Youn-Joong Jeong

Determining the geographical origin of Chinese cabbages using multielement composition and strontium isotope ratio analyses

Recently, the Korean market has seen many cases of Chinese cabbage (Brassica rapa ssp. pekinensis) that have been imported from China, yet are sold as a Korean product to illegally benefit from the price difference between the two products. This study aims to establish a method of distinguishing the geographical origin of Chinese cabbage. One hundred Chinese cabbage heads from Korea and 60 cabbage heads from China were subjected to multielement composition and strontium isotope ratio ((87)Sr/(86)Sr) analyses. The (87)Sr/(86)Sr ratio differed, based on the geological characteristics of their district of production. In addition, the content of many elements differed between cabbages from Korea and China. In particular, the difference in the content of Sr and Ti alone and the combination of Sr, Ca, and Mg allowed us to distinguish relatively well between Korea and China as the country of origin. The present study demonstrates that the chemical and Sr isotopic analyses exactly reflect the geology of the production areas of Chinese cabbage.

Simultaneous multiple collector-ICP-MS measurement of Nd isotopic composition and Sm/Nd ratio in geological reference materials by interference corrections and external calibration using matrix-matched standards

This study introduces an improved multiple collector-ICP-MS protocol to simultaneously determine the Nd isotopic composition and Sm/Nd ratio of geological samples without isotope dilution. Our pretreatment procedure simply consists of sample digestion and single-step group separation of Sm and Nd. The Nd isotopic composition was conventionally corrected for Sm isobaric interference by using the exponential mass fractionation law and selected Sm isotopic compositions, and the Sm/Nd ratio was externally corrected by the standard-sample bracketing method. This protocol yielded the corrected 143Nd/144Nd ratios of the USGS GRMs (BHVO-2, BCR-2, AGV-2, and RGM-1) mostly in good agreement with previously recommended values. By contrast, their Sm/Nd ratios were consistently higher (up to 3.4%) than the recommended values when the measured ratios were corrected simply using data of an aqueous standard solution. Further calibration using a matrix-matched GRM as a secondary standard significantly reduced the discrepancies with previous ratios to within a 0.3% difference. Therefore, we recommend that the matrix of calibration standard should be matched with that of the samples as closely as possible in the inter-elemental ratio measurement of geological samples.

Geochemistry, Isotope Properties and U-Pb Sphene Age of the Jeongeup Foliated Granite, Korea

In this paper, we investigate the geochemical and isotope properties of the Jeongeup foliated granite (hereafter, the JFG) in the Jeongeup area, aiming at establishing the movement age of the Honam shear zone by U-Pb sphene geochronology. In the AMF diagram, the JFG corresponds to the calc alkalic rock series, and belongs to the magnesia region in the diagram of silica versus . Additionally, in the Rb-Ba-Sr diagram, it is classified as granodiorite and anomalous granite with distinctive negative Eu-anomaly in the REE patterns. According to the silica and trace element contents, the JFG falls on the type VAG+syn-COLG, which implies that this was formed under the circumstance of compressional continental margin or volcanic arc. isotope ratios range from 0.511495 to 0.511783 and are calculated to be about . U-Pb sphene ages of the JFG are and , based on and ages, respectively. Presumably, the dextral ductile shearing in the Jeongeup area has occurred after 173 Ma.

SHRIMP U-Pb Zircon Geochronology and Geochemistry of Drill Cores from the Pohang Basin

SHRIMP zircon U-Pb ages and major element and Sr-Nd isotopic compositions were determined for drill cores (374-3390 m in depth) recovered from three boreholes in the Pohonag basin, southeastern Korea. Shallow-seated volcanic rocks and underlain plutonic rocks were geochemically classified as rhyolite and gabbro-granite, respectively. They showed high-K calc-alkaline trends on the and AFM diagrams. Zircons from volcanic rocks of borehole PB-1 yielded concordia ages of (n

Correction of spike contribution for strontium isotopic measurement by thermal ionization mass spectrometry: a test for spike-standard mixed solutions

BackgroundThe Rb-Sr isotope system has long been used for radiometric dating and petrogenetic investigation. The concentrations of Rb and Sr could be precisely measured by isotope dilution thermal ionization mass spectrometry combined with chemical purification of these elements. For the simultaneous measurement of Sr isotopic composition and isotope dilution, the contribution from the added spike should be carefully corrected.FindingsReliable 87Sr/86Sr ratios of the spike-standard mixed solutions were obtained using the new mass bias factor calculated on the basis of measured Sr isotopic ratios. This correction yielded reasonable 87Sr/86Sr ratios for overspiked standard solutions whose spike fractions reaching 25 wt.%.ConclusionsThe correction procedure described in this study shows that the simultaneous measurement of Sr isotopic composition and isotope dilution is available for the case that the spike proportion in the sample-spike mixture is significantly high (84Sr/86Sr > 3.7). The principle of this correction protocol can also be applied to other isotope systems such as Sm-Nd and Lu-Hf pairs.

