The results of a combined paleomagnetic, rock magnetic and petrographic study of Middle and Lower Triassic from Qinshui Basin, North China Block are reported. The characteristic remanent magnetization from the Ermayin...The results of a combined paleomagnetic, rock magnetic and petrographic study of Middle and Lower Triassic from Qinshui Basin, North China Block are reported. The characteristic remanent magnetization from the Ermaying Formation (Middle Triassic) is carried by both magnetite and hematite. In stratigraphic coordinates, the direction (Dec = -28°, Inc. =44°, N=10, α95=4°) passes the (incremental) fold test and fabric test. The corresponding paleopole is 64°N, 6° E. The remanent magnetization of samples from the bottom of the Liujiagou Formation (Lower Triassic) is carried mainly by magnetite, which shows an inverse magnetic fabric and an abnormal magnetization direction. This is probably caused by a bedding-parallel compression. A comparison of Triassic paleopoles from this locality with others in North China reveals a significant tectonic rotation of the eastern North China Block and Korean Peninsula with respect to the western North China Block. The rotation probably occurred during the Indosinian Movement.展开更多
Anisotropy of magnetic susceptibility (AMS) studies were carried out on a precisely dated (2216.0 ± 0.9 Ma),450 km long NeS striking dyke in the Dharwar Craton,to determine the magma flow direction along the dyke...Anisotropy of magnetic susceptibility (AMS) studies were carried out on a precisely dated (2216.0 ± 0.9 Ma),450 km long NeS striking dyke in the Dharwar Craton,to determine the magma flow direction along the dyke length.In order to use the imbrication of the magnetic foliation,forty eight samples were collected from 13 locations along the length of the dyke.Magnetogranulometry studies show that AMS fabric is dominated by medium grained interstitial Ti-poor multidomain magnetite.The corrected anisotropy degree (Pj) of the samples was found to be low to moderate,between 1.007 and 1.072,which indicates primary magnetic fabric.The magnetic ellipsoid is either triaxial,prolate or oblate and clearly defines normal,intermediate and inverse magnetic fabrics related to magma flow during the dyke emplacement.The maximum susceptibility axes (Kmax) of the AMS tensor of the dyke is predominantly inclined at low angles (<30°),with no systematic variation in depth along the NeS profile,indicating sub-horizontal flow even at mid crustal levels which could probably be governed by location of the focal region of the magma source (mantle plume?),flow dynamics together with the compressive stresses exerted by the overlying crust.展开更多
Anisotropy of magnetic susceptibility is used in the present study to reveal thedepositional fabric on the original (windblown) loess and secondary (redeposited) loess. The two kinds of sediments mentioned above can b...Anisotropy of magnetic susceptibility is used in the present study to reveal thedepositional fabric on the original (windblown) loess and secondary (redeposited) loess. The two kinds of sediments mentioned above can be distinguished in terms of their susceptibility anisotropy, e.g. anisotropy degree, magnetic foliation and lineation parameters. On this basis the magnetic fabric of the Pliocene red soil underlaying the loess is studied, and compared with the results of a typical residue-deposited red clay in South China. Considering its geological features, the red soil in Xifeng is regarded probably as aeolian in origin also.展开更多
基金Project supported by the National Natural Science Foundation of China.
文摘The results of a combined paleomagnetic, rock magnetic and petrographic study of Middle and Lower Triassic from Qinshui Basin, North China Block are reported. The characteristic remanent magnetization from the Ermaying Formation (Middle Triassic) is carried by both magnetite and hematite. In stratigraphic coordinates, the direction (Dec = -28°, Inc. =44°, N=10, α95=4°) passes the (incremental) fold test and fabric test. The corresponding paleopole is 64°N, 6° E. The remanent magnetization of samples from the bottom of the Liujiagou Formation (Lower Triassic) is carried mainly by magnetite, which shows an inverse magnetic fabric and an abnormal magnetization direction. This is probably caused by a bedding-parallel compression. A comparison of Triassic paleopoles from this locality with others in North China reveals a significant tectonic rotation of the eastern North China Block and Korean Peninsula with respect to the western North China Block. The rotation probably occurred during the Indosinian Movement.
基金supported by the NGRI MLP 6513INDEX project funds
文摘Anisotropy of magnetic susceptibility (AMS) studies were carried out on a precisely dated (2216.0 ± 0.9 Ma),450 km long NeS striking dyke in the Dharwar Craton,to determine the magma flow direction along the dyke length.In order to use the imbrication of the magnetic foliation,forty eight samples were collected from 13 locations along the length of the dyke.Magnetogranulometry studies show that AMS fabric is dominated by medium grained interstitial Ti-poor multidomain magnetite.The corrected anisotropy degree (Pj) of the samples was found to be low to moderate,between 1.007 and 1.072,which indicates primary magnetic fabric.The magnetic ellipsoid is either triaxial,prolate or oblate and clearly defines normal,intermediate and inverse magnetic fabrics related to magma flow during the dyke emplacement.The maximum susceptibility axes (Kmax) of the AMS tensor of the dyke is predominantly inclined at low angles (<30°),with no systematic variation in depth along the NeS profile,indicating sub-horizontal flow even at mid crustal levels which could probably be governed by location of the focal region of the magma source (mantle plume?),flow dynamics together with the compressive stresses exerted by the overlying crust.
基金Project supported by the National Natural Science Foundation of China.
文摘Anisotropy of magnetic susceptibility is used in the present study to reveal thedepositional fabric on the original (windblown) loess and secondary (redeposited) loess. The two kinds of sediments mentioned above can be distinguished in terms of their susceptibility anisotropy, e.g. anisotropy degree, magnetic foliation and lineation parameters. On this basis the magnetic fabric of the Pliocene red soil underlaying the loess is studied, and compared with the results of a typical residue-deposited red clay in South China. Considering its geological features, the red soil in Xifeng is regarded probably as aeolian in origin also.
