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2014 Vol.30, Issue 5 Preview Page
Physical Properties Related to Metamorphic Grade of the Hornfels Exposed Around Mt. Palgong

팔공산 주변 혼펠스의 변성도에 따른 물리적 특성

Kuk-Jin Shin1
,
Je-Heon Oh2
,
Yong-Wook Jung2
,
Gyo-Won Kim3*
신 국진1
,
오 제헌2
,
정 용욱2
,
김 교원3*
1Department of Geology, Kyungpook National University
2Advanced Construction Materials Testing Center, Keimyung University
3Department of Geology, Kyungpook National University
1경북대학교 지질학과
2계명대학교 첨단건설재료실험센터
3경북대학교 지질학과
*교신저자. *Corresponding Author. 
31 May 2014. pp. 25-35
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Abstract

The sedimentary rocks exposed around Mt. Palgong were subjected to metamorphism due to a granitic magma intrusion at late Cretaceous, and they eventually metamorphosed to hornfels by the action of both hydrothermal solution and high temperature supplied from the magma. The hornfels zone around the granite body ranges from 2.0 to 3.5 km in width but the boundary between hornfels and sedimentary rocks is not obviously defined because the metamorphic grade gradually decreases with distance from the granite boundary. A series of laboratory tests on 350 core specimens made by 35 fresh rock blocks obtained from 5 selected locations around Mt. Palgong are performed to verify the variation of physical and mechanical properties related to metamorphic grade of the rock. Water content and absorption ratio of the hornfels linearly increase with distance to the granite boundary whereas dry unit weight, p-wave velocity, point load strength, and slake durability index linearly decrease with the distance. These results imply that the metamorphic grade of the hornfels also linearly decrease with the distance to granite boundary. Empirical equations for the variation of properties with the distance to granite boundary and relationship between a property and another one are deduced by regression analyses. And a criteria for classification of hornfels exposed in the study area based on the P-wave velocity and point load strength is proposed.

Keywords
Absorption ratio
Contact metamorphism
Hornfels
Metamorphic grade
Point load strength

팔공산 주변의 퇴적암은 백악기 후기 화강암질 마그마의 관입에 의해서 접촉변성암인 혼펠스로 변성되었다. 이 혼펠스는 팔공산 화강암체 주변 2.0∼3.5km 범위로 분포하고 있으며 퇴적암과 혼펠스의 경계는 명확하지 않다. 본 연구에서는 5개 선별된 지역의 35개 지점에서 채취한 신선한 암석시료에서 350개의 공시체를 성형하여 실내시험을 수행하였다. 시험결과 함수비와 흡수율은 화강암 경계부와 멀어질수록 증가하였지만, 단위중량, 초음파속도, 점하중 강도 및 슬레이크 내구성 지수는 감소하였다. 이는 화강암 경계부로부터 멀어질수록 혼펠스의 변성도가 낮아짐을 의미하는데, 거리에 따른 특성치의 변화 및 특성치와의 상관성을 회귀 분석하여 관계식을 제시하였다. 또 시험 결과 중 P파속도와 점하중강도를 바탕으로 혼펠스의 역학적 등급분류 기준을 제안하였다.

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Received : December 11th, 2013
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Revised  : March 24th, 2014
17
Accepted : March 31st, 2014
Information
  • Publisher :The Korean Geotechnical Society
  • Publisher(Ko) :한국지반공학회
  • Journal Title :Journal of the Korean Geotechnical Society
  • Journal Title(Ko) :한국지반공학회 논문집
  • Volume : 30
  • No :5
  • Pages :25-35
  • Received Date : 2013-12-11
  • Revised Date : 2014-03-24
  • Accepted Date : 2014-03-31
  • DOI :https://doi.org/10.7843/kgs.2014.30.5.25
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