Age, Geochemistry, and Tectonic Implications of Dulaerqiao Granite, Inner Mongolia

Abstract

Dulaerqiao granite is located at the Xinlin-Xiguitu-Toudaoqiao suture zone between the Erguna massif and the Xing’an massif, northeast of Inner Mongolia. The rocks are mainly composed of K-feldspar, quartz, and plagioclase. Zircon LA-ICP-MS U-Pb data show that this granite was deposited in the Late Carboniferous Period (308.7±2.0 Ma). The samples are rich in alkali, Fe, and Al and low in Mg, Ca, and P. Chondrite-normalized REEs exhibit right-inclined patterns with significant negative Eu anomalies. Additionally, the granite shows high quantities of trace elements such as Zr, Hf, Th, K, and Rb and decreased quantities of Sr, P, and Ti. The chemical characteristics identified herein and a series of diagrams that distinguish different types of granite show that Dulaerqiao alkali-feldspar granites belong to the aluminous A-type granite group. Meanwhile, the initial magma crystallizes under high-temperature, low-pressure conditions resulting from a tectonic extension setting. The formation of Dulaerqiao aluminous A-type granite is related to the rejuvenation of the ancient Xinlin-Xiguitu- Toudaoqiao suture zone, which was activated by the interaction between the combined Erguna-Xing’an massif and the Songnen massif in the Late Paleozoic Era. This aluminous A-type granite was deposited about 30 Ma after the collision.