The location of the suture zone between the South China Block (SCB) and the Indochina Block (IB) is disputed. Recently, along the Song Chay (Chay river) belt, a mélange zone was proposed as a potential suture zone of the SCB and IB. However, the provenance and age of the Song Chay mélange is poorly known. In order to better constrain the age and provenance of the elements forming the Song Chay mélange, nine samples of detrital material, and one orthogneiss were subjected to zircon U-Pb and Hf isotope analysis. Detrital zircons from the silty matrix of the Song Chay mélange record three major Neoproterozoic age clusters at 580–650, 700–800, and 900–1,000 Ma, which correspond well to the substratum of the SCB. Two minor Late and Early Paleozoic age groups at 270–330, and 420–500 Ma, with mainly negative ε_Hf(t) values were also recovered. We consider that the zircons in the matrix of the mélange were mainly derived from the subducting plate, namely the SCB. This interpretation is supported by the occurrence of lensoid sandstone blocks, representing the substratum of the SCB, included into the mélange. The deposition age of the Song Chay mélange is between 310 and 250 Ma. Our results demonstrate that in an ophiolitic mélange, the detrital material does not invariably come from the overriding plate, but at the onset of the collision, the subducting continental plate may also supply the terrigenous material.

中文翻译：

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Song Chay缝合带（越南东北部）陆源沉积物中碎屑锆石U-Pb年龄分布和Hf同位素约束及其对东部古特提斯演化的古地理意义

华南地块（SCB）和印度支那地块（IB）之间的缝合带位置存在争议。最近，在 Song Chay（Chay 河）带，一个混合带被提议作为 SCB 和 IB 的潜在缝合带。然而，Song Chay 混酿的出处和年代却鲜为人知。为了更好地限制形成 Song Chay 混杂岩的元素的年龄和来源，对 9 个碎屑材料样品和 1 个正方麻岩进行了锆石 U-Pb 和 Hf 同位素分析。来自 Song Chay 混杂岩粉质基质的碎屑锆石在 580-650、700-800 和 900-1,000 Ma 处记​​录了三个主要的新元古代年龄簇，它们与 SCB 的基质很好地对应。270-330 和 420-500 Ma 两个次要的晚古生代和早古生代年龄组，主要为负的 ε _Hf(t) 值也被恢复。我们认为混杂岩基体中的锆石主要来自俯冲板块，即SCB。这种解释得到了透镜状砂岩块的支持，透镜状砂岩块代表 SCB 的底层，包含在混杂物中。Song Chay 混杂岩的沉积时代在 310 至 250 Ma 之间。我们的结果表明，在蛇绿岩混杂岩中，碎屑物质并非总是来自上覆板块，但在碰撞开始时，俯冲大陆板块也可能提供陆源物质。