• Title/Summary/Keyword: 해양도 현무암

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Mantle Source Lithologies of Late Cenozoic Basaltic Rocks and Two Varieties of Enriched Mantle in the Korean Peninsula (한반도 신생대 후기 현무암의 근원 맨틀 암상과 두 종류의 부화 맨틀)

  • Choi, Sung Hi
    • Korean Journal of Mineralogy and Petrology
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    • v.35 no.3
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    • pp.183-197
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    • 2022
  • Geochemical data, including Sr-Nd-Pb-Mg-Zn isotopes, reported on the late Cenozoic intraplate basaltic rocks in the Korean Peninsula (Mt. Baekdu, Jeongok, Baengnyeong Island, Pyeongtaek, Asan, Ganseong, Ulleung Island, Dok Island, and Jeju Island) are summarized to constrain their mantle source lithologies, and the nature of mantle end-members required. In the Sr-Nd isotope correlation diagram, Jeju basalts plot in the field of EM2-type oceanic island basalts (OIB), while the other basalts fall in the EM1-type OIB field. In Pb-Pb isotope space, Jeju basalts show a mixing array between Indian MORB and EM2 component, whereas the other basalts display an array with EM1 component. The Korean basalts were derived from a hybrid source of garnet lherzolite and recycled stagnant slab materials (eclogite/pyroxenite, pelagic sediments, carbonates) in the mantle transition zone. The EM1 component could be ancient (~2.0 Ga) K-hollandite-bearing pelagic sediments that were isolated for a long period in the mantle transition zone due to their neutral buoyancy. The EM2 component might have been relatively young (probably Pacific slab) and recently recycled clay-rich pelagic sediments. Eclogite and carbonates are unlikely to account for the EM components, but they are common in the mantle source of the Korean basalts.

Volcanism and Petrogenesis of Dodong Basaltic Rocks in the Ulleung Island, East Sea (울릉도 도동현무암질암류의 화산작용과 암석성인)

  • Hwang, Sang Koo;Kim, Jae Ho;Jang, Yundeuk
    • The Journal of the Petrological Society of Korea
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    • v.26 no.4
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    • pp.361-371
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    • 2017
  • We investigated geochemical characteristics of the Dodong Basaltic Rocks in the lower part of the Ulleung Island. They have lithological range of alkali basalt to trachybasalt, belonging to Na and K subseries of alkaline series. They mostly fall within the field of alkalline within-plate basalts on tectonic discrimination diagrams, and then plot in the field of oceanic island basalt (OIB). Geochemically, extension of lithospheric mantle and asthenospheric upwelling after East Sea under an Cenozoic extensional tectonic setting might be a heat source for partial melting of the enriched lithospheric mantle, which might generate the basaltic magma. But we cannot exclude that mantle plume might also be a heat source for melting of the lithospheric mantle.

Geochemical Comparison Study on the Amphibolite in the Central Gyeonggi massif and Southeastern Okcheon metamorphic belt (중부 경기육괴와 동남부 옥천변성대의 각섬암에 대한 지화학적 비교 연구)

  • Na Ki Chang;Cheong Won Seok
    • The Journal of the Petrological Society of Korea
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    • v.13 no.4
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    • pp.201-213
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    • 2004
  • The Precambrian amphibolites in the central Gyeonggi massif, Yangsuri, Gyeonggido and southeastern Okcheon metamophic belt, Mungyeonggun, Gyeongsangbukdo, Korea, were studied on the geochemical characteristics of major and trace elements, and discussed petrogenetically and geotectonically. The characteristics of major elements of the amphibolites in these study areas are igeous origin such as tholeiitic-, subalkaline and alkaline basalt. Geotectonic distinction diagrams of trace elements such as Ti-Zr-Y and Zr-Nb-Y show basaltic igneous activity of island arc and mid ocean ridge environment at central Gyunggi massif, and within plate environment at southeastern Okcheon metamorphic belt. This result shows that genetic environments of study areas are different. Especially, origin of amphibolites in central Gyeonggi massif is similar with that of western Gyeonggi massif but different with the amphibolites of Chuncheon area. Genetic environment estimated of fractional crystallization of plagioclase has no particular effect on the origin of magma because value of LREE is higher than that of HREE and Eu anomaly definitely don't be exposed.

Petrology and Geochemistry of Miocene Alkaline Basalt (Huangsongpu Basalt) from the Mt. Baekdu Area (백두산 지역의 마이오세 알칼리 현무암(황송푸 현무암)의 암석학적/지화학적 특성)

