摘要
采用主成分分析方法、线性谱法和LINFIND方法，分离了塔里木盆地中生代岩石的多磁成分，并采用岩石磁学和褶皱检验等方法研究了剩磁稳定性．对于塔里木盆地三叠系、侏罗系的岩石其携磁矿物以磁铁矿为主，具有两组次生磁性成分和一组原生剩磁成分；原生剩磁成分的解阻温度为550℃，而两组次生成分的解阻温度分别为175－250℃和300一375℃，可能为生物剩磁和次生氧化形成的剩磁．白垩纪岩石的携磁矿物以亦铁矿为主，同样具有两组次生剩磁和一组原生剩磁；两组次生剩磁分别为现代地磁场的粘滞剩磁和岩石变形过程中形成的构造剩磁．塔里木盆地中生代早期极移不明显，处于一个相对平静时期；侏罗纪至白垩纪盆地则主要表现有一定规模的南移，伴有顺时针旋转运动。盆地白垩纪的古纬度与现在纬度相比，仍存在17°－20°左右的纬度等，这一纬度差是通过白垩纪以后塔里木板块的北向漂移和板块北部造山带的压缩及边界的大型走滑作用来缩小；另外，压实作用也可能是由垩纪磁倾角变低的一个原因。
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.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
1997年第1期47-55,共9页
Chinese Journal of Geophysics
基金
国家自然科学基金
国家科技攻关项目资助
关键词
塔里木盆地
中生代
古地磁
极移曲线
构造意义
Tarim basin, Paleomagnetic study in Mesozoic, Analysis ofremanence, APW path
