The Beishan orogenic zone is a key area to understand evolution of the Central Asian Orogenic Belt that is an accretionary factory well-enough preserved in the Paleozoic. In early Paleozoic, the tectonic mélange ...The Beishan orogenic zone is a key area to understand evolution of the Central Asian Orogenic Belt that is an accretionary factory well-enough preserved in the Paleozoic. In early Paleozoic, the tectonic mélange zone containing the coherent unit and mélange unit is triggered by the complicated accretionary process of the Beishan area. The early Paleozoic tectonic evolution of the Beishan orogenic zone is investigated in this study using sedimentology and stratigraphic correlations of the lowe Paleozoic deposits. From the Cambrian to the middle Ordovician, this region was characterized by geographically extensive, flat-bedded siliceous mudstone, indicating the existence of a large ocean basin. The oceanic plate entered the convergence phase in terms of the Wilson Circle during the Middle Ordovician, when numerous magmatic arcs formed along two opposite sides of the ocean. The magmatic arcs became the widest during the Silurian, suggesting that the Hongliuhe-Niujuanzi-Xichangjing Ocean(HNX;a southern branch of the Paleo Asian Ocean) was reduced to a small residual ocean in the central Beishan region by that time, and probably lasted till the Carboniferous or later by newly published data.展开更多
The International Stratigraphic Guide defined that all stratified or quasi-stratified rock bodies of the earth crust, including sedimentary, igneous, metamorphic, solidified and unsolidified ones, should be considered...The International Stratigraphic Guide defined that all stratified or quasi-stratified rock bodies of the earth crust, including sedimentary, igneous, metamorphic, solidified and unsolidified ones, should be considered as research contents of stratigraphy. Traditional stratigraphy mainly involves strata formed under gravity mechanism, plus a few kinds of bedded volcanic rocks such as lava, pyroclastic rock and volcanic ash, as well as metamorphic sedimentary and volcano-sedimentary rocks. These traditional strata are regarded as Smithian strata in this paper. In modern stratigraphy, mechanism of strata formation includes not only gravity but also thermal (ophiolite), mechanic and tectonic forces (orogenic mélange and tectonite). In these above-mentioned non-gravitative conditions, the strata, formed complying with their own mechanisms but not with the law of superposition of Smithian stratigraphy, are called non-Smithian strata here. In mélange regions from orogenic belt, formations of non-Smithian strata could be classified into subduct-scrape-match, subduct-return-match, and subduct- overthrust types.展开更多
基金funded by the National Natural Science Foundation(No.41772107)the Geological Survey Program(No.DD20190370 and No.DD20190812)of the People's Republic of Chinathe National Key Research,Development Program of China(No.2016YFC0601005)。
文摘The Beishan orogenic zone is a key area to understand evolution of the Central Asian Orogenic Belt that is an accretionary factory well-enough preserved in the Paleozoic. In early Paleozoic, the tectonic mélange zone containing the coherent unit and mélange unit is triggered by the complicated accretionary process of the Beishan area. The early Paleozoic tectonic evolution of the Beishan orogenic zone is investigated in this study using sedimentology and stratigraphic correlations of the lowe Paleozoic deposits. From the Cambrian to the middle Ordovician, this region was characterized by geographically extensive, flat-bedded siliceous mudstone, indicating the existence of a large ocean basin. The oceanic plate entered the convergence phase in terms of the Wilson Circle during the Middle Ordovician, when numerous magmatic arcs formed along two opposite sides of the ocean. The magmatic arcs became the widest during the Silurian, suggesting that the Hongliuhe-Niujuanzi-Xichangjing Ocean(HNX;a southern branch of the Paleo Asian Ocean) was reduced to a small residual ocean in the central Beishan region by that time, and probably lasted till the Carboniferous or later by newly published data.
文摘The International Stratigraphic Guide defined that all stratified or quasi-stratified rock bodies of the earth crust, including sedimentary, igneous, metamorphic, solidified and unsolidified ones, should be considered as research contents of stratigraphy. Traditional stratigraphy mainly involves strata formed under gravity mechanism, plus a few kinds of bedded volcanic rocks such as lava, pyroclastic rock and volcanic ash, as well as metamorphic sedimentary and volcano-sedimentary rocks. These traditional strata are regarded as Smithian strata in this paper. In modern stratigraphy, mechanism of strata formation includes not only gravity but also thermal (ophiolite), mechanic and tectonic forces (orogenic mélange and tectonite). In these above-mentioned non-gravitative conditions, the strata, formed complying with their own mechanisms but not with the law of superposition of Smithian stratigraphy, are called non-Smithian strata here. In mélange regions from orogenic belt, formations of non-Smithian strata could be classified into subduct-scrape-match, subduct-return-match, and subduct- overthrust types.
