ip03-02-09.hwpApplication of short-wave infrared spectroscopy to define alteration zones associated with the Mugeug Au-Ag deposit, Korea
Pak Sang Joon, Choi Seon Gyu, Lee Dong Eun
Abstract : Short-wave infrared reflectance spectra obtained from a Portable Infrared Mineral Analyser (PIMA) have been used to define alteration zones at the Mugeug gold-silver mineralized area. Hydrothermal alteration in this area is characterized as following ; vein → phyllic zone → subphyllic zone → propylitic zone → subpropylitic zone. The spectroscopic study was worked by key minerals such as biotite, illite(sericite), chlorite, and kaolinite of hydrothermal origin. Alteration Index as illite contents can be classified as follows: subprophylitic zone by 50%, prophylitic zone by 50∼75%, subphyllic zone by 75∼90%, phyllic zone by 90∼100%. Argillic zone is characterized by detection of kaolinite more than 5%. Another method by spectral parameters indicate that asymmetry value in kaolinite due to double peak around 2200nm are greater than 1.2. Applying to this area, this value can be well adopted to argillic zone. Chlorite/illite ratio(D2250/D2200) in two end-members experiment show that illite-dominant regime is up to 0.32. The assemblages to get greater than 0.32 can be categorized into chlorite-dominant regime. Comparing results of experiments with the previous our alteration data in the Mugeug area, it harmonizes through the all zones. The results of application to this area also accord with facts that the Geumbong mine is featured by subphyllic and/or phyllic zone or illite-dominant zone, while the Taegeug mine is by propylitic and/or subpropylitic zone or chlorite-dominant zone.
Key words : Mugeug, PIMA, SWIR, Hydrothermal Alteration, Spectral parameter
요약 : 무극광화대의 금은광상과 관련된 열수변질대의 특성을 규명하기 위하여 휴대용 적외선 광물분석기(PIMA; Portable Infrared Mineral Analyzer)의 단파장 적외선 스펙트럼자료에 따라 변질지수(Alteration Index)와 특성변수(spectral parameters)를 적용하여 변질 광물조합과 함량비에 근거한 정량적 분대를 구분하였다. 열수변질대의 분포양상은 석영맥으로부터 아프로필리틱대, 프로필리틱대, 아견운모대, 견운모대, 점토대로 배열되는 특징을 보이며, 지시광물의 함량변화과 특성변수를 통해 정량화 하였다. 본 연구에서 사용된 지시광물은 흑운모, 녹니석, 견운모, 카올리나이트로 견운모에 의한 분대별 변질지수는 아프로필리틱대가 50%, 프로필리틱대가 50∼75%, 아견운모대가 75∼90% 견운모대가 90∼100%를 보이며, 점토대는 5%이상의 카올리나이트 함량으로 설정된다. 2200nm 영역 흡수도를 이용한 특성변수는 녹니석/견운모의 비가 아프로필리틱대와 프로필리틱대에서 0.32 이상의 값을 보이는 반면, 아견운모대와 견운모대에서는 0.32 이하의 값을 보여 견운모와 녹니석의 함량변화 특징을 잘 반영한다. 점토대의 경우 카올리나이트 2200nm 영역의 왜곡도가 1.2이상으로 타 변질대와 잘 구분되는 특징을 보인다. 이 결과들은 X-선 회절분석 및 현미경관찰 결과와 잘 일치하고 있다. 무극-금왕-금봉광산의 열수변질대에서는 견운모화 작용이 우세한 경향을 보이지만, 태백광산에서는 녹니석화 작용이 우세하게 관찰되며, 이는 광화대 북측과 남측에서 변질대의 상이한 분포양상을 보인다.
주요어 : 무극광화대, PIMA, 단파장 적외선 열수변질, 특성변수
1. Introduction
2. Geology and Hydrothermal Alterartion
3. Methodology
4. Results and Interpretation
5. Conclusion
Reference
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