PALEOMAGNETIC STUDY AND ITS TECTONIC SIGNIFICANCE FOR TARIM BASIN IN MESOZOIC
PALEOMAGNETIC STUDY AND ITS TECTONIC SIGNIFICANCE FOR TARIM BASIN IN MESOZOIC
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发表时间：
1997
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通讯作者：
D. Fang;X. Tan
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作者：
D. Fang;X. Tan
在塔里木盆地中生代系统古地磁研究的基础上，采用主成分分析、LSA和LINEFIND等分离技术对塔里木盆地中生代岩石进行多组分分离。通过等温剩磁和与退磁温度相关的磁化率的测量，揭示了岩石中的磁性矿物。进行了包括折叠试验、反盐试验等在内的田间试验，以确定分离组分的稳定性和来源。对于三叠系和侏罗系样品，主要的磁性载体是磁铁矿，天然剩磁由三个组分组成，这些组分是从逐步退磁的载体中分离出来的。与生化效应和氧化有关的两种叠印组分的解封温度分别为175200℃和300375℃，原始剩磁的解封温度为550℃，并通过了折叠试验和反转试验。白垩纪样品的主要磁性载体为赤铁矿，天然剩磁由三组分组成。复印成分为粘性剩磁和结构剩磁，原始剩磁通过反转试验。在中生代早期，塔里木盆地的APW路径漂移不明显，代表了一段构造平静时期。从侏罗纪到白垩纪，塔里木盆地经历了10°的南移，并伴有少量顺时针旋转。白垩纪与现今的纬度相差约17-20°，塔里木盆地北部碰撞造山带的挤压和塔里木盆地边界的走滑断层的剪切使这一纬度差距缩小。
On the basis of systematic paleomagnetic study for Tarim basin in Mesozoic, theauthors employ the separating techniques such as PCA, LSA and LINEFIND to isolatethe multi-components of Mesozoic rocks. Magnetic minerals in rock were revealedthrough measurements of isothermal remanent magnetization and magneticsusceptibility related to demagnetizing temperature. Field tests including fold test, reversaltest and so on were carried to determine stabilities and origins of isolatedcomponents. For Triassic and Jurassic specimens the dominant magnetic carrier wasmagnetite and natural remanence was composed of three components isolated fromstepwise demagnetized vectors. The unblocking temperature for the two overprint components which related to biochemical effect and oxidation is about 175-200℃ and300-375℃; the unblocking temperature for the primary remanence is 550℃ and theremanence passed the fold test and reversal test. For Cretaceous specimens the dominantmagnetic carrier was haemite and natural remanence was composed of three componentstoo. The overprint components were viscosity remanence and structural remanence, andthe primary remanence passed reversal test. In the early Mesozoic, APW path for Tarimbasin drifted unobviously, which represented a period of tectonic quiet. FromJurassic to Cretaceous Tarim basin had undergone 10° southward displacement accompanied by a little clockwise rotation. Comparing the latitude between Cretaceousand present, there was a difference about 17-20°, this difference of latitude had beenminimized by the compression in collision orogenic zone located to the north ofTarim basin and by the shearing of strike-slip fault in the boundary of Tarim basin.