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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Primary Carboniferous and Permian paleomagnetic results from the Yili Block (NW China) and their implications on the geodynamic evolution of Chinese Tianshan Belt
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Primary Carboniferous and Permian paleomagnetic results from the Yili Block (NW China) and their implications on the geodynamic evolution of Chinese Tianshan Belt

机译：伊犁地块（中国西北）的原始石炭纪和二叠纪古磁结果及其对中国天山带地球动力学演化的影响

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摘要

In order to better understand the tectonic role of the Yili Block on the Paleozoic evolution of the Chinese Tianshan Belt, we performed a primary paleomagnetic study on Carboniferous and Permian rocks from different areas in the Yili Block, NW of China. More than 320 sedimentary and volcanic samples were collected from 39 sites. Except for the Ordovician samples showing a weak and unstable magnetic remanence, the majority of this collection presents characteristic remanent magnetization carried by magnetite and hematite. In the study area, though positive fold test has been observed on the Early Carboniferous rocks, a general re-magnetization of these rocks has been identified and attributed to the Late Carboniferous magmatism. Moreover, all Early and Late Carboniferous samples from the interior of the Yili Block yield stable and coherent magnetic directions with exhaustively reverse magnetic polarity. The Late Carboniferous (C-2) is considered as the magnetic remanence age since these rocks are covered or intruded by synchronous magmatic rocks of the Yili arc, which lasted until to similar to 310 Ma. The C-2 paleomagnetic pole is therefore calculated at 68.6 degrees N, 290.6 degrees E with A(95) = 6.4 degrees and n = 5. The Late Carboniferous rocks located close to a deformation zone present a consistent magnetic inclination but significant different declination with respect to other areas and are suspected to have probably experienced a local rotation. Although no fold test can be performed due to the monoclinal bedding, stable magnetic components are isolated from Late Permian (P-2 red beds in the interior of the Yili Block with also a solo reverse magnetic polarity, the P2 paleomagnetic pole of the Yili Block has been, therefore, calculated from the characteristic remanent magnetization: 79.7 degrees N, 172.0 degrees E with A(95) = 11.3 degrees and n= 5. Keeping important uncertainties in mind, comparisons of the C-2 and P-2 paleomagnetic poles of the Yili Block with available coeval poles of Junggar, Tarim and Siberia indicate (1) no significant relative motion between the Yili and Junggar blocks since the Late Carboniferous, (2) no significant or weak latitudinal relative motion occurred since the Late Carboniferous among these blocks, but (3) the 46.2 degrees +/- 15. 1 degrees and the 3 1.6 degrees +/- 15. 1 degrees counterclockwise rotations of the Yili-Junggar blocks with respect to Tarim and Siberia took place during C-2 to P-2. These rotations are accommodated by the Permian dextral strike-slip faults along the northern and southern sides of Tianshan Belt and sinistral strike-slip faulting along the Erqishi Fault of Allay Belt, resulting in about 1000 kin and 600 kin lateral displacements in the Tianshan and Altay belts, respectively. (c) 2007 Published by Elsevier B.V.
机译：为了更好地了解伊犁地块对中国天山带古生代演化的构造作用，我们对中国西北伊犁地块不同地区的石炭纪和二叠纪岩石进行了古地磁研究。从39个地点收集了320多个沉积和火山样品。除了奥陶纪样品显示出弱的和不稳定的剩磁，该集合的大多数都表现出磁铁矿和赤铁矿携带的特征性剩磁。在研究区，尽管已在早期石炭纪岩石上观察到正褶皱试验，但已确定这些岩石普遍重新磁化，并归因于晚期石炭纪岩浆作用。此外，来自伊犁地块内部的所有早石炭世和晚石炭世样品都产生了稳定且相干的磁方向，并具有完全相反的磁极性。晚石炭纪（C-2）被认为是剩磁时代，因为这些岩石被伊犁弧的同步岩浆岩覆盖或侵入，一直持续到类似于310 Ma。因此，计算得出的C-2古地磁极在北纬68.6度，东经290.6度，A（95）= 6.4度和n = 5的情况下。位于变形区附近的晚石炭纪岩石呈现出一致的磁倾角，但​​磁偏角与尊重其他地区，并怀疑可能经历了本地轮换。尽管由于单斜层床无法进行褶皱测试，但已从晚二叠世（伊犁地块内部的P-2红层中分离出了稳定的磁性成分，并具有单独的反磁极性，伊犁地块的P2古地磁极）因此，根据剩余的磁化强度计算得出：N为79.7度，E为172.0度，A（95）= 11.3度，n =5。牢记重要的不确定性，C-2和P-2古磁极的比较带有准co尔，准gar尔，塔里木和西伯利亚等世代极的伊犁地块的特征表明（1）自石炭纪晚期以来伊犁和准gar尔块之间没有显着的相对运动，（2）自这些石炭纪晚期以来，没有发生过明显的或较弱的纬向相对运动（3）伊利准gar尔块相对于塔里木和西伯利亚的逆时针旋转是46.2度+/- 15. 1度和3 1.6度+/- 15度是在C-2至P期间发生的-2。这些旋转被天山带南北两侧的二叠系右旋走滑断裂和阿拉伊带的二七十断裂沿左旋走滑断裂所调节，导致天山和阿尔泰发生了约1000 kin和600 kin横向位移。皮带。 （c）2007年由Elsevier B.V.

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