Geochronological Framework of Paleoproterozoic Intrusive Rocks and Its Constraints on Tectonic Evolution of the Liao-Ji Belt, Sino-Korean Craton

Abstract

The Liao-Ji belt (LJB) is one of the Paleoproterozoic tectonic belts located in the North China Craton. A large number of Paleoproterozoic meta-volcanic-sedimentary rock and intrusive rocks are preserved in the LJB, which provide reliable carriers for the study of the Paleoproterozoic tectonic evolution of the North China Craton. The Paleoproterozoic intrusive rock in the LJB can be divided into the following seven types: syenogranite, quartz diorite, porphyry granite, migmatitic granite, syenite, metamorphic plutonic rock, and granitic pegmatite and metagabbro (metamorphic diabase). Zircon U-Pb dating of 15 samples from intrusive rocks was carried out in this study. The chronology framework of the Paleoproterozoic intrusive rock in the LJB was established, and the magmatism of intrusive rocks can be divided into three stages: 2 200 to 2 110, 2 010 to 1 937, 1 900 to 1 820 Ma. The chronological framework supported the evolution model of subduction accretionary arc-continent collision in the LJB effectively. Combined with previous geochemical work, it was a passive continental margin environment at approximately 2 200 Ma, and then transformed into and active continental margin. The bimodal intrusive rocks between 2 180 and 2 150 Ma indicated a back-arc tension environment which lasted until approximately 2 110 Ma with a large number of basic intrusive rocks. And then the back-arc basin began to contract and the magmatic activities were reduced, with only a small number of intrusive rock activities occurring at approximately 2 040, 2 010 and 1 937 Ma. After the orogenic activities, there was a post-orogenic extension stage from 1 900 to 1 820 Ma. Magmatic activities caused by the environmental extension started to occur more frequently and subsequently resulted in the large-scale intrusive rocks in eastern Liaoning.