• Economic and Environmental Geology
• /
• v.49 no.4
• /
• pp.249-267
• /
• 2016

The Hongseong area of the central-western Korean Peninsula is considered to be a part of collision zone that is tectonically correlated to the Qinling-Dabie-Sulu belt of China. The area includes the elliptical-shaped serpentinized ultramafic bodies, together with mafic rocks. The studied bodies are in contact with the surrounded Neoproterozoic alkali granites at the Baekdong and Wonnojeon bodies and the Paleoproterozoic Yugu gneiss at the Bibong body. The Baekdong body contains the blocks of the Neoproterozoic alkali granites and the Late Paleozoic metabasites. The Bibong body also includes the Neoproterozoic alkali granite blocks. The Mesozoic intrusive rocks are also recognized at the Baekdong, Wonnojeon and Bibong bodies. On the other hand, the Early Cretaceous volcanic rocks are occurred at the Bibong body. The detrital zircon SHRIMP U-Pb ages of the serpentinites at three bodies range variously from Neoarchean to Middle Paleozoic at the Baekdong body, and from Neoarchean to Early Cretaceous at the Wonnojeon and Bibong bodies. Although serpentinization does not generally produce minerals suitable for direct isotopic dating, the youngest Middle Paleozoic age at the Baekdong body and the Early Cretaceous age at the Wonnojeon and Bibong bodies indicate the possible upper age limit for the (re)serpentinization. Especially, the Early Cretaceous serpentinization ages may be related to the widespread Early Cretaceous igneous activity in the central-southern Korean Peninsula. Age results for the serpentinite bodies and the included blocks of the studied serpentinized ultramafic bodies in the Hongseong area, therefore, provide several possible interpretations for the serpentinization ages of the ultramafic rocks as well as the geotectonic implications of serpentinization, requiring more detailed study including other serpentinized ultramafic bodies in the Hongseong area.

• Mass Spectrometry Letters
• /
• v.7 no.2
• /
• pp.31-40
• /
• 2016

The analysis of nuclear materials and environmental samples is an important issue in nuclear safeguards and nuclear forensics. An analysis technique for safeguard samples has been developed for the detection of undeclared nuclear activities and verification of declared nuclear activities, while nuclear forensics has been developed to trace the origins and intended use of illicitly trafficked nuclear or radioactive materials. In these two analytical techniques, mass spectrometry has played an important role in determining the isotope ratio of various nuclides, contents of trace elements, and production dates. These two techniques typically use similar analytical instruments, but the analytical procedure and the interpretation of analytical results differ depending on the analytical purpose. The isotopic ratio of the samples is considered the most important result in an environmental sample analysis, while age dating and impurity analysis may also be important for nuclear forensics. In this review, important aspects of these techniques are compared and the role of mass spectrometry, along with recent progress in related technologies, are discussed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2005.03a
• /
• pp.11-17
• /
• 2005

Along the Ulsan Fault System, many Quaternary faults have been reported and investigated with outcrop observation and trench excavation to clarify the neotectonic movements and fault parameters such as length, displacement, slip rate and recurrence interval. In the northern part of the Ulsan fault system, we have interpreted small scale(1:10,000) aerial photographs and extracted lineaments by geomophological features to select trench site. After precise field survey and tracing for lineaments, two trench sites at Galgokri, Gyeongju were selected on the lineament to elucidate the fault movement history. One is successful in finding faults but the other is not. In the Galgok-Chisil trench(3m(w) x 1.5m(d) x 10m(l)), very closed two Quaternary faults cut the alluvial deposits of which age shows about 10-3ka. More than three times of fault movements can be inferred by geologic structures and C-14 dating. Repeatedly fault movements had been occurred before 10 ka, between 10ka-4.9 ka, between 4.9-1.4 ka at Galgok-Chisil trench section.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.14 no.2
• /
• pp.1-10
• /
• 2011

