塔里木盆地西北缘四石厂地区下二叠统沉积与物源记录及其反映的构造演化

石炭纪-二叠纪南天山洋-塔里木盆地北部陆缘构造演化众说纷纭.选择塔里木盆地内紧靠南天山的四石厂剖面，针对下二叠统康克林组露头，在沉积、碎屑组分、重矿物组合分析基础上，重点通过LA-ICP-MS分析砂岩样品碎屑锆石的原位U-Pb和Lu-Hf同位素特征，解析其年代学、物源特征及构造演化等信息.研究显示，砂岩样品碎屑组分基本都落入陆块物源区和成熟岩石与稳定构架合并处，重矿物组合以稳定重矿物为主，反映稳定的大地构造背景.砂岩碎屑锆石定年结果显示5组年龄:407~501 Ma、755~873 Ma、889~1 129 Ma、1 792~2 079 Ma、2 393~2 496 Ma，主要反映了5期构造热事件.对比潜在物源区，塔里木盆地内古隆起可能为主物源，与西昆仑-阿尔金造山带剥蚀物源相关的塔里木盆地内前二叠纪沉积也可能提供部分再旋回物源.物源特征显示，虽然南天山洋已经闭合，但直到早二叠世阿瑟尔期仍然没有大规模隆升，洋盆闭合事件对塔里木盆地西北缘构造格局和物源体系影响较小.对比前人研究成果认为，早二叠世从阿瑟尔期至萨克马尔期，柯坪地区的物源结构发生重大变化，由盆地内古隆起单一物源转变为盆内和造山带双重物源.已经闭合的南天山洋盆在萨克马尔期开始隆升造山，成为塔里木西北缘的一个重要物源区. 

Depositional and Provenance Records of Lower Permian Sandstones from Sishichang Area,Northwestern Tarim Basin: Implications for Tectonic Evolution

Carboniferous-Permian is the critical tectonic evolution period of the South Tianshan Ocean and the northern margin of Tarim basin. The Carboniferous-Permian outcrop, located in the northwestern margin of Tarim basin, near the South Tianshan orogen, is well exposed in the Sishichang area, and is selected to analyze this problem. Based on depositional system, sandstone skeleton component, heavy minerals, especially detrial zircon geochronology analysis by LA-ICP-MS in situ U-Pb and Lu-Hf isotope, this study further explores provenance, tectonic evolution and its geodynamic mechanism about the Tarim basin and the periphery orogenic belt. The results show that sandstone grains are dotted in the continental block provenances and the merger of fields for mature rocks with stable frameworks; the main proportions of heavy mineral assemblages are the stable heavy minerals. These results reflect that tectonic setting may be stable. The geochronological samples show multiphase tectono-thermal events with age groups of 407-501 Ma, 755-873 Ma, 889-1 129 Ma, 1 792-2 079 Ma, and 2 393-2 496 Ma. Compared with the potential source areas, the main provenance may be the Tarim palaeohigh. The redeposition of pre-Permian strata in the Tarim basin, associated with the erosion source in the Kunlun-Altun orogen, may also have some contribution. In other words, although the South Tianshan Ocean may have been closed, the South Tianshan orogenic belt did not uplift on a large scale until the Asselian. And the tectonic pattern and provenance of northwestern margin of Tarim basin changed little because of the closure. Referring to the previous data, it is concluded that the single source of the Tarim palaeohigh has developed into the dual sources of the Tarim basin and orogenic belt form Asselian to Sakmarian, and the provenance system of Keping area changes greatly. Furthermore, the South Tianshan Ocean, closed in Carboniferous, began to uplift in Sakmarian, and became an important source to the northwestern margin of Tarim basin.