Neoproterozoic bimodal volcanism in the central Ogcheon belt, Korea: age and tectonic implication
Neoproterozoic bimodal volcanism in the central Ogcheon belt, Korea: age and tectonic implication
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DOI：
10.1016/s0301-9268(97)00077-6
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发表时间：
1998-05
影响因子：
3.8
通讯作者：
Kwang-Sik Lee;H. Chang;Kye‐Hun Park
中科院分区：
文献类型：
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作者：
Kwang-Sik Lee;H. Chang;Kye‐Hun Park
对韩国梧川带中部文殊里组变质火山岩进行了锆石U-Pb年龄测定。分析了四个锆石组分，其中三个几乎一致;数据定义了一个不一致，上截距为755.8 ± 1.3 Ma，下截距为160 ± 19 Ma（MSWD = 0.72）。上交点年龄被解释为指示双峰式火山作用的时间，下交点年龄被解释为反映侏罗纪热变质作用。这是第一个明确的证据，支持存在的一个形成，至少在一部分晚前寒武纪在Ogcheon带。斜长角闪岩和长英质变火山岩的Nd同位素和微量元素地球化学特征表明，它们起源于大陆裂谷环境下的地幔源区。裂谷似乎还没有成熟到足以形成洋壳，因为没有显示深海环境的岩石。几位作者提出的“梧川带是中国东部碰撞带的延伸”的可能性，并没有得到现有证据的支持。
UPb zircon ages were determined for a metavolcanic rock from the Munjuri Formation in the central Ogcheon belt, Korea. Four zircon fractions were analyzed of which three are nearly concordant; the data define a discordia with an upper intercept at 755.8 ± 1.3 Ma and a lower intercept at 160 ± 19 Ma (MSWD = 0.72). The upper intercept age is interpreted to indicate the timing of bimodal volcanism, and the lower intercept age is interpreted to reflect Jurassic thermal metamorphism. This is the first definite evidence supporting the existence of a formation in the Ogcheon belt that is at least in part late Precambrian. Nd isotope and trace element geochemistry of the amphibolites and felsic metavolcanics suggests that they originated from a mantle source in a continental rift environment. The rift does not appear to have matured enough to develop oceanic crust, since rocks indicating deep sea environments are absent. The possibility that the Ogcheon belt is an extension of the east Chinese collision belt, as suggested by several authors, is not supported by the available evidence.