• 자원환경지질
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• 제10권1호
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• pp.19-35
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• 1977

The study area is located in between Hacheonri and Weolgulri, Jecheon-gun where the formations of Okcheon group and Chosun group come in contact and the stratigraphy and geological age of the Okcheon group have been debated among previous workers. The dolomitic limestone which distributed at Cheongam and Dumusil is clarified as the Hyangsanri dolomite formation and the quartzite distributed at Cheongam and Howeunri as Taehyangsan quartzite formation. The newly named Soorumsan schist interbedded in the Great Limestone Series was previously classified Seochangri formation. It is also classified that the formation formerly named as Seochangri was divided into newly named Manji schist which seems to be correlated to Kemyeongsan and Munjuri formation. The formation formerly named as Buknori is clarified as Hwanggangri formation. The Samtaesan formation has been clarified as the lower and upper limestone beds which belong to the Great Limestone Series. The area divided into two groups, that is, Okcheon system of Pre-cambrian age occupies western part and the Great Limestone Series of Chosun system of Cambro-Ordovician age eastern part of this area. Okcheon system consists in ascending order of Manji schist, Hyangsanri dolomite, Taehyangsan quartzite, Munjuri schist, and Hwanggangri formation of meta-tillite. The Great Limestone Series of Chosun group consists in ascending order of lower limestone, Soorumsan schist, Hoosanri quartzite and upper limestone formations. Busan augen gneiss seems to be igneous origin. Unmetamorphosed shale interbed can be traced in the Soorumsan schist. Previous study (Kims, 1974) reveals that meta-volcanic rocks are distributed from south to north along contact zone of the Okcheon and Chosun groups, and it has been confirmed that the meta-volcanics crop out continuously from the adjacent southern quardrangle into the southern part of the area studied, intruding along the fault zone between the Okcheon and Chosun groups which seems to be upthrust as in the area south. This evidence coincides with Kims' work (1974) which states that the Precambrian Okcheon group is largely overturned and thrusted over the Chosun group.

• 자원환경지질
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• 제1권1호
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• pp.35-46
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• 1968

Some of geologists in Korea recently postlated that Okchon system previously known to be precambrian age was the metamorphosed sediments of post-Chosen (Ordovician and pre-Kyeongsang (late Jurassic to Cretaceous) periods, or even definitely of Triassic period simply on the basis of the fact that Okcheon system overlies the Great Limestone series of Chosen system of Camber-ordovician age, and of other few assumptions of minor importance. As a result of such correlation, thick series of metasediments and Okcheon system of unknown age were established in this particular region and vaguely correlated to Paleozoic and Mesozoic sediments. Recent study done by the author reveled that: 1) only the upper Okcheon bed of S. Nakamura was true Okcheon system, and the middle and lower Okcheon beds were excluded, because they were correlated to Cambrian and Permian sediments resfectively, 2) Sangnaeri, Seochangri, and rengam formations of unknown age, and Baekhwasan, Jobong, and Ihwaryeong formations of Okcheon system of also unknown age were the metamorphosed Yangdeok system of Cambrian age, all of these formations were differentiated by the previous workers and were equivalent to the middle Okcheon system of S. Nakamure, and. 3) These metamorphosed Yangdeok system overlaid apparently the Great Limestone series in forms of overthrust and klippe which were produced by the orogeny took place during post-Daedong and pre-Kyeongsang period (probably middle to the Jurassic). The Sobaeksan Range, folded mountain Chains was also formed by this orogeny. Thus, Okcheon system newly defined by the author is precambrain age and consists in ascending order of Kemyenogsan, Hyangsan dolomite, and Daehangsan quartzite formation which were previously classified into metasediments of unknown age, and Munjuri, and Hwangkanri, formations which were differentiated into Okcheon system unknown age by the previous workers, but are of reversed sequence. Myeongori and Bukrori formations of Okcheon System are regard by the author as part of Hwangkanri formation. Few other assumption of minor important taken by the previous workers as their positive evidences are carefully explained that they were misinterpreted.

