• Proceedings of the KSEEG Conference
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• 2007.04a
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• pp.164-166
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• 2007

• Proceedings of the KSEEG Conference
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• 2007.04a
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• pp.167-169
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• 2007

• Proceedings of the KSEEG Conference
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• 2007.04a
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• pp.176-179
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• 2007

• Economic and Environmental Geology
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• v.40 no.2 s.183
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• pp.223-236
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• 2007

The eastern extension of the Cordilleran-type orogenic belt continues from southeastern China to the Chukot Peninsula through the Korean Peninsula. The Gyeongsang basin, located in the southeastern part of the Korean Peninsula and the Inner Zone of southwest Japan are characterized by extensive distribution of Cretaceous to Tertiary I-type calc-alkaline series of intrusive rocks. These intrusive rocks are possibly the result of intensive magmatism which occurred in response to the subduction of the Izanagi Plate beneath the northeastern part of the Eurasian Plate. The Jindong granitoids within the Gyeongsang basin are reported to be adakites, whose signatures are high $SiO_2,\;Al_2O_3$, Sr, Sr/Y La/Yb and, low Y and Yb contents. The major and trace element contents of the Jindong granitoids fall well within the adakitic field, whereas other Cretaceous granites in the same basin are plotted in the island arc ADR area in discrimination diagrams. Chondrite normalized REE patterns show generally enriced LREEs (La/Yb)C = 3.6-13.8) and slight negative to flat Eu anomalies. The mean Rb-Sr whole rock isotopic age of the Jindong granitoids is $114.6{\pm}9.1$ Ma with an initial Sr isotope ratio of 0.70457. These values suggest that the magma has mantle signature and intruded into the area during Early Cretaceous. The Jindong granitoids have similar paleogeographical locations, paleotectonic environments and intrusion ages to those of the Shiraishino granodiorites of Kyushu Island and the Tamba granitoids of San'yo belt located on southwestern Japanese arc.

• Journal of the Korean earth science society
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• v.30 no.4
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• pp.427-443
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• 2009

Cretaceous intrusive and extrusive rocks in the southwestern part of the Yeongnam Massif are possibly the result of intensive magmatism which occurred in response to subduction of the Pacific plate beneath the northeast portion of the Eurasian plate. Geochemical and petrological study on the granitic rocks were carried out in order to constrain the petrogenesis of the granitic magma and to establish the paleotectonic environment of the area. Whole rock chemical data of the granitic rocks from the study area indicate that all the rocks have characteristics of calc-alkaline series in the subalkaline field. The overall geochemical features show systematic variations in each granitic body, but the source materials of each granitic body are thought to have been different in their chemical composition. The granodiorites distributed around Donggyori in the Bognae area (DGd) are different from other granitic rocks within the study area in the contents and differentiation trends of $Al_2O_3$ and MgO as well as in the contents of the trace elements such as Ba, Sr, Pb, Ni, Cr and Y DGd have geochemical features similar to slab-derived adakites such as high $Al_2O_3$, Sr contents and high Sr/Y, La/Yb ratios, but low Y and Yb contents. The major and trace element contents of the DGd fall well within the adakitic field, whereas other Cretaceous granites in the study area are plotted in the island arc ADR area in Sr/Y vs. Y diagram. On the ANK vs. A/CNK and tectonic discrimination diagrams, parental magma type of the granites corresponds to I-type and volcanic arc granite (VAG). Interpretations of the chemical characteristics of the granitic rocks favor their emplacement in a compressional tectonic regime at continental margin during the subduction of Pacific plate. The geochemical and tectonic features reveal that adakite-like signatures of the DGd were generated by the interaction of mantle peridotite and subducted slab-derived adakitic melts (caused by the thermal effect of ridge subduction), and which slightly modified by crustal contamination during emplacement.

• Economic and Environmental Geology
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• v.52 no.5
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• pp.337-345
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• 2019

The hypothesis of ridge subduction which explains the Cretaceous igneous activities in East Asia including China, Korea and Japan, has been widely accepted in the society. Especially, the hypothesis explains the southwest-to-northeast migration of the Cretaceous adakite emergence in Southwest Japan. However, the hypothesis has several issues because the geochemical analyses and plate reconstruction model are not consistent with the consequences of the ridge subduction. To resolve the issues, a new hypothesis of the plume-continent and plume-slab interaction is suggested, which explains the igneous activities during the Cretaceous. In this review, I briefly introduce the two hypotheses and suggest an additional future study to prove the new hypothesis.

• Journal of the Korean earth science society
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• v.34 no.4
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• pp.313-328
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• 2013

