بررسي ساختاري مجموعه دگرگوني موسسات (شاهين دژ)

Structural Study of Soresat Metamorphic Complex(Shahin-Dej)

The meta-sedimentary and granitoid rocks of the Soresat metamorphic complex (SMC) occur along the northern margin of the Sanandaj-Sirjan zone in NW Iran. Field and petrographic studies indicate that the protoliths of the meta-sediments were shale, siltstone and graywake with carbonate, arkosic sandstone and pyroclastic intercalations. Porphyroblasts of andalusite, sillimanite (fibrolite), staurolite and cordierite are common in the meta-sedimentary rocks that were rich in clay minerals. Four different deformational events are recorded in SMC (D1-D4). Dl and D2 events are recorded by Fl and F2 folds and SI and S2 foliations, which indicate NNE-SSW regional shortening. The Dl fabric has been largely over-printed during D2 and only relics of SI foliation survive either in S2 microlithons, or as inclusion trails within inter-tectonic porphyroblasts of andalusite and staurolite. The prominent, regional penetrative foliation (S2) generally parallels bedding planes (SO) within meta-sedimentary rocks. S2 is axial planar to an isoclinal overturned fold of regional scale that was generated by D2. No foliation was recognised for D3. Inclined D3 folds refold the overturned D2 structure. D3 resulted from NNW-SSE horizontal shortening. D4 event is recorded by normal faulting, which, together with erosion, exposed the Soresat metamorphic complex.