Paleozoic Granitic Rocks from the Telmen Complex in the Tarvagatai Block, Central Mongolia: Petrogenesis, U-Pb geochronology, and its tectonic implications

Abstract

The Tarvagatai Block is located in the northern part of Central Mongolia, which is a widespread occurrence and occupies roughly 60% of the whole exposure along the Khangai fault and the Tarvagatai uplift. Granitic magmatism was emplacement during the Middle Paleozoic, which is predominantly composed of granite-granodiorite and gabbro-diorite and rarely gabbro. This article represents petrographical, geochemical, and U-Pb zircon age data from the Telmen Complex of the Tarvagatai Block, Central Mongolia. The U-Pb dating of zircon yields a Late Silurian emplacement age (419±3 Ma) for the Telmen Complex. Geochemically, the Telmen Complex is an I-type intrusion of metaluminous nature with a SiO2 content ranging from 53.06 to 72.25 wt.% and mainly of medium to high K calc-alkaline series. Telmen Complex granites show enrichments in light rare earth elements, depletion in heavy rare earth elements, with a ratio of 4.053, (La/Yb)N =9.15, and weak positive or normal Eu anomalies. A spider diagram indicates that these rocks are enriched in Ba, K, Pb, and Sr and depleted in Nb, Ta, and Ti. The Early Paleozoic Telmen Complex granitics have trace element features, for example, Nb-Ta depletions, which indicate that these rock units were emplaced in a convergent-margin setting and typical of the lower continental crust. In addition, the geochemical data show that the volcanic arc tectonic setting and, moreover, the continental arc array setting display on the Nb/Yb versus TiO2/Yb diagrams. Therefore, we suggest that they were probably positioned in an active continental setting and in a Silurian ~419 Ma.

Keywords

• magmatism
• geochemistry
• ordovician-silurian granitic rocks
• geodynamic settings