• Journal of the Korean earth science society
• /
• v.22 no.1
• /
• pp.10-19
• /
• 2001

There are three scoria cones and their eruptive materials in Sarabong-Byeoldobong-Hwabukbong area Cheju Island. And they made complicated volcanic stratigraphy. In Byeoldobong tuff, basalt and granite xenoliths are present. It is presumed that the granite is a kind of basement of Cheju island. And Biseokgeori hawaiite has many kaersutite phenocrysts. Therefore, this area is very important for the study about history of volcanic activity of Cheju island. The lowest beds are Shinheung basalt and Byeoldobong tuff. Byeoldobong tuff has xenoliths of granite and phenocrystalline basalt. After the formation of these rocks, the Hwabukbong volcanism commenced. First of all this volcanism formed Biseokgeori hawaiite that has lots of kaersutite, a member of amphibole group, characteristically. Over this rock, Hwabukbong scoria cone was formed. The next Sarabong volcanism effused Keonipdong hawaiite that has lots of plagioclase and olivine phenocrysts and then Sarabong scoria cone was made up. Basalt xenolith in Byeoldobong tuff is different from Shinheungri basalt with regard to petrography, therefore this offers suggestion about existence of another basalt between basement and Shinheungri basalt. Granite xenolith derived from the basement of this area has features of the Jurassic granite in the Korea Peninsula, for example a lot of myrmekitic texture, microcline, and absolute age (172.4 Ma) by K-Ar method.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.23 no.4
• /
• pp.53-59
• /
• 1981

This experiment was carried out to find out the effectiveness of soil cement stabilization about the Song-I in Cheju province. The results are summarized as follows; 1.The increasing ratio of unconfined compressive strength according to the increment of cement content was markedly low compared with the weathered granite soil, so the effect of stabilization was low. 2.The moisture content of the sample of Song-I indicates the maximum unconfined compressive strength showed at the 5% or so of dry side than the optimum moisture content and the change of the unconfined compressive strength according to the change of moisture content was not sensitive compared with the weathered granite soil. 3.Generally the primary strength of curing age within 7 days of the sulfate resisting cement was low compared with the normal portland cement and the strength of 28 curing days showed a similar tendency, especially in case of Song-I, and it seemed that the sulfate resisting cement was a little more effective than the normal portland cement. 4.As the unconfined compressive strength of grain size controlled Song-I was low compared with the weathered granite soil, so the rate of weight loss by the durability test was great, therefore it was thought that the durability was weak.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.10a
• /
• pp.389-392
• /
• 2000

This paper provide nondestructive test method of concrete by applying ultrasonic pulse test. Whinstone aggregates produced from cheju island are used for coarse aggregate. The purpose of this study is to contribute to the standardization of nondestructive test for estimating compressive strength of concrete manufactured from cheju island. According to experimental results, it is found that compressive strength of Whinstone aggregates concrete shows higher than that of granite stone concrete, whereas ultrasonic pulse of Whinstone aggregates concrete shows lower that of granite concrete Based on the results of this study, estimation formula compressive strength by ultrasonic pulse test are presented in Fig 2.

• Proceedings of the KSEEG Conference
• /
• 2001.04a
• /
• pp.218-218
• /
• 2001

• Economic and Environmental Geology
• /
• v.28 no.5
• /
• pp.513-518
• /
• 1995

A granite drilling core (-1200 m) obtained near the Majang cave in east part of the Cheju island. The rock is pinksh in color and has miarolitic cavities. It is coarse-grained rock and consists of quartz, plagioclase, alkali feldspar, biotite and magnetite. The rock shows characteristically micrographic texture. The alkali feldspar is subhedral to anhedral and generally interstitial grains and fonns micrographic texture. K/Ar age of alkali feldspar in the core specimen is $58.14{\pm}1.4Ma $ (early Tertiary). The age, rock features and whole rock chemistry of the rock has strong resemblance to micrographic granites, so called "masanite", in southeastern part of the Korean peninsular. The granitic fragments from drilling core (- 920 m) obtained in Jungmun area in south part of the Cheju island consist of quartz, plagioclase, alkali feldspar and biotite. The fragments in the Jungmun area are similar to granitic xenolith near the Cheju city for the absence of micrographic texture and different alkali feldspar.