• 자원환경지질
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• 제13권2호
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• pp.91-103
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• 1980

In spite of the fact that the Okcheon system has been rather intensively studied by many geologists since 1945, it still remains as a controversal problem as to its stratigraphy and geologic age. Present study has mainly focused on the upper members of the Okcheon system, namely the Hwanggangri and the Kunjasan formations so as to clarify the lithology, the depositional environment and the tectonic evolution of the formations. The Kunjasan formation lying unconformably over the Hwanggangri formation which is supposed to be a meta-tillite is interpreted as a metamorphosed calcareous argillaceous and/or arenaceous sediments on contract to the idea postulated by some geologists that it was a derivative of silicified Hwanggangri formation. Lithology of the Kunjasan and the Hwanggangri formation is quite different in that the former is white in color, contains few pebbles, and mostly composed of diopside and detrital quartz, whereas the latter is black to dark in color, contains abundant and variable kinds of pebbles, and composed of more argillacous matrix that has been metamorphosed to hornfels. The Hwanggangri and the Kunjasan formations were deposited in the rather deep sea which has transgressed toward northeast from southwest in the late Precambrian time, and the writer (1970) had formerly designated it as Okcheon Paleogeosyncline. With the beginning of Paleozoic era, Okcheon neogeogyncline was formed to the northeast of the old paleogeogyncline area. The transgression of the sea had proceeded toward southwest in which Cambrian strata were accumulated. During this period the area occupied formerly by the paleogeosyncline was uplifted, so that most of the Hwanggangri and the Kunjasan formations were eroded away except in the area close to the neogeosyncline sea coast. This is the reason why the Hwanggangri and the Kunjasan formations are cropped out presently in the area of the vicinity of contact zone of the paleo- and neogeosyncline zones. The age of the Okcheon system has been reconfirmed to be Precambrian from the view of the facts that 1) the Hanggangri formation, the upper member of the Okcheon system is meta-tillite and correlated to the Precambrian tillite in the Yantze basin in China, 2) the Okcheon system has been moderately metamorphosed while other formations of the same age, if it is Paleozoic or later, have not been metamorphosed, and 3) tectonic history and limited areal distribution of the Hwanggangri and the Kunjasan formations is suggestive of Precambian age.

• 자원환경지질
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• 제7권3호
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• pp.101-122
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• 1974

The study area is located in between Susanri and Hwanggangri where the formations of Okcheon group and Chosun group supposedly come in contact so that the area is structurally very import. Present study reveals that the meta-volcanic rocks distribute from south to north along contact zone of Okcheon and Chosun groups in the center of the area. Meta-volcanic rocks seem to be originated from the andesite or andesitic basalt rocks which was known to be Surchangri formation consist of phyllite and black slate by previous workers. The meta-volcanic rocks intruded along the fault zone one existed between Okcheon and Chosun groups but obliterated at present by the intrusion of volcanic rocks. The fault seems to be overthrust, and one of the positive evidences of thrust fault is the Yamisan nappe structure in Yamisan near Susanri. This interpretation coincides with O.J. Kim's work which states that the Precambrian Okcheon group is largely overturned and thrusted over the Chosun group. The relation between the Surchangri and the Majeonri formation marks facies change. This fact together with northpluging anticlinal structure made it possible that both formation came into contact along direction without fault. Yongam formation is not overlain unconformably used to be believed by previous workers, but interbed in the Great Limestone series of Chosun goup. It is also clarified that the rock formerly designated as limesilicate rock was meta-liparite. The origin of amphibole pebbles in the Kunjasan formation is of primary and secondary ones; the secondary pebbles were formed by metamorphism of the fragments of limestone or dolomite.