Six pine trees (Pinus densiflora S. et Z.) at the Euilimji Lake Park in Jecheon were collected to investigate tree ages, growth decline pattern and the years of death. Tree-ring measurement was carried out using the Lintab with a resolution of 0.01mm. Tree age were 80-176 years. Cross-dating between the tree-ring series of each tree and the local chronology from Worak Mountain resulted that four and two trees died in 1998 and 1999, respectively. Three dead trees had only formed earlywood in the outermost tree ring and the others had incomplete latewood. Therefore, it was proven that the former trees died between spring and early summer, whereas the later ones died during late summer and/or autumn. The simultaneous deaths of trees suggest the insect damage and/or drought may be the crucial reason of the death, but frequent reaction woods, which were formed by leaning stem, and scars formed by physical damage may also contribute to the death.

• Journal of The Geomorphological Association of Korea
• /
• v.17 no.2
• /
• pp.53-61
• /
• 2010

In this study, pollen analysis and a dating were performed on the alluvial deposits in the Tangjeong Plains in Asan-Si, Chungcheongnam-Do. Specimens were collected at the altitude of about 12m, which belongs to the mid-forest belt in the cool temperate zone. The followings show the results. In general, the target zone passed through TJ-I (the coniferous forest age in which the Pinus forest was dominant), TJ-II (the mixed conifer and deciduous broad-leaved forest age in which Pinus and Quercus were dominant) and TJ-III (the coniferous forest age in which the Pinus was dominant) respectively. TJ-II was subdivided into TJ-IIa and TJ-IIb. TJ-I is presumed to be between about 2,810 and 1,500yrB.P.; TJ-IIa to be between about 1,500 and 1,370yrB.P.; and TJ-IIb to be between about 1,370 and 770yrB.P. As for TJ-III, it is presumed to begin after about 770yrB.P. In comparison with the nationwide pollen zone during the Postglacial, TJ-I and TJ-II are contrasted with the R-IIIa period and also TJ-III is contrasted with RIIIb (so-called human interference age). It is also presumed that Pinus luxuriated there after about 770yrB.P. as forests began to be markedly destroyed in the Tangjeong Plains.

• The Journal of the Petrological Society of Korea
• /
• v.23 no.3
• /
• pp.239-247
• /
• 2014

The (U-Th)/He dating utilizes the production of alpha particles ($^4He$ atoms) during natural radioactive decays of $^{238}U$, $^{235}U$ and $^{232}Th$. (U-Th)/He age can be determined from the abundances of the parent nuclides $^{238}U$, $^{235}U$ and $^{232}Th$ and the radiogenic $^4He$. Because helium is one of the noble gases (non-reactive) with a relatively small radius, it diffuses rapidly in many geological materials, even at low temperatures. Therefore, ingrowth of $^4He$ during radioactive decay competes with diffusive loss at elevated temperatures during the geologic time scale, determining the amount of $^4He$ existing today in natural samples. For example, He diffusion in apatite is known to be very rapid compared to that in most other minerals, causing a significant diffusive loss at ${\sim}80^{\circ}C$ or higher. At ${\sim}40^{\circ}C$, He diffusion in apatite becomes slow enough to preserve most $^4He$ in the sample. Thus, an apatite's (U-Th)/He age represents the timing when the sample passed through the temperature range of $80-40^{\circ}C$. The crustal depth corresponding to this temperature range is called a "partial retention zone." Normal closure temperatures for a typical grain size and cooling rate are ${\sim}60-70^{\circ}C$ for apatite and ${\sim}200^{\circ}C$ for zircon and titanite. Because the apatite He closure temperature is lower than that of most other thermochronometers, it can provide critical constraints on relatively recent or shallow-crustal exhumation histories.

