Reconnaissance on inclination shallowing effect of Lower Triassic red beds from North China Block by the anisotropy of remanence
-
摘要:
本文报道利用岩石剩磁组构对华北下三叠统红层进行磁倾角浅化效应的进一步识别与校正研究结果.首先，采用45°等温剩磁各向异性方法，即通过沿与样品原始水平面（即层面）呈45°夹角方向施加磁化场获得等温剩磁，并进行逐步热退磁，获得平行于层面和垂直于层面的等温剩磁分量随外加磁场和热退磁温度的变化趋势，计算获得浅化因子f=0.70.其次，应用高场等温剩磁各向异性方法，结合峰值为100 mT的交变退磁和120℃热退磁处理，分离获得碎屑赤铁矿对剩磁各向异性的贡献；由直接测量获得的单颗粒碎屑赤铁矿的各向异性度（a=1.35），计算获得f=0.59.该结果与前人对刘家沟组红层进行E/I法磁倾角浅化校正的结果（f=0.60）具有很好的一致性；表明华北下三叠统刘家沟组红层磁倾角浅化效应显著，其浅化因子为f=0.59；高场等温剩磁各向异性方法是红层磁倾角浅化校正的最有效方法.同时，如果有足够的独立样品数，且特征剩磁来自于单一剖面或有证据表明多条采样剖面之间未发生显著的相对运动，E/I法对红层磁倾角浅化因子的估计也是可信的.
-
关键词:
- 剩磁各向异性 /
- 高场等温剩磁各向异性 /
- 磁倾角浅化 /
- 红层 /
- 赤铁矿
Abstract:A magnetic anisotropy study was performed on red beds of Early Triassic Liujiagou Formation from the Qinshui Basin, North China Block (NCB). First, a magnetic field was applied at 45° to the cylinder axis in a plane and then the samples were subjected to successively thermal demagnetization up to about 680 ℃. Measurements of isothermal remanent magnetizations along specimen's axial and radial axes yielded an inclination shallowing (IF) factor of 0.70. Second, high-field isothermal remanent magnetization was used in conjunction with 100 mT alternating field and 120 ℃ thermal demagnetization to isolate the contribution of hematite to the remanence anisotropy, and we finally obtained an IF factor of 0.59 in the light of a direct measurement of remanence anisotropy of single hematite grain (a=1.35). The IF factor isolated from the anisotropy of high-field isothermal remanent magnetization (hf-AIR) is more consistent with that calculated previously from E/I (elongation/inclination) method (f=0.60). This further indicates that the Early Triassic red beds in the NCB suffered from a conspicuous IF with a factor of 0.59. Noting that the hf-AIR measurements is an effective method for identifying and correcting possible IF in red beds, the E/I method is also available to estimate the IF factor of red beds given that enough individual remanence directions are obtained from single sampling section/locality or from multiple sections/localities without significant relative motions within them.
-
-
图 1
山西安泽地区区域地质简图(修改自周庭红等，2018)，其中，1安泽剖面，2沁水剖面，3长子剖面
Figure 1.
Simplified regional geological map of the Anze area showing paleomagnetic sampling areas after Zhou et al. (2018). 1 Anze Section, 2 Qinshui Section, 3 Changzi Section
图 2
剩磁各向异性测量的九个方向(改自Bilardello, 2016)
Figure 2.
The 9-position orientation scheme of Girdler (1961) to measure anisotropy of remanence (modified from Bilardello, 2016)
图 3
(a) 刘家沟组红层代表性样品沿与岩层层面呈45°方向逐步递增外加磁场过程中，IRMX(平行于地层层面)和IRMZ(垂直于地层层面)对比图；(b) 外加磁场强度10~800 mT过程中IRMZ/IRMX对比图；(c) 热退磁过程中IRMZ/IRMX对比图
Figure 3.
(a) Plots of IRMX (parallel to bedding) and IRMZ (perpendicular to bedding) acquisitions produced by applying magnetic fields at 45° to bedding as function of increasing field. (b) The IRMZ/IRMX as a function of pulse magnetic field up to 800 mT; and (c) the IRMZ/IRMX as a function of thermal demagnetization up to 680 ℃. The slope (IRMZ/IRMX) of the least-squares-fit for data points between 300 and 800 mT and between 600 and 680 ℃ is used to estimate the magnetic anisotropy of hematite, respectively
表 1
刘家沟组红层样品45°AIR数据表
Table 1.
