• Proceedings of the KSEEG Conference
• /
• 2007.04a
• /
• pp.486-488
• /
• 2007

• Geophysics and Geophysical Exploration
• /
• v.11 no.3
• /
• pp.167-176
• /
• 2008

Lau basin of the south Pacific, as an active back arc basin, is promising area bearing seafloor massive hydrothermal deposit that is located in a subduction zone between the Pacific ocean plate and Indo-Australian continental plate. We performed multi-beam bathymetry survey in the Lau basin using EM120, to find out high hydrothermal activity Bone. Fonualei Rift and Spreading Center (FRSC) and Mangatolou Triple Junction (MTJ) area were selected for precise site survey through seafloor morphology investigation. The result of surface and deep-tow magnetometer survey showed that Central Anomaly Magnetization High (CAMH) recorded which is associated with active ridge in FRSC-2 and revealed very low magnetic anomalies that can be connected to past or present high hydrothermal activity in MTJ-1 seamount area. Moreover, the physical and chemical tracers of hydrothermal vent flume, i.e., transmission, hydrogen ion concentration (pH), adenosine triphosphate (ATP), methane (CH4) by use of CTD system, showed significant anomalies in those areas. From positive vent flume results, we could conclude that these areas were or are experiencing very active volcanic activities. The acquired chimney and hydrothermal altered bed rock samples gave us confidence of the existence of massive hydrothermal deposit. Even though not to use visual exploration equipment such as ROV, DTSSS, etc., traditional marine geophysical investigation approach might be a truly cost-effective tool for exploring seafloor hydrothermal massive deposit.

• The Science & Technology
• /
• no.8 s.411
• /
• pp.38-45
• /
• 2003

아프리카 동남쪽에 있는 마다가스카르섬에서도 800km나 떨어진 곳에는 레위니옹이라는 섬이 있다. 인구 70만명인 작은 섬 인근 해역에 2000년에 발견된 인도양 열수 지역이 있다. 이른 바 '활동중인 해저화산' 이다. 카레이 필드(Kairei field)로 이름 지어진 이곳의 수많은 열수 굴뚝에서는 활화산이 뿜어내는 검은 연기가 뭉게뭉게 솟아오르고 열수 굴뚝에서는 수많은 심해 생물들이 뒤엉켜 살고 있었다.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2011.06a
• /
• pp.235-235
• /
• 2011

Lau basin of south Pacific, as an active back arc basin, is promising area bearing seafloor massive hydrothermal deposit that is located in a subduction zone between the Pacific ocean plate and Indo-Australian continental plate. Korea Ocean Research and Development Institute tracked from 2004 to 2006 the hydrothermal activity to the extension of the northeast Lau Basin, targeting seamount. hydrothermal activity by tracking was found hydrothermal evidences. In this study, Marine seismic survey was carried out in the Lau basin seamount of the possibility of hydrothermal deposit. In particular, Marine magnetic survey and seismic survey was carried out at the same time in TA-12 seamount and noise characteristics were found in the seamount. the main process of data processing is Bandpass filter, FK filter, Deconvolution for noise attenuation such backscatter and multiple reflections. the migration is performed to compensate for reflection points followed by seamount of a slope. In this study, bedrock and upper strata could be identified and in the Future, the comparative method with Multi Beam Echo Sounder(MBES) are likely to derive the correct velocity model, the marine magnetic survey results should be considered.

• Economic and Environmental Geology
• /
• v.41 no.1
• /
• pp.81-92
• /
• 2008

Fonualei Rift and Spreading Center(FRSC) and Mangatolu Triple function(MTJ) caldera are located in northeastern part of Lau basin which is the active back-arc basin. Deep-tow and surface-tow magnetic surveys are carried out in FRSC. In deep-tow magnetic survey, to compensate for influence of uneven distance between bathymetry and sensor height, magnetic anomaly is continued upward to a level plane by using the Guspi method. We calculate crustal magnetization using Parker and Huestis's inversion algorithm, and try to find the hydrothermal vent and understand the structure of ocean floor crust. The result of deep-tow magnetic survey at FRSC showed that Central Anomaly Magnetization High(CAMH) recorded the max value of 4.5 A/m which is associated with active ridge. The direction of SSW-NNE corresponds with the direction of the principal spreading ridge in Lau basin. The low crustal magnetizaton$(174^{\circ}35.1'W,\;16^{\circ}38.4'S)$ of -4.0 A/m is supposed to correlate with submarine hydrothermal vent. Surface-tow magnetic data were collected in MTJ caldera$(174^{\circ}00'W,\;15^{\circ}20'S)$. The prevailing SSW-NNE direction of collapsing walls and the presence of CAMH at the center of caldera strongly indicate the existence of active spreading ridge in ancient times.