• Journal of the Korean Geographical Society
• /
• v.35 no.4
• /
• pp.641-647
• /
• 2000

한반도 중부지방의 사면형성과정을 검토하기 위하여 이 지역에 광범위하게 분포하는 쥬라기의 화강암과 선캄브리아기의 편마암으로 구성된 산지 소유역에서 수문관측을 실시하였다. 화강암 유역의 면적은 0.0546$\textrm{km}^2$이며, 기복비는 0.35이다. 편마암 유역은 다소 넓어 면적은 0.0754$\textrm{km}^2$이나 기복비는 0.36으로 거의 같다. 두 유역의 사면은 모두 사림으로 피복되어 있다. 관입시험 결과에 의하면 화강암유역 토층의 층후는 20cm 이하로 얇고 도처에 기반암이 보출된다. 반면에 편마암 유역의 층후는 50cm 이상으로 상대적으로 두껍게 나타난다. 관측은 1999년 5월부터 시작하였으며, 현재도 계속되고 있다. 강우에 대한 유출방응은 편마암 유역이 화강암 유역에 비하여 신속하게 나타난다. 첨두유량과 기저유량 모두 화강암유역보다는 편마암유역에 전반적으로 높게 관측되어 편마암 유역 사면에서의 저류량이 큰 것으로 생각된다. 또한 편마암사면에서 우수의 체류시간을 반영하여 전기전도도는 편마암 유역이 화강암유역보다 2배 정도 높게 관측된다.

• The Korean Journal of Quaternary Research
• /
• v.21 no.2
• /
• pp.28-31
• /
• 2007

• The Journal of Engineering Geology
• /
• v.28 no.4
• /
• pp.661-672
• /
• 2018

Radon concentration was measured in a total of 5,453 groundwater samples from wells across Korea. The radon concentrations showed the values ranging from 0.1 Bq/L to 7,218.7 Bq/L, with a median of 48.8 Bq/L which is lower than those of other countries having similar geological conditions. The distribution of radon concentrations was lognormal. The median value is high in the granite areas (63.5-105.1 Bq/L) while it is low in the sedimentary rocks and Cheju volcanic area (16.0-20.3 Bq/L). When grouping the groundwater with well depth, the median radon value is high in weathering and/or upper bedrock zone (61.4 Bq/L) while it is low in alluvium and/or weathering zone (28.5 Bq/L). About 17.7% of the total samples exceeded 148 Bq/L of USEPA guideline value. The exceeding radon ratio more than 148 Bq/L in groundwater is highest in Jurassic granite area, however, the exceeding radon rates more than 300 Bq/L and 500 Bq/L are highest in CGRA area.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 1998.11a
• /
• pp.119-122
• /
• 1998

Chemical analysis, measurement of pumping rates of 60 production wells and depth to water tables of 57 monitoring wells were carried to protect depletion of water resources and deterioration of water quality for the commercial portable ground-water. Borehole depth of production well averages 149m(31 boreholes), casing depth is 28m(29 boreholes), production rate is 70 $m^3$/day and depth to water table of monitoring well is 23.26m, respectively. The geology of 60 wells can be divided into Daebo granite(20), Okchun metarmorphic complex(18), Precambrian granitic gneiss(15), Bulguksa granite(4), Cheju volcanics(2), Cretaceous sedimentary rock(1). Average electrical conductivity and pH are 152$\mu$S/cm, and 7.35, respectively. The contents of major cation and anion predominantly $Ca^{2+}$>N $a^{+}$>M $g^{2+}$> $K^{+}$ and HC $O_{3}$$^{－}$ >S $O_{4}$$^{2-}$>Cl￣>F￣. Water type is predominantly $Ca^{2+}$-HC $O_{3}$$^{－}$(81.7%). It's possible that water chemistry of some wells were affected not only by the geology of boreholes penetrated but by inflows of surface water or shallow ground-water. Therefore, it is strongly necessary to steadily monitor the water quality and hydrogeologic conditins of production wells.ells.ls.ells.

• Journal of Soil and Groundwater Environment
• /
• v.12 no.5
• /
• pp.98-104
• /
• 2007

A survey was performed to evaluate the distribution of radon concentrations in groundwater of South Korea. Groundwaters of 615 wells were sampled for this study during the four years from 1999 to 2002. The results showed radon values ranging from 4 pCi/L to 40,010 pCi/L with a mean and a median of 1,862 pCi/L and 920 pCi/L, respectively. The samples were classified into five groups according to the rock types; granite, sedimentary rocks, metamorphic rocks, Ogcheon metamorphic rocks, and Cheju volcanics. Mean radon concentrations were highest (2,595 pCi/L) in granites and lowest (238 pCi/L) in Cheju volcanic rocks. The groundwaters generally showed the highest radon content (2,298 pCi/L) in the weathered and the fractured bedrock complex and the lowest level (672 pCi/L) in the alluvium. The results showed that the radon concentrations in South Korea are low relative to those reported from other countries. But further investigations are suggested to confirm our results.