Cambrian Kherlen ophiolite in northeastern Mongolia and its tectonic implications: SHRIMP zircon dating and geochemical constraints

• Kherlen ophiolite in northeastern Mongolia formed in Late Cambrian at ca. 500 Ma.
• Kherlen ophiolite was tectonically emplaced prior to 440 Ma, likely at the earliest Silurian.
• Mafic rocks of the Kherlen ophiolite originated from N-MORB- and E-MORB-like mantle sources.
• Kherlen ophiolite belt is the eastern extension of the Bayanhongor belt，forming an early Paleozoic suture in NE Mongolia.

The Kherlen terrane, which contains the Kherlen ophiolitic complex, is located between two Precambrian continental blocks in the northeastern Mongolia. We present new geochemical and SHRIMP zircon U–Pb data for the Kherlen ophiolitic complex and for granitic plutons intruding the complex, providing constraints on the regional evolution in Early Paleozoic time. The Kherlen ophiolite, which is geochemically similar to SSZ-type ophiolites, was originated from two distinct mantle sources, a N-MORB-like source and an E-MORB-like source. A gabbro and a plagiogranite dike intruding the gabbro from the Kherlen ophiolite yielded similar SHRIMP zircon U–Pb ages of ca. 500 Ma, suggesting that the ophiolite formed in Late Cambrian time. Post- or syn-collisional granites intruding the ophiolitic complex yielded crystallization ages of ca. 440 Ma, which is interpreted to record the minimum age of the tectonic emplacement of the ophiolite. These new data demonstrate that the Kherlen ophiolite belt is an Early Paleozoic suture between the Ereendavaa and the Idermeg continental terranes, which is generally coeval with the Bayankhongor belt in central Mongolia, indicating that they are regionally correlated, and thus they define a major Early Paleozoic suture between two Precambrian continental blocks in the central-northeastern Mongolia.