Crustal growth history of the Korean Peninsula: Constraints from detrital zircon ages in modern river sediments

U-Pb analyses were carried out on detrital zircon grains from major river-mouth sediments draining South Korea to infer provenance characteristics and the crustal growth history of the southern Korean Peninsula, using a laser ablation inductively coupled plasma mass spectrometer（LA-ICP-MS）. The Korean Peninsula is located in the East Asian continental margin and mainly comprises three Precambrian massifs and two metamorphic belts in between them. We obtained 515 concordant to slightly discordant zircon ages ranging from ca. 3566 to ca. 48 Ma. Regardless of river-mouth location, predominance of Mesozoic（249e79 Ma） and Paleoproterozoic（2491e1691 Ma） ages with subordinate Archean ages indicates that the zircon ages reflect present exposures of plutonic/metamorphic rocks in the drainage basins of the South Korean rivers and the crustal growth of the southern Korean Peninsula was focused in these two periods. Comparison of detrital zircon-age data between the North and South Korean river sediments reveals that the Paleoproterozoic zircon age distributions of both regions are nearly identical,while the Neoproterozoice Paleozoic ages exist and the Mesozoic ages are dominant in southern Korean Peninsula. This result suggests that Precambrian terrains in Korea record the similar pre-Mesozoic magmatic history and that the influence of Mesozoic magmatism was mainly focused in South Korea.

Cluster Analysis of Tropical Cyclones Making Landfall on the Korean Peninsula

Cluster analysis has been performed on the tracks of 51 Tropical Cyclones （TCs） that made landfall on the Korean Peninsula （KP） for the period of 1951-2004. The classification technique of the landfalling tracks used in this study was the fuzzy clustering method （FCM） and the resultant silhouette coefficient suggested four clusters as an optimal cluster number. Most TCs of Cluster 2 and Cluster 3 （C-23） tended to pass through China's Mainland before landfall, but those of Cluster 1 and Cluster 4 （C-14） tended to mostly land after moving northward from the East China Sea （ECS） without passing over China's Mainland. The TC landfalling frequency of C-14 has begun to clearly increase since the late 1980s, particularly the maximum landfalling frequency in the early 2000s set a record for the 54-year analysis period. The ridge axis of the western North Pacific high （WNPH） of C-23 bends more equatorward than that of C-14, so that the monsoon trough of C-23 is located more equatorward than that of C-14. As a consequence, most TCs of C-23 tend to recurve inland of China, but over the ECS for C-14.

Precambrian crustal evolution in Rangrim Massif,Korean Peninsula

Petrological,chronological and geotectonic geological analysis of Precambrian metamorphic rock in Korean Peninsula shows that the remnants(>3.4 Ga) of continental nuclei crust were formed in the Paleoarchean in the Rangrim Massif.In the massif,the main formation ages of continental crust range from 3.2 Ga to 2.5 Ga,its important growing period was 2.8-2.5 Ga.The subsequent expansion period of the Rangrim Massif was 2.4-2.2 Ga.The division events occurred in 1.85 Ga and in the Late Paleoproterozoic--Early Mesopro-terozoic,respectively.Since then the massif was relatively stable.However,the last division of the Rangrim Massif occurred at 793 Ma.

Damage of 1975 Haicheng M_s7.3 earthquake in the Korean Peninsula and its effect on Kyushu,Japan

The 1975 Haicheng Ms7.3 earthquake affected whole Korean Peninsula and even Kyushu, Japan. In this paper isoseismal map of this earthquake was drawn for these areas by sorting out and analyzing data systematically collected, furthermore, the characteristics of the earthquake damage were discussed. In the northern Korean Peninsula, the intensity is V in great majority of this area except local area with intensity VI, and the damage is basically in accordance with typical characteristics of corresponding intensity grade. In the southern Korean Peninsula, the intensity is IV in large part of the area, however, in some big cities such as Seoul etc., not only high buildings shook strongly, but also some people appeared perceptions such as feeling dizzy and so on, and electrical service was interrupted on one or two districts because of transformer tripping. These phenomena could be caused by the effect of long-period wave generated from a large earthquake on far-field.

