An approach for estimating the magnetization direction of magnetic anomalies

Li, Jinpeng; Zhang, Yingtang; Yin, Gang; Fan, Hongbo; Li, Zhining

doi:10.1016/j.jappgeo.2016.12.009

Cited by 26 publications

(18 citation statements)

References 12 publications

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“…The NSS (Beiki et al, ; Clark, ; Guo et al, ; Pilkington & Beiki, ; Zhou et al, ) was shown to be a superior transformation, showing less sensitivity to the magnetization direction than the magnitude magnetic anomaly or the analytic signal. J. Li et al () proposed to estimate the magnetization direction, based on their correlations (the NSS‐RTP method), as expressed by

R = ℜ ((),, μ, T_{rtp}),

where μ is the NSS of the magnetic anomaly. Similar to equation , the magnetization direction corresponding to the maximum correlation is considered as the appropriate direction.…”

Section: Methodsmentioning

confidence: 99%

“…J. Li et al (2017) estimated the magnetization direction of magnetic anomalies through correlation of normalized source strength (NSS) anomalies with the RTP field. Four of these methods will be tested in the current study and are described in more detail in the following section.…”

Section: 1029/2017jb015364mentioning

confidence: 99%

“…J. Li et al (2017) proposed to estimate the magnetization direction, based on their correlations (the NSS-RTP method), as expressed by…”

Section: Estimation Of Total Magnetization Directionmentioning

confidence: 99%

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Extracting Induced and Remanent Magnetizations From Magnetic Data Modeling

Liu

Fedi

et al. 2018

JGR Solid Earth

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To investigate the crustal magnetic structure, it is important to assess the susceptibility and remanence properties of rocks and ores. In this paper, we propose a method to extract the contributions of induced and remanent magnetization from modeling of magnetic anomalies. We first estimate the direction of the total magnetization vector by studying the reduced‐to‐pole anomaly and its correlation with different magnitude magnetic transforms. Then we invert the magnetic data to obtain the volumetric distribution of the magnetization intensity. As the third step, based on a priori information about the Koenigsberger ratio derived from petrophysical measurements, we extract the distributions in the source volume of the induced and remanent magnetization intensities, based on a generalized relationship involving the total and remanent magnetizations, and the true susceptibility. In this way, we are able to produce separate maps of the anomaly fields attributed to the physical magnetic source parameters: remanent and induced magnetization. After validating the method with synthetic data, we analyze the data relative to the Mesozoic and Cenozoic igneous rocks in Yeshan region, eastern China. The analysis of the separated magnetization components reveals that the intrusion of dioritic and basaltic rocks occurred at different geological periods, and the basaltic rocks were magnetized by a reversed geomagnetic field. The uncertainty analysis shows that a larger Koenigsberger ratio is beneficial to extract more reliable remanence and susceptibility information.

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R = ℜ ((),, μ, T_{rtp}),

where μ is the NSS of the magnetic anomaly. Similar to equation , the magnetization direction corresponding to the maximum correlation is considered as the appropriate direction.…”

Section: Methodsmentioning

confidence: 99%

Section: 1029/2017jb015364mentioning

confidence: 99%

See 1 more Smart Citation

Extracting Induced and Remanent Magnetizations From Magnetic Data Modeling

Liu

Fedi

et al. 2018

JGR Solid Earth

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show abstract

“…One of these transformations is related to the reduced-to-pole (RTP) anomaly, which is sensitive to the assumed magnetization directions; the other transform is related to some magnetic quantities that are weakly sensitive to the directions of the source magnetization, such as total gradient (Nabighian, 1972;Roest et al, 1992), amplitude data T a (Stavrev and Gerovska, 2000), and normalized source strength (NSS) (Wilson, 1985). Several combinations of these two types of anomalies have been published, e.g., the vertical derivative of the RTP anomaly (RTP z ) and the total gradient of the RTP anomaly (RTP xyz ) (Dannemiller and Li, 2006), the RTP anomaly and T a (Gerovska et al, 2009), and the RTP anomaly and NSS (Rao et al, 2016;Li et al, 2017). Considering that the two types of anomalies should have the same decay rates with the distance to the source (Dannemiller and , RTP z may be a better choice than RTP when combined with NSS.…”

