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남극 킹죠지섬 필데스반도의 화산암류에 대한 지구화학적 연구
좌용주,이종익 한국지구과학회 1992 韓國地球科學會誌 Vol.13 No.2
Tertiary volcanic activity in the Fildes Peninsula can be divided into three stages (I, II, III) of magmatism. Evolutionary process of each stage was examined from the geochemical characteristics. For stage I, olivine, orthopyroxene and clinopyroxene of low Fe/Mg ratio as well as Ca-plagioclase begin to crystallize and fractionate. Stage II magma, which is more differentiated than stage I magma, shows the fractionation of Ca-plagioclase and olivine and orthopyroxene of high Fe/Mg ratio. Stage III magma, which is slightly more differentiated than stage I magma but less than stage II magma, intruded into the area when stage II magmatism was weakened. The volcanic rocks on the Fildes Peninsula show, as a whole, tholeiitic natures. From the previous studies on Sr isotopic ratio, the origin of the volcanic magma in the area was assumed to be upper mantle. Accordingly, the volcanic rocks in the area were originated from tholeiitic magma which generated by the partial melting of upper mantle under island-arc environment.
전자현미경을 이용한 흑요석 내 미세결정의 형태와 조직 관찰
좌용주,황가현 한국지구과학회 2018 韓國地球科學會誌 Vol.39 No.6
Microlite is crystallized under the supercooled condition of volcanic magma. This study reports the morphology and texture of microlites included in the obsidians from the Baekdusan (Mt. Baekdu), Kyushu (Japan), Hokkaido (Japan) and Lipari Island (Italy) by using a scanning electron microscope (SEM). Morphology and texture observed from the back scattered electron (BSE) image could give more detailed information on the microlite crystallization which cannot be acquired from the conventional optical microscope. Ten types of microlites are newly described according to the 14 morphological types of microlites by Clark (1961): Lath, Crenulite, Bacillite, Margarite, Belonites, Trichites, Arculites, Furculite, Scopulites, Scopulitic growth. Detailed description of the ten microlites can be used to interpret the crystallization and paragenetic relations of crystals during the cooling of acidic volcanic magma. 흑요석 내 미세결정은 화산암질 마그마의 과냉각 조건에서 정출된 아주 작은 결정이다. 백두산, 일본 규슈와 홋카이도, 그리고 이태리 리파리 섬에서 산출되는 흑요석을 대상으로 그 내부에 포함된 미세결정의 형태와 조직을 전자현미경을 사용하여 관찰하여 정리하였다. 전자현미경의 후방산란전자 이미지로부터 관찰한 보다 자세한 미세결정에 대한 형태학적 분류는 기존의 광학현미경으로 얻을 수 없는 미세결정의 결정화에 대한 정보를 제공해 준다. 이 논문에서는 Clark (1961)의 미세결정 형태 분류 14가지 중에서 10가지에 대해 새로이 기재하였다. 즉, Lath, Crenulite, Bacillite, Margarite, Belonites, Trichites, Arculites, Furculite, Scopulites, Scopulitic growth 등의 미세결정에 대한 형태와 조직적 특징을 구체적으로 살펴보았다. 이런 기재적 연구로부터 향후 산성 마그마의 냉각과정동안 흑요석 내 미세결정의 결정작용과 광물 공생관계를 밝히는데 활용될 것이다.
Eruption age of the Kusandong Tuff in the Cretaceous Gyeongsang Basin, Korea
좌용주,이용일,Yuji Orihashi 한국지질과학협의회 2009 Geosciences Journal Vol.13 No.3
The Kusandong Tuff has been regarded as a key bed for the subdivision of the Upper Cretaceous strata in the Gyeongsang Basin. Since the Kusandong Tuff has the wide range of the K−Ar whole-rock ages (82~103 Ma) due to contamination and alteration, it is difficult to estimate the eruption age of the tuff. For the precise eruption age of the Kusandong Tuff, zircon grains from the tuff were analyzed using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The zircon U−Pb ages of the Kusandong Tuff are 97.1 ± 2.0 Ma and 97.3 ± 1.8 Ma, indicating that the tuffaceous bed formed during the middle Cenomanian. Accidental zircons in the tuff have a U−Pb age of 107.9 ± 3.0 Ma, which corresponds to the earlier Cretaceous igneous activity during the early Albian in age.