Rock magnetism and geophysical interpretation of the Black Hill Norite South Australia

Shanti Rajagopalan; Phillip Schmidt; David Clark

doi:10.1071/EG993209

Rock magnetism and geophysical interpretation of the Black Hill Norite South Australia

Shanti Rajagopalan, Phillip Schmidt, David Clark

Research output: Contribution to journal › Article › peer-review

13 Citations (Scopus)

Abstract

The Black Hill Norite is a mafic intrusion which formed around 487 Ma ago. It intruded sediments of the Kanmantoo Group and Adelaide Supergroup which were deformed and metamorphosed during the Delamerian Orogeny. The Norite gives rise to an unusual magnetic anomaly, a major negative to the north-east with a similar positive to the south-west, which is atypical of the present magnetic inclination of ?65° and declination of +8°. Measurements of natural remanent magnetization on oriented samples revealed a high magnetic susceptibility (2000 to 5000*10⁻⁵ SI units) and a very stable remanent magnetization with the following properties: declination 221.2°, inclination 7.6° (α₉₅ = 4°) and a Koenigsberger ratio of approximately 2. The Black Hill Norite is inferred to have formed at equatorial latitudes. Surface measurements are probably representative of the rock at depth since forward modelling incorporating remanent magnetization gave a good match between observed and modelled magnetic anomalies.

Original language	English
Pages (from-to)	209-212
Number of pages	4
Journal	Exploration Geophysics
Volume	24
Issue number	2
DOIs	https://doi.org/10.1071/EG993209
Publication status	Published - 1993

Keywords

Black Hill Norite
Delamerian Orogeny
Magnetic anomaly
Natural remanent magnetization

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10.1071/EG993209

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abstract = "The Black Hill Norite is a mafic intrusion which formed around 487 Ma ago. It intruded sediments of the Kanmantoo Group and Adelaide Supergroup which were deformed and metamorphosed during the Delamerian Orogeny. The Norite gives rise to an unusual magnetic anomaly, a major negative to the north-east with a similar positive to the south-west, which is atypical of the present magnetic inclination of ?65° and declination of +8°. Measurements of natural remanent magnetization on oriented samples revealed a high magnetic susceptibility (2000 to 5000*10−5 SI units) and a very stable remanent magnetization with the following properties: declination 221.2°, inclination 7.6° (α95 = 4°) and a Koenigsberger ratio of approximately 2. The Black Hill Norite is inferred to have formed at equatorial latitudes. Surface measurements are probably representative of the rock at depth since forward modelling incorporating remanent magnetization gave a good match between observed and modelled magnetic anomalies.",

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AU - Schmidt, Phillip

AU - Clark, David

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N2 - The Black Hill Norite is a mafic intrusion which formed around 487 Ma ago. It intruded sediments of the Kanmantoo Group and Adelaide Supergroup which were deformed and metamorphosed during the Delamerian Orogeny. The Norite gives rise to an unusual magnetic anomaly, a major negative to the north-east with a similar positive to the south-west, which is atypical of the present magnetic inclination of ?65° and declination of +8°. Measurements of natural remanent magnetization on oriented samples revealed a high magnetic susceptibility (2000 to 5000*10−5 SI units) and a very stable remanent magnetization with the following properties: declination 221.2°, inclination 7.6° (α95 = 4°) and a Koenigsberger ratio of approximately 2. The Black Hill Norite is inferred to have formed at equatorial latitudes. Surface measurements are probably representative of the rock at depth since forward modelling incorporating remanent magnetization gave a good match between observed and modelled magnetic anomalies.

AB - The Black Hill Norite is a mafic intrusion which formed around 487 Ma ago. It intruded sediments of the Kanmantoo Group and Adelaide Supergroup which were deformed and metamorphosed during the Delamerian Orogeny. The Norite gives rise to an unusual magnetic anomaly, a major negative to the north-east with a similar positive to the south-west, which is atypical of the present magnetic inclination of ?65° and declination of +8°. Measurements of natural remanent magnetization on oriented samples revealed a high magnetic susceptibility (2000 to 5000*10−5 SI units) and a very stable remanent magnetization with the following properties: declination 221.2°, inclination 7.6° (α95 = 4°) and a Koenigsberger ratio of approximately 2. The Black Hill Norite is inferred to have formed at equatorial latitudes. Surface measurements are probably representative of the rock at depth since forward modelling incorporating remanent magnetization gave a good match between observed and modelled magnetic anomalies.

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Rock magnetism and geophysical interpretation of the Black Hill Norite South Australia

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Keywords

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