Reply [to “>Comment on ‘Can remanent magnetization in the deep crust contribute to long wavelength magnetic anomalies?’”]

1989 ◽  
Vol 16 (6) ◽  
pp. 599-600 ◽  
Author(s):  
Peter N. Shive
Keyword(s):  
Remanent Magnetization ◽  
Magnetic Anomalies ◽  
Long Wavelength ◽  
Deep Crust

Interpretation of Long Wavelength Magnetic Anomalies

1981 ◽  
pp. 231-255 ◽  
Author(s):  
Paolo Gasparini ◽  
Marta S. M. Mantovani ◽  
Wladimir Shukowsky
Keyword(s):  
Magnetic Anomalies ◽  
Long Wavelength

The IDQ curve: A tool for evaluating the direction of remanent magnetization from magnetic anomalies

Geophysics ◽  
2020 ◽  
Vol 85 (5) ◽  
pp. J85-J98
Author(s):  
Shuang Liu ◽  
Xiangyun Hu ◽  
Dalian Zhang ◽  
Bangshun Wei ◽  
Meixia Geng ◽  
...  
Keyword(s):  
Remanent Magnetization ◽  
Field Data ◽  
Eastern China ◽  
Synthetic Data ◽  
Magnetic Anomalies ◽  
Natural Remanent Magnetization ◽  
Magma Intrusion ◽  
Magnetization Direction ◽  
Ore Bodies ◽  
Using Data

Natural remanent magnetization acts as a record of the previous orientations of the earth’s magnetic field, and it is an important feature when studying geologic phenomena. The so-called IDQ curve is used to describe the relationship between the inclination ( I) and declination ( D) of remanent magnetization and the Köenigsberger ratio ( Q). Here, we construct the IDQ curve using data on ground and airborne magnetic anomalies. The curve is devised using modified approaches for estimating the total magnetization direction, e.g., identifying the maximal position of minimal reduced-to-the-pole fields or identifying correlations between total and vertical reduced-to-the-pole field gradients. The method is tested using synthetic data, and the results indicate that the IDQ curve can provide valuable information on the remanent magnetization direction based on available data on the Köenigsberger ratio. Then, the method is used to interpret field data from the Yeshan region in eastern China, where ground anomalies have been produced by igneous rocks, including diorite and basalt, which occur along with magnetite and hematite ore bodies. The IDQ curves for 24 subanomalies are constructed, and these curves indicate two main distribution clusters of remanent magnetization directions corresponding to different structural units of magma intrusion and help identify the lithologies of the magnetic sources in areas covered by Quaternary sediments. The estimated remanent magnetization directions for Cenozoic basalt are consistent with measurements made in paleomagnetism studies. The synthetic and field data indicate that the IDQ curve can be used to efficiently estimate the remanent magnetization direction from a magnetic anomaly, which could help with our understanding of geologic processes in an area.

The distribution of surface magnetization in the English River and Kenora subprovinces of the Archean shield in Manitoba and Ontario

1979 ◽  
Vol 16 (9) ◽  
pp. 1764-1777 ◽  
Author(s):  
D. H. Hall ◽  
R. L. Coles ◽  
J. M. Hall
Keyword(s):  
High Surface ◽  
Magnetic Anomalies ◽  
Ambient Temperatures ◽  
Long Wavelength ◽  
Red Lake ◽  
Surface Magnetization ◽  
The Vertical Distribution ◽  
Granite Suite ◽  
Opaque Minerals ◽  
Distribution Of Magnetization

Surface magnetizations (induced and remanent) have been measured from almost 600 oriented cores collected over an area of 50 000 km2 covering portions of the Kenora, English River, and Red Lake subprovinces of the western Archean shield, between latitudes 49 and 51 °and longitudes 93 and 96°. These surface magnetizations reflect major geological provinces in the area, and throw light on the vertical distribution of magnetization and on the associated long wavelength magnetic anomalies. A major belt of high surface magnetization lies over the granodiorite–granite suite in the southern part of the English River subprovince and a major belt of low magnetization over the metasedimentary gneiss belt in the northern part of the subprovince. Remanent magnetization is prevalent, but is very unstable, apparently due to viscous remanence, and subparallel to the present-day geomagnetic field. This fact is of importance because rocks of this type, if deeply buried and at ambient temperatures above surface values, may lead to rather large intensities of magnetization. The magnetization is almost entirely due to magnetite, and titanomagnetite is only rarely encountered. The prevalent opaque minerals are magnetite, ilmenite, pyrite, pyrrhotite, and hematite.

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