• Journal of the Korean Geographical Society
• /
• v.28 no.4
• /
• pp.285-297
• /
• 1993

For the application of the diffusion equation, slope height and maximum slope angle are calculated from the plotted slope profile. Using denudation rate as a solution for the diffusion equation, an apparent age index can be calculated, which is the total amount of denudation through total time. Plots of slope angle versus slope height and apparent age index versus slope height are useful for determining relative or absolute ages and denudation rates. Mathematical simulation plots of slope angle versus slope height can generate equal denudation-rate lines for a given age. Mathematical simulations of slope angle versus age for a given slope height, for equal denudation-rate at a particular profile site, and for comparing to other sites having controlled ages.

• Journal of the Korean Geographical Society
• /
• v.38 no.6
• /
• pp.922-934
• /
• 2003

On top of several peaks of Seoraksan National Park. many extensive blockfields are found. After initial report was made in year 2000, further field work and analysis of satellite image have been made. Blockfields on top of mountain peaks exhibit evidence of chemical weathering including gnammas and grooves. Also, several lichen colonies larger than 80 cm in diameter have been found on the surface of many blocks. High resolution IKONOS image has been used to delineate the boundary of blockfields which are hard to access during the field trip. Blockfields of Mt. Seoraksan lack fine material necessary for age dating and clay mineral analysis because they experienced long period of wash and erosion during the Holocene. The ages of blockfields seem to be pre-Holocene on the basis of size of lichen colony and weathering pits.

• Analytical Science and Technology
• /
• v.20 no.6
• /
• pp.508-515
• /
• 2007

Age determination was carried out with the bricks relating to Muryong Royal Tomb of the Baekje Kingdom, for which there is no information on the external gamma dose rate, by using the subtraction method of luminescence dating. In the subtraction method, each paleodose for fine grain and for quartz inclusion is required for the sample to be dated. In this study, the paleodose for the fine grain was estimated by thermoluminescence measurement and the paleodose for the quartz inclusion was determined using optically stimulated luminescence. The resultant ages among the bricks showed good agreement with standard deviation of 6 % error. Finally the bricks relating to Muryong Royal Tomb were evaluated as AD $530{\pm}50yrs$($1{\sigma}$ SD).

• Korean Journal of Clinical Laboratory Science
• /
• v.37 no.1
• /
• pp.56-60
• /
• 2005

Human chorionic gonadotrophin (hCG) and unconjugated estriol (uE3) were added to AFP to make what is commonly known as the Triple test. The Triple test combines results from these three tests and has been a standard screening procedure for several years. Recent studies have demonstrated the usefulness of adding inhibin-A to Down's syndrome risk assessment. The Quad test adds dimeric Inhibin-A (DIA) to the three other markers and uses the same computer program to calculate risk factors. Testing was performed between 14 and 21 weeks of gestation. Sample size were 648 samples and period of study was from 1, July, 2004 to 30, September, 2004. Used analytical methods for AFP, hCG and uE3 were radioimmunoassay (RIA) and dimeric inhibin A was enzyme-linked immunosorbent assay (ELISA). Adding dimeric inhibin-A as a fourth marker to the standard triple test increases the detection rate from 62 % to 75 % with a false-positive rate of 5%. The DIA based Quad test has been shown to be the most effective second trimester screening test for Down's syndrome suitable for routine use. Increased DIA values are observed during normal pregnancy where a bimodal pattern response is seen. Values increase during the first trimester, decline after 14 weeks, and re-ascend between 17-25 weeks. Values for DIA may be additionally elevated during a Down's syndrome pregnancy. Dimeric inhibin A is a glycoprotein hormone made by the ovary and placenta. DIA levels are twice as high in Down's syndrome pregnancies. AFP, hCG, and uE3 levels vary with gestational age, and incorrect gestational dating will influence results. DIA levels do not vary substantially with gestational age, resulting in greater screening accuracy. Although the Quad test is an improvement over the Triple test, it is important to underscore the fact that a positive test on both should be done. Most women who initially screen positive will be found to be carrying normal babies when amniocentesis and definitive diagnostic chromosome analysis are done.