The shallowing factor of 45°AIR for the Liujiagou Formation
采点 IRMZ/IRMX
(300~800 mT获得)IRMZ/IRMX
(600~680 ℃获得)Site1 0.6339 0.7467 Site2 0.8221 0.8224 Site3 0.6048 0.6354 Site4 0.6151 0.6905 Site5 0.6510 0.6980 Site6 0.6162 0.6838 f 0.6572 0.7128 σ 0.0752 0.0588 注：f为浅化因子，σ为标准差. 
下载: 导出CSV
表 2
沁水盆地刘家沟组红层高场等温剩磁各向异性张量的特征值和特征向量数据表
Table 2.
Hf-AIR eigenvalues and eigenvectors of the unleached samples from the Liujiagou Formation, Qinshui Basin
Sample Kmin Dec Inc Kint Dec Inc Kmax Dec Inc %RMS L F 1-3 0.32088175 347.96 86.97 0.33222669 238.92 0.99 0.34689155 148.88 2.87 0.03 1.0441 1.0354 1-4 0.31622094 114.82 8.98 0.32214069 281.44 80.78 0.36163837 24.49 2.10 0.03 1.1226 1.0187 1-5 0.30762869 53.02 82.04 0.34308791 150.48 1.04 0.34928340 240.63 7.89 0.04 1.0181 1.1153 1-9 0.31086367 205.33 81.66 0.33687297 328.92 4.64 0.35226333 59.48 6.91 0.03 1.0457 1.0837 1-10 0.31664458 90.41 85.62 0.33711034 296.74 3.93 0.34624508 206.60 1.94 0.03 1.0271 1.0646 2-3 0.32431120 112.56 64.70 0.33376652 252.09 19.78 0.34192231 347.67 15.13 0.03 1.0244 1.0292 2-5 0.32132798 167.45 67.60 0.33396357 41.36 13.65 0.34470844 306.99 17.42 0.03 1.0322 1.0393 2-8 0.32315037 155.35 67.89 0.33547482 307.01 19.68 0.34137478 40.51 9.69 0.03 1.0176 1.0381 2-10 0.32135636 170.58 69.55 0.33256698 274.48 5.12 0.34607667 6.33 19.75 0.03 1.0406 1.0349 3-5 0.32028690 274.76 80.58 0.33538401 67.54 8.39 0.34432909 158.17 4.25 0.05 1.0267 1.0471 3-9 0.31979981 155.11 85.83 0.33708069 353.51 3.96 0.34311950 263.42 1.31 0.05 1.0179 1.0540 5-1 0.31155932 280.96 71.07 0.32122377 71.53 16.63 0.36721691 164.17 8.78 0.06 1.1432 1.0310 5-9 0.31376299 94.14 74.33 0.33704117 239.38 12.98 0.34919584 331.39 8.63 0.06 1.0361 1.0742 8-1 0.31760779 45.17 58.88 0.33538893 238.61 30.42 0.34700331 145.11 5.95 0.09 1.0346 1.0560 8-3 0.31655568 44.18 77.75 0.33679661 197.18 10.95 0.34664771 288.23 5.43 0.08 1.0292 1.0639 8-4 0.31213912 50.02 59.54 0.33991507 252.04 28.6 0.34794581 156.74 9.61 0.08 1.0236 1.0890 8-6 0.30675119 46.83 63.30 0.34302604 168.38 14.74 0.35022280 264.40 21.74 0.08 1.0210 1.1183 8-7 0.30744728 60.26 59.65 0.34344280 256.91 29.29 0.34910992 162.81 7.25 0.09 1.0165 1.1171 注：Kmin、Kint、Kmax分别是最小、中间、最大特征值；Dec、Inc分别是它们的偏角和倾角；% RMS是测量数据与二阶张量之间的均方根误差；L、F分别是磁线理和磁面理.
下载: 导出CSV
表 3
E/I法与剩磁各向异性法磁倾角校正数据表
Table 3.