Characteristics of carbonatites from the northern part of the Korean Peninsula: A perspective from distribution, geology and geochemistry

The present study introduces the carbonatite in the northern part of the Korean Peninsula for the first time.Recent exploration and development of the phosphorus-bearing carbonate rocks in the area have accumulated new geological data which gave us an opportunity to study origin of the carbonate rocks.We conducted geological survey,geochemical analyses of trace elements and rare earth elements,and carbon and oxygen isotope analyses for the carbonatites from Ssangryong,Pungnyon,Yongyu and Puhung districts of the northern part of the Korean Peninsula.This research confirms that the phosphorus-bearing carbonate rocks are carbonatite originating from the mantle.The studied carbonatites are distributed at the junctions of ring and linear structures or around their margins and contain a greater amount of REEs,Y,and Sr than carbonate rocks.The carbonatites in Yongyu and Puhung area show evidence that they were formed from mantle plume generated at the lower mantle and display similar fractionation characteristics to carbonatites in Barrado Itapirapua in Brazil and Kalkfeld and Ondurakorume in Namibia.REE patterns of the carbonatites are typical of carbonatites and the carbon and oxygen isotope analyses demonstrate that the carbonatites were originated from mantle.The carbonatites from the northern part of the Korean Peninsula have a great potential for sources of REE,Y,PGE(platinum group elements),copper,and gold.

Research in historical earthquakes in the Korean peninsula and its circumferential regions

The historical earthquake data is one of the important foundations for seismic monitoring, earthquake fore-cast and seismic safety evaluation. However, the recognition of earthquake is limited by the scientific and techno-logical level. Therefore, the earthquake can only be described using perfect earthquake catalogue after the seismo-graph is invented. Before this time, the earthquake parameters were determined according to the earthquake disas-ter on the surface and the written records in history, and the earthquake level was measured using earthquake in-tensity. ……

On Russia' s Korean Peninsula Policy

The past two years have witnessed great fluctuations ininternational oil prices,and diplomatic efforts,both above andunder the table,by major powers around this issue.The currenttension in the war-threatened Iraq has added more uncertainties to thefuture world oil situation.Will the world oil supply and demand change?What impact would this exert on big powers’ oil strategy choices,geopolitics as well as world economy?What should China do in such asituation?To find the answers to these questions,at the invitation of theeditor of the Contemporary International Relations,seven experts fromChina Institute of Contemporary International Relations gathered to have adiscussion in early February this year.Naturally,they have differentviews over many issues.Still,we hope our readers would find theirdiscussion interesting.Following is the list of participants.

THE KOREAN PENINSULA

Both North Korea and South Korea will be busily occupied with their internalaffairs in 1997. (1) Regime building will be the central task for North Korea before and af-ter Kim Jong-il takes over the country’ s leadership. After Kim Jong-il’s 3-yearmourning period expires on July 8, he may formally assume his office as generalsecretary of the Korean Worker’ s Party and president of the state sometime be-

Winter Olympics Diplomacy,South Korea-DPRK Contacts and US-DPRK Summit:Historic Changes for Korean Peninsula?

The ⅩⅩⅢ Olympic Winter Games in South Korea lit a flame for the dramatic development of inter-Korean relations. Rapid changes in the geopolitical situation on the peninsula since the Winter Olympics in Pyeongchang have included high-level DPRK talks with South Korea, China and the United States. President Xi Jinping＇ s meetings with DPRK leader Kim Jong-un in Beijing and Dalian, and the upcoming Trump-Kim summit on June 12 are all about timing. A new diplomacy on DPRK＇ s part has unfolded out of the extemal pressure the DPRK experienced from the US, China and the international community but also out of the difficulties the DPRK faces in advancing its nuclear options. Unless the DPRK makes substantial concessions, the US will not alter policy. Real success means historic change, not only a reunion of families and an official end to the Korean War, but also a potential shift in the Asian power structure. There are diverse possibilities and much at stake. The fundamental way forward is restarting Six Party Talks and regional mechanism.

Late Paleozoic tectonic evolution in northern Korean Peninsula

Since Late Proterozoic era, the Korean Peninsula has been evolved into a state with relatively stable regions and orogenic belts which were developed differently each other. The Late Paleozoie （Late Carboniferous-Early Triassic） sediments are well developed in the Korean Peninsula, and called the Pyongan System. The Pyongan System from Late Carboniferous to Lower Triassic is distributed in the Pyongnan and Hyesan-Riwon Basins, and Rangrim Massif, and divided into Hongjom （ C2 ）, Ripsok （ C2 ）, Sadong （ C2-P1 ）, Kobangsan and Rokam （Taezhawon） （P2-T1） sequences. The sediments of the Tumangang Orogenic Belt are called Tuman System which is composed of the Amgi Series, consisting of elastic formation with mafic effusive material, overlaid by the Kyeryongsan Series, consisting mainly of marie volcano sediments. The Songsang Series which rests on the Kyeryongsan Series mainly consists of elastic formation with minor felsic effusive material. In the Tumangang Orogenic Belt the tectonic movement, called Tumangang Tectonic Movement, occurred in the Lower Permian-Lower Triassic.

