Possible relationship between western North Pacific tropical cyclone activity and Arctic Oscillation   总被引：1，自引：0，他引：1  

Ki-Seon Choi  Hi-Ryong Byun 《Theoretical and Applied Climatology》2010,100(3-4):261-274

This study found that Arctic Oscillation (AO) has a significant influence on tropical cyclone (TC) activities in the western North Pacific during the boreal summer (July, August, and September). During low- (high-) AO years, more TCs formed over east (west) of 150° E, recurved in the east (west), and passed over the midlatitudes (southeast Asian region), including Korea and Japan (South China Sea and south China), compared to the high- (low-) AO years. In particular, the TC passage frequency difference between the two periods showed a dipole-like pattern between the regions of Southeast and Northeast Asia. The differences between these two periods were caused by a stronger anticyclonic circulation located around Korea and Japan during high-AO years. This circulation played a significant role in blocking the movement of TCs toward Korea and Japan during high-AO years. Instead, TCs moved westward toward the SCS and southern China along the easterly and southeasterly steering flow of this anticyclonic circulation. As a result, TC lifetime and intensity were shorter and weaker during high-AO years.  相似文献   

Genesis and Age Constraints on Gold Deposits of the Daerae Mine, Sangju Area, Central-Northern Sobaegsan Massif, Korea     

Seong–Taek YUN  Seung–Jun YOUM  Chil–Sup SO  Seon–Gyu CHOI  De–Quan ZHANG  Yong–Kwon KOH 《Resource Geology》2001,51(3):205-215

Abstract: Gold mineralization of the Daerae mine represents the first recognized example of the Jurassic gold mineralization in the Sangju area, Korea. It occurs as a single stage of quartz veins that fill fault fractures in Precambrian gneiss of the central‐northern Sobaegsan Massif. The mineralogical characteristics of quartz veins, such as the simple mineralogy and relatively gold‐rich (65–72 atomic % Au) nature of electrum, as well as the CO₂–rich and low salinity nature of fluid inclusions, are consistent with the ‘mesothermal‐type’ gold deposits previously recognized in the Youngdong area (about 50 km southwest of the Sangju area). Ore fluids were evolved mainly through CO₂ immiscibility at temperatures between about 250 and 325 C. Vein sulfides characteristically have negative sulfur isotopic values (–1.9 to +0.2 %), which have been very rarely reported in South Korea, and possibly indicate the derivation of sulfur from an ilmenite‐series granite melt. The calculated O and H isotopic compositions of hydrothermal fluids at Daerae (δ¹⁸O_water = +5.2 to +5.9 %; δD_water = –59 to –67 %) are very similar to those from the Youngdong area, and indicate the important role of magmatic water in gold mineralization. The ⁴⁰Ar–³⁹Ar age dating of a pure alteration sericite sample yields a high‐temperature plateau age of 188.3 0.1 Ma, indicating an early Jurassic age for the gold mineralization at Daerae. The lower temperature Ar‐Ar plateau defines an age of 158.4 2.0 Ma (middle Jurassic), interpreted as reset by a subsequent thermal effect after quartz vein formation. The younger plateau age is the same as the previously reported K‐Ar ages (145–171 Ma) for the other ‘mesothermal–type’ gold deposits in the Youngdong and Jungwon areas, Korea, which are too young in view of the new Jurassic Ar‐Ar plateau age (around 188 Ma).  相似文献   

Decreasing trend of tropical cyclone genesis frequency in July-August over the western North Pacific in the last 20 years     

Ki-Seon Choi  Hae-Dong Kim  Sung-Dae Kang  Chang-Sup Shim 《Theoretical and Applied Climatology》2016,124(1-2):241-266

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朝鲜半岛咸北地区晚二叠世基性火山岩的地球化学特征:岩石成因与地质意义   总被引：5，自引：4，他引：1  

