【摘要】 仲巴微地体夹持在拉萨地块和特提斯喜马拉雅之间,两侧均被蛇绿混杂岩带所围限,是雅鲁藏布江西段重要的地质单元。揭示其构造亲缘性对于探讨新特提斯洋构造演化和青藏高原多地体拼合过程具有重要意义。仲巴微地体中段马攸木地区较好地出露一套志留系—石炭系沉积地层,其中志留系为片理化钙质片岩、大理岩夹砂岩,泥盆系为一套片理化的结晶灰岩夹钙质片岩,石炭系为一套砂岩、粉砂岩夹钙质片岩的碎屑岩组合。碎屑锆石年代学数据表明,志留系、泥盆系和石炭系均表现出约530 Ma和950 Ma的特征年龄峰值,年龄分布样式与西羌塘地体和喜马拉雅地体具有高度的相似性,缺乏拉萨地体以约1 170 Ma的特征的年龄峰值。结合区域地层对比,认为在志留纪—石炭纪,仲巴微地体具有明显的喜马拉雅亲缘性,其构造位置临近印度大陆北缘,是西羌塘—大印度—特提斯喜马拉雅构造体系的一部分。更多还原

【Abstract】 Zhongba microterrane is an important geological unit in the western Yarlung Zangbo suture zone.It exposes between the Lhasa terrane and the Tethyan Himalayan Sedimentary Sequence(THS),combined by ophiolite belt on both northern and southern sides.It has great significance of tectonic affinity analysis for the process of multi-block assembling of the Tibetan Plateau and Neo-Tethys.The Silurian-Carboniferous strata cropping out in the Mayum region,middle Zhongba microterrane,are studied by this research with detrital zircon chronology.The Silurian strata consist of foliated calcareous schist,marble with thin sandstone interlayer.The Devonian strata are mainly composed by foliated crystalline limestone and calcareous schist.The Carboniferous strata are characterized by a suite of fine clastic rocks with thin interlayered calcareous schist.Results of detrital zircons U-Pb dating show that the Silurian-Carboniferous strata have the similar age distributions in the relative U-Pb age probability diagram.All the samples yield ages clustering at ca.530 Ma and ca.950 Ma,which have a great similarity to the detrital zircons age distribution patterns of the western Qiangtang terrane and the Tethyan Himalayan Sedimentary Sequence.However,there is no age clustering at ca.1 170 Ma,which is the typical feature of Lhasa terrane.Therefore,the detrital zircons geochronologic results reveal that the Zhongba microterrane located near the Indian Plate and was a part of the western Qiangtang-Great India-Tethyan Himalayan continental margin system during the Silurian to Carboniferous.更多还原