Meso-Cenozoic basin evolution in northern Korean Peninsula

In the Korean Peninsula the Meso-Cenozoic basins were mainly formed due to fault block and block movement. The Mesozoic fracture structures correspond basically to modem large rivers in direction. Such faults were usually developed to rift and formed lake-type tectonic basin, such as the Amrokgang-, Taedonggang-, Ryesonggang-, Hochongang-, Jangphari-, Susongchon-, Pujon-, and Nampho basins. The Mesozoic strata are considered to be divided into the Lower Jurassic Taedong System, Upper Jurassic Jasong System, Upper Jurassic-early Lower Cretaceous Taebo System, and the Upper Cretaceous-Paleocene （ Chonjaebong, Hongwon, Jaedok Series）. The Cenozoic block movement succeeded the Mesozoic fault block movement. The Kilju-Myongchon Graben and Tumangang Basin, etc, are the basins related to the fault zones developed from the Oligocene to Miocene. In addition, the Tertiary basins were formed in many areas in the Miocene （e. g. Sinhung, Oro, Hamhung, Yonghung, Anbyon, Cholwon, etc）. The Cenozoic sedimentation occurred mainly from the late Oligocene to Miocene. The Kilju-Myongchon Graben was the fore deep connected to the sea and the basins inclined in the Chugaryong Fault Zone are intramountain basins. Therefore, coal-beating beds and clastic rocks in the intramountain basins and rare marine strata and terrigenous clastic rocks are main sedimentary sequences in the Cenozoic.

The Korean Peninsula at Present and in the Future

In 2017,the tense situation on the Korean Peninsula has been marked by ongoing crises.However,the situation is one of conflict without complete break.There is neither dialog nor mitigation in the overall situation,nor is there strong condemnation leading to the military conflict.However,with increasingly fierce competition among countries related to the Korean Peninsula,uncertainty and complexity becomes

Permo-Triassic high-pressure metamorphism in the central western Korean Peninsula, and its link to Paleo-Tethyan Ocean closure: Key issues revisited

Permo-Triassic high-pressure(HP) mafic granulites, together with the Bibong retrogressed eclogite,preserved along the central western Korean Peninsula provide important insights into the Late Permian to Triassic collisional orogeny in northeast Asia. The metamorphic pressureetemperatureetime(P-T-t)paths of these rocks, however, remain poorly constrained and even overestimated, owing to outdated geothermobarometers and inaccurate isopleth techniques. Here we evaluate the metamorphic Pe T conditions of Triassic HP mafic granulites including those in Baekdong, Sinri and Daepan and the Bibong Triassic retrogressed eclogite in the Hongseong area, and the Permo-Triassic Samgot mafic granulite in the Imjingang Belt of the central western Korean Peninsula through the application of modern phase equilibria techniques. The Baekdong and Samgot mafic granulites and the Bibong retrogressed eclogite yield a range of 12.0 -16.0 kbar and 800 -900℃, representing HP granulite facies conditions. The Sinri and Daepan granulites from the Hongseong area show relatively lower grade metamorphic conditions between HP granulite and normal granulite facies, and are characterized by sub-isothermal decompression during exhumation. The similarities in the metamorphic ages and the post-collisional igneous activity from the central western Korean Peninsula indicate that the Triassic ages represent the retrograde stage of the metamorphic Pe T paths. In contrast, the Late Permian metamorphic ages, which are older than protolith ages of the post-collisional igneous rocks, correspond to the possible prograde stage of metamorphism. The P-T-t paths presented in this paper, together with the metamorphic ages and post-orogenic igneous events reported from these areas suggest trace of the subduction, accretion and exhumation history, and indicate a tectonic linkage among the northeast Asian continents during the Paleo-Tethyan Ocean closure.

Analysis of Landscaping Characteristic of Ancient Korean Peninsula

Based on relevant remnant documents,landscaping characteristics of gardens on ancient Korean Peninsula in Unified Silla,Goryeo and Korea Dynasty had been analyzed by selecting natural landscape gardens sprouting at the end of Unified Silla and developing in Goryeo as research objects,including Anhak Palace in Pyongyang of Goguryeo Dynasty,Yanya Pool in Kyongju of Unified Silla Dynasty,some temple landscapes of Goryeo Dynasty and palace gardens and residential landscapes of Korea Dynasty.Generally,its ancient landscaping characteristic could be summarized as "unskillful" natural landscape.

