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)

Abstract

The Coloured Mélange Complex is part of the North Makran domain (SE Iran) and consists of an assemblage of metric- to decametric-thick slices mainly represented by volcanic rocks, locally stratigraphically associated with radiolarian cherts. In this paper, we present 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-types, which are: 1) normal-type mid-ocean ridge basalts (N-MORB); 2) oceanic plateau basalts (OPB); 3) alkaline basalts; 4) calc-alkaline basalts, basaltic andesites, and andesites; 5) volcanic arc tholeiitic basalts and andesites, and high pressure - low temperature metabasalts formed in deep levels of an accretionary wedge. The volcanic arc tholeiites range from Early (late Hauterivian - early Aptian) to Late (latest Cenomanian - lower late Campanian) Cretaceous, whereas the calc-alkaline 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 forearc, 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.