• The Journal of the Petrological Society of Korea
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• v.20 no.4
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• pp.207-217
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• 2011

Here we report major element composition, trace and rare earth element abundance, Sm-Nd and Rb-Sr isotopic composition from Deokgu leucogranite. Chondrite-normalized REE pattern and its Eu anomaly are divided into 3 types systematically, and have close relationship with $SiO_2$ contents. Such geochemical characteristic indicates that the leucogranite was derived by feldspar fractionation from a common source magma. Sm-Nd and Rb-Sr whole rock ages are $1,785{\pm}180Ma$ (initial $^{143}Nd/^{144}Nd\;ratio=0.51003{\pm}0.00016,\;2{\sigma}$; ${\varepsilon}_{Nd}(T)=-5.9$) and $1,735{\pm}260Ma$ (initial $^{87}Sr/^{86}Sr\;ratio=0.702{\pm}0.046,\;2{\sigma}$), respectively. Initial ${\varepsilon}_{Nd}$ value indicates that the magma should be derived from the crustal material. This initial ${\varepsilon}_{Nd}$ value also corresponds well with those from the Precambrian granitoids from North-China Craton rather than those of South-China Craton.

• The Journal of the Petrological Society of Korea
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• v.10 no.1
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• pp.27-35
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• 2001

The charnockite of Jirisan area occurs within the Precambrian high grade metamorphic terrane associated with anorthosite body as many foreign examples. Sm-Nd ages were determined from whole rock-garnet pairs, which turned out $1827\pm$32($2\sigma$) Ma for the massive charnockite and $1820\pm$22(2$\sigma$) Ma for the foliated charnockite with $$\varepsilon$_{Nd}(T)$ of $-5.5\pm$0.2 and $-6.0\pm$0.5 respectively. $^{87}Sr/^{86}Sr$ initial ratios calculated with the these ages are 0.71319 and 0.71532 respectively. The fact that massive and foliated charnockites show identical age, identical Nd isotopic initial ratio, and similar Sr isotopic initial ratios suggest that they were generated at the same time from the same material even through their present textures are different. Initial ratios of Nd and Sr of the charnockites are quite distinct from the mantle values indicating the influence of continental crust. Sm-Nd age determined from the titanium bearing anorthositic rocks intruding the anorthosite body, using mineral separates of garnet, plagioclase, and mafic fraction, is $1792\pm$90(2$\sigma$) Ma with $$\varepsilon$_{Nd}(T)=-3.9$\pm$0.2$. The ^${87}Sr/^{86}Sr$ initial ratios calculated with this age are 0.70616~0.70619. The charnockites and the anorthositic rocks occurring in contact each other also reveal the same age within the error, which suggest a genetic relationship between them. However, chemical compositions of the charnockites and Hadong-Sancheong anorthosites cannot be explained by igneous differentiation. Their differences in Nd and Sr initial isotopic ratios indicate different source materials. Therefore, temporal association between them suggests the possibility of the anorthosite acting as a thermal source for the generation of the charnockite as other studies.

• The Journal of the Petrological Society of Korea
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• v.14 no.3 s.41
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• pp.127-140
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• 2005

The Samyuri area of Jeoksang-myeon, Muju-gun at the Middle Yeongnam Massif consists of granitic gneiss, porphyroblastic gneiss and leucocratic gneiss, which correspond to Precambrian Wonnam Series. Here we discuss a geochemical implication of the data based on major element composition, trace element, rare earth element (REE), Sm-Nd and Rb-Sr isotope systematics of the boring cores in the granite gneiss area. The boring cores are granitic gneiss (including biotite gneiss) and amphibolite. The major and trace element compositions of granitic gneiss and amphibolite suggest that the protolith belongs to TTG (Tonalite-Trondhjemite-Granodiorite) and tholeiitic series, respectively. Chondrte-normalized REE patterns vary in LREE, HREE and Eu anomalies. The granitic gneiss and amphibolite have Sm-Nd whole rock age of $2,026{\pm}230(2{\sigma})$ Ma with an initial Nd isotopic ratio of $0.50979{\pm}0.00028(2{\sigma})$ (initial ${\epsilon}_{Nd}=-4.4$), which suggests that the source material was derived from old crustal material. Particularly, this initial ${\epsilon}$ Nd value belongs to the range of the geochemical evolution of Archean basement in North-China Craton, and also corresponds to the initial Nd isotope evolution line by Lee et al. (2005). In addition, chondrite-normalized REE pattern and initial Nd value of amphibolite are very similar to those of juvenile magma in crustal formation process.

• Proceedings of the Petrological Society of Korea Conference
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• 1999.06a
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• pp.88-88
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• 1999

• The Journal of the Petrological Society of Korea
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• v.9 no.1
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• pp.29-39
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• 2000

For the determination of metamorphic age of the metamorphic rocks distributed in the Ji-san area of Youngnam massif, Sm and Nd isotopic compositions were analyzed for the whole rock and garnet separates. As the result, we obtained 1799 + 11 Ma from the porphyroblastic gneiss, 1776 +30 Ma from the metapelite, 1714+35 Ma from the mafic granulite xenolith within the porphyroblastic gneiss, and 1776+30 Ma from the metapelite occurred as a xenolith within the quartzofeldspathic gneiss. There have been reports of geologic ages similar to such metamorphic ages of Jirisan area from the other portion of the Youngnam massif, which reveals that very intense metamorphism took place over the vast area of Youngnam massif during the period of 1.7-1.8 Ga ago. The granulite facies metomorphism of the Gyeonggi massif also shows the age similar to this period. Such resemblance in their metamorphic ages suggests that these massifs experienced similar tectonothermal events occurred at about the same Precambrian periods, which implies the possibility that the extension of the collision belt between the north and south China blocks does not extend through some places between the Youngnam and Gyeonggi massifs. On the other hand a quarzofeldspathic xenolith of porphyroblastic gneiss show 1928 +42 Ma which is older than above age of the metamorphism and is identical with the zircon U-Pb age of porphyroblastic gneiss indicating the formation age of the protolith of the porphyroblastic gneiss.