Paleozoic tectonic evolution of the proto-Korean Peninsula along the East Asian continental margin from detrital zircon U-Pb geochronology and Hf isotope geochemistry

Detrital zircon geochronology and Hf isotope analysis can be used for inferring provenance characteristics,and to evaluate the tectonic evolution of sedimentary basins and their link with regional orogenesis.The Paleozoic sequences of the Okcheon Belt consist of the Lower Paleozoic Joseon and the Upper Paleozoic Pyeongan supergroups with Middle Paleozoic hiatus locally on top of the Neoproterozoic bimodal volcanic rocks,reflecting an intracontinental rift setting between the two basements(viz.Gyeonggi and Yeongnam massifs)at southern part of the Korean Peninsula.Our detrital zircon U-Pb ages and Lu-Hf isotope results show that all these Paleozoic strata commonly have Paleoproterozoic and Paleozoic zircon ages with rare Meso-to Neoproterozoic ages.The individual zircon populations display following features,allowing estimation of their sedimentary provenances:(i)The Paleoproterozoic zircons(ca.1.85 Ga and 2.50 Ga)with similar ranges ofεHf(t)values are most common in the basement rocks of the Korean Peninsula,and were sourced from both the Gyeonggi and Yeongnam massifs.(ii)The Meso-to Neoproterozoic zircons,preserved only in the Middle to Late Cambrian clastic sedimentary rocks within the carbonate sequences probably reflect proximal provenance.(iii)The youngest Paleozoic zircons of each formation,almost coincident with their deposition ages,suggest presence of syndepositional magmatism,indicating proximal magmatic sources during their deposition.(iv)The Cambrian-Ordovician zircons,from the Lower Paleozoic sequences,but rare in the successive Upper Paleozoic sequences,suggest a provenance change after the hiatus between the two sedimentary successions.(v)The Permian zircons showing differentεHf(t)values indicate that detrital sources were varied at that time.The integrated results in our study suggest provenance variability linked to diverse tectonic environments,reflecting prolonged subduction-related crustal evolution of the proto-Korean Peninsula during the Paleozoic.

Middle Paleozoic metamorphic and sedimentary events in the central Korean Peninsula and their geological implications

The Middle Paleozoic tectonic evolution of the central Korean Peninsula(Gyeonggi Massif,Hongseong-Imjingang,and Okcheon zone of Okcheon Belts)remains controversial.Particularly,the occurrence of high-grade metamorphism and sedimentation need further examination.In this study,we conducted zircon U-Pb-rare earth element analyses from in the ultramafic-mafic complex in the central Korean Peninsula(Cheonan and Gapyeong areas)and the Paleozoic metasedimentary rocks in the Okcheon Zone of the Okcheon Belt to constrain the timing of maximum depositional and metamorphic ages.We also examined the metamorphic P-T-t path from garnet-bearing amphibolite in the central Korean Peninsula by pseudosection modeling and geothermobarometer.The results show that(i)some of the ultramafic-mafic complex and metasedimentary rocks in the central Korean Peninsula formed during the Middle Paleozoic(ca.450–374 Ma);(ii)garnet-bearing amphibolite underwent successive metamorphism from amphibolite facies condition(7.5–8.0 kbar and 540–630℃)at pre-peak stage to granulite facies condition(10.9–11.8 kbar and 740–820℃)at peak stage,and then retrograded into amphibolite facies condition(5.7–7.7 kbar and 530–670℃)along the clockwise P–T path during ca.403–362 Ma.This and previous studies suggest that the central Korean Peninsula underwent subduction-related orogenic events during the Middle Paleozoic era,and it is well correlated to those of the orogenic events in the North Qinling belt.

The Prospect of Korean Nuclear Issue:Several Focal Points

For over two decades the international community has been perplexed by the Korean nuclear issue.A clear-eye is needed to see that“no”is the realistic answer to these questions:Will the DPRK give up nuclear capability completely?Will the US resolve the issue with force?Can the DPRK collapse under maximum pressure?On the other hand,what could happen if Six-Party Talks resumed and the international community would“acquiesce”in a nuclear DPRK?Arguing the slippery slope that others in Northeast Asia will become nuclear is delusional:Japan and the ROK are unlikely to join the nuclear arms race.The most plausible next step is that the DPRK holds on to its hard-won nuclear capability,the international community acquiesces,and Six-Party Talks resume.It is an opportunity for China to play a leading role in resolving the nuclear issue and advancing Northeast Asian diplomacy.

中美战略博弈视域下中国的东北亚地缘政治风险

当今世界局势动荡,中美战略博弈持续升级,呈现出复合、立体、全方位的对峙局面。美国企图将美中关系推向“新冷战”,此举无疑给全球稳定与发展带来不确定性。在东北亚地区,朝鲜半岛局势持续紧绷,韩国尹锡悦政府奉行“亲美媚日”政策使得中韩关系面临严峻考验。与此同时,美日同盟升级及日本参与奥库斯共同遏制中国的行动,加剧地区紧张局势。朝韩关系破裂及美日韩合作机制强化,对朝鲜形成巨大军事压力,迫使其加速核导开发,深化与俄罗斯的合作。面对复杂局面,中国需着力管控中美分歧,避免矛盾激化,加强中日韩合作,以遏制美日韩反华同盟,坚定维护中朝关系,推动半岛无核化进程,深化中韩政治互信,引导其回归“均衡外交”轨道。