© 2000 Elsevier Science B.V. All rights reserved.
Keywords
:
Yeongnam massif; Gyeonggi massif; Pb – Pb age; Suture zone
1. Introduction
Recent studies on the continent collision be- tween the North Sino-Korean and South China
Yangtze blocks Huang and Wu, 1992; Ames et al., 1993, 1996; Li et al., 1993; Yin and Nie, 1993;
Li, 1994; Ernst and Liou, 1995 have generated a growing interest in the possibility that the colli-
sion zone may extend to the Korean peninsula. Despite the lack of definitive evidence for conti-
nent collision and associated high-pressure meta- morphism such as diamond, coesite, and eclogite,
several tectonic units of South Korea including the Imjingang belt, the Gyeonggi massif, and the
Ogcheon belt Fig. 1A have been proposed as possible candidates for the eastern continuation of
the Chinese collision belt Liu, 1993; Yin and Nie, 1993; Ernst and Liou, 1995; Chang, 1996; Ree et
al., 1996.
Although the characteristics of Korean base- ment rocks could be potentially important to this
kind of debate, there still remain many ambigui- ties regarding their ages, isotopic signatures, and
tectono-metamorphic evolution processes. On the basis of Paleozoic faunal differences, Kobayashi
1966 suggested that the Gyeonggi massif has an
Fig. 1. A Simplified tectonic map for northeastern Asia. The geology of the Korean peninsula is composed of seven tectonic provinces NM, Nangrim massif; PB, Pyeongnam basin; IB, Imjingang belt; GM, Gyeonggi massif; OB, Ogcheon belt; YM,
Yeongnam massif; GB, Gyeongsang basin. The Yeongnam massif bounds with the Ogcheon belt by the dextral strike-slip ductile shear zone, called the Honam shear zone HSZ. B The distribution of Precambrian basement rocks in South Korea. C Schematic
geologic map of the Pyeonghae area, northeastern Yeongnam massif modified after Hwang et al., 1996.
affinity to the South China block, and the Yeong- nam massif to the North China block. This idea
provided a principal background for later tectonic interpretations of the Korean peninsula by Cluzel
et al. 1991 and Yin and Nie 1993. Cluzel et al. 1991 suggested that the Gyeonggi massif and the
Ogcheon belt of South China affinity have been juxtaposed with the Yeongnam massif of North
China affinity as a result of Triassic dextral dis- placement of the order of 200 km along the
Honam shear zone. Yin and Nie 1993 adopted Cluzel et al. 1991’s idea and further proposed an
indentation model for explaining the diachronic nature of the Chinese collision belt and develop-
ment of the Tan-lu and Honam fault systems. If Kobayashi 1966’s scheme is valid, it is expected
that the two massifs are different in terms of isotopic signatures and ages of crustal formation
and tectono-metamorphic events, considering a presumed distinction between the North and
South China blocks Ma and Wu, 1981; Jahn et al., 1990; Zhang et al., 1997; Chen and Jahn,
1998.
In this study, we address this problem by Pb and Nd isotope data. First, we present Pb – Pb
ages and Nd isotopic data of basement rocks from the Pyeonghae area, northeastern Yeong-
nam massif Fig. 1B. Using the Pb and Nd isotope data of this study and previous works, we
compare geochronology and isotopic characteris- tics between the Gyeonggi and Yeongnam mas-
sifs. Second, we compare Nd isotopic signatures of Korean basement rocks with those of Chinese
blocks on the basis of compiled data set, and discuss their tectonic implications for the hypoth-
esis of continuation of the Chinese collision belt to the Korean peninsula.
2. Geologic setting