张晓晖  张艳斌  袁玲玲  李永植  崔远正  金宪 《岩石学报》2016,32(10):3070-3082

晚古生代火山作用既是探究朝鲜半岛北部大地构造归属的基本要素,又是认识东北亚大陆两大构造域转折之际地球动力学过程的关键窗口。针对咸北地区会宁基性火山岩开展的离子探针锆石U-Pb年代学和地球化学研究表明,其喷发时代为晚二叠世(257±3Ma);主要岩石类型包括玄武安山岩和安山岩,其Si O2含量介于51.9%~55.3%,Mg#变化于40~58,属于钙碱性系列;岩石富集大离子亲石元素、亏损高场强元素(如Nb,Ta,Ti),并具有高正的锆石εH f(t)(+10~+16)值。元素-同位素地球化学示踪指示该基性火山岩的岩浆源区为俯冲沉积物熔体交代而形成的不均一岩石圈地幔,其部分熔融则可能归因于俯冲后的板内伸展背景。会宁基性火山岩不仅为判定咸北地块属于中亚造山带在朝鲜半岛的东延部分提供了岩石学证据,而且与中国相邻地块上的同期岩浆事件一道,构成见证古亚洲洋东段沿西拉木伦-长春-延边一线断裂带最终闭合的空间标记。  相似文献   

Paucity of sulfide in a large slab of Esquel: New perspectives on pallasite formation     

FINN ULFF-M LLER  BYEON-GAK CHOI  ALAN E. RUBIN  JACQUELYN TRAN  JOHN T. WASSON 《Meteoritics & planetary science》1998,33(2):221-227

Abstract— The 0.7 ton Esquel meteorite, found in Patagonia before 1951, is a typical main-group pallasite in most respects. We examined petrographically a slab ～1 m long having an area of 3000 cm² that shows the typical pallasitic texture with fragmental olivine. Phase abundances (in vol%) are olivine (66%), metal (32%), schreibersite (0.76%), troilite (0.46%) and chromite (0.31%). Esquel can be divided into four lithologies: (1) “pallasitic” matrix consisting of olivine fragments embedded in metal (81%); (2) large (>5 cm) olivine nodules having low metal contents (18%); (3) massive metal (0.3%); and (4) zones dominated by FeS and fine olivine (0.7%). Main-group pallasites appear to have formed by the intrusion of a highly evolved (low Ir, high Ni, Au and S) metallic magma into fragmented olivine. This model implies that FeS should be abundant in main-group pallasites, and we had speculated that examination of an exceptionally large slab might reveal a high troilite content. We found instead an exceptionally low FeS content. New compositional data confirm that Esquel has a lower Au content than other main-group pallasites having similar Ir contents. Literature data (based, however, on relatively small sections) suggest that high-Au pallasites have higher S contents than Esquel but have lower S contents than expected from a trapped-melt model. We conclude that a relatively complex model is required to explain the origin of main-group pallasites. After intrusion, the degree of crystallization of the metallic magma varied from location to location but, in almost all cases, an FeS-rich liquid either escaped or formed FeS-rich pallasitic rocks that are underrepresented in the meteorite inventory.  相似文献   

中韩河流沉积物微量元素地球化学研究   总被引：6，自引：1，他引：6  

杨守业  李从先  Jung Hoi-Soo  Lim Dong-Il  CHOI Man-sik 《海洋地质与第四纪地质》2003,23(2):19-24

长江和黄河以及韩国的Keum和Yeongsan江，具有不同的微量元素地球化学特征。韩国河流沉积物中微量元素含量多介于长江和黄河之间，以Li、Rb和Th较高为特征，粒级效应明显。长江富铁族和铜族元素，黄河则Sr最高，其他元素均低于其他3条河流；韩国河流中Sr主要赋存于长石中，而长江和黄河中则主要赋存于碳酸盐矿物中。根据沉积物中元素的赋存相态及含量，我们认为Ti、Cr/Th、Ti/Nb和Zr/Nb等可以作为判剐西太平洋边缘海，尤其是黄海中长江、黄河与韩国河流物质贡献的可靠地球化学参数，但在运用中必须注意粒级效应影响。  相似文献   