Section: Introductionmentioning

confidence: 99%

Constrained 3D inversion of magnetic data with structural orientation and borehole lithology: A case study in the Macheng iron deposit, Hebei, China

2019

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We have developed a case study on the use of constrained inversion of magnetic data for recovering ore bodies quantitatively in the Macheng iron deposit, China. The inversion is constrained by the structural orientation and the borehole lithology in the presence of high magnetic susceptibility and strong remanent magnetization. Either the self-demagnetization effect caused by high susceptibility or strong remanent magnetization would lead to an unknown total magnetization direction. Here, we chose inversion of amplitude data that indicate low sensitivity to the direction of magnetization of the sources when constructing the underground model of effective susceptibility. To reduce the errors that arise when treating the total-field anomaly as the projection of an anomalous field vector in the direction of the geomagnetic reference field, we develop an equivalent source technique to calculate the amplitude data from the total-field anomaly. This equivalent source technique is based on the acquisition of the total-field anomaly, which uses the total-field intensity minus the magnitude of the reference field. We first design a synthetic model from a simplified real case to test the new approach, involving the amplitude data calculation and the constrained amplitude inversion. Then, we apply this approach to the real data. The results indicate that the structural orientation and borehole susceptibility bounds are compatible with each other and are able to improve the quality of the recovered model to obtain the distribution of ore bodies quantitatively and effectively.

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“…Gerovska et al inverted the magnetization direction by correlating RTP and the magnitude magnetic anomalies [18]. Li et al estimated the magnetization direction of magnetic anomalies through the correlation between normalized source strength and RTP [19]. The above magnetization direction estimation approaches are more amenable for simple and isolated anomalies because usually a unique magnetization direction is achieved.…”

Section: Introductionmentioning

confidence: 99%

Inversion and Interpretation of Magnetic Anomaly in the Presence of Significant Remanence and Self-Demagnetization Based on Magnetic Amplitude

Liu¹,

Hu²

2018

Geophysics

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Remanent magnetization and self-demagnetization effects of high-susceptibility body distort the intensity and direction of internal magnetization and hence complicate the inversion and interpretation of magnetic anomaly. The magnitude magnetic anomaly, which is weakly sensitive to the magnetization direction, provides an indirect way to investigate these complex anomalies. We study the sensitivity characteristics of 2D magnitude magnetic anomaly to magnetization direction and source shapes, implement the magnetization intensity inversion, and further estimate the magnetization direction by inverting for the total field data. The magnetic amplitude inversion is tested by the use of synthetic data, which are caused by prism models with strong remanent magnetization and high susceptibility. It is also applied to the field data of an iron-ore deposit in South Australia. The primary advantage of magnitude anomaly inversion is that the magnetization directions are not assumed to parallel the geomagnetic field. The magnetization intensity inversion and magnetization direction estimation make full use of the amplitude and phase information of magnetic anomalies. Magnetic amplitude inversion including other amplitude quantities such as normalized source strength and analytic signal offers an effective approach to investigate and interpret the magnetic anomalies affected by complicated remanence and self-demagnetization.

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An approach for estimating the magnetization direction of magnetic anomalies

Cited by 26 publications

References 12 publications

Extracting Induced and Remanent Magnetizations From Magnetic Data Modeling

Extracting Induced and Remanent Magnetizations From Magnetic Data Modeling

Constrained 3D inversion of magnetic data with structural orientation and borehole lithology: A case study in the Macheng iron deposit, Hebei, China

Inversion and Interpretation of Magnetic Anomaly in the Presence of Significant Remanence and Self-Demagnetization Based on Magnetic Amplitude

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