Comparison of E/I and remanence anisotropy correction methods
Method f IChRM Icorr E/I 0.60 30.9° 44.0° 45°AIR 0.70 30.9° 40.5° hf-AIR 0.59 30.9° 45.4° 注：f为浅化因子，IChRM为特征剩磁磁倾角，Icorr为校正后的磁倾角.
下载: 导出CSV
-
Bilardello D, Kodama K P. 2009. Measuring remanence anisotropy of hematite in red beds: anisotropy of high-field isothermal remanence magnetization (hf-AIR). Geophysical Journal International, 178(3): 1260-1272. doi: 10.1111/j.1365-246X.2009.04231.x
Bilardello D. 2016. Magnetic anisotropy: theory, instrumentation, and techniques. Reference Module in Earth Systems and Environmental Sciences, Elsevier, doi: 10.1016/B978-0-12-409548-9.09516-6.
Cheng J, Wang X W, Wang X N. 2009. The thermal history of the Qinshui basin in Shanxi province. Geoscience (in Chinese), 23(6): 1093-1099. http://www.cqvip.com/QK/96868X/200906/32551006.html
Dekkers M J, Linssen J H. 1991. Grain-size separation of haematite in the < 5 μm range for rockmagnetic investigation. Geophysical Journal International, 104(2): 423-427. doi: 10.1111/j.1365-246X.1991.tb02522.x
Enkin R J, Yang Z Y, Chen Y, et al. 1992. Paleomagnetic constraints on the geodynamic history of the major blocks of China from the Permian to the present. Journal of Geophysical Research: Solid Earth, 97(B10): 13953-13989. doi: 10.1029/92JB00648
Gilder S, Chen Y, Sen S. 2001. Oligo-Miocene magnetostratigraphy and rock magnetism of the Xishuigou section, Subei (Gansu Province, western China) and implications for shallow inclinations in central Asia. Journal of Geophysical Research: Solid Earth, 106(B12): 30505-30521. doi: 10.1029/2001JB000325
Girdler R W. 1961. The measurement and computation of anisotropy of magnetic susceptibility of rocks. Geophysical Journal International, 5(1): 34-44. doi: 10.1111/j.1365-246X.1961.tb02927.x
Hodych J P, Buchan K L. 1994. Early Silurian palaeolatitude of the Springdale Group redbeds of central Newfoundland: a palaeomagnetic determination with a remanence anisotropy test for inclination error. Geophysical Journal International, 117(3): 640-652. doi: 10.1111/j.1365-246X.1994.tb02459.x
Huang B C, Zhou Y X, Zhu R X. 2008. Discussions on Phanerozoic evolution and formation of continental China, based on paleomagnetic studies. Earth Science Frontiers (in Chinese), 15(3): 348-359. http://www.researchgate.net/publication/284779212_Discussions_on_Phanerozoic_evolution_and_formation_of_continental_China_based_on_paleomagnetic_studies
Huang B C, Yan Y G, Piper J D A, et al. 2018. Paleomagnetic constraints on the paleogeography of the East Asian blocks during Late Paleozoic and Early Mesozoic times. Earth-Science Reviews, 186: 8-36. doi: 10.1016/j.earscirev.2018.02.004
Jackson M J, Banerjee S K, Marvin J A, et al. 1991. Detrital remanence, inclination errors, and anhysteretic remanence anisotropy: quantitative model and experimental results. Geophysical Journal International, 104(1): 95-103. doi: 10.1111/j.1365-246X.1991.tb02496.x
King R F. 1955. The remanent magnetism of artificially deposited sediments. Geophysical Journal International, 7(S3): 115-134.