• Economic and Environmental Geology
• /
• v.44 no.5
• /
• pp.359-372
• /
• 2011

TA26 seamount, which is located at south part of Tonga arc, occurs widely hydrothermal plume and is area that sampled hostrock, hydrothermal ore and hydrothermal alteration rock for this study. Hostrocks are basalt and basaltic andesite. Altered rocks by hydrothermal solution consists of plagioclase, pyroxene, pyrite, ilmenite, amorphous silica, barite, smectite, iron sulfates, Fe-Si sulfates and Fe silicates. Gains and losses of major, trace and rare earth elements during wallrock alteration suggest that $K_2O$(+0.04~+0.45 g), $SiO_2$(-6.52~+10.56 g), $H_2O$(-0.03~+6.04 g), $SO_4$(-0.46~+17.54 g), S(-0.46~+13.45 g), total S(-0.51~+16.93 g), Ba(-7.60~+185078.62 g), Sr(-36.18~+3033.08 g), Ag(+54.83 g), Au(+1467.49 g), As(-5.80~+1030.80 g), Cd(+249.78 g), Cu(-100.57~+1357.85 g), Pb(+4.91~+532.65 g), Sb(-0.32~+66.59 g), V(-113.58~+102.94 g) and Zn(-49.56~+14989.92 g) elements are enriched from hydrothermal solution. Therefore, gained(enriched) elements(($K_2O$, $H_2O$, $SO_4$, S, total S, Ba, Sr, Ag, Au, As, Cd, Cu, Pb, Sb, V, Zn) represent a potentially tools for exploration of sea-floor hydrothermal deposits from the Tonga arc.

• Journal of the Mineralogical Society of Korea
• /
• v.27 no.4
• /
• pp.169-181
• /
• 2014

Korea government has consistently investigated the development of economic mineral deposits in the Tofua volcanic arc, Tonga since 2008 for the secure of sea floor mineral resources. We studied the composition and distribution of minerals formed by hydrothermal activity around TA 25 seamounts of the Tofua volcanic arc, Lau Basin, Tonga, using X-ray diffraction analysis, scanning electron microscopy, X-ray fluorescence spectrometry, and inductively coupled plasma atomic emission spectrometry. We used 7 core samples and 9 surface sediment samples. Barite, sphalerite, and clinoclase are present in the most volcanic vent area. Gypsum, smectite, and kaolin mineral are distributed in vent A area, chalcopyrite, pyrite, smectite, and kaolin mineral are in vent B and C area, and gypsum, chalcopyrite, pyrite, and goethite are in vent D area. From the study of clay fraction, smectite and few kaolinite are detected in the most studied area except inner part of caldera, which suggest that argillic alteration are dominant in the volcanic vent areas. Various sulfide or arsenide minerals were found in the hydrothermal vent B, C, and D. The mineralogy and geochemistry suggest higher hydrothermal activities in volcanic vent B, C, and D compared to vent A and inner caldera area. Therefore higher probabilities of massive sulfide deposits may occur in hydrothermal vent B, C, and D.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.13 no.3
• /
• pp.271-279
• /
• 2008

