阿尔金断裂两侧早古生代沉积建造与构造演化

阿尔金断裂两侧地质体能否对比，是中国西部地质领域里的重大科学问题，长期存在争议。以沉积建造和地质构造为基础，结合古生物和古地磁资料，对比分析早古生代阿尔金断裂两侧地质特点，认为早古生代阿尔金断裂两侧的岩相古地理及其他地质特征都具有很大差别:1）早寒武世塔里木陆块主要是伸展环境，缺少火山活动，祁连地区主要是收缩环境，发育火山活动；中寒武世塔里木北缘深水盆地里普遍出现含磷钒铀沉积，祁连地区主要形成火山岩及蛇绿岩；寒武纪中晚期柴达木北缘出现红色泥岩建造，而塔里木无论是盆地区还是盆地边缘，均缺少这套沉积；奥陶纪，祁连地区继承寒武纪构造特点，塔里木则转化为收缩环境；志留纪，塔里木南北两侧形成弧后扩张盆地，祁连地区俯冲作用基本消失，南祁连形成弧后海相前陆盆地。2）寒武纪至奥陶纪塔里木、柴达木、祁连地区生物分别具有亚—奥生物区、华北生物区和华北与华南型混生特点；中晚志留世塔里木和祁连地区分别为温带和亚热带—温带生物特点。3）寒武纪塔里木、柴达木—中祁连及阿拉善等陆块位于南半球低纬度地区；奥陶纪塔里木明显南移，阿拉善、柴达木徘徊在赤道附近；志留纪到泥盆纪，塔里木北移大于33°，柴达木与阿拉善分别北移约5°和10°；各陆块有明显不同的运动轨迹。4）寒武纪阿尔金地块漂浮于阿尔金洋中，寒武纪晚期开始阿尔金洋向两侧陆块俯冲后消亡。因此，早古生代阿尔金断裂两侧具有完全不同的岩相古地理特征，应当使用不同的思路和方法进行资源勘查。

Sedimentary Formation and Tectonic Evolution on Both Sides of the Altun Fault in the Early Paleozoic Era

Correlation of the geological characteristics on both sides of the Altun Fault is an important geoscientific question in the geology of western China. Based on sedimentary formation and geological structures combined with paleontological and paleomagnetic data， Early Paleozoic geological characteristics were studied in the Altun area. It was concluded that there are clear differences in the lithofacies and geological structures on either side of the Altun Fault， mainly manifested by the following aspects.（1） The Tarim area was subject to a background of tectonic spreading and lacked volcanic activity， whereas the Qilian area had mainly a contractive background with much volcanic activity during the Early Cambrian. Sediments bearing phosphorus， vanadium and uranium were deposited in the deep water basin located at the northern margin of the Tarim block， in comparison to the mainly volcanic rocks and ophiolites in the Qilian area during the Middle Cambrian. Reddish mudstone appears at the northern margin of the Qaidam block， but is not found in middle and late Cambrian rocks in the Tarim block. In the Qilian area the Cambrian tectonic characteristics were inherited in the Ordovician， but tectonic stress in the Tarim Basin changed from extension in the Cambrian to contraction in the Middle-to-Upper Ordovician. Back-arc spreading basins occurred in the north and south of the Tarim block and oceanic subduction seems to have faded in the Qilian area； back-arc marine foreland basins were formed in the Silurian， but only in the southern Qilian area.（2） Asian-Australian （southern type） biota appear in the Tarim block， but mixed northern China biota and South China biota are evident in the Qilian area during the Cambrian and Ordovician periods. The biota were typical of a temperate climate zone in the Tarim block， but typical of a subtropical?temperate climate zone in the Qilian area during the middle and late Silurian.（3） The Tarim， Qaidam?middle Qilian and Alashan blocks were all located in the low latitudes of the southern hemisphere in the Cambrian period. The Tarim block clearly moved southward in the Ordovician， while the Alashan and Qaidam blocks remained near the equator. From the Silurian to the Devonian， the Tarim block moved rapidly northwards by as much as 33 degrees of latitude， and the Qaidam and Alashan blocks moved northwards by about 5 degrees and 10 degrees， respectively. These blocks were all independent and moved along completely different tracks.（4） In the Cambrian， the Altun block was surrounded by the Altun Ocean， and subduction began to take place on both sides of the block in the later Cambrian and Early Ordovician periods.In summary， throughout the Early Paleozoic era the Tarim and Qaidamu?middle Qilian blocks followed completely different tectonic activity paths， and they possess different sedimentological and structural characteristics. Therefore， different exploration strategies are required for oil-gas and/or non-oil-gas exploration on either side of the Altun Fault.