  • Kim, Eunju;Hirata, Chiharu;Jeong, Hoon Young;Kil, Youngwoo;Yang, Kyounghee
    • Korean Journal of Mineralogy and Petrology
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    • v.33 no.4
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    • pp.307-324
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    • 2020
  • Major and trace elements, and Sr, Nd, isotopic composition analysis have been carried out on the Miocene basalt (Huangsongpu basalt, 20 Ma) 25 km to northeast from the Mt. Baekdu. The basalt has Na2O+K2O=3.5~4.7 wt.%, and MgO=9.9~11.1 wt.%, containing Mg-rich olivine (Mg#=75~86), clinopyroxene (Mg#=72~85) and Ca-rich plagioclase micro-phenocrysts. These data suggest that the basalt belongs to the alkaline magma series with a primitive nature, crystallized at a near-liquidus. The basalt is also characterized by high Cr (394~479 ppm) and Ni (389~519 ppm) contents, Nb-Ta enrichment anomalies and OIB-like trace elements patterns, displaying identical signatures to those of typical intraplate magmas. The rare earth element (REE) patterns of the basalt and high (Gd/Yb)sample/(Gd/Yb)PM ratio (=2.8~3.5) suggest the parental magma was derived from relatively low-degree (3~5%) partial melting of garnet peridotite. The 143Nd/144Nd and 87Sr/86Sr composition of the basalt are higher than those of BSE. The high 87Sr/86Sr (= ~0.7058) ratio of the basalt indicates a contribution of recycled ancient oceanic crust or continental crust on the Pacific slab suggesting that the Huangsongpu basalt was generated from metasomatized mantle.

Petrology on the Late Miocene Basalts in Goseong-gun, Gangwon Province (강원도 고성군 일대의 후기 마이오세 현무암의 암석학적 연구)

  • Koh Jeong Seon;Yun Sung-Hyo
    • Journal of the Korean earth science society
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    • v.26 no.1
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    • pp.78-92
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    • 2005
  • Petrographical and petrochemical analyses for late Miocene basalts in Goseong-gun area. Gangwon province, were carried out to interpret the characteristics and the origin of magma. The basaltic rocks occurred as plug-dome in the summit of several small mountain and developed columnar jointing with pyroxene-megacryst bearing porphyritic texture. And the basalt contains xenoliths of biotite granite (basement rocks), gabbro (lower crustal origin) and Iherzolite(upper mantle origin). The basalts belong to the alkaline basalt field in TAS diagram and partly belong to picrobasalt and trachybasalt field. On the tectonomagmatic discrimination diagram f3r basalt in the Goseong-gun area. they fall into the fields for the within plate and oceanic island basalt. The characteristics of trace elements and REEs shows that primary magma for the basalt magma would have been derived from partial melting of garnet-peridotite mantle. This late Miocene basalt volcanism is related to the hot spot within the palte.

Velocity-porosity relationships in oceanic basalt from eastern flank of the Juan de Fuca Ridge: The effect of crack closure on seismic velocity (Juan do Fuca 해저산맥의 동쪽 측면으로부터 얻은 해양성 현무암의 속도와 공극률의 관계: 균열닫힘이 탄성파 속도에 미치는 영향)

  • Tsuji, Takeshi;Iturrino, Gerardo J.
    • Geophysics and Geophysical Exploration
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    • v.11 no.1
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    • pp.41-51
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    • 2008
  • To construct in situ velocity-porosity relationships for oceanic basalt, considering crack features, P- and S-wave velocity measurements on basaltic samples obtained from the eastern flank of the Juan de Fuca Ridge were carried out under confining pressures up to 40 MPa. Assuming that the changes in velocities with confining pressures are originated by micro-crack closure, we estimated micro-crack aspect ratio spectra using the Kuster-$Toks{\ddot{o}}z$ theory. The result demonstrates that the normalised aspect ratio spectra of the different samples have similar characteristics. From the normalised aspect ratio spectrum, we then constructed theoretical velocity-porosity relationships by calculating an aspect ratio spectrum for each porosity. In addition, by considering micro-crack closure due to confining pressure, a velocity-porosity relationship as a function of confining pressure could be obtained. The theoretical relationships that take into account the aspect ratio spectra are consistent with the observed relationships for over 100 discrete samples measured at atmospheric pressure, and the commonly observed pressure dependent relationships for a wide porosity range. The agreement between the laboratory-derived data and theoretically estimated values demonstrates that the velocity-porosity relationships of the basaltic samples obtained from the eastern flank of the Juan de Fuca Ridge, and their pressure dependence, can be described by the crack features (i.e. normalised aspect ratio spectra) and crack closure.

Stratigraphic Implication of the Daljeon Basalt in the Miocene Pohang Basin, SE Korea (한반도 동남부 마이오세 포항분지 내 달전현무암의 층서적 의미)

  • Song, Cheol Woo;Kim, Hyeonjeong;Kim, Jong-Sun;Kim, Min-Cheol;Son, Moon
    • The Journal of the Petrological Society of Korea
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    • v.24 no.4
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    • pp.323-335
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    • 2015
  • Although the Daljeon Basalt in the Pohang Basin is important for interpreting the basin evolution, its relative chronology, stratigraphic position, and isotopic age still remain controversial. In order to clear up the controversies, this study carried out detailed field investigation to determine its distribution and occurrence together with reanalysis of its previous geochemical data and $^{40}Ar/^{39}Ar$ age dating. Based upon the field investigation, the basalt occurring in the central part of the Pohang basin is composed of three main bodies and a dozen of minor dikes and sills that intruded into the Yeonil Group. Their mineral assemblages consist of phenocrysts such as olivine and clinopyroxene and fine groundmasses of clinopyroxene, plagioclase, olivine, and opaque oxide, impling the porphyritic texture of alkaline basalt. All their geochemical data also show the similar geochemical characteristics in TAS, Zr-Ti, and REE/trace elements distribution diagrams. The samples are plotted on alkalic field in the total alkali-versus-silica diagram and show similar patterns to enrichment oceanic basalt or within plate basalt in trace elements. In addition, $^{40}Ar/^{39}Ar$ isochron age of 13.82Ma is obtained. These results indicate that the Daljeon Basalt is an alkaline intrusive rock belonging to the middle Miocene Yeonil Group.

