西准噶尔晚古生代熔积岩的厘定与构造格局重建

West Junggar is bounded by the Altai orogen to the north, the Tianshan orogen to the south, the Kazakhstan plate to the west and the Junggar basin to the east. It is located at the east end of the Kazakhstan orocline and is considered to be part of the triple junction where the Siberian, Tarim and Kazakhstan plates are sutured. Therefore, West Junggar is a key area for the reconstruction of the evolutionary history of the Central Asian Orogenic Belt (CAOB). The Late Palaeozoic is a critical period of oceanic closure and continental amalgamation, yet there is so far no consensus on the orogenic processes and tectonic evolution during this period. Peperites are generated by magma intruding and mingling with wet unconsolidated or poorly consolidated sediment and exhibit a range of complex textures. Generally, peperites are distributed along the contacts of intrusions, lava flows or hot volcaniclastic deposits with sediments. Peperites provide information on the mechanisms by which magma interacts with wet sediment. The occurrence of peperites indicates approximate contemporaneity of magmatism and sedimentation. Therefore, the study of peperites is also important for relative chronology. In the prophase study, we have made new discoveries about peperites formed by interaction of basaltic lava and neritic sediments in a Late Paleozoic ocean basin in West Junggar, China. The purpose of this proposal is first to describe the range of textural types of peperite and to determine their age. We then use the undeformed stratigraphic setting of the peperites as an important marker unit to constrain the Late Paleozoic tectonic and palaeoenvironmental setting in West Junggar.

西准噶尔地区位于中亚造山带的东、西构造单元结合部位，是解剖中亚造山带大陆动力学过程的关键所在。近期新的研究进展相继提出了不同的构造演化模型，如增生杂岩模式、洋脊俯冲板片窗模式和残余洋盆模式等。应答新的科学问题和挑战，要从新的视角入手、瞄准关键所在。熔积岩是沉积与岩浆活动同期作用的产物，是一种特殊成因类型火山碎屑岩,熔积岩作为良好的指相标志性岩石，是确定盆地沉积过程中同时伴有岩浆活动的直接证据，是确定火山岩定位环境的标志之一。前期的研究中，申请人在西准不同地段发现多处典型的熔积岩露头，本项目将以西准地区新发现的熔积岩为主要目标，选择典型剖面系统鉴别不同类型的熔积岩，系统刻画与描述熔积岩的结构特征，以新厘定的熔积岩层系为标识，对比西准噶尔地区不同区段的熔积岩层系发育特征，结合火山岩和沉积层系相互关系的研究，恢复熔积岩形成时的地质背景和环境，为重建晚古生代西准地区古构造格局提供新的关键证据。

西准噶尔地区是连接中亚造山带不同单元和解剖中亚造山带构造格局的关键地段。在西准噶尔达拉布特断裂带两侧太勒古拉泉、白碱滩附近、石奶闸、卡拉休卡和大棍等多个露头点，系统厘定并鉴别出了各类典型的熔积岩露头，分析了其形成环境和机制。以熔积岩为标志层，重建了西准噶尔地区古生代大地构造格架，提出了达拉布特和白碱滩蛇绿混杂岩带不是传统意义上的板块缝合带，而是形成于残余洋盆中的洋壳断裂带混杂岩这一新认识。在此基础上，项目组进而在峨眉山大火成岩省核心区的大理地区、塔里木大火成岩省、北山造山带等多个中国地学研究热点地区，均发现了以熔积岩为代表的基性火山碎屑沉积（MVD），并最先将熔积岩这一火山学研究推广应用到古生代大地构造格架重建和大火成岩省的研究中。项目组在中国多处发现的典型熔积岩和应用，具有创新示范意义。.项目研究成果发表了7篇标注论文，其中5篇发表在国外SCI检索著名刊物如TECTONICS, GSAB, GR, JVGR等上面。依托项目培养毕业2名博士研究生