Jurassic granitoids in the northeastern part of the Yeongnam Massif are possibly the result of intensive magmatic activities that occurred in response to subduction of the proto-Pacific plate beneath the northeast portion of the Eurasian plate. Geochemical studies on the granitic rocks are carried out in order to constrain the petrogenesis of the granitic magma and to establish the paleotectonic environment of the area. Whole rock chemical data of the Uljin granitoids in the northeastern part of the Yeongnam Massif indicate that all of the rocks have the characteristics of calcalkaline series in subalkaline field. The overall major element trends show systematic variations in each granitic body, but the source materials of each granitoids seem to have different chemical composition. The Uljin granitoids are different from other granitic rocks, which distributed vicinity of the study area, in the contents of $Al_2O_3$ and trace elements such as Cr, Co, Ni, Sr, Y and Nb. The Uljin granitoids have geochemical features similar to slab-derived adakites such as high $Al_2O_3$, Sr contents and high Sr/Y, La/Yb ratios, but they have low Y and Yb contents. The major ($SiO_2$, $Al_2O_3$, MgO) and trace element (Sr, Y, La, Yb) contents of the Uljin granitoids fall well within the adakitic field. The Uljin granitoids have similar geochemical characteristics, paleotectonic environments and intrusion ages to those of the Yatsuo plutonic rocks of Hida belt located on northwestern part of Japan. Chondrite normalized REE patterns show generally enriched LREEs ($(La/Yb)_{CN}=10.6-103.4$) and are slight negative to flat Eu anomalies. On the ANK vs. A/CNK and tectonic discrimination diagrams, parental magma type of the granites corresponds to I-type and volcanic arc granite (VAG). Interpretations of the chemical characteristics of the granitic rocks favor their emplacement in a compressional tectonic regime at the continental margin during the subduction of Izanagi plate in Jurassic period.

• The Journal of the Petrological Society of Korea
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• v.21 no.2
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• pp.193-202
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• 2012

There were three cycles of igneous activities from the late Paleozoic to early Cenozoic; Permian to Triassic, Jurassic, and Cretaceous to Paleogene. After the beginning of each igneous activity cycle, igneous activity became more frequent until its climax. It is noteworthy that A-type magmatisms are reported from near the ends of the all three igneous activity cycles. In addition, adakitic magmatisms occurred at the beginning of both the Permian-Triassic and the Cretaceous-Paleogene cycles. Most of the igneous activities during the late Paleozoic to early Cenozoic period were subduction-related. Therefore, transitions among beginning, proceeding, and closing of the igneous activity cycles would be intimately related with changes in directions of plate movements. In this context, I suggest following hypotheses. The closing of the Permian-Triassic igneous cycle was possibly a consequence of radical adjustment of plate motion occurred due to continental collision between north and south China blocks. Considering that no appreciable tectonic activities were recognized from the east Asian continent at the closing of the Jurassic igneous cycle, it seems that one of the strong events related with Gondwanaland-breakup and subsequent birth of the new oceans, which might cause sudden adjustments of plate motions. The closing of the Cretaceous-Paleogene igneous cycle seems to be caused as a consequence of the collision between India and Asia continents. Meanwhile, adakitic igneous bodies emplaced at the beginnings of the Permian-Triassic and Cretaceous-Paleogene cycles could be products of slab-melting during the early stages of the subduction.

• The Journal of the Petrological Society of Korea
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• v.25 no.2
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• pp.121-142
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• 2016

The Satkatbong pluton was studied with other plutons together, but some fundamental petrological characteristics were missing. This study mainly reports the petrography and geochemistry of the Satkatbong pluton comparing with the Daebo and the Bulguksa granitoids in south Korea. The Satkatbong pluton, which is host rock including a number of Mafic Magmatic Enclaves (MME), is north-south shaped dioritic pluton, located along the east coast of south Korea. The Satkatbong pluton seems to be unconformable with Cretaceous sedimentary rocks from fieldwork result. In geochemistry, the Satkatbong pluton, which is roughly similar with the Daebo granitoids, is classified into calc-alkali series rock and volcanic arc granitoid Tectonically. The fact that AlT value in marginal parts of amphiboles in the Satkatbong pluton is lower than other granitoids implies emplacement depth of the Satkatbong pluton was relatively shallow. The Satkatbong pluton shows different geochemical feature compared to the adjacent adakitic Yeongdeok granite. This seems to be caused by mafic mantle material expected from the occurrence of MMEs.

• Economic and Environmental Geology
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• v.39 no.5 s.180
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• pp.555-566
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• 2006

Major, trace and rare earth elements data of the Cretaceous Jindong granitic rocks were investigated in order to constrain the magma source characteristics and to establish the paleotectonic environment of the southwestern part of the Gyeongsang Basin. Geochemical signatures of the granitic rocks from the study area indicate that all of the rocks have characteristics of calc-alkaline series in the subalkaline field, and progressively shift from metaluminous to peraluminous with differentiation. In the variation diagrams, the overall geochemical features of the granites show systematic variations in major and trace elements. Chondrite normalized REE patterns show generally enriched LREE((La/Yb)c=4.2-12.8) and slight negative to flat Eu anomalies. Rb-Sr isotope data of the Jindong granites show that the whole rock age and Sr initial ratio are $114.6{\pm}9.1Ma$ and 0.70457, respectively. The Sr initial ratio of the Jindong granites is very similar to those of the Creataceous granites from Masan, Kimhae and Busan area($^{87}Sr/^{86}Sr=0.7049-0.707$). These results suggest that the magma have the mantle signature and intruded into the area during the early Cretaceous age. The Jindong granites have higher $Al_{2}O_{3},\;Na_{2}O$, Sr and lower $K_{2}O$, Y concentrations compared with typical calc-alkaline granitic rocks. These adakitic signatures are similar to those of adakitic pluton on Kyushu Island, southwest Japan arc. On the ANK vs. ACNK and tectonic discrimination diagrams, parental magma type of the granites corresponds to I-type, VAG granite. Interpretations of the geochemical characteristics of the granitic rocks favor their emplacement at continental margin during the subduction of Izanagi plate.