Polymetallic sulphides means hydrothermally formed deposits of sulphide minerals which contain concentrations of metals including, inter alia, copper, lead, zinc, gold and silver. Nautilus is the first company to commercially explore the seafloor polymetallic sulphide deposits. The Company holds exploration licences and exploration applications for more than 370,000 $km^2$ in the jurisdictional seas of Papua New Guinea, Fiji, Tonga, the Solomon Islands and New Zealand along the western Pacific Ocean's Rim of Fire. Neptune Minerals is also a leading explorer and developer in this field, with exploration licences awarded totalling more than 270,000 $km^2$ in the territorial seas or EEZ of New Zealand, Papua New Guinea and the Federated States of Micronesia. These two companies now carry out the most active investment activities for seafloor polymetallic sulphide deposits with a goal of commercial production by 2010. China and Japan carry out exploration activities for the seafloor polymetallic sulphide deposits to secure supplies of strategic metals. China carries out national R&D projects relating to deep sea mineral resources in the world ocean through China Ocean Mineral Resources R&D Association(COMRA). And Japan investigates her own EEZ for exploration of the seafloor polymetallic sulphide deposits. In consideration of aforementioned international activities of coastal nations as well as private companies for exploring the sulphide deposits, Korea shall prepare strategic plans : First, consolidation of the authorities concerned and legislative support; second, determination of main entity of the project; third, securing government's decisive investment of sufficient budget; and lastly, establishment of the mid, long-term plan for development of seafloor polymetallic sulphides deposits.

• Economic and Environmental Geology
• /
• v.47 no.4
• /
• pp.395-404
• /
• 2014

We conducted the geophysical survey of possible hydrothermal vent sites at 2009, in the Lau Basin, the south western Pacific and analyzed the magnetic characteristics of TA19-1 and TA19-2 seamounts. TA19-1 is a cone-shaped seamount with a caldera summit. TA19-2 seamount is bigger and shows more complicated topography than TA19-1 seamount. TA19-2 has a large caldera, a summit in the west side of the caldera and several crests. Simple dipole anomalies with a high over the north and a low over the south occur in TA19-1 seamount. High magnetic anomalies are located in the northern flank and the summit of TA19-2 seamount and low anomalies around the summit and the caldera. The results of bathymetry and magnetic data suggest that TA19-2 seamount might have more complicated magmatic process than TA19-1. Low magnetization zones are located over the summit, the calderas and the caldera rims. The magnetization lows indicate that submarine hydrothermal vents, along faults and fracture zones, could have caused an alteration of magnetic minerals. The magnetization highs over the summit and the calderas might have been related with later magmatisms like volcanic sills, intrusions.

• Economic and Environmental Geology
• /
• v.44 no.5
• /
• pp.373-386
• /
• 2011

Geochemical study was performed on black slates and interbedded U-bearing coaly slates in Deokpyeongri area, the representative uranium mineralized district of the Ogcheon Metamorphic Belt, to discuss the genetic environments of the uranium deposit. REE concentration (254 ppm) of the black slates is higher than that (169 ppm) of the coaly slates and NASC-normalized REE patterns of the coaly slates show remarkable positive Eu anomaly. l11e redox-sensitive trace elements such as V, Cr, Co, Ni, Mo and U in the coaly slates are highly enriched compared to the black slates, especially for V of 24 times, Mo of 62 times, and U of 60 times. In additions, Pd and Pt are also enriched in the coaly slates. Positive Eu anomaly and the noticeable enrichment of the elements listed above compared to those of NASC indicate that those elements were not derived from common seawater but deposited under high temperature and reducing environment of submarine hydrothermal activities. Wide compositional ranges of major elements ($SiO_2/Al_2O_3$: 3.98~11.88, $Al_2O_3/Na_2O$: 25.6~139.06, $K_2O/Na_2O$: 6.80~46.85) also suggest that the source rocks of the sediments are mixtures of sedimentary rocks and igneous rocks. Higher sulfur contents in the coaly slates, 2.6 wt.%, than those in the black slates, 0.6 wt.% also indicates that the former was influenced by hydrothermal activities containing much sulfur. These geochemical characteristics are similar to the genetic environments of South China type PGE deposits (Mo-Ni-Zn-PGE) which is geotectonically correlated with the Ogcheon Metamorphic Belt and is known as sedimentary-exhalative deposits. In conclusions, the uranium and other metallic elements mineralization seems to have occurred in the sedimentary basin that was affected by submarine hydrothermal activities and rich in organic materials under oxygen-poor environments as well.