Kodama K P. 2009. Simplification of the anisotropy-based inclination correction technique for magnetite-and haematite-bearing rocks: a case study for the Carboniferous Glenshaw and Mauch Chunk Formations, North America. Geophysical Journal International, 176(2): 467-477. doi: 10.1111/j.1365-246X.2008.04013.x
McCabe C, Jackson M, Ellwood B B. 1985. Magnetic anisotropy in the Trenton Limestone: Results of a new technique, anisotropy of anhysteretic susceptibility. Geophysical Research Letters, 12(6): 333-336. doi: 10.1029/GL012i006p00333
Néel L. 1953. Some new results on antiferromagnetism and ferromagnetism. Reviews of Modern Physics, 25(1): 58-63. doi: 10.1103/RevModPhys.25.58
Ren Q, Zhang S H, Wu H C, et al. 2016. Further paleomagnetic results from the ~155 Ma Tiaojishan Formation, Yanshan Belt, North China, and their implications for the tectonic evolution of the Mongol-Okhotsk suture. Gondwana Research, 35: 180-191. doi: 10.1016/j.gr.2015.05.002
Stamatakos J, Van der Voo R, van der Pluijm B, et al. 1994. Comment on: 'early Silurian palaeolatitude of the Springdale group redbeds of central Newfoundland: a palaeomagnetic determination with a remanence anisotropy test for inclination error' by J. P. Hodych and K. L. Buchan. Geophysical Journal of the Royal Astronomical Society, 119(3): 1009-1013. doi: 10.1111/j.1365-246X.1994.tb04034.x
Tan X D, Fang D J, Yuan Y R, et al. 1991. Paleomagnetic study on red beds, Liujiaogou Formation (TRL) from Taoyuan, Yaoqu, Jixian, Shanxi province. Acta Geophysica Sinica (in Chinese), 34(6): 736-743. http://en.cnki.com.cn/Article_en/CJFDTOTAL-DQWX199106007.htm
Tan X D, Kodama K P. 2002. Magnetic anisotropy and paleomagnetic inclination shallowing in red beds: evidence from the Mississippian Mauch Chunk Formation, Pennsylvania. Journal of Geophysical Research: Solid Earth, 107(B11): EPM 9-1-EPM 9-17. doi: 10.1029/2001JB001636
Tan X D, Kodama K P, Fang D J. 2002. Laboratory depositional and compaction-caused inclination errors carried by haematite and their implications in identifying inclination error of natural remanence in red beds. Geophysical Journal International, 151(2): 475-486. doi: 10.1046/j.1365-246X.2002.01794.x
Tan X D, Kodama K P, Chen H L, et al. 2003. Paleomagnetism and magnetic anisotropy of Cretaceous red beds from the Tarim basin, northwest China: Evidence for a rock magnetic cause of anomalously shallow paleomagnetic inclinations from central Asia. Journal of Geophysical Research: Solid Earth, 108(B2): 2107, doi:10.1029/2001JB001608.
Tarling D H, Hrouda H. 1993. The Magnetic Anisotropy of Rocks. London: Chapman & Hall, 217.
Tauxe L, Kent D V. 1984. Properties of a detrital remanence carried by haematite from study of modern river deposits and laboratory redeposition experiments. Geophysical Journal of the Royal Astronomical Society, 76(3): 543-561. doi: 10.1111/j.1365-246X.1984.tb01909.x
Tauxe L, Kent D V. 2004. A simplified statistical model for the geomagnetic field and the detection of shallow bias in paleomagnetic inclinations: was the ancient magnetic field dipolar?.//Channell J E T, Kent D V, Lowrie W, et al eds. Timescales of the Paleomagnetic Field. Washington: American Geophysical Union, 145: 101-115.
Tauxe L, Kodama K P, Kent D V. 2008. Testing corrections for paleomagnetic inclination error in sedimentary rocks: A comparative approach. Physics of the Earth and Planetary Interiors, 169(1-4): 152-165. doi: 10.1016/j.pepi.2008.05.006
Tauxe L, Shaar R, Jonestrask L, et al. 2016. PmagPy: software package for paleomagnetic data analysis and a bridge to the magnetics information consortium (MagIC) database. Geochemistry, Geophysics, Geosystems, 17(6): 2450-2463. doi: 10.1002/2016GC006307
Torsvik T H, Van Der Voo R, Preeden U, et al. 2012. Phanerozoic polar wander, palaeogeography and dynamics. Earth-Science Reviews, 114(3-4): 325-358. doi: 10.1016/j.earscirev.2012.06.007
Van der Voo R, van Hinsbergen D J J, Domeier M, et al. 2015. Latest Jurassic-earliest Cretaceous closure of the Mongol-Okhotsk Ocean: A paleomagnetic and seismological-tomographic analysis.//Anderson T H, Didenko A N, Johnson C L, et al eds. Late Jurassic Margin of Laurasia-A Record of Faulting Accommodating Plate Rotation. Geological Society of America Special Paper, 513: 589-606, doi: 10.1130/2015.2513(19).