Wave Hindcast for the Neighbouring Seas of Korea Based on Loosely Coupled Wave-Tide-Surge Model     

CHOIByung-Ho  EUMHyun-Min  JEONSang-Soo 《中国海洋工程》2002,16(2):165-181

A hindcast simulation of 75 typhoons and winter monsoons which affected the coastal areas of Korean Peninsula is performed by use of a third generation ocean wave prediction model, WAM-cycle 4 model, loosely coupled with a com-bined tide and surge model. Typhoon wind fields are derived from the planetary marine boundary layer model for effective neutral winds embedding the vortical storm wind from the parameterized Rankin vortex type model in the limited areas of the overall modeled region. The hindcasted results illustrate that significant wave heights (SWH) considering the wave-tide-surge coupled process are significantly different from the results via the decoupled case especially in the region of the estuaries of the Changjiang Estuary, The Hangzhou Bay, and the southwestern tip of Korean Peninsula. This extensive model simulation is the first attempt to investigate the strong wave-tide-surge interaction for the shallow depth area along the coasts of the Yellow Sea and the East China Sea Continental  相似文献   

Temporal population dynamics of dinoflagellate Prorocentrum minimum in a semi-enclosed mariculture pond and its relationship to environmental factors and protozoan grazers     

许恒龙  MIN Gi-Sik  CHOI Joong-Ki  朱明壮  姜勇  AL-RASHEID Khaled A.S. 《中国海洋湖沼学报》2010,(1)

The ecological processes and interrelationships between protists,either autotrophic or heterotrophic,and environmental factors in mariculture ponds are largely unknown.This study investigated the temporal dynamics of potentially harmful dinoflagellate,Prorocentrum minimum (Pavillard) Schiller,and its relationship to physico-chemical factors and protozoan grazers over a complete cycle in a semi-enclosed shrimp-farming pond near Qingdao,Northern China.P.minimum occurred frequently in low numbers from June to ...  相似文献   

A possible relationship between East Indian Ocean SST and tropical cyclone affecting Korea     

Ki-Seon Choi  Sangwook Park  Ki-Ho Chang  Jong-Ho Lee 《Natural Hazards》2015,76(1):283-301

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Thermal histories of Cretaceous basins in Korea: Implications for response of the East Asian continental margin to subduction of the Paleo‐Pacific Plate     

TAEJIN CHOI  YONG IL LEE 《Island Arc》2011,20(3):371-385

Thermal histories of Cretaceous sedimentary basins in the Korean peninsula have been assessed to understand the response of the East Asian continental margin to subduction of the Paleo‐Pacific (Izanagi) Plate. The Izanagi Plate subducted obliquely beneath the East Asian continent during the Early Cretaceous and orthogonally in the Late Cretaceous. First, the Jinan Basin, a pull‐apart basin, was studied by illite crystallinity and apatite fission‐track analyses. Analytical results indicate that Jinan Basin sediment was heated to a maximum temperature of approximately 287°C by burial. The sediment experienced two cooling episodes during ca 95–80 Ma and after ca 30 Ma, with a quiescent period between them. A similar cooling pattern is recognized in the Gyeongsang Basin, the largest Cretaceous basin in Korea. The Jinan and Gyeongsang Basins were cooled mainly by exhumation between ca 95 and 80 Ma, but the former was exhumed slightly earlier than the latter by transpressional force due to the subduction direction change of the Izanagi Plate. Comparison of thermal history of Korean Cretaceous basins with those of granitoids in northeastern China and the accretionary complexes in southwestern Japan reveals that the Upper Cretaceous regional exhumation of the East Asian continental margin including the Korean peninsula during ca 95–80 Ma was facilitated by the subduction of the Izanagi–Pacific ridge, which migrated northeastwards with time, resulting in the end of regional exhumation at ca 80 Ma in this region.  相似文献