원동 중석 스카른대에서의 관입암류와 스카른광물에 대한 U-Pb(SHRIMP) 및 K-Ar 연대

박창윤; 송윤구; 지세정; 강일모; 이기욱; 정동훈

한국광물학회 광물과 암석 원동 중석 스카른대에서의 관입암류와 스카른광물에 대한 U-Pb(SHRIMP) 및 K-Ar 연대

KCI 등재

U-Pb(SHRIMP) and K-Ar Age Dating of Intrusive Rocks and Skarn Minerals at the W-Skarn in Weondong Deposit

박창윤 ( Chang Yun Park ) , 송윤구 ( Yun Goo Song ) , 지세정 ( Se Jung Chi ) , 강일모 ( Ll Mo Kang ) , 이기욱 ( Kee Wook Yi ) , 정동훈 ( Dong Hoon Chung )

한국광물학회 2013.09

광물과 암석 26권 3호 161-174(14pages)

UCI I410-ECN-0102-2015-400-001965769

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초록

원동지역은 스카른형 다중금속 광상으로서, 최근에는 회중석을 포함하는 텅스텐 광체의 유망광구로 주목받고 있다. 본 연구는 관입암체와 스카른 광물에 대한 연대측정을 통하여 스카른 형성 시기에 대한 지질연대학적 정보를 제공하고자 한다. 원동 지역의 층서는 석탄기와 트라이아스기, 캠브리아기와 오르도비스기의 층으로 이루어져있다. SHRIMP U-Pb 연대측정으로 원동지역 일대에 분포하고 있는 관입암류인 석영반암(79.37 ± 0.94 Ma)과 장석반암암맥(50.64 ± 0.44 Ma)의 정치고결시기를 결정하였다. K-Ar 연대측정으로 거정질의 금운모(49.1 ± 1.1 Ma), 괴상의 금운모(49.2 ± 1.2 Ma), 스카른광물과 공생하는 금운모(49.9 ± 3.6 Ma), 그리고 열수변질작용의 산물인 일라이트(48.3 ± 1.1 Ma)의 생성시기를 밝혀내었다. 열수 변질된 석영반암에서의 SHRIMP U-Pb 연대는 59.7∼38.7 Ma까지 다양한 연대분포를 보이는데, 저어콘의 조직과 관련하여 메타믹티제이션(metamictization) 받은 저어콘 조직에서는 Pb 손실이 발생하여 연대 신뢰도가 떨어지는 반면, 용해-침전작용을 받은 부분의 연대 값은 동위원소 재평형 작용의 가능성이 있어 또다른 열수변질시기 혹은 화성활동시기에 대한 정보를 제공할 수 있다. 연대측정 결과와 광물 공생관계, 그리고 야외조사에서 확인된 석영반암 내 혹은 균열대에 발달해 있는 스카른용액 침투흔적으로 볼 때, 연구지역에서의 중석 스카른 광화시기는 약 50 Ma일 가능성이 높지만, 스카른 광체 선후관계 및 장석반암과 스카른 광체의 지질학적 연관관계에 대한 연구가 추가적으로 이루어져야 할 필요가 있다.

The geology of the weondong deposit area consists mainly of Cambro-Ordovician and Carboniferous-Triassic formations, and intruded quartz porphyry and dyke. The skarnmineralized zone in the weondong deposit is the most prospective region for the useful W-mineral deposits. To determine the skarn-mineralization age, U-Pb SHRIMP and K-Ar age dating methods were employed. The U-Pb zircon ages of quartz porphyry intrusion (WD-A) and feldspar porphyry dyke (WD-B) are 79.37 Ma and 50.64 Ma. The K-Ar ages of coarse-grained crystalline phlogopite (WD-1), massive phlogopite (WDR-1), phlogopite coexisted with skarn minerals (WD-M), and vein type illite (WD-2) were determined as 49.1 ± 1.1 Ma, 49.2 ± 1.2 Ma, 49.9 ± 3.6 Ma, and 48.3 ± 1.1 Ma, respectively. And the ages of the high uranium zircon of hydrothermally altered quartz porphyry (WD-C) range from 59.7 to 38.7 Ma, which dependson zircon’s textures affected by hydrothermal fluids. It is regarded as the effect of some hydrothermal events, which may precipitate and overgrow the high-U zircons, and happen the zircon`s metamictization and dissolution-reprecipitation reactions. Based on the K-Ar age datings for the skarn minerals and field evidences, we suggest that the timing of W-skarn mineralization in weondong deposit may be about 50 Ma. However, for the accurate timing of skarn mineralization in this area, the additional researches about the sequence of superposition at the skarn minerals and geological relationship between skarn deposits and dyke should be needed in the future.

키워드

원동광상

저어콘 U-Pb(SHRIMP) 연대측정

zircon U-Pb (SHRIMP) age dating

K-Ar age dating

high Uranium zircon

zircon metamictization texture

zircon dissolution-reprecipitation texture

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