North China block, Jiao-Liao-Korea block and Tanlu fault

Abstract: In the Sinian (680 Ma), the Sino-Korean plate began to break up into two different tectonic units, the Jiao-Liao-Korea block (JLKB) and North China block (NCB). The boundary of the two blocks is called the Paleo-Tanlu fault (PTLF). The position of this fault is coincident with he present Tanlu fault, which extends from Hefei northward via the Bohai Sea to east of Shenyang and then turns NE and goes to southern Jilin. Strong earthquake records in Sinian carbonate rocks in the vicinity of the PTLF and corresponding diabase emplacement are basic geological evidence for the intraplate break-up of the Sino-Korean plate. The break-up period of the PTLF (intraplate seismic zone) is consistent with that of Proterozoic Rodinia. Archean basement rocks in the two blocks are different and the Proterozoic and Paleozoic histories of the two blocks on the eastern and western sides of the PTLE are different. The two blocks were again amalgamated in the Late Carboniferous Moscovian stage. The Rimjin River zone on the central Korea Peninsula was considered the eastward extension of the Dabie-Jiaonan orogenic belt. However, the Rimjin River zone is only an ordinary fault and China's Jiaonan ultrahigh-pressure belt bas not been found on the Korea Peninsula. Considering the similarity in the Paleozoic between the southern main area of ??the Korea Peninsula and the Liaodong Peninsula, the southern boundary of the Sino-Korean plate, i. e. the southern boundary of the JLKB is placed on Jizhou Island south of the Korea Peninsula in the paper. It joins the Jiaonan orogenic belt with the presumed Yellow Sea transform fault. Diamondiferous kimberlites in Wafangdian (originally called Fuxian County) of Liaoning Province and Mengyin of Shandong Province are distributed on the eastern and western sides of the Tanlu fault over a longitudinal distance of ~ 550km. The age of the kimberlites in the two areas ranges from 500 to 450Ma, i. e. the rock was emplaced at the end of the Middle Ordovician. Since the kimberlites in the two areas have similarities in some aspects such as petrography, mineralogy and emplacement age and are both close to the Tanlu fault, some geologists think that the kimberlites of the two areas were possibly very close to each other during their emplacement and belong to the same province; therefore they always explain the distance letween the Wafangdian and Mengyin kimlerlite provinces with the great displacement of the Tanlu fault. The Tanlu fault is a deep fault cutting through the lithosphere. Comparison of the differences and similarities between the lithosphere profiles of Wafangdian and Mengyin provides significant evidence for judging whether the Tanlu fault has a great displacement. Study of the mantle samples in the kimberlites reveals that the profiles of the paleo-lithosphere that the kimberlites in the two areas cut through during their emplacement are very different. This indicates that the two areas are neither contiguous nor close to each other at that time. On the basis of the above-mentioned sample study, combined with the new understanding got from a study of the regional geological structure, the authors find that the two kimberlites were actually emplaced separately into two different tectonic units of the Sino-Korean plate and the distance between the two areas is independent of displacement. This finding does not support the view of the great displacement caused by the Tanlu fault.