Econ. Environ. Geol. 2003; 36(4): 305-312

Published online August 31, 2003

© THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY

Gravity Survey Around the Palgongsan Granitic Body and Its Vicinity

Jong-Sun Hwang1*, Kyung Duck Min1, Chul Choi1 and Sang Hoon Yu1

1Department of Earth System Sciences, Yonsei University, Seoul 120-749, Korea

Correspondence to :

Jong-Sun Hwang

hjs@gephy.ynsei.ac.kr

Received: July 5, 2003; Accepted: August 11, 2003

Abstract

This study was performed to delineate the subsurface geology, geologic structure, and distribution pattern of the Palgongsan granitic body, and to reveal the relationship between the Kyeongsang basin and Yongnam massif by gravity survey. The study area is located between the latitude of 35o45'-36o21'N and longitude of 128o15'-129o00'E. Total of 966 gravity data measured by Seoul National University, KIGAM(Korea Institute of Geology, Mining & Materials), Pusan National University and Yonsei University were used. The Bouguer gravity anomaly in the study area ranges from -12.88 to 26.01 mgal with a mean value of 11.27 mgal. A very low anomaly zone is located in the Yongnam massif in west of the study area. The anomaly value increases going from west to east. A low anomaly
distribution in Palgongsan granite and Yongnam massif is interpreted as the effect of their lower density than that of Kyeongsang Super Group. Power spectrum analysis is applied to evaluate the average depth of basement the Kyeongsang Basin and Conrad discontinuity from gravity anomaly. The average depths of density discontinuities are calculated 10.45 km and 4.9 km, and these are interpreted as Conrad discontinuity and depth of basement of the Kyeongsang Basin, respectively. The depth of Palgongsan granite is derived by means of 2-dimensional modeling and it decreases gradually toward the east. The gravity anomaly east of the study area decreases abruptly due to Shingryeong fault and Nogosan ring fault. Two deepest and sharp roots of Palgongsan granite are recognized by 2-
dimensional medeling of each profiles. The depths of those roots are 5.3 km on a profile AA' and 7 km on a profile BB' which is the maximum depth of Palgongsan granite. Small granitic bodies are also seen to be intruded around the Palgongsan granite. The root of Palgongsan granite is shown by 3-dimensional analysis based on the interpolation of 2-dimensional modeling along each profiles to exist in the southwest vicinity of Palgongsan granite. The total volume of Palgongsan granite is approximately 31.211 km3.

Keywords gravity survey, Palgongsan granite, power spectrum analysis, 2-dimensional modeling, 3-dimensional analysis

Article

Econ. Environ. Geol. 2003; 36(4): 305-312

Published online August 31, 2003

Copyright © THE KOREAN SOCIETY OF ECONOMIC AND ENVIRONMENTAL GEOLOGY.

Gravity Survey Around the Palgongsan Granitic Body and Its Vicinity

Jong-Sun Hwang1*, Kyung Duck Min1, Chul Choi1 and Sang Hoon Yu1

1Department of Earth System Sciences, Yonsei University, Seoul 120-749, Korea

Correspondence to:

Jong-Sun Hwang

hjs@gephy.ynsei.ac.kr

Received: July 5, 2003; Accepted: August 11, 2003

Abstract

This study was performed to delineate the subsurface geology, geologic structure, and distribution pattern of the Palgongsan granitic body, and to reveal the relationship between the Kyeongsang basin and Yongnam massif by gravity survey. The study area is located between the latitude of 35o45'-36o21'N and longitude of 128o15'-129o00'E. Total of 966 gravity data measured by Seoul National University, KIGAM(Korea Institute of Geology, Mining & Materials), Pusan National University and Yonsei University were used. The Bouguer gravity anomaly in the study area ranges from -12.88 to 26.01 mgal with a mean value of 11.27 mgal. A very low anomaly zone is located in the Yongnam massif in west of the study area. The anomaly value increases going from west to east. A low anomaly
distribution in Palgongsan granite and Yongnam massif is interpreted as the effect of their lower density than that of Kyeongsang Super Group. Power spectrum analysis is applied to evaluate the average depth of basement the Kyeongsang Basin and Conrad discontinuity from gravity anomaly. The average depths of density discontinuities are calculated 10.45 km and 4.9 km, and these are interpreted as Conrad discontinuity and depth of basement of the Kyeongsang Basin, respectively. The depth of Palgongsan granite is derived by means of 2-dimensional modeling and it decreases gradually toward the east. The gravity anomaly east of the study area decreases abruptly due to Shingryeong fault and Nogosan ring fault. Two deepest and sharp roots of Palgongsan granite are recognized by 2-
dimensional medeling of each profiles. The depths of those roots are 5.3 km on a profile AA' and 7 km on a profile BB' which is the maximum depth of Palgongsan granite. Small granitic bodies are also seen to be intruded around the Palgongsan granite. The root of Palgongsan granite is shown by 3-dimensional analysis based on the interpolation of 2-dimensional modeling along each profiles to exist in the southwest vicinity of Palgongsan granite. The total volume of Palgongsan granite is approximately 31.211 km3.

Keywords gravity survey, Palgongsan granite, power spectrum analysis, 2-dimensional modeling, 3-dimensional analysis

    KSEEG
    Jun 30, 2024 Vol.57 No.3, pp. 281~352

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