New Approach on the Extinction of Spreading at the Phoenix Ridge, Antarctica (남극 피닉스 해령 확장작용 소멸시기에 대한 새로운 고찰)

  • Choe Won Hie;Lee Jong Ik;Lee Mi Jung;Hur Soon Do;Jin Yaung Keun
    • The Journal of the Petrological Society of Korea
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    • v.14 no.1
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    • pp.73-81
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    • 2005
  • K-Ar ages have been determined for the submarine basalts dredged from the P2 and P3 segments of the Phoenix Ridge, Drake Passage, Antarctica, for better understanding on the extinction of seafloor spreading. At the P3 segment, the K-Ar ages of the rifted ridge basalts are 3.5-6.4 Ma, and those for the axial seamount basalts are 1.5-3.1 Ma. The K-Ar ages for the basalts at the rifted ridge and axial central high in the P2 segment are 2.1 and 1.4-1.9 Ma, respectively. We suggest that the extinction of seafloor spreading at the P3 and P2 segments occurred at 3.3 and 2.0 Ma, respectively, on the basis of ridge structure and formation time of basalts. This result favors a stepwise extinction model rather than a simultaneous one on the extinction of the Phoenix Ridge.

Geochemistry and Petrogenesis of the Badwater Greenstones from Crystal Falls Terrane in Northeastern Wisconsin, U.S.A. (위스콘신주 북동부 지역에 분포하는 Badwater녹암에 대한 지화학적 연구)

  • Wee, Soo-Meen
    • Economic and Environmental Geology
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    • v.29 no.3
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    • pp.281-291
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    • 1996
  • Samples of Badwater greenstones from the Crystal Falls terrane in northeastern Wisconsin have been analyzed for major, trace and rare earth elements. Geochemical characteristics of the rocks provide clues to the petrologic character and paleotectonic environment of basaltic magma generation. They have chemical composition typical of continental tholeiites. The low Mg values and abundances of Ni and Cr indicate that the lavas were extensively fractionated prior to extrusion. The variations of incompatible elements suggest that the rocks were affected by interaction with crustal rocks. The samples least affected by contamination have trace element compositions similar to those of T-type mid-ocean ridge basalts. The parent was modified by crustal contamination process and this process shifted the rock compositions to that of continental tholeiites as the rock evolved. Interpretations of the chemical characteristics of the rocks, based on modem analogs, favor their emplacement in an extensional tectonic regime.

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Petrological study on the intermediate to mafic lavas distributed in Janggi area (1): General geology and petrochemical characteristics (장기 지역에 분포하는 중성~염기성 용암에 관한 암석학적 연구(1): 일반 지질 및 암석화학적 특징)

  • 박주희;김춘식;김진섭;성종규;김인수;이준동;백인성
    • The Journal of the Petrological Society of Korea
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    • v.8 no.3
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    • pp.149-170
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    • 1999
  • The volcanic lavas in the Janggi area are plotted on basalt, basaltic andesite and andesite field (SiO$_2$; 48-61 wt.%) in the TAS diagram and belong to subalkaline series. Nineteen chenmical analyses of lavas show two distinct differentiation trends; tholeiitic and calc-alkaline. Calc-alkaline basaltic andesites composed of plagioclase and two-pyroxenes (cpx, opx) in their phenocrysts. Tholeiitics basaltic lavas can be classified into two sub-types. The one is porphyritic basalts composed of plagioclase, clinopyroxene and olivine phenocryst, and the other is aphyric basalt and more evolved lavas (aphyric basaltic andesite) with the same mineral phases. Incompatible elements and REE patterns show the enrichment of LILE and depletion of HFSE. This characteristics indicate that these lavas are evolved from the magmas related to subduction. Howeverm calc-alkaline basaltic andesite lavas show that slightly higher enrichment of LILE and the depletion of HFSE than those of tholeiitic basaltic lavas. On the tectonic discriminant diagram such as Ba/Th and La/Th ratios, calc-alkaline basaltic andesite lavas belong to orogenic medium to high-K suites, whereas tholeiitic basaltic lavas belong to medium-K suites and MORB. On the other diagram, such as La/Yb vs. Th/Yb, the volcanic lavas in the study area plotted in the field of oceanic arc basalt. Tholeiitic basaltic lavas are located in more prinitive environment than calc-alkaline andesitic lavas.

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