Petrology and Geochemistry of Serpentinites from Dalampar ophiolite mélange, NW Iran: Insights into Geodynamic Evolution and Metasomatic Processes due to fluid/melt-rock interactions


1 Department of Mineral Resource & Groundwater, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran

2 Department of Mineral Resource and Groundwater, Faculty of Earth Sciences, Shahid Beheshti University, Tehran, Iran.

3 Department of Earth Sciences, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan. Iran

4 Department of Geology, Faculty of Earth Sciences, Shahid Chamran University of Ahvaz,,Ahvaz, Iran


The Dalampar ophiolite is an unknown part of the Neo-Tethys ophiolite and is located NW of Iran between Piranshahr and Salmas ophiolites within the Sanandaj-Sirjan metamorphic belt. Serpentinized peridotites, pillow basalt, various gabbro, pelagic limestone, and radiolarite along with volcano-sedimentary units are the main rock types in the area. These rocks are mixed together in most places as tectonic and “coloured” mélanges. Peridotite rocks in the complex were replaced by serpentinite completely or partly due to hydrothermal alteration. Dalampar serpentinites exhibit affinity to the typical metamorphic peridotites with Harzburgitic and Dunitic protolith compositions. Petrographically, they are composed essentially of chrysotile and lizardite with subordinate amounts of chrome spinel, magnetite, talc, calcite, tremolite and chlorite. geochemical features marked by LILE-LREE enrichment, HFSE depletion, and U-shaped chondrite-normalized REE pattern with (La/Sm)N > 1 and (Gd/Yb)N < 1, Suggest multistage petrogenetic processes including refertilization of a depleted, refractory mantle wedge by subduction-derived fluids and boninitic mantle melts operative in an intraoceanic fore-arc environment. The calculated phase diagram for the studied samples shows that serpentinites probably formed in two metamorphism events; the first one includes alteration and hydration of harzburgite in T< 200 Co and P < 4 kbar, while the second one occurred due to increasing T and P to more than 400 Co and 4 kbar.


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