Jurassic dioritic to granitic igneous rocks extensively intrude into the southern Korean Peninsula, including the Yuseong area located at the boundary between the southern margin of the Gyeonggi Massif and the northern margin of the Okcheon Belt. In this study, the petrogenesis and sources of Jurassic igneous rocks in the Yuseong area were investigated. The U–Pb zircon age data from the Jurassic plutonic rocks in the Yuseong area give two igneous ages, ca. 178–177 Ma and 169–168 Ma, indicating that two stages of igneous activity occurred in the Yuseong area during the Jurassic. The geochemical characteristics of Jurassic diorites indicate that they originated from enriched mid-ocean ridge basalt (E-MORB; Nb/Yb = 5.63–7.27; Zr/Yb = 118–156). The enriched Th/Yb ratios (5.5–8.0) in the diorites imply that they experienced crustal contamination during magma ascent. The Jurassic granitoids in the Yuseong area are divided into I- and S-type granites. The Jurassic I-type granitoids may have formed via the partial melting of mafic rocks with mixtures of 10–40% pelite-derived melt, while the S-type granites originated from felsic pelite. The Jurassic diorites have low Nb/Th ratios with depletion of the Nb and Ta components, indicating that they formed in a volcanic arc tectonic environment. On the other hand, the Jurassic granitoids show two different tectonic environments: a volcanic arc, and a syncollisional environment. The granites with syncollisional character are S-type granites, and may give incorrect information about tectonic setting because of the changes in the trace elements of the S-type granite due to fractional crystallization. Early Jurassic (200–190 Ma) igneous rocks are distributed only in the southeastern Korean Peninsula, including the Yeongnam Massif; Jurassic igneous rocks formed at ca. 190–180 Ma occur mainly in the Okcheon Belt and southern Gyeonggi Massif, which includes the Yuseong area. Middle Jurassic igneous rocks widely intruded from the Okcheon Belt, through the Gyeonggi and Nangrim massifs in the Korean Peninsula, to the Liaoning area in the North China Craton at 180–160 Ma. This distribution pattern of the Jurassic granitoids suggests that flat subduction started after 180 Ma in Northeast Asia.

中文翻译：

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朝鲜半岛京畿道南缘裕城地区侏罗纪的火成岩活动及其对东北亚构造演化的启示

侏罗纪的闪长岩到花岗岩的火成岩广泛侵入朝鲜半岛的南部，包括位于京畿道地块南缘和Okcheon地带北缘之间的玉城地区。本研究探讨了玉城地区侏罗系火成岩的成因和成因。玉城地区侏罗系岩溶岩的U–Pb锆石年龄数据给出了两个火成岩年龄。178–177 Ma和169–168 Ma，表明侏罗纪时期的裕城地区发生了两个阶段的火成活动。侏罗纪闪长岩的地球化学特征表明它们起源于富集的中海脊玄武岩（E-MORB； Nb / Yb = 5.63–7.27； Zr / Yb = 118–156）。丰富的Th / Yb比（5.5-8。0）在闪长岩中暗示他们在岩浆上升期间经历了地壳污染。玉城地区的侏罗纪花岗岩分为I型和S型花岗岩。侏罗纪I型花岗岩可能是由于镁铁质岩石与10–40％的源自白云母的熔体混合而部分熔融而形成的，而S型花岗岩则起源于长英质的花岗岩。侏罗纪硅藻土的Nb / Th比值较低，并且Nb和Ta组分耗尽，表明它们是在火山弧构造环境中形成的。另一方面，侏罗纪花岗岩显示出两种不同的构造环境：火山弧和共生环境。具有滑囊特征的花岗岩是S型花岗岩，可能会由于分步结晶而导致S型花岗岩中微量元素发生变化，从而给出有关构造背景的错误信息。侏罗纪早期（200-190 Ma）的火成岩仅分布在朝鲜半岛的东南部，包括Yeongnam地块。侏罗纪火成岩形成于约。190-180 Ma主要发生在Okcheon地带和京畿断层山脉南部，其中包括Yuseong地区。中侏罗纪火成岩广泛地从Okcheon带侵入，穿过朝鲜半岛的京畿道和Nangrim地块，到达华北克拉通的辽宁地区（180-160 Ma）。侏罗纪花岗岩的这种分布模式表明，东北亚180 Ma之后就开始了平面俯冲。侏罗纪早期（200-190 Ma）的火成岩仅分布在朝鲜半岛的东南部，包括Yeongnam地块。侏罗纪火成岩形成于约。190-180 Ma主要发生在Okcheon地带和京畿断层山脉南部，其中包括Yuseong地区。中侏罗纪火成岩广泛地从Okcheon带侵入，穿过朝鲜半岛的京畿道和Nangrim地块，到达华北克拉通的辽宁地区（180-160 Ma）。侏罗纪花岗岩的这种分布模式表明，东北亚180 Ma之后就开始了平面俯冲。侏罗纪早期（200-190 Ma）的火成岩仅分布在朝鲜半岛的东南部，包括Yeongnam地块。侏罗纪火成岩形成于约。190-180 Ma主要发生在Okcheon地带和京畿断层山脉南部，其中包括Yuseong地区。中侏罗纪火成岩广泛地从Okcheon带侵入，穿过朝鲜半岛的京畿道和Nangrim地块，到达华北克拉通的辽宁地区（180-160 Ma）。侏罗纪花岗岩的这种分布模式表明，东北亚180 Ma之后就开始了平面俯冲。通过朝鲜半岛的京畿道和南陵地块，到达华北克拉通的辽宁地区，海拔180-160 Ma。侏罗纪花岗岩的这种分布模式表明，东北亚180 Ma之后就开始了平面俯冲。通过朝鲜半岛的京畿道和南陵地块，到达华北克拉通的辽宁地区，海拔180-160 Ma。侏罗纪花岗岩的这种分布模式表明，东北亚180 Ma之后就开始了平面俯冲。