• The Journal of the Petrological Society of Korea
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• v.2 no.2
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• pp.130-138
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• 1993

Kyeonggi Gneiss complex forming Korean Precambrian basement is mainly composed of high-grade metasedimentary rocks, which are generally difficult to determine their absolute ages. We examined the feasibility of successive absolute age determination method for the marbles from this basement. We used hydrochloric acid for the selective dissolution of carbonate minerals from the marbles. Trace element analysis shows that most of Zr and Rb are concentrated in the residues. U in the residue is more abundant than that in HC1-dissolved parts. Pb, Sr, Sm, and Nd are somewhat evenly distributed between HC1-dissolved parts and the residues. }Th shows rather complex behavior. Sr isotopic compositions of the HC1-dissolved parts reveal mixing with Sr from non-carbonate minerals having much higher $^{87}Sr/^{86}Sr$ ratios. We suggest that the most reliable method in the age determination for the marbles of this area is measuring Pb isotopic ratios of the pieces of pure marbles.

• The Journal of the Petrological Society of Korea
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• v.5 no.2
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• pp.135-141
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• 1996

La-Ce method is one of new geochronological methods developed recently. La and Ce are one of the rare earth elements, and, with Sm-Nd system. La-Ce system is very useful in understanding the evolution processes of crust and mantle. In this paper, I introduce the basic concept of the La-Ce method, and apply it in clarifying LREE pattern of source material of leuco-granitic gneisses from the Imweon area, Kangwon-do, and K-rich granite from the Anshan area in Liaoning Province, NE China. Sm-Nd data on the Anshan K-rich granites give an age of $3.16{\pm}0.06$ Ga($2{\sigma}$), with initial $^{143}Nd/^{144}Nd$=$0.50846{\pm}0.00005$ (${\epsilon}_{Nd}$=-1.5). On the basis of Ce and Nd isotopic ratio, leucogranitic gneiss and K-rich granite has been fractionated from the source material which had had similar to CHUR (chundritic uniform reservoir). And the initial ${\epsilon}_{Nd}$ value suggest that the crustal formation age of the Liaoning Province area, NE China was early Archean.

• The Journal of the Petrological Society of Korea
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• v.21 no.4
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• pp.431-439
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• 2012

A column chemistry is the most useful tools for isolating the elements of interest in isotope geochemistry. Here we introduce the chemical experimental procedure for Sm, Nd, La and Ce separation such as Teflon powder or Ln-resin method using HDEHP of KIGAM, KBSI, KOPRI and ${\alpha}$-HIBA(${\alpha}$-Hydroxy Isobutyric acid) method of Nagoya University, Japan. This technical report will provide an useful information in selecting the experiment method for rare earth element isotope system study such as Sm-Nd and La-Ce isotope system.

• Proceedings of the Petrological Society of Korea Conference
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• 2006.05a
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• pp.49-51
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• 2006

• The Journal of the Petrological Society of Korea
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• v.14 no.3 s.41
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• pp.169-179
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• 2005

Acidic metavolcanic rocks distributed around the Chungju iron deposit show significantly high abundances of rare earth elements and high field strength elements. Relatively high ${\epsilon}_{Nd}$(0) values and lack of negative Nb anomaly suggest that assimilation of crustal material is not involved in their generation. They are plotted within the within-plate environment according the tectonic discrimination diagrams. Such geochemical characteristics are very similar to the acidic metavolcanic rocks of Munjuri Formation. They also show geochemical characteristics of Al-type magma of Eby (1992). All such diagnostic characters indicate differentiation of mantle-derived magma produced from the rift environment, related to the breakup of continent. In contrast to the alkali granites and the rare metal deposit both having age of c. 330 Ma, Sm-Nd isotopic data of the acidic metavolcanic rocks do not form well defined isochron. However, the alkali granites reveal low ${\epsilon}_{Nd}$(0) values, while the acidic metavolcanic rocks and the rare metal deposit both have significantly higher ${\epsilon}_{Nd}$(0) values. Considering such differences, we propose following generation hypothesis: The acidic metavolcanic rocks around Chungju iron deposit was erupted at 750 Ma as rest of the acidic metavolcanic rocks of Gyemyeongsan and Munjuri Formations. About 330 Ma ago, partial melting of existing Al-type igneous materials and some old crustal materials produced alkali granite. The rare metal deposit was also produced by redistribution of related materials within the acidic volcanics due to hydrothermal activities occurred at the same time. Sm-Nd isotopic systematics of the acidic metavolcanic rocks were disturbed during the regional metamorphic event at ca. 280 Ma.