• 암석학회지
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• 제12권4호
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• pp.155-169
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• 2003

옥천변성대의 북서부 충주지역에 분포하는 계명산층 내 변성화성암은 기존에 보고 된 동일 인근 지역 내 문주리층의 변성화성암에 비해 주성분 원소, 미량 원소 및 희토류 원소들이 넓은 성분범위를 나타내며 대륙내 열개환경에 따른 쌍모식 화성활동을 잘 반영하지 않는다. 그리고 문주리층 내의 변성화성암은 단일 마그마로부터 진화된 경향을 잘 보여주나 계명산층 내의 변성화성암은 다양한 마그마로부터 형성되었을 가능성이 높다. 계명산층의 산성 변성화산암의 지화학적 특징은 문주리층 내 산성 변성화산암과 비교할 때 Eu의 부(-) 이상정도가 작으나 LREE와 HREE의 경사의 기울기는 거의 비슷하다. 그리고 문주리층의 염기성 변성화성암이 Eu의 이상치를 보여주지 않는 반면 계명산층에서는 중간정도의 부(-)부터 정(+)까의 이상정도(0.59

• 자원환경지질
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• 제42권1호
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• pp.9-25
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• 2009

충주지역 북서부 옥천변성대는 문주리층, 대향산규암, 향산리돌로마이트, 계명산층이 분포하고 있으며 현재까지 층서적 관계가 논란이 되고 있는 지역이다. 충주지역에 분포하는 북서부 옥천변성대에 대한 층서적 연구를 위해 충주호일대에 두 지점의 노두를 선정하여 단면에 대한 정밀기재 및 인근지역에 대한 야외조사를 실시하였다 문주리층과 대향산규암의 경계는 정이적인 변화가 인지되나 경계부는 층리면과 평행한 단층이 발달한다 대향산규암과 향산리돌로마이트는 정합적인 것으로 판단된다. 향산리돌로마이트와 계명산층은 단층을 경계로 접하고 있다. 연구지역의 북부에는 $41^{\circ}/280^{\circ}$의 습곡축을 가지는 습곡이 분포하는 것이 확인되었으며, 두 층의 경계에 발달하는 단층은 충상단층일 가능성도 있으나 습곡이 형성되는 동안 나타나는 단층일 가능성도 있다. 본 연구에서 확인된 점이적인 암상변화와 기존 연구 결과를 볼 때 경계부의 단층은 습곡이 형성되는 동안 층리면과 평행하게 발달하는 단층으로 판단된다 향산리돌로마이트와 계명산층의 경계부에 발달하는 단층은 층리면과 평행하게 발달하며, 돌로마이트가 반복적으로 나타나고 있는 점을 볼 때 충상단층으로 판단된다. 두 층이 충상단층 관계일 경우 상부의 계명산층이 문주리층 아래에 놓이게 된다. 하지만 계명산층과 문주리층은 비슷한 암상분포를 보이며, 신원생대의 절대연령을 나타내는 점을 볼 때 두 층이 동일한 층일 가능성이 있을 것으로 생각되며 충상단층에 의해 반복적으로 분포하는 것으로 판단된다. 이러한 결과를 종합해 볼 때 충주지역 북서부 옥천변성대의 층서는 하부로부터 계명산층/문주리층, 대향산규암, 향산리돌로마이트의 정합적 관계로 판단된다.

• 자원환경지질
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• 제28권6호
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• pp.599-612
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• 1995

Some REE ore deposits are located in the middle part the of Korean peninsula. Geotectonically, the REE ore deposits situated on the Kyemyeongsan Formation of northern margin of the Okcheon geosynclinal belt and in the transitional zone between Kyeonggi massif and the Okcheon belt, with a deep-seated fracture separating the two tectonic units. The Kyemyeongsan Formation are different in lithology and metamorphic grade from the Gyeonggi massif and the Okcheon super group. The sequence of Kyemyeongsan Formation is dominantly composed of acidic metavolcanic and volcaniclastic rocks associated with alkaline igneous rocks which are related to volcano-plutonism. The REE ore deposits contain mainly Ce-La, Ta-Nb, Y, Y-Nd and Nd-Th group minerals. More than 15 RE and REE minerals have been found in the deposits, such as allanite, fergusonite, thorite bestnaesite, euxenite, polyclase, monazite, columbite, (Nb)-rutile, okanoganite, sphene, zircon, illmenite and some other unknown minerals. According to the characteristics of the mineral association, the REE ore deposits may be divided into 4 ore types; Zircon-REE, allanite-REE, feldspar-REE and fluorite-REE type. The Sm-Nd isochron age of the REE ore is 330 Ma, and the Sm-Nd model age is 1.11 Ga with ${\varepsilon}_{Nd(t)}$ being - 2.9. This data suggest that the REE ore deposit was formed in the early Carboniferous, and the ore-forming material came from the mantle. The REE ores show distinct light REE enrichment with strong negative Eu anomaly. The REE patterns of schistose rocks from Kyemyeongsan Formation are similar to felsic volcanics from rifts or back arc basins in or near continental crust. The genesis of the REE ore deposit is quite complicated. Different geologic processes are displayed in the studied area; sedimentation, volcanic activity, metamorphism and hydrothermal replacement. Alkali granite has suffered extensive post-magmatic metasomatism of a high temperature to produce alkali metasomatites. Geochemical charateristics show that metasomatism of alkaline fluid was probably the dominant ore-forming process in Chungju district.

