Jiao-Liao-Ji Belt

From Wikipedia, the free encyclopedia

This article or section needs to be wikified to meet Wikipedia's quality standards. Please help improve this article with relevant internal links. (July 2007)

The paleoproterozoic Jiao-Liao-Ji Belt lies at the eastern margin of the Eastern Block (North China Craton), with its northern segment intervening between the Northern Liaoning-Southern Jilin Complex and the Southern Liaoning-Nangrim Complex and its southern segment extending across the Bohai Sea into the Eastern Shandong Complex. The belt consists of greenschist to lower amphibolite facies sedimentary and volcanic successions and associated granitic and mafic intrusions. The sedimentary and volcanic successions, including the Fengzishan and Jingshan Groups in eastern Shandong, the South and North Liaohe Groups in eastern Liaoning, the Ji’an and Laoling Groups in southern Jilin and possibly the Machollyong Group in North Korea, are transitional from a basal clastic-rich sequence and a lower bimodal-volcanic sequence, through a middle carbonate-rich sequence, to an upper pelite-rich sequence. Stratigraphically, the Fenzishan Group in eastern Shandong is well correlated with the North Liaohe Group in Liaoning and the Laoling Group in southern Jilin. Similarly, the Jingshan Group in eastern Shandong can also be stratigraphically correlated with the South Liaohe Group in Liaoning and the Ji’an Group in southern Jilin. Therefore, the Jiao-Liao-Ji Belt itself can be further subdivided into a northern belt, which comprises the Fenzishan, North Liaohe and Laoling Groups, and a southern belt that consists of the Jingshan, South Liaohe and Ji’an Group. Separating the two belts are ductile shear zones and faults. Associated with the sedimentary and volcanic rocks in the Jiao-Liao-Ji Belt are voluminous Paleoproterozoic granitoid and mafic intrusions. The granitoid plutons, named the Liaoji Granites in eastern Liaoning and southern Jilin, are composed of deformed A-type granites and undeformed alkaline syenites and rapakivi granites. Mafic intrusions consist of gabbros and dolerites, most of which have been metamorphosed to greenschist and amphibolite facies, although igneous textures (ophitic textures) are preserved.

Controversy has surrounded the tectonic nature of the Jiao-Liao-Ji Belt, with some people proposing that the Jiao-Liao-Ji Belt represents a continent–arc–continent collisional belt, whereas others believe that the Jiao-Liao-Ji Belt invokes the opening and closing of an intra-continental rift along the eastern continental margin of the North China Craton