Verosub K L. 1977. Depositional and postdepositional processes in the magnetization of sediments. Reviews of Geophysics, 15(2): 129-143. doi: 10.1029/RG015i002p00129
Wu L, Kravchinsky V A, Potter D P. 2017. Apparent polar wander paths of the major Chinese blocks since the Late Paleozoic: Toward restoring the amalgamation history of east Eurasia. Earth-Science Reviews, 171: 492-519. doi: 10.1016/j.earscirev.2017.06.016
Yang Z Y, Ma X H, Huang B C, et al. 1998. Apparent polar wander path and tectonic movement of the north China Block in Phanerozoic. Science in China Series D: Earth Sciences, 41(Supp. ): 51-65. doi: 10.1007/BF02984513
Zhang D H, Huang B C, Zhao J, et al. 2018. Permian paleogeography of the eastern CAOB: paleomagnetic constraints from volcanic rocks in central-eastern Inner Mongolia, NE China. Journal of Geophysical Research: Solid Earth, 123(4): 2559-2582. doi: 10.1002/2018JB015614
Zhao G C, Wang Y J, Huang B C, et al. 2018. Geological reconstructions of the East Asian blocks: From the breakup of Rodinia to the assembly of Pangea. Earth-Science Reviews, 186: 262-286. http://www.sciencedirect.com/science/article/pii/S0012825218305701
Zhao J, Dong Y P, Huang B C. 2020. Paleomagnetic constraints of the Lower Triassic strata in South Qinling Belt: Evidence for a discrete terrane between the North and South China blocks. Tectonics, 39(3): e2019TC005698, doi:10.1029/2019TC005698.
Zhao Q, Wang B, Zhang H D, et al. 2017. Inclination shallowing of the Early Cretaceous red beds in the Sichuan Basin. Chinese Journal of Geophysics (in Chinese), 60(5): 1825-1837, doi:10.6038/cjg20170518.
Zhao X X, Coe R S. 1987. Palaeomagnetic constraints on the collision and rotation of North and South China. Nature, 327(6118): 141-144. doi: 10.1038/327141a0
Zhou T H, Huang B C, Jia S F, et al. 2018. Paleomagnetic inclination shallowing in lower Triassic Liujiagou Formation from Qinshui Basin, North China block. Acta Scientiarum Naturalium Universitatis Pekinensis (in Chinese), 54(3): 521-534. http://en.cnki.com.cn/Article_en/CJFDTotal-BJDZ201803009.htm
承金, 汪新文, 王小牛. 2009. 山西沁水盆地热史演化特征. 现代地质, 23(6): 1093-1099. doi: 10.3969/j.issn.1000-8527.2009.06.013
黄宝春, 周烑秀, 朱日祥. 2008. 从古地磁研究看中国大陆形成与演化过程. 地学前缘, 15(3): 348-359. doi: 10.3321/j.issn:1005-2321.2008.03.031
谈晓冬, 方大钧, 袁友仁等. 1991. 山西吉县沃曲桃园下三叠统刘家沟组红层的古地磁研究. 地球物理学报, 34(6): 736-743. doi: 10.3321/j.issn:0001-5733.1991.06.008 http://www.geophy.cn//CN/abstract/abstract4582.shtml
杨振宇, 马醒华, 黄宝春等. 1998. 华北地块显生宙古地磁视极移曲线与地块运动. 中国科学(D辑), 28(增刊): 44-56. https://www.cnki.com.cn/Article/CJFDTOTAL-JDXK1998S1005.htm
赵千, 王彬, 张浩东等. 2017. 四川盆地早白垩世红层磁倾角偏低研究. 地球物理学报, 60(5): 1825-1837, doi:10.6038/cjg20170518. http://www.geophy.cn//CN/abstract/abstract13734.shtml
周庭红, 黄宝春, 贾舒斐等. 2018. 华北地块沁水盆地下三叠统刘家沟组古地磁倾角浅化研究. 北京大学学报(自然科学版), 54(3): 521-534. https://www.cnki.com.cn/Article/CJFDTOTAL-BJDZ201803009.htm
-
图(5)
表(3)
计量
- 文章访问数:
- PDF下载数:
- 施引文献: 0