• 암석학회지
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• 제17권2호
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• pp.51-56
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• 2008

옥천변성대 암석의 생성시기는 화석의 발견과 동위원소 연대측정으로 대부분 고생대 및 신원생대인 것으로 밝혀지고 있다. 한편 동위원소 연대자료가 축적됨과 더불어 옥천변성대의 변성시기가 페름기 초기인가 혹은 페름기 말기-트라이아스기 초기인가 하는 문제가 대두되었다. 이 문제는 달리 표현하면 위의 두 시기에 해당하는 2번의 중요한 변성작용이 있었는가 혹은 후자 시기에 해당하는 한번의 변성작용인가 하는 것이다. 변성시기를 직접 지시할 수 있는 자료를 비교할 때 페름기 초기의 변성시기에 대한 자료(석류석 내 U-Pb 갈렴석 연대)는 전체적으로 오차가 클 뿐만 아니라 페름기 말기-트라이아스기 초기를 지시하는 자료(CHIME 갈렴석 연대 및 변성 저콘의 U-Pb 연대)와 어느 정도 중첩된다. 따라서 독립적인 두 종류의 자료에 의해 지지되는 후자가 보다 신빙성이 있는 것으로 생각되며, 이 시기는 임진강대와 경기육괴에서 대륙충돌과 관련되어 나타나는 중요한 변성시기와 유사하기 때문께 대륙충돌의 영향이 한반도 넓은 지역에 퍼져 있음을 시사한다.

• 한국지구과학회지
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• 제32권1호
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• pp.12-20
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• 2011

변성암복합체, 옥천층군, 조선누층군 및 화성암류에서 지하 지질분포 및 밀도 불연속면을 파악하기 위해 충주호 주변에 있는 256개 지점에서 중력측정을 실시하였다. 부게 중력이상은 옥천층군에서 높은 값을 가지며 조선누층군으로 갈수록 상대적으로 낮은 값의 분포를 보였다. 지하 밀도 불연속면의 평균심도는 약 2.0 km이며, 전반적으로 문주리층과 황강리층이 서창리층보다 중력기반 심도가 상대적으로 얇으며, 옥천계 동측에 위치한 조선누층군이 옥천층군보다 비교적 두꺼운 기반 심도로 분포된 것으로 파악되었다.

• 암석학회지
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• 제22권4호
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• pp.291-298
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• 2013

옥천변성대 계명산층 변성화산암에서 분리한 저어콘의 일부 입자들 연변부에는 덧성장 누대가 잘 발달되어 있음이 발견되었다. 이러한 덧성장 누대들은 대체로 낮은 Th/U 비율을 갖는 것으로 확인되었으며, 계명산층 변성화산암이 변성작용을 받는 동안에 생성된 것으로 판단된다. 이 중에서 비교적 넓은 폭을 가진 구역들에 대하여 SHRIMP U-Pb 분석을 할 수 있었다. 분석결과 $259.7{\pm}3.3Ma$ (n=8, $2{\sigma}$)의 일치곡선 연령을 구할 수 있었으며, 이 연령은 계명산층 변성화산암의 변성시기를 나타낸다.