New insights into the geodynamics of Neo-Tethys in the Makran area: evidence from age and petrology of ophiolites from the Coloured Mélange Complex (SE Iran).

In the Makran region, SE Iran, one of the largest worldwide accretionary wedges is exposed. This accretionary wedge is regarded as the result of the northward subduction of the oceanic lithosphere of the Oman Sea beneath the Lut and Afghan continental blocks. To the north, the accretionary wedge is bounded by the north Makran domain that can be regarded as the backstop of the accretionary wedge. The north Makran domain is represented by an imbricate stack of continental and oceanic units including the Coloured Melange Complex, also referred as the Imbricate Zone. The Coloured Mélange Complex is part of the north Makran domain (SE Iran) and consists of an assemblage of metric-to dccamctric-thick slices mainly represented by volcanic rocks, locally stratigraphically associated with radiolarian cherts. We had got new geochemical data on volcanic rocks and biochronological data on the associated cherts. Our data indicate the occurrence of a wide range of volcanic rocks-typcs, which are: 1) normal-type mid-ocean ridge basalts (N-MORB); 2) oceanic plateau basalts (OPB); 3) alkaline basalts; 4) calcalkalinc basalts, basaltic andesites, andesites, and dacites; 5) volcanic arc tholeiitic basalts and dacites, and high pressure-low temperature metabasalts formed in deep levels of an accretionary wedge. The volcanic arc tholeiites range from Early (Late Hautcrivian-Early Aptian) to Late (latest Ccnomanian-lower Late Campanian) Cretaceous, whereas the calcalkalinc rocks and OPBs are Late Cretaceous in age (Early Coniacian- Santonian and Early Turonian-Early Campanian, respectively). Alkaline basalts, OPBs, and N-MORBs represent remnants of the Mesozoic Neo-Tethys oceanic branch located between the Arabian plate and the Lut block. In this paper we document that this oceanic sector was characterized by the development of an oceanic plateau in the Late Cretaceous. In contrast, calc-alkaline and volcanic arc tholeiitic rocks represent remnants of a continental volcanic arc and forcare, respectively, developed onto the southernmost realm of the Lut block. The petrogenesis and age of volcanic rocks allow us to propose a new tectono-magmatic model for the evolution of the convergent margin developed in the northern sector of the Neo-Tethys from Early to Late Cretaceous. This model is basically constrained by the collision of the oceanic plateau with the continental arc, which led to the jump of the subduction toward the south, as well as to the formation of the imbricate pile of different units today observed in the north Makran area