U-Pb dating on single detrital zircon grains from the Triassic Songpan-Ganze flysch (Central China): provenance and tectonic correlations
U-Pb dating on single detrital zircon grains from the Triassic Songpan-Ganze flysch (Central China): provenance and tectonic correlations
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DOI：
10.1016/s0012-821x(97)00138-6
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发表时间：
1997-11-01
影响因子：
5.3
通讯作者：
Malavieille, J
中科院分区：
文献类型：
--
作者：
Bruguier, O;Lancelot, JR;Malavieille, J
Songpan-ganze Flysch腰带（中国中部）覆盖了超过20万公里（2）的巨大三角形区域，并受到中国南部北部和藏族高原的大陆街区的界定。使用U-PB方法对谷物分析了从收集在皮带中央的三个飞蝇样品中提取的碎屑锆石。在皮带的不同位置收集的两个中间三叠纪砂岩样品提供了相同的结果，这表明相似的源区域，碎屑锆石产生了很大的年龄，并指示其主要衍生物来自原植物学中部（1.8-2.0 GA）来自晚期的岩石（大约2.5-2.6 GA）材料的岩石。低U锆石的不和谐和PB损失模式表明，在随后的事件中可能是喀里多尼亚时代的干扰，如CA，420和450 MA的一致性锆石晶粒所建议的那样。在Palang Shan Pass区内收集的一个样品可在230 mA（231 +/- 1 MA和233 +/- 1 MA）处提供一致的锆石晶粒。这些三叠纪的年龄是与苍蝇沉积同步的，并在当时在靠近盆地的地区暗示了强烈的地质活性（钙碱性火山症？）。数据支持弹性材料的起源，主要是从东北陆地开始的，与中国克拉顿的南部边缘相对应，较小程度，是从杨氏克拉通的输入，可能是从盆地北部边缘（Kunlun are）的输入。也检测到。上三叠纪砂岩的年龄光谱显着差异，并且显示出辛尼亚人（大约760 mA）晶粒的优势，这可能来自杨氏克拉顿。源区域的这种变化被解释为反映了该地区的构造演变，尤其是与中国南部和中国南部之间的三叠纪碰撞有关。在中间的三叠纪中，尽管中国板块以北的鸣式海俯冲仍在发生，但达比地区中国南部的大陆俯冲负责提升覆盖板（即中国克拉顿），该板提供了大型大型大型沉积物的体积。在晚期三叠纪晚期，中国南部的顺时针旋转使Qinling带的印度西尼亚人升高，并关闭了盆地。随着沿北部南部边缘的增生楔正在增厚，源自该来源地区的碎屑无法到达苍蝇盆地。碎屑锆石提出的年龄光谱表明，源自扬格特顿北部边缘的源区域的Sinian物质占主导地位。直到这个时期一直被中国克拉顿的luliang材料淹没的来源区域。 （c）1997 Elsevier Science B.V.
The Songpan-Ganze flysch belt (Central China) covers a huge triangular area of more than 200,000 km(2) and is bounded by the continental blocks of South Chins North China and the Tibetan plateau. Detrital zircons extracted from three flysch samples collected in the central part of the belt were analyzed grain by grain using the U-Pb method. Two samples of Middle Triassic sandstones, collected at different locations in the belt, provide identical results, which suggests similar source regions, The detrital zircons yield a wide range of ages and indicate their principal derivation from Mid-Proterozoic (1.8-2.0 Ga) source rocks with minor contribution from late Archean (ca. 2.5-2.6 Ga) material. The discordance and Pb loss patterns from low-U zircons indicate disturbances during a subsequent event which may be of Caledonian age, as suggested by concordant zircon grains at ca, 420 and 450 Ma. One sample collected within the Palang Shan Pass zone provides concordant zircon grains at around 230 Ma (231 +/- 1 Ma and 233 +/- 1 Ma). These Triassic ages are synchronous to flysch deposition and suggest intense geological activity (calc-alkaline volcanism?) at that time in the area close to the basin. The data support an origin of the elastic material mainly from a northeastern landmass, corresponding to the southern margin of the Sino-Korean craton, To a lesser degree, inputs from the Yangtze craton and possibly from the northern margin of the basin (Kunlun are) are also detected. The age spectrum from the Upper Triassic sandstone is significantly different and shows predominance of Sinian (ca. 760 Ma) grains, probably derived from the Yangtze craton. This change in the source region is interpreted as reflecting the tectonic evolution of this area and in particular as being linked to the late Triassic collision between South China and North China. In the Middle Triassic, while subduction of the Songpan sea northward beneath the North China plate was still taking place, continental subduction of South China in the Dabie region was responsible for uplift of the overriding plate (i.e. the Sino-Korean craton) which supplied large volumes of sediments. During the Late Triassic, clockwise rotation of the South China block uplifted the Indo-Sinian part of the Qinling belt and closed the basin. As the accretionary wedge was thickening along the southern margin of North China, detritus derived from this source region were unable to reach the flysch basin. The age spectrum presented by detrital zircons indicates predominance of Sinian material derived from source area located on the northern margin of the Yangtze craton; a source region which was until this period swamped by Luliang material from the Sino-Korean craton. (C) 1997 Elsevier Science B.V.