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We describe two previously unreported, 5-7 km long normal fault scarps (NFS) occurring atop fault-related anticlines in the coastal ranges of the Dinarides fold-and-thrust belt in southern Montenegro, a region under predominant contraction. Both NFS show well-exposed, 6-9 m high, striated and locally polished fault surfaces in limestones, documenting active faulting during the Holocene. Sharply delimited ribbons on free rock faces show different color, varying karstification and lichen growth and suggest stepwise footwall exhumation, typical of repeated normal faulting earthquake events. Displacements, surface rupture lengths and geometries of the outcropping fault planes imply paleoearthquakes with Mw ~ 6 ± 0.5 and slip rates of c. 0.3-0.5 mm/yr since the Last Glacial Maximum. Slip rates based on cosmogenic 36Cl data from the scarps are significantly higher: modeling suggests 1.5 ± 0.1 mm/yr and 6-15 cm slip every c. 35-100 yrs, commencing c. 6 kyr ago. The total throw on both NFS - although poorly constrained - is estimated to max. 200 m, and offsets the basal thrust of a regionally important tectonic unit. Both NFS are incipient extensional structures that postdate growth of the fault-related anticlines on top of which they occur. Interestingly, the position of the extensional features agrees with recent geodetic data, suggesting that our study area is located exactly at the transition from NE-SW-directed shortening in the northwest to NE-SW-directed extension to the southeast. While the contraction reflects ongoing Adria-Europe convergence taken up along the frontal portions of the Dinarides, the incipient extensional structures might be induced by rollback of the Hellenic slab in the SE, whose effects on the upper plate appear to be migrating along-strike the Hellenides towards the northwest. The newly found NFS provide evidence for a kinematic change of a thrust belt segment over time. Alternatively, the NFS might be regarded as second-order features accommodating changes in dip of the underlying first-order thrust faults to which they are tied genetically. [ABSTRACT FROM AUTHOR]

The ultramafic Kukes Massif is located in the eastern part of the Mirdita ophiolite (N Albania), which is recognised as representing Supra-Subduction lithosphere. It comprises a thick (0.8-2.5 km) dunite zone containing abundant occurrences of chromite ores and is cut by orthopyroxenitic and clinopyroxenitic veins. In this paper we focus on the genesis and evolution of olivine and chromite forming dunite in the northern part of the Kukes Massif. The chemical composition of minerals in dunites is highly variabile and apparent at outcrop scale. The most significant changes are recorded by olivine, which contains over 90 Fo in the host dunite but decreases to 87.5 in proximity of clinopyroxenitic veins. The composition of spinel is also sensitive to the presence of veins: in host dunite its Cr# is over 80 (chromite type I), whereas the presence of veins causes its decrease to 68 (type II). Clinopyroxene in vein-forming clinopyroxenite has Mg# from 86 to 92 and is Al-rich (Al2O3 0.8-2.6 wt. %). Orthopyroxene forms orthopyroxenites (Mg# 90-93, Al2O3 0.2-1.6 wt. %), but also screens (Mg# 83-91, Al2O3 0.8-2.4 wt. %) at the contact between clinopyroxenite veins and the host dunite. The thick dunitic sequence at Kukes must have been formed as a result of intensive percolation of possibly boninitic melt through parental harzburgite. Another step in the evolution of the Kukes massif was related to intrusion of the pyroxenitic veins. These melts were not equilibrated with the host dunite and led to metasomatic modification of chromite and olivine, increasing Al2O3 content in former (from 6-8 up to 18 wt. %) and decreasing Fo (extremely from 92 to 87.5) in the latter. The process is evident proximal to clinopyroxenite veins, but a subtle effect is also recorded in the chemical composition of dunite contacting orthopyroxenite, leading to increase in Fe2O3 content. Metasomatism modified the composition of dunites in a zone of 0.5 m around pyroxenites. Our studies indicate a multistage evolution of the SSZ peridotites and show that its deciphering requires careful mineralogical examination. [ABSTRACT FROM AUTHOR]