Sm-Nd isotopic analysis of mixed standard solutions by multi-collector inductively coupled plasma mass spectrometry: evaluations on isobaric interference correction of Nd isotopic composition and external calibration of Sm/Nd ratio

BackgroundThe Sm-Nd isotope system has long been used to provide information on the age and geochemical evolution of terrestrial rocks and extraterrestrial objects. Traditional thermal ionization mass spectrometry requires a refined chemical separation of Sm and Nd. Here, we present multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) Sm-Nd isotopic results for a series of mixed standard solutions with different Sm/Nd ratios to test the validity of isobaric interference corrections of Nd isotopic composition and external calibration of Sm/Nd inter-elemental ratio.FindingsReliable 143Nd/144Nd and 145Nd/144Nd ratios of the mixed solutions were obtained by using the exponential law and selected Sm isotopic compositions. The Sm/Nd ratios of the mixed solutions corrected by the standard bracketing method were consistent with the gravimetric values mostly within 1% difference.ConclusionsThis study provides a simple and high-throughput technique that can simultaneously measure Nd isotopic composition and Sm/Nd ratio without chemical separation between Sm and Nd.

U–Th isotopic microanalysis of zircon reference materials and KBSI working standards

BackgroundThe 238U–230Th disequilibrium dating of the mineral zircon (ZrSiO4) provides an efficient tool for investigating the time scales of Quaternary magmatic processes. In situ mass spectrometric U–Th microanalysis of zircon requires careful calibration and correction of the measured isotope data, particularly for the instrumental fractionation of U and Th isotopes.FindingsFor the selection of suitable calibration materials for U–Th isotopic analysis using a laser ablation multiple collector inductively coupled plasma mass spectrometer (LA-MCICPMS), we estimated the homogeneity of four reference zircons (91500, TEMORA 2, FC1, and Plešovice) and two zircon working standards (LKZ-1 and BRZ-1) in terms of their 232Th/238U ratios, based on the Pb isotopic compositions measured by a sensitive high-resolution ion microprobe (SHRIMP). The measured LA-MCICPMS 232Th/238U ratios of the zircons were calibrated externally using the SHRIMP 208Pb/206Pb-based average value of the 91500 zircon, 232Th/238U = 0.351 ± 0.035 (error corresponds to 1 standard deviation). The molecular interference-corrected 230Th/232Th ratios of the zircons were calibrated based on the assumption that the Plešovice zircon is in 238U–230Th secular equilibrium. After the calibration and correction, the activity ratios of 230Th/232Th and 238U/232Th for all reference zircons and working standards were plotted on the equiline.ConclusionsThis study confirms that the 91500 zircon is relatively homogeneous in terms of U/Th ratios (relative standard deviation = ~ 10%) and does not support a recent claim that the Plešovice zircon is not in 238U–230Th radioactive equilibrium. The working standards LKZ-1 and BRZ-1 can be used to check the reliability of U–Th isotopic analyses for Quaternary zircons.

Lead isotope mapping of galena from base metal deposits in the southern Korean Peninsula

The purpose of this study is to investigate the differences in sources of discrete four zones that are represented by the lead isotope map of metal mines using galena samples. The lead isotope map has been constructed based on 119 galena samples from 38 metal mines in the southern Korean Peninsula, together with previously published data, using spatial and zoning distribution analysis. The spatial pattern of 206Pb/204Pb ratio shows relatively dense distribution with highest value at the northeastern region, while 207Pb/204Pb and 208Pb/204Pb ratios are the lowest at the southeastern region. These results indicate possible subdivision of the lead isotope maps based on geotectonic subdivisions and geographical locations of the Korean Peninsula. This subdivision has been checked by linear discriminant analysis (LDA). The range of lead isotopic composition for zone 1 has fairly homogeneous values (206Pb/204Pb = 18.156–18.591, 207Pb/204Pb = 15.482–15.644, and 208Pb/204Pb = 37.870–38.768), and are geographically similar to the Gyeongsang Basin. Lead isotopic compositions of zone 2 show the highest ratios (206Pb/204Pb = 18.625–20.483, 207Pb/204Pb = 15.708–16.068, 208Pb/204Pb = 37.734–40.463) in the southern Korean Peninsula, that are geographically corresponding to the Taebaeksan Basin and the northeastern Yeongnam Massif. Relatively lower values (206Pb/204Pb = 17.149–17.817, 207Pb /204Pb = 15.497–15.731, 208Pb /204Pb = 37.847–39.773) along the western Gyeonggi Massif are grouped as zone 4, while the rest of the areas, including the Okcheon metamorphic belt, most of the Gyeonggi Massif, and the Yeongnam Massif, might represent zone 3. The results clearly indicate the possible differences in the source reservoirs that are similar to the geotectonic provinces of the Korean Peninsula.

Strontium isotope geochemistry of archaeological human tooth enamel excavated from Jeonju, southwestern Korea

Strontium isotopes of archaeological skeletal tissues have provided useful information to trace past human migration. This study presents strontium isotope data of human tooth enamel excavated from a group of medieval Joseon tombs in Jeonju, southwestern Korea. The enamel samples are divided into two isotopic populations yielding average 87Sr/86Sr of 0.71077 ± 0.00031 (group I) and 0.71233 ± 0.00032 (group II). Considering the gender distribution, 87Sr/86Sr ratios of group I may better represent the local value of biologically available strontium. Contrasting 87Sr/86Sr patterns of acetic acid extracts and residues of enamel fragments from a male of group I and a female of group II suggest their different residential mobility during childhood. The 87Sr/86Sr range of group I enamel is considerably lower than that reported from basement granites in the Jeonju area. Strontium in this group may have been conveyed from rainfall, and soluble soil fractions composed mainly of low-Rb/Sr minerals such as plagioclase.