塔里木盆地和南天山泥盆-石炭纪沉积记录与陆缘构造差异演化

For the late Paleozoic amalgamation-accretion in the north margin of Tarim Block, especial attention is given to a coupled evolutional evidence between South Tianshan Ocean and North Tarim Continental Margin. Through a multidisciplinary research led by sedimentary geology, this project emphasize to establish and correlate the Devonian-Carboniferous sedimentary records in the South Tianshan and North Tarim Continental Margin, from which relatively successive and high-resolving informations, including depositional environment, detrital provenance, sea-level change and tectonic attributes, be extracted and deeply analyzed. Based on source-sink systemic analysis method, the project further identify and constitute varied sedimentary-tectonic relationships, probably existed among pre-Carboniferous orogens or uplift belts around Tarim block, continental margin of northern Tarim block and South Tianshan Ocean, and their spatial differentiation. Consequently a series of paleogeographic frameworks on the studied basin-range will be ruled, which will contribute to understand the late Paleozoic ocean-continent transition of South Tianshan and basin-range transition of North Tarim Continental Margin and their differently tectonic evolutions in subsection, that will perfect tectonic geodynamic models on the Central Asia basin-range system. In addition, this project will also provide important sedimentary and tectonic basis to explore probable tectonic relations between North Tarim Continental Margin and Paleotethys Ocean or Paleoasia one and to service petroleum exploration and prediction on the Paleozoic strata in the Tarim basin.

针对塔里木块体北缘盆山体系在晚古生代的"拼合-增生过程"，以南天山洋与塔里木北部大陆边缘可能的耦合演化迹象为切入点，通过沉积地质学主导下的多学科研究，重点建立和对比南天山-塔里木盆地（陆缘）泥盆-石炭纪沉积记录，提取和深入解析比较连续、高分辨率的沉积环境、碎屑物源、海平面演变及其构造属性信息；以源-汇体系分析为纽带，识别和建立塔里木及周缘前石炭纪造山带或隆起带、塔里木北部大陆边缘与南天山洋的沉积-构造关系和这种关系在空间上的分异；在此基础上厘定盆山古地理格局，认识晚古生代南天山洋-陆转换与塔里木北部大陆边缘盆-山转换机制及其构造演化的分段性，完善中亚地区相关山盆体系形成演化的构造动力学模式。此外这一研究对探索塔里木板块北缘构造体系与区域古特提斯洋和古亚洲洋的演变关系，并对塔里木盆地古生界石油勘探预测具有重要的沉积学和构造学基础意义。

聚焦南天山-塔里木北部陆缘泥盆-石炭纪沉积记录，项目重点提取和深入解析碎屑沉积环境、碎屑物源、海平面变化及构造信息；进一步厘定盆山古地理格局，完善认识晚古生代南天山拼合-增生过程及其与塔里木北部大陆边缘分段性差异演化的构造关系。项目获得如下主要研究进展：.（1）塔里木北缘下石炭统野云沟组砂岩碎屑锆石U-Pb年龄以新元古代中-晚期为主体，与“泛非”造山事件的持续时间较为一致，此类沉积记录在该地区也是首次大量发现。相应的碎屑锆石的εHf(t)值几乎全为负值，是古老陆壳熔融的产物。而其他层位的砂岩碎屑锆石均无“泛非”造山事件的明显信息，反映了与“泛非”造山作用有关的结晶基底的快速隆升和短暂剥露。.（2）泥盆纪-早石炭世维宪早期，塔里木块体北缘东部发育不稳定和差异显著的碎屑组合，并具有接近地层年龄的碎屑锆石，指示了由南而北相对近距离的源汇体系、活动陆缘和混杂沉积的特征；而西部砂岩呈现的较高的成分成熟度和来自塔里木陆块相当数量的锆石年代学特征，具有被动大陆边缘沉积属性。.（3）早石炭世维宪晚期-晚石炭世，塔里木块体北缘东部成分成熟度增高，并出现了一定数量的来自塔里木陆块的碎屑锆石，以及相当部分390~460Ma锆石的εHf(t)显示特征的正值，具有主体再旋回混合造山带的物源构造属性、中-近距离源汇体系和残留海沉积特征；而在塔里木块体北缘西部，较之前更加明显的较高砂岩成分成熟度和来自塔里木陆块的大量锆石年代学特征，说明具有远距离源汇体系特征，可能指示了更加广阔的残留洋或残留海沉积。这说明尽管南天山洋在早石炭世维宪期以后已经关闭，但直到晚石炭世仍未明显造山。