MORB geochemical affinities, in contrast to the adjacent eastern-type ophiolites with SSZ affinities. The Orliakas locality in Pindos (Greece) and Krrabi in the Mirdita ophiolite (Albania) are two characteristic localities, representative of the south and north branches respectively of the Pindos western-type ophiolitic belt. Both localities include rodingitized gabbroic dykes hosted in highly serpentinized peridotites.

We report the occurrence of gabbronorite and olivine gabbro dykes of comparable thickness (0.5- 1.0 m) that were partly affected by rodingitization processes. In some cases, the gabbroic protoliths were found almost intact at the central parts of the dykes. Protoliths from the two localities exhibit highly comparable whole-rock geochemical properties: SiO₂: 48.1-49.3 wt.%, TiO₂: 0.08-0.11 wt.%, Al₂O₃: 16.7-18.0 wt.%, MgO: 12.2-13.5 wt.%; analogous REE patterns [(La/Yb)_CN=0.2-0.4; Eu_CN/Eu*= 1.65-1.82]. PM-normalized multi-element patterns are also evidently comparable: noticeable LILE enrichments (e.g. Cs, Ba), higher Th_PM-N and U_PM-N compared to Nb_PM-N and Ta_PM-N, striking positive Pb and Sr anomalies, negative Zr and Ti anomalies.

Within the same dykes from the two localities, rodingites are also highly comparable in terms of: i) participating minerals and modal composition; ii) presence of hydrogarnets of similar composition (Avg. Adr_4.0Grs_94.3Prp_1.6Sps_0.1Uv_0.1); iii) subparallel whole-rock PM-normalized multi-element patterns. In addition, the REE patterns obtained from LA-ICP-MS of the garnets, vesuvianites and clinopyroxenes display similar profiles. These features signify that similarities between the south and north branches of the Pindos ophiolitic belt are likely not limited to their magmatic lithotypes but may have also experienced comparable post-magmatic rodingitization processes, assigned to extensive infiltration of alkaline, Ca-rich, and Si-poor fluids.