Petrogenetic and geodynamic evolution of plutonic rocks from the Chadormalu district, Kashmar-Kerman tectonic zone, Central Iran

Abstract

Late Precambrian–Early Paleozoic igneous rocks constitute volumetrically minor components of the Iranian Plateau but preserve important information about the magmatic and tectonic history of the northern Gondwana margin. The Chadormalu intrusions are part of Central Iran, which includes Late Precambrian–Early Paleozoic continental crust that is now embedded in the Alpine-Himalayan orogenic system. New zircon U-Pb and Sr-Nd-Pb isotope data and whole-rock geochemical analyses are presented on gabbroic to granitic rocks of the Chadormalu district to constrain the magmatic history of the Cadomian orogeny in a disrupted fragment of the northern Gondwana margin. The geochemical data identify I-type calc-alkaline magmatism with typical continental-arc features. The laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb zircon ages range from 531.1 ± 1.6 Ma to 539.8 ± 2.2 Ma, consistent with previous data on the Cadomian basement of Central Iran, and document Early Cambrian subduction and extension along northern Gondwana. Whole rock Sr-Nd isotope data for gabbro (ɛNd_i= 0.4; i stands for initial; t = 533 Ma) and granites (ɛNd_i= -3.6 to -3.0; t = 531–539 Ma) along with radiogenic Pb isotope data attest to melting of older continental crust triggered by mantle melts. The subduction regime was followed by slab retreat ± delamination in an extensional environment which allowed Ediacaran-early Cambrian flare up of magmatism along the northern Gondwana margin at a regional scale.